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  • 1. Aikio, A T
    et al.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Yamauchi, M
    On the origin of the high-altitude electric field fluctuations in the auroral zone1996Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 101, nr A12, s. 27157-27170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Intense fluctuations in the electric field at high altitudes in the auroral zone are frequently measured by the Viking satellite. We have made an analysis of the origin of electric and magnetic fluctuations in the frequency range of 0.1 - 1 Hz by assuming four different sources for the signals: (I) spatial structures, (2) spatial structures with a parallel potential drop below the satellite, (3) traveling; shear Alfven waves, and (4) interfering shear Alfven waves. We will shaw that these different sources of the signals may produce similar amplitude ratios and phase differences between the perpendicular electric and magnetic fields. Since the different sources have different frequency dependencies, this can be used as an additional test if the signals are broadband. In other cases, additional information is needed, for example, satellite particle measurements or ground; magnetic measurements. The ideas presented in the theory were tested for one Viking eveningside pass over Scandinavia, where ground-based magnetometer and EISCAT radar measurements were available. The magnetic conditions were active during this pass and several interfering shear Alfven waves were found. Also, a spatial structure with a parallel potential drop below the satellite was identified. The magnitude of the 10-km-wide potential drop was at least 2 kV and the upward field-aligned current 26 mu A m(-2) (value mapped to the ionospheric level). The held-aligned conductance was estimated as 1.3 - 2.2x10(-8) S m(-2).

  • 2. Alexeev, I. I.
    et al.
    Belenkaya, E. S.
    Bobrovnikov, S. Yu.
    Kalegaev, V. V.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Magnetopause mapping to the ionosphere for northward IMF2007Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 25, nr 12, s. 2615-2625Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the topological structure of the magnetosphere for northward IMF. Using a magnetospheric magnetic field model we study the high-latitude response to prolonged periods of northward IMF. For forced solar wind conditions we investigate the location of the polar cap region, the polar cap potential drop, and the field-aligned acceleration potentials, depending on the solar wind pressure and IMF B-y and B-x changes. The open field line bundles, which connect the Earth's polar ionosphere with interplanetary space, are calculated. The locations of the magnetospheric plasma domains relative to the polar ionosphere are studied. The specific features of the open field line regions arising when IMF is northward are demonstrated. The coefficients of attenuation of the solar wind magnetic and electric fields which penetrate into the magnetosphere are determined.

  • 3. Andre, M
    et al.
    Norqvist, P
    Andersson, L
    Eliasson, L
    Eriksson, A I
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Erlandson, R E
    Waldemark, J
    Ion energization mechanisms at 1700 km in the auroral region1998Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, ISSN 0148-0227, Vol. 103, nr A3, s. 4199-4222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations obtained by the Freja satellite at altitudes around 1700 km in the high-latitude magnetosphere are used to study ion energization perpendicular to the geomagnetic field. Investigations of ions, electrons, plasma densities, electric and magnetic wave fields, and field-aligned currents are used to study O+ heating mechanisms. Three ion heating events are studied in detail, and 20 events are used in a detailed statistical study. More than 200 events are classified as belonging to one of four major types of ion heating and are ordered as a function of magnetic local time. The most common types of ion heating are associated with broadband low-frequency electric wave fields occurring at all local times. These waves cover frequencies from below one up to several hundred hertz and correspond to the most intense O+ energization. Heating by these waves at frequencies of the order of the O+ gyrofrequency at 25 Hz seems to be the important energization mechanism, causing O+ ion mean energies up to hundreds of eV. The broadband waves are associated with Alfven waves with frequencies up to at least a few hertz and with field-aligned currents. Other types of O+ energization events are less common. During these events the ions are heated by waves near the lower hybrid frequency or near half the proton gyrofrequency. These waves are generated by auroral electrons or in a few cases by precipitating ions.

  • 4. Bahnsen, Axel
    et al.
    PEDERSEN, BM
    JESPERSEN, M
    UNGSTRUP, E
    ELIASSON, L
    MURPHREE, JS
    ELPHINSTONE, RD
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    HOLMGREN, G
    ZANETTI, LJ
    Viking observations at the source region of auroral kilometric radiation1989Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, ISSN 0148-0227, Vol. 94, nr A6, s. 6643-&Artikel i tidskrift (Refereegranskat)
  • 5. Bale, S. D.
    et al.
    Maksimovic, M.
    Vaivads, A.
    Andre, M.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Antenna design considerations for the Radio and Plasma Wave (RPW) experiment on solar orbiter2006Ingår i: European Space Agency, (Special Publication) ESA SP, Athens, 2006, nr SP-641Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electric fields in the solar wind are very poorly studied; there have been no instruments dedicated to measuring solar wind electric fields and plasma waves at low frequencies. Here we discuss some of the important physics of LF electric fields, including dissipation of MHD turbulence, shock acceleration of particles, and solar wind magnetic reconnection. We then present some antenna sensor and instrument designs that will potentially satisfy the goal of measuring both DC/low frequency electric fields AND higher frequency radio and thermal noise emissions. We discuss trades between science goals and complexity of the designs.

  • 6.
    Barabash, Stas
    et al.
    Swedish Institute of Space Physics, Kiruna.
    André, Mats
    Swedish Institute of Space Physics, Uppsala.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lundin, Rickard
    Swedish Institute of Space Physics, Kiruna.
    Marklund, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Rathsman, Peter
    Swedish Space Corporation, Solna, Sweden.
    von Schéele, Fredrik
    Swedish Space Corporation, Solna, Sweden.
    Wahlund, Jan-Erik
    Swedish Institute of Space Physics, Uppsala.
    Mars Orbiting Plasma Surveyor (MOPS)2006Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions, 2006, s. 227-232Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Mars Orbiting Plasma Surveyor (MOPS) is a microsatellite mission focused on studies of the near -Mars environment and the planet - solar wind interaction. The recent findings by the ESA Mars Express mission further highlighted the complexity of the processes taking place at the planet resulting from the solar wind interaction that strongly affect the

    planet's atmosphere. However, despite many previous Martian missions carrying different types of space plasma experiments, a comprehensive investigation including simultaneous measurements of particles, fields, and waves has never been performed.

    We consider a spinning spacecraft of a wet mass of 76.1 kg with a 9.7 kg payload, which can “hitchhike” on another platform until Mars orbit insertion, and then be released into a suitable orbit. The spacecraft design is based on the experience gained in very successful

    Swedish space plasma missions, Viking, Freja, Astrid-1, and Astrid-2. In the present mission design, the MOPS spacecraft is equipped with its own 1m high gain antenna for direct communication with the Earth. The payload includes a wave experiment with wire booms,

    magnetometer with a rigid boom, Langmuir probes, electron and ion energy spectrometers and an ion mass analyzer. An energetic neutral atom imager and an UV photometer may complete the core payload. One of the proposed scenarios is piggy - backing on the Russian Phobos - Grunt mission to be launched to Mars in 2011.

  • 7.
    Barabash, Stas
    et al.
    Swedish Institute of Space Physics, Kiruna.
    Norberg, Olle
    Swedish Space Corporation, Esrange.
    Wahlund, Jan-Erik
    Swedish Institute of Space Physics, Uppsala.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Grahn, Sven
    Swedish Space Corporation, Solna, Sweden.
    Persson, Staffan
    Swedish Space Corporation, Solna, Sweden.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Towards low-cost Swedish planetary missions2004Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    As a continuation of the Swedish tradition of designing small and high-quality spacecrafts such as Freja, Astrid, Munin, and SMART-1, Swedish scientists and engineers have proposed aggressive but feasible missions as the next national-level target: (1) an interplanetary plasma module (or subsatellite) Saga, and (2) a technology mission Prisma. The Saga micro-satellite contains a separation mechanism, technologically-challenging communication package, and plasma payload with an estimated total mass of 37kg to make the mission possible with a piggy-back launch or by attaching to another planetary mission. The Prisma mission consists of a semi-coordinated dual micro- and nano-satellites flying together in Earth orbit with state-of-art instruments to test. Both projects aim to develop and test new key spacecraft technologies.

  • 8.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Mercury's magnetosphere, exosphere and surface: Low-frequency field and wave measurements as a diagnostic tool1997Ingår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 45, nr 1, s. 143-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diagnostics that can be made with combined electric and magnetic field measurements at Mercury are reviewed. Fundamental electrodynamic questions which can be answered by means of a Mercury Orbiter are discussed. These include, solar wind-magnetosphere coupling, coupling to low altitude, exospheric or planetary surface conductivity, auroral particle acceleration, and magnetospheric substorms. It is concluded that a comprehensive instrumentation package for low-frequency fields and waves on a future Mercury Orbiter mission may yield significant new information of interest to magnetospheric as well as to planetary physics in general. (C) 1997 Elsevier Science Ltd.

  • 9.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Micro-satellite Mission Analysis: Theory Overview and Some Examples2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Rudimentary mission analysis for micro-satellites has been carried out, in particular for ionospheric/thermospheric “dipper” missions. The basic equations of orbital mechanics are summarized and commented on. General properties of near-Earth orbits are discussed and exemplified in figures and tables. In addition, a few specific mission scenarios are described and discussed.

  • 10.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Potential- och konduktivitetsfördelningar i jonosfären under inflytande av Birkelandströmmar1986Självständigt arbete på avancerad nivå (masterexamen), 12 poäng / 18 hpStudentuppsats (Examensarbete)
  • 11.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Viking observations of dayside high-latitude electric fields1994Ingår i: Physical Signatures of Magnetospheric Boundary Layer Processes, 1994Konferensbidrag (Refereegranskat)
  • 12.
    Blomberg, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Diagnosing the Mercury Plasma Environment Using Low-Frequency Electric Field Measurements2006Ingår i: Advances in Geosciences, Volume 3: Planetary Science / [ed] Anil Bhardwaj, World Scientific Co., Pte. Ltd., Singapore , 2006, s. 63-70Konferensbidrag (Refereegranskat)
  • 13.
    Blomberg, Lars G.
    et al.
    KTH.
    Cumnock, J. A.
    Diagnosing the mercury plasma environment using low-frequency electric field measurements2006Ingår i: Advances in Geosciences: Volume 3: Planetary Science (PS), World Scientific Publishing Co , 2006, s. 69-70Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The magnetosphere ofMercury is most intriguing because of its extreme nature, with scale sizes vastly different from the corresponding terrestrial ones, and a harsh environment at a comparatively small solar distance. The present brief paper summarizes some scientific topics where electric field measurements at low frequency will make a significant contribution to the understanding of the Mercury plasma environment, and discusses possible diagnostics. © 2006 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.

  • 14.
    Blomberg, Lars G.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, J. A.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Eriksson, A. I.
    The martian plasma environment: Electric field and Langmuir probe diagnostics2003Ingår i: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 31, nr 6, s. 1232-1236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The plasma environment of Mars has been studied by a small handful of spacecraft. From the sparse observations that exist, one may conclude that the solar wind-Martian magnetosphere interaction is different in significant ways from the solar wind's interaction with Earth's magnetosphere. Mars offers an opportunity to make significant advances in our understanding of the fundamentals of the solar wind's interaction with cold celestial bodies, with suitable plasma instrumentation orbiting the planet. We briefly review what is known about Mars' plasma environment and address some scientific topics that can be studied by proper plasma instrumentation in Mars' vicinity, in particular the scientific potential of Langmuir probe measurements. Finally, we exemplify how the studies may contribute to an enhanced understanding not only of the plasma surrounding Mars, but also of the planet itself and its neutral atmosphere.

  • 15.
    Blomberg, Lars G.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Electrodynamics of transpolar aurorae2005Ingår i: SOLAR WIND-MAGNETOSPHERE-IONOSPHERE DYNAMICS AND RADIATION MODELS, 2005, Vol. 36, nr 10, s. 1785-1790Konferensbidrag (Refereegranskat)
    Abstract [en]

    Polar UV image and Astrid-2 electric and magnetic field data are used to study the evolution of the electrodynamical configuration of the high-latitude ionosphere during a 5-h transpolar arc event. During the course of the event we observe Sunward convection in narrow regions associated with pairs Of upward and downward transpolar are-related field-aligned currents. We also observe Sunward convection deriving from more remotely located field-aligned currents as well as stagnant convection in the centre of the polar region associated with a decoupling of the dawn and dusk side current systems. Schematic pictures of the current closure and convective flows are presented for a variety Of configurations. The different states evolve naturally into each other and do not represent fundamentally different magnetospheric configurations.

  • 16.
    Blomberg, Lars G.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Cumnock, Judy
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    On electromagnetic phenomena in Mercury's magnetosphere2004Ingår i: Mercury, Mars and Saturn / [ed] Grard, R; Masson, PL; Gombosi, TI, OXFORD: Pergamon Press, 2004, Vol. 33, nr 12, s. 2161-2165Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury's and Earth's magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury's magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.

  • 17.
    Blomberg, Lars G.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, Judy A.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Kasaba, Y.
    Matsumoto, H.
    Kojima, H.
    Omura, Y.
    Moncuquet, M.
    Wahlund, J. -E
    Electric fields in the Hermean environment2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 4, s. 627-631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Returning to Mercury with the BepiColombo mission will provide a unique opportunity to obtain in situ information on the electric field in Mercury's magnetosphere. The electric field plays a crucial role for plasma transport in the magnetosphere, for transfer of energy between different parts of the system, and for propagation of information. Measuring the electric field, we will be able to better understand plasma motion and wave propagation in Mercury's magnetosphere. Together with knowledge of the magnetic field a better understanding will be derived of the magnetospheric current systems and their closure at or near the planetary surface. Further, insight into possible substorms at Mercury will be gained. We here focus on the expected amplitudes and frequencies of the electric fields concerned and the requirements for instrument capability that they pose.

  • 18.
    Blomberg, Lars G.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Alexeev, I.I.
    Belenkaya, E. S.
    Bobrovnikov, S. Y.
    Kalegaev, V. V.
    Transpolar aurora: time evolution, associated convection patterns, and a possible cause2005Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, nr 5, s. 1917-1930Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present two event studies illustrating the detailed relationships between plasma convection, field-aligned currents, and polar auroral emissions, as well as illustrating the influence of the Interplanetary Magnetic Field's y-component on theta aurora development. The transpolar are of the theta aurorae moves across the entire polar region and becomes part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the POLAR UVI instrument provides measurements of auroral emissions. Ionospheric electrostatic potential patterns are calculated at different times during the evolution of the theta aurora using the KTH model. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Paraboloid Model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed.

  • 19.
    Blomberg, Lars G.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Glassmeier, K. H.
    Treumann, R. A.
    Plasma waves in the Hermean magnetosphere2007Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 132, nr 04-feb, s. 575-591Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Hermean magnetosphere is likely to contain a number of wave phenomena. We briefly review what little is known so far about fields and waves around Mercury. We further discuss a number of possible phenomena, including ULF pulsations, acceleration-related radiation, bow shock waves, bremsstrahlung (or braking radiation), and synchrotron radiation. Finally, some predictions are made as to the likelihood that some of these types of wave emission exist.

  • 20.
    Blomberg, Lars G.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Eriksson, Stefan
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Cumnock, Judy A.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Yamauchi, M.
    Clemmons, J. H.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Karlsson, Tomas
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lundin, R.
    Solar windmagnetosphere-ionosphere coupling: an event study based on Freja data2004Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 66, nr 5, s. 375-380Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Freja data are used to study the relative contributions from the high-latitude (reconnection/direct entry) and low-latitude (viscous interaction) dynamos to the cross-polar potential drop. Convection streamlines which are connected to the high-latitude dynamo may be identified from dispersed magnetosheath ions not only in the cusp/cleft region itself but also several degrees poleward of it. This fact, together with Freja's orbital geometry allows us to infer the potential drop from the high-latitude dynamo as well as to obtain a lower limit to the potential drop from the low-latitude dynamo for dayside Freja passes. All cases studied here are for active magnetospheric conditions. The Freja data suggest that under these conditions at least one third of the potential is generated in the low-latitude dynamo. These observations are consistent with earlier observations of the potential across the low-latitude boundary layer if we assume that the low-latitude dynamo region extends over several tens of Earth radii in the antisunward direction along the tail flanks, and that the majority of the potential drop derives from the sun-aligned component of the electric field rather than from its cross-boundary component, or equivalently, that the centre of the dynamo region is located quite far down tail. A possible dynamo geometry is illustrated.

  • 21.
    Blomberg, Lars G.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    High-Latitude Convection Patterns For Various Large-Scale Field-Aligned Current Configurations1991Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 18, nr 4, s. 717-720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The large-scale field-aligned current system for persistent northward interplanetary magnetic field (IMF) is typically different from that for persistent southward IMF. One characteristic difference is that for northward IMF there is often a large-scale field-aligned current system poleward of the main auroral oval. This current system (the NBZ current) typically occupies a large fraction of the region poleward of the region 1 and 2 currents. The present paper models the high-latitude convection as a function of the large-scale field-aligned currents. In particular, a possible evolution of the convection pattern as the current system changes from a typical configuration for southward IMF to a configuration representing northward IMF (or vice versa) is presented. Depending on additional assumptions, for example about the y-component of the IMF, the convection pattern could either turn directly from a two-cell type to a four-cell type, or a three-cell type pattern could show up as an intermediate state. An interesting although rather surprising result of this study is that different ways of balancing the NBZ currents has a minor influence on the large-scale convection pattern.

  • 22.
    Blomberg, Lars G.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Primdahl, F.
    Brauer, P.
    Bylander, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Eriksson, Stefan
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Ivchenko, Nickolay V.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Karlsson, Tomas
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Kullen, Anita
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Merayo, J. M. G.
    Pedersen, E. B.
    Petersen, J. R.
    EMMA - the electric and magnetic monitor of the aurora on Astrid-22004Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, nr 1, s. 115-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Astrid-2 mission has dual primary objectives. First, it is an orbiting instrument platform for studying auroral electrodynamics. Second, it is a technology demonstration of the feasibility of using micro-satellites for innovative space plasma physics research. The EMMA instrument, which we discuss in the present paper, is designed to provide simultaneous sampling of two electric and three magnetic field components up to about 1 kHz. The spin plane components of the electric field are measured by two pairs of opposing probes extended by wire booms with a separation distance of 6.7 m. The probes have titanium nitride (TiN) surfaces. which has proved to be a material with excellent properties for providing good electrical contact between probe and plasma. The wire booms are of a new design in which the booms in the stowed position are wound around the exterior of the spacecraft body. The boom system was flown for the first time on this mission and worked flawlessly. The magnetic field is measured by a tri-axial fluxgate sensor located at the tip of a rigid. hinged boom extended along the spacecraft spin axis and facing away from the Sun. The new advanced-design fluxgate magnetometer uses digital signal processors for detection and feedback, thereby reducing the analogue circuitry to a minimum. The instrument characteristics as well as a brief review of the science accomplished and planned are presented.

  • 23.
    Blomberg, Lars G.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Matsumoto, H.
    Bougeret, J. -L
    Kojima, H.
    Yagitani, S.
    Cumnock, Judy A.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Eriksson, A. I.
    Marklund, Göran T.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Wahlund, J. -E
    Bylander, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Åhlen, L.
    Holtet, J. A.
    Ishisaka, K.
    Kallio, E.
    Kasaba, Y.
    Matsuoka, A.
    Moncuquet, M.
    Mursula, K.
    Omura, Y.
    Trotignon, J. G.
    MEFISTO - An electric field instrument for BepiColombo/MMO2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 4, s. 672-679Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    MEFISTO, together with the companion instrument WPT, are planning the first-ever in situ measurements of the electric field in the magnetosphere of planet Mercury. The instruments have been selected by JAXA for inclusion in the BepiColombo/MMO payload, as part of the Plasma Wave Investigation coordinated by Kyoto University. The magnetosphere of Mercury was discovered by Mariner 10 in 1974 and will be studied further by Messenger starting in 2011. However, neither spacecraft did or will measure the electric field. Electric fields are crucial in the dynamics of a magnetosphere and for the energy and plasma transport between different regions within the magnetosphere as well as between the magnetosphere and the surrounding regions. The MEFISTO instrument will be capable of measuring electric fields from DC to 3 MHz, and will thus also allow diagnostics of waves at all frequencies of relevance to the Hermean magnetosphere. MEFISTO is a double-probe electric field instrument. The double-probe technique has strong heritage and is well proven on missions such as Viking, Polar, and Cluster. For BepiColombo, a newly developed deployment mechanism is planned which reduces the mass by a factor of about 5 compared to conventional mechanisms for 15 in long booms. We describe the basic characteristics of the instrument and briefly discuss the new developments made to tailor the instrument to flight in Mercury orbit.

  • 24.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Viking observations of electric fields1992Ingår i: Study of the Solar-Terrestrial System, 1992, Vol. 346, s. 269-274Konferensbidrag (Övrigt vetenskapligt)
  • 25.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner.
    Marklund, Göran
    KTH, Tidigare Institutioner.
    A Numerical Model of Ionospheric Convection Derived From Field-Aligned Currents and the Corresponding Conductivity1988Rapport (Övrigt vetenskapligt)
  • 26.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    A Numerical Model of Ionospheric Convection Derived From Field-Aligned Currents and the Corresponding Conductivity1991Rapport (Övrigt vetenskapligt)
  • 27.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    High-latitude electrodynamics and aurorae during northward IMF1993Ingår i: Auroral Plasma Dynamics, Washington, DC: American Geophysical Union (AGU), 1993, s. 55-68Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The large-scale auroral morphology and its associated electrodynamics for northward interplanetary magnetic field (IMF) is characteristically different from that for southward IMF. For northward IMF significant auroral activity is often present poleward of the “normal” auroral oval, and a number of different polar auroral configurations can occur. Two extreme situations which are considered here are either one where one or more discrete arcs separated from the “normal” oval are present in the polar region, or one where diffuse auroral activity is found in a large fraction of this region. The latter case might be associated with so-called NBZ (field-aligned) currents. We briefly review the typical signatures in terms of optical emissions, field-aligned currents, electric fields, and plasma convection usually encountered in the polar region when IMF Bz<0, and their interrelationships. This is the starting point for a more detailed discussion, driven by modeling results, of the relationships between electric field, field-aligned current, and conductivity in the two distinct situations mentioned. In particular we discuss the influence the polar field-aligned currents have on the convection pattern, on the small as well as on the large scale. As expected, currents associated with discrete isolated arcs give rise mainly to small-scale modifications, whereas currents related to auroral activity in an expanded oval can modify the overall convection pattern substantially.

  • 28.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner.
    Marklund, Göran
    KTH, Tidigare Institutioner.
    The Influence of Conductivities Consistent With Field-Aligned Currents on High-Latitude Convection Patterns1988Rapport (Övrigt vetenskapligt)
  • 29.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    The influence of conductivities consistent with field-aligned currents on high-latitutde convection patterns1988Ingår i: Journal of Geophysical Research - Space Physics, ISSN 0148-0227, Vol. 93, nr A12, s. 14493-14499Artikel i tidskrift (Refereegranskat)
  • 30.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Bylander, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Atrid-2: An advanced auroral microprobe1999Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    Astri-2 is an advanced auroral microprobe with dual primary mission objectives; to do high-quality in situ measurements of the physical processes behind the aurora, and to demonstrate the usefulness of microspacecraft as advanced research tools. Mission success will open up entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space. This long-desired kind of in situ measurements are the next major step forward in experimental space physics. Astrid-2 has platform dimensions of 45×45×30 cm, a total mass of just below 30 kg, and carries scientific instruments for measuring local electric and magnetic fields, plasma density and density fluctuations, ions and electrons, as well as photometers for remote imaging of auroral emissions. Attitude determination is provided by a high-precision star imager. Some 250 Mbytes' worth of scientific data will be received each day at the two ground stations. Astrid-2 will be launched as a piggy-back on a Russian Kosmos-3M launcher into an 83 deg inclination circular orbit at 1000 km altitude. Nodal regression will give complete coverage of all local time sectors every 3.5 months. © 1999 Elsevier B.V. All rights reserved.

  • 31.
    Blomberg, Lars
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Marklund, Göran
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Primdahl, F.
    Brauer, P.
    Bylander, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Cumnock, Judy
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Eriksson, S.
    Ivchenko, Nickolay
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Karlsson, Tomas
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Kullen, Anita
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Merayo, J. M. G.
    Pedersen, E. B.
    Petersen, J. R.
    The EMMA Instrument on the Astrid-2 Micro-Satellite2003Rapport (Övrigt vetenskapligt)
  • 32.
    Blomberg, Lars
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Wahlund, Jan-Erik
    Swedish Institute of Space Physics, Uppsala.
    Cumnock, Judy
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Morooka, Michiko
    Swedish Institute of Space Physics, Uppsala.
    André, Mats
    Swedish Institute of Space Physics, Uppsala.
    Eriksson, Anders
    Swedish Institute of Space Physics, Uppsala.
    Electric Field Diagnostics in the Jovian System: Brief Scientific Case and Instrumentation Overview2006Ingår i: Proceedings of the 6th IAA International Conference on Low-Cost Planetary Missions, 2006, s. 335-340Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Jovian plasma environment exhibits a variety of plasma flow interactions with magnetised as well as unmagnetised bodies, making it a good venue for furthering our understanding of solar wind - magnetosphere / ionosphere interactions.

    On an overall scale the solar wind interacts with the Jovian magnetosphere, much like at Earth but with vastly different temporal and spatial scales. Inside the Jovian magnetosphere the co-rotating plasma interacts with the inner moons. The latter interaction is slower and more stable than the corresponding interaction between the solar wind and the planets, and can thus provide additional information on the principles of the interaction mechanisms.

    Because of the wealth of expected low-frequency waves, as well as the predicted quasi-static electric fields and plasma drifts in the interaction regions between different parts of the Jovian system, a most valuable component in future payloads would be a double-probe electric field instrument. Recent developments in low-mass instrumentation facilitate electric field measurements on spinning planetary spacecraft, which we here exemplify.

  • 33. Boardsen, Scott A.
    et al.
    Sundberg, Torbjorn
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Slavin, James A.
    Anderson, Brian J.
    Korth, Haje
    Solomon, Sean C.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury's magnetosphere during MESSENGER's third flyby2010Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 37, artikel-id L12101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the third MESSENGER flyby of Mercury on 29 September 2009, 15 crossings of the dusk-side magnetopause were observed in the magnetic field data over a 2-min period, during which the spacecraft traveled a distance of 0.2 R-M (where R-M is Mercury's radius). The quasi-periodic nature of the magnetic field variations during the crossings, the characteristic time separations of similar to 16 s between pairs of crossings, and the variations of the magnetopause normal directions indicate that the signals are likely the signature of surface waves highly steepened at their leading edge that arose from the Kelvin-Helmholtz instability. At Earth, the Kelvin-Helmholtz instability is believed to lead to the turbulent transport of solar wind plasma into Earth's plasma sheet. This solar wind entry mechanism could also be important at Mercury. Citation: Boardsen, S. A., T. Sundberg, J. A. Slavin, B. J. Anderson, H. Korth, S. C. Solomon, and L. G. Blomberg (2010), Observations of Kelvin-Helmholtz waves along the dusk-side boundary of Mercury's magnetosphere during MESSENGER's third flyby, Geophys. Res. Lett., 37, L12101, doi: 10.1029/2010GL043606.

  • 34. Boehm, M. H.
    et al.
    CLEMMONS, J
    WAHLUND, JE
    ERIKSSON, A
    ELIASSON, L
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    KINTNER, P
    HOFNER, H
    Observations of an  upward-directed electron beam with the perpendicular temperature of the cold ionosphere1995Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 22, s. 2103-2106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Freja TESP electron spectrometer has repeatedly observed similar to 100 eV - 1 keV upward-directed, anti-field-aligned electron beams near 1700 km altitude in the auroral zone. A particularly intense event, at energies up to 2 keV, is described. The beam perpendicular temperature T perpendicular to(e)), was as low as 0.1-0.2 eV at 100-200 eV parallel energy. The 10-15 s period of upward fluxes was coincident with a low density (similar to 10 cm(-3)) period and a similar to 5 keV ion conic. Strong low frequency waves and the lack of any downward motion in the simultaneously observed ion conic suggest a strong element of wave acceleration, while electric field and ion loss cone measurements provide limited evidence of potential acceleration to a fraction of the observed energies.

  • 35.
    Collier, Andrew
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Hughes, Arthur Robert W
    University of KwaZulu-Natal, Durban, South Africa.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Sutcliffe, P. R.
    Evidence of standing waves during a Pi2 pulsation event observed on Cluster2006Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 24, nr 10, s. 2719-2733Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations of Pi2 pulsations at middle and low latitudes have been explained in terms of cavity mode resonances, whereas transients associated with field-aligned currents appear to be responsible for the high latitude Pi2 signature. Data from Cluster are used to study a Pi2 event observed at 18:09 UTC on 21 January 2003, when three of the satellites were within the plasmasphere (L=4.7,4.5 and 4.6) while the fourth was on the plasmapause or in the plasmatrough (L=6.6). Simultaneous pulsations at ground observatories and the injection of particles at geosynchronous orbit corroborate the occurrence of a substorm. Evidence of a cavity mode resonance is established by considering the phase relationship between the orthogonal electric and magnetic field components associated with radial and field-aligned standing waves. The relative phase between satellites located on either side of the geomagnetic equator indicates that the field-aligned oscillation is an odd harmonic. Finite azimuthal Poynting flux suggests that the cavity is effectively open ended and the azimuthal wave number is estimated as m similar to 13.5.

  • 36.
    Cumnock, J. A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Sharber, J. R.
    Heelis, R. A.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Germany, G. A.
    Spann, J. F.
    Coley, W. R.
    Interplanetary magnetic field control of theta aurora development2002Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, nr A7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [1] We ascertain the influence of the B-y component of the interplanetary magnetic field (IMF) on theta aurora evolution. During most cases where a transpolar arc is observed to move across the polar region, and form a theta aurora, there are brief (minutes) southward excursions of IMF B-z, however northward IMF is required prior to theta aurora formation. Observations show that theta aurora can form during strictly northward IMF with its motion consistent with a change in sign of IMF B-y. It is important to note that since transpolar arcs can persist for 20-30 min after the IMF turns southward, errors will occur in assigning instantaneous IMF conditions to snapshots'' of particular auroral patterns. We consider the entire evolution of the theta aurora and the changing IMF conditions. The influence of IMF B-y is best illustrated by examples which occur during steady northward IMF as compared to times when the IMF is northward on average. We show examples, provided by the Polar UV imager, when the IMF is steady northward. For one case, DMSP F13 and F14 provide in situ measurements of precipitating particles, ionospheric plasma flows and ion density. This unique data set enables us to analyze in detail the evolution of a theta aurora, in one case crossing the entire polar region. No sign change in B-z is needed for theta aurora formation.

  • 37.
    Cumnock, Judy A.
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Transpolar arc evolution and associated potential patterns2004Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, nr 4, s. 1213-1231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present two event studies encompassing detailed relationships between plasma convection, field-aligned current, auroral emission, and particle precipitation boundaries. We illustrate the influence of the Interplanetary Magnetic Field B, component on theta aurora development by showing two events during which the theta originates on both the dawn and dusk sides of the aurora] oval. Both theta then move across the entire polar region and become part of the opposite side of the aurora] oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the Polar UVI instrument provides measurements of auroral emissions. Utilizing satellite data as inputs, the Royal Institute of Technology model provides the high-latitude ionospheric electrostatic potential pattern calculated at different times during the evolution of the theta aurora, resulting from a variety of field-aligned current configurations associated with the changing global aurora.

  • 38.
    Cumnock, Judy A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Alexeev, I. I.
    Belenkaya, E. S.
    Bobrovnikov, S. Yu.
    Kalegaev, V. V.
    Simultaneous polar aurorae and modelled convection patterns in both hemispheres2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 8, s. 1685-1693Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an event study illustrating the relationships between plasma convection and polar auroral emissions, as well as illustrating the influence of the interplanetary magnetic field's y-component on theta aurora development in both hemispheres. Transpolar arcs (TPAs) are often observed during northward IMF with duskside (dawnside) formation of the TPA and dawnward (duskward) motion occurring when B-y changes from positive to negative in the northern (southern) hemisphere. POLAR UVI provides images in the northern hemisphere while DMSP provides ionospheric plasma flow and precipitating particle data in both hemispheres. Concurrent solar wind plasma and interplanetary magnetic field measurements are provided by the ACE satellite. Utilizing the satellite data as inputs, the Royal Institute of Technology (KTH) numerical model provides the high-latitude ionospheric electrostatic potential patterns in both hemispheres calculated at different times during the evolution of the theta aurora resulting from a variety of field-aligned current configurations associated with the changing global aurora. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Moscow State University's (MSU) paraboloid model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed.

  • 39.
    Cumnock, Judy A.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Kullen, Anita
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Karlsson, Tomas
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Sundberg, K. Å. Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Small-scale characteristics of extremely high latitude aurora2009Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, nr 9, s. 3335-3347Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine 14 cases of an interesting type of extremely high latitude aurora as identified in the precipitating particles measured by the DMSP F13 satellite. In particular we investigate structures within large-scale arcs for which the particle signatures are made up of a group of multiple distinct thin arcs. These cases are chosen without regard to IMF orientation and are part of a group of 87 events where DMSP F13 SSJ/4 measures emissions which occur near the noon-midnight meridian and are spatially separated from both the dawnside and duskside auroral ovals by wide regions with precipitating particles typical of the polar cap. For 73 of these events the high-latitude aurora consists of a continuous region of precipitating particles. We focus on the remaining 14 of these events where the particle signatures show multiple distinct thin arcs. These events occur during northward or weakly southward IMF conditions and follow a change in IMF B-y. Correlations are seen between the field-aligned currents and plasma flows associated with the arcs, implying local closure of the FACs. Strong correlations are seen only in the sunlit hemisphere. The convection associated with the multiple thin arcs is localized and has little influence on the large-scale convection. This also implies that the sunward flow along the arcs is unrelated to the overall ionospheric convection.

  • 40.
    Cumnock, Judy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Baker, J. B. H.
    Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, USA.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    On the stability of high-latitude plasma convection during northward IMF: an event study2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We investigate the stability of the ionospheric convection pattern during northward IMF by studying an event where two DMSP satellites repeatedly traversed the Southern polar region. The Cluster satellite’s ionospheric footprint is located near the DMSP satellite tracks, moving slowly in the noon-midnight direction. TIMED/GUVI data confirm the presence of auroral activity at high latitude. SuperDARN plasma velocity data partially complete the picture. From the event studied we conclude that whereas the DMSP satellites observe local variations in the convection pattern between consecutive passes, Cluster confirms the existence of persistent sunward convection in the high-latitude ionosphere on a time scale of several hours.

  • 41.
    Cumnock, Judy
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    The Mercury Environment: A Literature Survey2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A literature survey was conducted focusing primarily on the plasma environment of planet Mercury, and secondarily on its neutral atmosphere and the electrical properties of the planetary surface. An extensive literature list, with narrative comments for selected publications is presented.

  • 42.
    Cumnock, Judy
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Spann, J. F.
    Germany, G. A.
    Blomberg, Lars
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Coley, W. R.
    Clauer, C. R.
    Brittnacher, M. J.
    POLAR UVI Observations of Auroral Oval Intensifications During a Transpolar Arc Event on December 7, 19962000Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The evolution of the northern hemisphere aurora is examined during a time when the IMF makes three brief southward excursions after a change in the sign of By during an extended period of northward IMF. POLAR UVI provides images of the aurora while DMSP F13 and F14 provide in situ measurements of precipitating particles, ionospheric plasma flows and ion density.

    Three different intensifications located in the nightside auroral oval occur during northward turnings of the IMF after brief periods of southward IMF. Spatial expansion, intensity of emissions and their duration are related to the length of time the IMF is southward prior to the northward turning. Thus the longer the period of enhanced magnetospheric convection the more intense the ionospheric response. Observations of a transpolar arc indicate that when the transpolar arc reaches highest latitudes it is located on a spatially narrow region of closed field lines, which extends along the noon-midnight meridian.

    UV observations indicate a connection between the transpolar arc and the nightside auroral enhancements. Precipitating particles associated with both features are attributed to a plasma sheet boundary layer source in the magnetotail implying a magnetospheric connection between the transpolar arc and the nightside auroral oval intensification.

  • 43. Eriksson, A. I.
    et al.
    Bostrom, R.
    Gill, R.
    Ahlen, L.
    Jansson, S. E.
    Wahlund, J. E.
    Andre, M.
    Malkki, A.
    Holtet, J. A.
    Lybekk, B.
    Pedersen, A.
    Blomberg, Lars G.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Lindqvist, Per-Arne
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Olsson, G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    et al.,
    RPC-LAP: The Rosetta Langmuir probe instrument2007Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 128, nr 04-jan, s. 729-744Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The Rosetta dual Langmuir probe instrument, LAP, utilizes the multiple powers of a pair of spherical Langmuir probes for measurements of basic plasma parameters with the aim of providing detailed knowledge of the outgassing, ionization, and subsequent plasma processes around the Rosetta target comet. The fundamental plasma properties to be studied are the plasma density, the electron temperature, and the plasma flow velocity. However, study of electric fields up to 8 kHz, plasma density fluctuations, spacecraft potential, integrated UV flux, and dust impacts is also possible. LAP is fully integrated in the Rosetta Plasma Consortium (RPC), the instruments of which together provide a comprehensive characterization of the cometary plasma.

  • 44.
    Eriksson, Stefan
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Ivchenko, Nickolay V.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Karlsson, Tomas
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field2001Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 19, nr 6, s. 649-653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cross-polar potential drop Phi (pc), and the low-latitude asymmetric geomagnetic disturbance field, as indicated by the mid-latitude ASY-H magnetic index, are used to study the average magnetospheric response to the solar wind forcing for southward interplanetary magnetic field conditions. The state of the solar wind is monitored by the ACE spacecraft and the ionospheric convection is measured by the double probe electric field instrument on the Astrid-2 satellite. The solar wind-magnetosphere coupling is examined for 77 cases in February and from mid-May to mid-June 1999 by using the interplanetary magnetic field B-z component and the reconnection electric field. Our results show that the maximum correlation between Phi (pc) and the reconnection electric field is obtained approximately 25 min after the solar wind has reached a distance of II R-E from the Earth, which is the assumed average position of the magnetopause. The corresponding correlation for ASY-H shows two separate responses to the reconnection electric field, delayed by about 35 and 65 min, respectively. We suggest that the combination of the occurrence of a large magnetic storm on 18 February 1999 and the enhanced level of geomagnetic activity which peaks at Kp = 7(-) may explain the fast direct response of ASY-H to the solar wind at 35 min, as well as the lack of any clear secondary responses of Phi (pc) to the driving solar wind at time delays longer than 25 min.

  • 45.
    Eriksson, Stefan
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Weimer, D. R.
    Comparing a spherical harmonic model of the global electric field distribution with Astrid-2 observations2002Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, nr A11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [1] Electric field measurements provided by the double probe instrument on the Astrid-2 satellite are compared with the empirical Weimer electric field model for all magnetic local times, except between 11 and 13 MLT, and poleward of 55degrees corrected geomagnetic latitude (CGLat). We focus the model evaluation on its ability to predict the latitudinal locations of the convection reversal boundaries for two-cell convection patterns and to estimate the magnitude of the electric field above 55degrees CGLat. A total number of 780 polar cap passes are employed from the Northern Hemisphere between January and July 1999. The measured average electric field magnitude in the dawn-dusk meridian plane above 55degrees CGLat is generally 25% larger than the predicted field independent of the interplanetary magnetic field (IMF) direction. The model shows a better correspondence with the observed electric field for southward IMF than for northward IMF, with most cases centered around B-z = -1.5 nT and r = 0.88. However, the agreement for northward IMF is promising, and a few examples are shown to corroborate this fact. The observed and predicted convection reversal boundary locations along the satellite track for southward IMF are on the average found 2-3degrees CGLat apart in the dawn-dusk meridian plane but may be as far apart as 9degrees CGLat. An initial investigation of the relative timing of a 20-min averaging window for the IMF along the 20-25 min polar cap crossing suggests that a time-dependent transfer function may be found that applies a higher weight to the input solar wind data early in the pass and a lower weight later in the pass for an IMF window that corresponds to the first half of the crossing and the opposite weight versus time dependence for an IMF window corresponding to the last half of the crossing.

  • 46.
    Eriksson, Stefan
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Bonnell, J. W.
    Blomberg, Lars G.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Ergun, R. E.
    Marklund, Göran T.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet. KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Carlson, C. W.
    Lobe cell convection and field-aligned currents poleward of the region 1 current system2002Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, nr A8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [1] We present a case and statistical study of plasma convection in the Northern Hemisphere during summer conditions using electric field, magnetic field, and particle data taken during dawn-dusk directed orbits of the FAST satellite. To our knowledge, this set provides the most comprehensive combination of data as yet presented in support of lobe cell convection from an ionospheric perspective this far from the noon sector. In particular, we study the current systems and convection patterns for all passes in July 1997 that show evidence for six large-scale field-aligned currents (FACs) rather than the usual system of four FACs associated with the region 1/region 2 current systems. A total of 71 passes out of 232 in the study had the extra pair of FACs. The extra pair of FACs in 30 of the 71 cases lies either on the dawnside or on the duskside of the noon-midnight meridian, and their position is strongly correlated with the polarity of the IMF By (negative and positive, respectively). This is consistent with the IMF dependence of a three-cell convection pattern of coexisting merging, viscous, and lobe-type convection cells. The occurrence of the asymmetric FAC pair was also strongly linked to conditions of IMF |B-y/B-z | > 1. The extra pair of FACs in these cases was clearly associated with the lobe cell of the three-cell convection system. The remaining 41 cases had the pair of FACs straddling the noon-midnight meridian. The extra pair of FACs was often (20 cases out of 30) observed at magnetic local times more than three hours away from noon, rather than being confined to regions near noon and the typical location of the cusp. Such a current system consisting of a pair of FACs poleward of the nearest region 1 current is consistent with the IMF B-y-dependent global MHD model developed by Ogino et al. [1986] for southward IMF conditions, as well as with other magnetospheric and ionospheric convection models that include the effects of merging occuring simultaneously at both low-latitude dayside and high-latitude lobe and flank magnetopause reconnection sites. Finally, the presence of the additional FACs and three-cell convection well away from noon show that the entire dayside ionosphere is affected by IMF-dependent processes, rather than only a limited region around noon.

  • 47.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Tyskland.
    Cluster satellite observations of mHz pulsations in the dayside magnetosphere2006Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 38, nr 8, s. 1730-1737Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    On 17 August 2002 the Cluster spacecraft moved through the dayside magnetosphere. Between 16:00 and 18:30 LIT clear monochromatic oscillations are seen in both electric field and magnetometer data. The frequency is 4.2 mHz in the spacecraft frame of reference. The oscillations have a clear spatial localisation. The magnetic field oscillations are radially polarised in the plane perpendicular to the background magnetic field, indicating that the wave is in the poloidal mode. From the difference in phase between the satellites we estimate the azimuthal wave number, in, to be about 130, consistent with the magnetic field polarisation. The frequency is stable for different L-values as well as over time. From the value of in, the Doppler shift due to satellite motion is estimated to 0.5 mHz. By looking at the phase of the electric and the magnetic field close to the equator we conclude that the oscillations are in a mode with an odd number of half wavelengths between the two ionospheres.

  • 48.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Schaefer, S.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    On the excitation of ULF waves by solar wind pressure enhancements2006Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 24, nr 11, s. 3161-3172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the onset and development of an ultra low frequency (ULF) pulsation excited by a storm sudden commencement. On 30 August 2001, 14: 10 UT, the Cluster spacecraft are located in the dayside magnetosphere and observe the excitation of a ULF pulsation by a threefold enhancement in the solar wind dynamic pressure. Two different harmonics are observed by Cluster, one at 6.8 mHz and another at 27 mHz. We observe a compressional wave and the development of a toroidal and poloidal standing wave mode. The toroidal mode is observed over a narrow range of L-shells whereas the poloidal mode is observed to have a much larger radial extent. By looking at the phase difference between the electric and magnetic fields we see that for the first two wave periods both the poloidal and toroidal mode are travelling waves and then suddenly change into standing waves. We estimate the azimuthal wave number for the 6.8 mHz to be m = 10 +/- 3. For the 27 mHz wave, m seems to be several times larger and we discuss the implications of this. We conclude that the enhancement in solar wind pressure excites eigenmodes of the geomagnetic cavity/waveguide that propagate tailward and that these eigenmodes in turn couple to toroidal and poloidal mode waves. Thus our observations give firm support to the magnetospheric waveguide theory.

  • 49.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Schaefer, S.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Sunward propagating Pc5 waves observed on the post-midnight magnetospheric flank2008Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, nr 6, s. 1567-1579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The overall focus on the driver of toroidal Pc5 waves has been on processes located at or acting on the dayside magnetopause and dayside flanks of the magnetosphere. These processes can generate waves that propagate tailward in the magnetosphere. However, an increasing number of studies, both theoretical and experimental, have looked at waves propagating sunward and that are caused by processes in the magnetotail. Here we present an ultra low frequency (ULF) wave observed in the post-midnight/morning sector of the magnetosphere at L=16 R-E. The wave has a toroidal mode polarization. We estimate the azimuthal wave number to m=3, consistent with a toroidal mode type pulsation. The positive sign indicates that the wave is propagating sunward and this is confirmed by looking at the Poynting flux of the wave. The frequency of the wave is not constant with time but shows a small increase in the beginning of the event up to over 2.0 mHz. Then the frequency decreases to 1.0 mHz. This decrease coincides with a drop in the total magnetic field strength and we speculate if this is related to an observed reversal of the sign of the interplanetary magnetic field (IMF) By-component. This event occurs during relatively quiet magnetospheric conditions with a solar wind speed of approximately 400 km/s. Thus this event is highly likely to be driven by a source in the magnetotail and the change in frequency is an excellent example that the frequency of an ULF wave may be modulated by changes of the plasma parameters on the resonant field line.

  • 50.
    Eriksson, Tommy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Blomberg, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Walker, A. D. M.
    School of Pure and Applied Physics, University of KwaZulu-Natal, Durban, South Africa.
    Glassmeier, K.-H.
    Institute for Geophysics and Extraterrestrial Physics, Technical University of Braunschweig, Germany.
    Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study2005Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 23, nr 7, s. 2679-2686Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimuthal separation between the satellites. Also, the polarisation of the electric and magnetic fields is examined in a field-aligned coordinate system, which, in turn, gives the mode of the oscillations. The large-inclination orbits of Cluster allow us to examine the phase relationship between the electric and magnetic fields along the field lines. The events studied have large azimuthal wave numbers (m similar to 100), two of them have eastward propagation and all are in the poloidal mode, consistent with the large wave numbers. We also use particle data from geosynchronous satellites to look for signatures of proton injections, but none of the events show any sign of enhanced proton flux. Thus, the drift-bounce resonance instability seems unlikely to have played any part in the excitation of these pulsations. As for the drift-mirror instability we conclude that it would require an unreasonably high plasma pressure for the instability criterion to be satisfied.

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