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  • 1.
    Dimmock, Andrew P.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen. Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Alho, M.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Kallio, Esa
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Pope, Simon Alexander
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield, S Yorkshire, England.
    Zhang, Tielong
    Harbin Inst Technol, Shenzhen, Peoples R China; Austrian Acad Sci, Space Res Inst, Graz, Austria.
    Kilpua, E.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    Pulkkinen, Tuija I.
    Aalto Univ, Sch Elect Engn, Dept Elect & Nanoengn, Espoo, Finland.
    Futaana, Y.
    Swedish Inst Space Phys, Kiruna, Sweden.
    Coates, Andrew J.
    UCL, Mullard Space Sci Lab, London, England.
    The Response of the Venusian Plasma Environment to the Passage of an ICME: Hybrid Simulation Results and Venus Express Observations2018Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, nr 5, s. 3580-3601Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Owing to the heritage of previous missions such as the Pioneer Venus Orbiter and Venus Express, the typical global plasma environment of Venus is relatively well understood. On the other hand, this is not true for more extreme driving conditions such as during passages of interplanetary coronal mass ejections (ICMEs). One of the outstanding questions is how do ICMEs, either the ejecta or sheath portions, impact (1) the Venusian magnetic topology and (2) escape rates of planetary ions? One of the main issues encountered when addressing these problems is the difficulty of inferring global dynamics from single spacecraft obits; this is where the benefits of simulations become apparent. In the present study, we present a detailed case study of an ICME interaction with Venus on 5 November 2011 in which the magnetic barrier reached over 250 nT. We use both Venus Express observations and hybrid simulation runs to study the impact on the field draping pattern and the escape rates of planetary O+ ions. The simulation showed that the magnetic field line draping pattern around Venus during the ICME is similar to that during typical solar wind conditions and that O+ ion escape rates are increased by approximately 30% due to the ICME. Moreover, the atypically large magnetic barrier appears to manifest from a number of factors such as the flux pileup, dayside compression, and the driving time from the ICME ejecta.

  • 2.
    Lakka, A.
    et al.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland.
    Pulkkinen, T. I.
    Aalto Univ, Dept Elect & Nanoengn, Espoo, Finland.
    Dimmock, Andrew P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Myllys, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland; CNRS, Lab Phys & Chim Environm & Espace, Orleans, France.
    Honkonen, I.
    Finnish Meteorol Inst, Helsinki, Finland.
    Palmroth, M.
    Univ Helsinki, Dept Phys, Helsinki, Finland.
    The Cross-Polar Cap Saturation in GUMICS-4 During High Solar Wind Driving2018Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, nr 5, s. 3320-3332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is well known that the Earth's ionospheric cross‐polar cap potential (CPCP) saturates as a response to the solar wind (SW) driver especially when the level of driving is high and the interplanetary magnetic field is oriented southward. Moreover, previous studies have shown that the upstream Alfvén Mach number may be an important factor in the saturation effect. While the CPCP is often viewed as a measure of the SW‐magnetosphere‐ionosphere coupling, the processes associated with the nonlinearity of the coupling remain an open issue. We use fourth edition of the Grand Unified Magnetosphere‐Ionosphere Coupling Simulation (GUMICS‐4) and artificial SW data to mimic weak and strong driving in order to study the CPCP response to a wide range of interplanetary magnetic field magnitudes (3.5–30 nT) and upstream Alfvén Mach number values (1.2–22). The results provide the first overview of the CPCP saturation in GUMICS‐4 and show that the onset of saturation is strongly dependent on the upstream Alfvén Mach number and the physical processes responsible for the saturation effect might take place both in the Earth's magnetosheath and in the upstream SW.

  • 3. Lockwood, M
    et al.
    Fazakerley, A
    Opgenoorth, Herman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Moen, J
    van Eyken, A P
    Dunlop, M
    Bosqued, J M
    Lu, G
    Cully, C
    Eglitis, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    McCrea, I W
    Hapgood, M A
    Wild, M N
    Stamper, R
    Denig, W
    Taylor, M
    Wild, J A
    Provan, G
    Amm, O
    Kauristie, K
    Pulkkinen, T
    Stromme, A
    Prikryl, P
    Pitout, F
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Balogh, A
    Reme, H
    Behlke, R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Hansen, T
    Greenwald, R
    Frey, H
    Morley, S K
    Alcayde, D
    Blelly, P L
    Donovan, E
    Engebretson, M
    Lester, M
    Watermann, J
    Marcucci, M F
    Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures2001Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 19, nr 10-12, s. 1613-1640Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    We study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ([X(GSM), Y(GSM), Z(GSM)] approximate to [2, 7, 9] R(E)). The events take place during an interval of northward IMF, as seen in the data from the ACE satellite and lagged by a propagation delay of 75 min that is well-defined by two separate studies: (1) the magnetospheric variations prior to the northward turning (Lockwood et al., 2001, this issue) and (2) the field clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth et al., 2001, this issue). With an additional lag of 16.5 min, the transient LLBL events cor-relate well with swings of the IMF clock angle (in GSM) to near 90degrees. Most of this additional lag is explained by ground-based observations, which reveal signatures of transient reconnection in the pre-noon sector that then take 10-15 min to propagate eastward to 15 MLT, where they are observed by Cluster. The eastward phase speed of these signatures agrees very well with the motion deduced by the cross-correlation of the signatures seen on the four Cluster spacecraft. The evidence that these events are reconnection pulses includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower latitudes; transient and travelling enhancements of the flow into the polar cap, imaged by the AMIE technique; and poleward-moving events moving into the polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15 satellite reveals that the open field lines near noon have been opened for some time: the more recently opened field lines were found closer to dusk where the flow transient and the poleward-moving event intersected the satellite pass. The events at Cluster have ion and electron characteristics predicted and observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with allowance for magnetospheric ion reflection at Alfvenic disturbances in the magnetopause reconnection layer. Like FTEs, the events are about 1 R(E) in their direction of motion and show a rise in the magnetic field strength, but unlike FTEs, in general, they show no pressure excess in their core and hence, no characteristic bipolar signature in the boundary-normal component. However, most of the events were observed when the magnetic field was southward, i.e. on the edge of the interior magnetic cusp, or when the field was parallel to the magnetic equatorial plane. Only when the satellite begins to emerge from the exterior boundary (when the field was northward), do the events start to show a pressure excess in their core and the consequent bipolar signature. We identify the events as the first observations of FTEs at middle altitudes.

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