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A Simulation Approach to High-Frequency Plasma Waves
KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Electrostatic waves in the form of Broadband Electrostatic Noise (BEN) have been observed in the Earth's auroral region associated with high geomagnetic activity. This broad frequency spectrum consists of three electrostatic modes, namely electron plasma, electron acoustic and beam-driven modes. These modes are excited in a plasma containing three electron components: hot, cool and beam electrons.

A 1D Particle-in-Cell (PIC) simulation was developed to investigate the characteristics of the electrostatic waves found in such a plasma. Dispersion, phase space and spatial electric field diagrams were constructed from the output of the PIC simulation which were used to describe the wave dispersion and spatial field structures found in a plasma. The PIC code used a three electron component plasma with Maxwellian distributions to describe the electron velocity distributions. Beam-driven waves were found to dominate the frequency spectrum while electron plasma and electron acoustic waves are damped for a high beam velocity. Furthermore, for a high beam velocity, solitary waves are generated by electron holes (positive potentials), giving rise to a bipolar spatial electric fi eld structure moving in the direction of the beam. Increasing the beam temperature allows the beam electrons to mix more freely with the hot and cool electrons, which leads to electron plasma and electron acoustic waves being enhanced while beam-driven waves are damped. Decreasing the beam density and velocity leads to damping of beam-driven waves, while electron plasma and electron acoustic waves are enhanced.

Measurements in Saturn's magnetosphere have found the co-existence of two electron (hot and cool) components. The electron velocities are best described by a kappa-distribution (instead of a Maxwellian) which has a high-energy tail. Using an adapted PIC simulation the study of electron plasma and electron acoustic waves was extended by using a kappa-distribution to describe the electron velocities with low indices. Electron acoustic waves are damped over most wave number ranges. Electron plasma waves are weakly damped at low wave numbers and damped for all other wave numbers.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , x, 33 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:64
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-106822OAI: oai:DiVA.org:kth-106822DiVA: diva2:574232
Presentation
2012-12-13, Seminarierum, Teknikringen 31, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20121205

Available from: 2012-12-05 Created: 2012-12-05 Last updated: 2012-12-05Bibliographically approved
List of papers
1. Particle-in-cell simulations of beam-driven electrostatic waves in a plasma
Open this publication in new window or tab >>Particle-in-cell simulations of beam-driven electrostatic waves in a plasma
2012 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 19, no 4, 042101- p.Article in journal (Refereed) Published
Abstract [en]

Using a particle-in-cell simulation, the characteristics of electrostatic waves are investigated in a three-electron component plasma including an electron beam. A Maxwellian distribution is used to describe the electron velocities. Three electrostatic modes are excited, namely electron plasma, electron acoustic, and beam-driven waves. These modes have a broad frequency spectrum and have been associated with intense broadband electrostatic noise observed in the Earth's auroral zone. The simulation results compare well with analytical dispersion and growth rate relations. This agreement serves to validate the simulation technique.

Keyword
Broadband electrostatic noise, Electron plasmas, Electron velocity, Electrostatic waves, Frequency spectra, Maxwellian distribution, Particle-in-cell simulations, Simulation technique, Electron beams, Electrons, Particle beam dynamics, Plasmas, Electrostatics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-98435 (URN)10.1063/1.3695402 (DOI)000309592100001 ()2-s2.0-84860432785 (Scopus ID)
Note

QC 20120627

Available from: 2012-06-27 Created: 2012-06-26 Last updated: 2017-12-07Bibliographically approved
2. A simulation approach of high-frequency electrostatic waves found in Saturn's magnetosphere
Open this publication in new window or tab >>A simulation approach of high-frequency electrostatic waves found in Saturn's magnetosphere
2012 (English)In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 19, no 4, 042102- p.Article in journal (Refereed) Published
Abstract [en]

Using a particle-in-cell simulation, the characteristics of electron plasma and electron acoustic waves are investigated in plasmas containing an ion and two electron components. The electron velocities are modeled by a combination of two kappa distributions. The model applies to the extended plasma sheet region in Saturn's magnetosphere where the cool and hot electron velocities are found to have low indices, kappa(c) similar or equal to 2 and kappa(h) similar or equal to 4. For such low values of kappa(c) and kappa(h), the electron plasma and electron acoustic waves are coupled. The model predicts weakly damped electron plasma waves while electron acoustic waves should also be observable, although less prominent.

Keyword
Electron acoustic waves, Electron component, Electron plasma waves, Electron plasmas, Electron velocity, Electrostatic waves, High frequency HF, Low index, Particle-in-cell simulations, Plasma sheet region, Simulation approach, Acoustic waves, Acoustics, Ion beams, Plasma waves, Plasmas, Electrons
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-98470 (URN)10.1063/1.3695404 (DOI)000309592100002 ()2-s2.0-84860487765 (Scopus ID)
Note

QC 20120626

Available from: 2012-06-26 Created: 2012-06-26 Last updated: 2017-12-07Bibliographically approved
3. Mid-latitude ionospheric signature of a weak solar flare in winter
Open this publication in new window or tab >>Mid-latitude ionospheric signature of a weak solar flare in winter
2013 (English)In: South African Journal of Science, ISSN 0038-2353, E-ISSN 1996-7489, Vol. 109, no 1-2, 83-87 p.Article in journal (Refereed) Published
Abstract [en]

Measurements of the amplitude and phase of very low frequency transmitter signals were used to evaluate the effects on the ionosphere of a moderate intensity solar flare that occurred on 13 December 2007. These measurements were compared to modelled results from the Long Wave Propagation Capability code. The ionospheric effects were found to be delayed by ∼1 min with respect to the 0.1-0.8 nm solar X-ray flux.

Keyword
VLF, solar flare, D-region, ionosphere, X-ray
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-106984 (URN)10.1590/sajs.2013/802 (DOI)000320212900016 ()2-s2.0-84873638665 (Scopus ID)
Note

QC 20130320. Updated from accepted to published.

Available from: 2012-12-05 Created: 2012-12-05 Last updated: 2017-12-07Bibliographically approved

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