Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines
The plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the di...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
1998-10-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/16/1226/1998/angeo-16-1226-1998.pdf |
| _version_ | 1811284040054996992 |
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| author | P. Guio J. Lilensten W. Kofman N. Bjørnå |
| author_facet | P. Guio J. Lilensten W. Kofman N. Bjørnå |
| author_sort | P. Guio |
| collection | DOAJ |
| description | The plasma dispersion function and the
reduced velocity distribution function are calculated numerically for any
arbitrary velocity distribution function with cylindrical symmetry along the
magnetic field. The electron velocity distribution is separated into two
distributions representing the distribution of the ambient electrons and the
suprathermal electrons. The velocity distribution function of the ambient
electrons is modelled by a near-Maxwellian distribution function in presence of
a temperature gradient and a potential electric field. The velocity distribution
function of the suprathermal electrons is derived from a numerical model of the
angular energy flux spectrum obtained by solving the transport equation of
electrons. The numerical method used to calculate the plasma dispersion function
and the reduced velocity distribution is described. The numerical code is used
with simulated data to evaluate the Doppler frequency asymmetry between the up-
and downshifted plasma lines of the incoherent-scatter plasma lines at different
wave vectors. It is shown that the observed Doppler asymmetry is more dependent
on deviation from the Maxwellian through the thermal part for high-frequency
radars, while for low-frequency radars the Doppler asymmetry depends more on the
presence of a suprathermal population. It is also seen that the full evaluation
of the plasma dispersion function gives larger Doppler asymmetry than the heat
flow approximation for Langmuir waves with phase velocity about three to six
times the mean thermal velocity. For such waves the moment expansion of the
dispersion function is not fully valid and the full calculation of the
dispersion function is needed.<br><br><b>Key words.</b> Non-Maxwellian electron velocity
distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response
function |
| first_indexed | 2024-04-13T02:22:39Z |
| format | Article |
| id | doaj.art-0608853ed7cf40b382c6566193cb5aae |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-04-13T02:22:39Z |
| publishDate | 1998-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-0608853ed7cf40b382c6566193cb5aae2022-12-22T03:06:54ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761998-10-01161226124010.1007/s00585-998-1226-zElectron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma linesP. Guio0J. Lilensten1W. Kofman2N. Bjørnå3The Auroral Observatory, University of Tromsø, N-9037 Tromsø, Norway, Fax: +47 77 64 62 80; e-mail: patrick@phys.uit.noCEPHAG Domaine Universitaire, BP 46, F-38402 St-Martin-D'hères, FranceCEPHAG Domaine Universitaire, BP 46, F-38402 St-Martin-D'hères, FranceThe Auroral Observatory, University of Tromsø, N-9037 Tromsø, Norway, Fax: +47 77 64 62 80; e-mail: patrick@phys.uit.noThe plasma dispersion function and the reduced velocity distribution function are calculated numerically for any arbitrary velocity distribution function with cylindrical symmetry along the magnetic field. The electron velocity distribution is separated into two distributions representing the distribution of the ambient electrons and the suprathermal electrons. The velocity distribution function of the ambient electrons is modelled by a near-Maxwellian distribution function in presence of a temperature gradient and a potential electric field. The velocity distribution function of the suprathermal electrons is derived from a numerical model of the angular energy flux spectrum obtained by solving the transport equation of electrons. The numerical method used to calculate the plasma dispersion function and the reduced velocity distribution is described. The numerical code is used with simulated data to evaluate the Doppler frequency asymmetry between the up- and downshifted plasma lines of the incoherent-scatter plasma lines at different wave vectors. It is shown that the observed Doppler asymmetry is more dependent on deviation from the Maxwellian through the thermal part for high-frequency radars, while for low-frequency radars the Doppler asymmetry depends more on the presence of a suprathermal population. It is also seen that the full evaluation of the plasma dispersion function gives larger Doppler asymmetry than the heat flow approximation for Langmuir waves with phase velocity about three to six times the mean thermal velocity. For such waves the moment expansion of the dispersion function is not fully valid and the full calculation of the dispersion function is needed.<br><br><b>Key words.</b> Non-Maxwellian electron velocity distribution · Incoherent scatter plasma lines · EISCAT · Dielectric response functionhttps://www.ann-geophys.net/16/1226/1998/angeo-16-1226-1998.pdf |
| spellingShingle | P. Guio J. Lilensten W. Kofman N. Bjørnå Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines Annales Geophysicae |
| title | Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines |
| title_full | Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines |
| title_fullStr | Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines |
| title_full_unstemmed | Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines |
| title_short | Electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons: application to incoherent-scatter plasma lines |
| title_sort | electron velocity distribution function in a plasma with temperature gradient and in the presence of suprathermal electrons application to incoherent scatter plasma lines |
| url | https://www.ann-geophys.net/16/1226/1998/angeo-16-1226-1998.pdf |
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