dc.contributor.author | Guio, Patrick | |
dc.contributor.author | Lilensten, J. | |
dc.date.accessioned | 2007-01-24T09:57:00Z | |
dc.date.available | 2007-01-24T09:57:00Z | |
dc.date.issued | 1999 | |
dc.description.abstract | In an incoherent scattering radar experiment,
the spectral measurement of the so-called up- and
downshifted electron plasma lines provides information
about their intensity and their Doppler frequency. These
two spectral lines correspond, in the backscatter geom-
etry, to two Langmuir waves travelling towards and
away from the radar. In the daytime ionosphere, the
presence of a small percentage of photoelectrons
produced by the solar EUV of the total electron
population can excite or damp these Langmuir waves
above the thermal equilibrium, resulting in an enhance-
ment of the intensity of the lines above the thermal level.
The presence of photo-electrons also modifies the
dielectric response function of the plasma from the
Maxwellian and thus influences the Doppler frequency
of the plasma lines. In this paper, we present a high
time-resolution plasma-line data set collected on the
EISCAT VHF radar. The analysed data are compared
with a model that includes the effect of a suprathermal
electron population calculated by a transport code. By
comparing the intensity of the analysed plasma lines
data to our model, we show that two sharp peaks in the
electron suprathermal distribution in the energy range
20±30 eV causes an increased Landau damping around
24.25 eV and 26.25 eV. We have identified these two
sharp peaks as the effect of the photoionisation of N2
and O by the intense flux of monochromatic HeII
radiation of wavelength 30.378 nm (40.812 eV) created
in the chromospheric network and coronal holes.
Furthermore, we see that what would have been
interpreted as a mean Doppler drift velocity for a
Maxwellian plasma is actually a shift of the Doppler
frequency of the plasma lines due to suprathermal
electrons. | en |
dc.format.extent | 1798295 bytes | |
dc.format.mimetype | application/pdf | |
dc.identifier.issn | 1432-0576 (elektronisk) | |
dc.identifier.uri | https://hdl.handle.net/10037/557 | |
dc.identifier.urn | URN:NBN:no-uit_munin_384 | |
dc.language.iso | eng | en |
dc.publisher | European Geophysical Society | en |
dc.relation.ispartofseries | Annales Geophysicae 17(1999), pp 903-912 | en |
dc.rights.accessRights | openAccess | |
dc.subject | ionosphere | en |
dc.subject | electric fields and currents | en |
dc.subject | solar radiation and cosmic ray effects | en |
dc.subject | VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437 | en |
dc.title | Effect of suprathermal electrons on the intensity
and Doppler frequency of electron plasma lines. | en |
dc.type | Journal article | en |
dc.type | Tidsskriftartikkel | no |