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| Titel |
Self-consistent electrostatic simulations of reforming double layers in the downward current region of the aurora |
| VerfasserIn |
H. Gunell, L. Andersson, J. De Keyser, I. Mann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 33, no. 10 ; Nr. 33, no. 10 (2015-10-30), S.1331-1342 |
| Datensatznummer |
250121263
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| Publikation (Nr.) |
 copernicus.org/angeo-33-1331-2015.pdf |
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| Zusammenfassung |
| The plasma on a magnetic field line in the downward current region
of the aurora is simulated using a Vlasov model.
It is found that an electric field parallel to the magnetic
fields is supported by a double layer moving toward higher
altitude.
The double layer accelerates electrons upward, and these electrons
give rise to plasma waves and electron phase-space holes through
beam–plasma interaction.
The double layer is disrupted when reaching altitudes
of 1–2 Earth radii where the Langmuir condition no longer
can be satisfied due to the diminishing density of electrons
coming up from the ionosphere.
During the disruption the potential drop is in part carried
by the electron holes.
The disruption creates favourable conditions for double layer
formation near the ionosphere and double layers form anew
in that region. The process repeats itself with a period of
approximately 1 min.
This period is determined by how far the double layer can reach
before being disrupted: a higher disruption altitude corresponds
to a longer repetition period. The disruption altitude is, in turn,
found to increase with ionospheric density and to decrease
with total voltage.
The current displays oscillations around a mean value. The period
of the oscillations is the same as the recurrence period of the
double layer formations. The oscillation amplitude increases
with increasing voltage, whereas the mean value of the current is
independent of voltage in the 100 to 800 V range covered by our
simulations. Instead, the mean value of the current is determined
by the electron density at the ionospheric boundary. |
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