 |
| Titel |
Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data |
| VerfasserIn |
P. Janhunen  , A. Olsson, N. A. Tsyganenko, C. T. Russell, H. Laakso , L. G. Blomberg |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 23, no. 5 ; Nr. 23, no. 5 (2005-07-28), S.1797-1806 |
| Datensatznummer |
250015267
|
| Publikation (Nr.) |
 copernicus.org/angeo-23-1797-2005.pdf |
|
|
|
|
|
| Zusammenfassung |
| We study the wave-related (AC) and static (DC) parallel Poynting
vector (Poynting energy flux) as a function of altitude in auroral field lines using Polar EFI and
MFE data. The study is statistical and contains 5 years of data in the
altitude range 5000–30000 km. We verify the low altitude part of the
results by comparison with earlier Astrid-2 EMMA Poynting vector
statistics at 1000 km altitude. The EMMA data are also used to
statistically compensate the Polar results for the missing zonal
electric field component. We compare the Poynting vector with previous
statistical DMSP satellite data concerning the electron precipitation
power. We find that the AC Poynting vector (Alfvén-wave related
Poynting vector) is statistically not sufficient to power auroral electron
precipitation, although it may, for Kp>2, power 25–50% of it. The
statistical AC Poynting vector also has a stepwise transition at
R=4 RE,
so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfvén waves being in
Landau resonance with electrons, so that wave-induced electron
acceleration takes place at this altitude range, which was earlier
named the Alfvén Resonosphere (ARS). The DC Poynting vector is ~3 times larger than electron precipitation and corresponds mainly to
ionospheric Joule heating. In the morning sector (02:00–06:00 MLT) we find
that the DC Poynting vector has a nontrivial altitude profile such that
it decreases by a factor of ~2 when moving upward from 3
to 4 RE radial distance. In other nightside MLT sectors the
altitude profile is more uniform. The morning sector nontrivial
altitude profile may be due to divergence of the perpendicular
Poynting vector field at R=3–4 RE.
Keywords. Magnetospheric physics (Auroral phenomena;
Magnetosphere-ionosphere interactions) – Space plasma
physics (Wave-particle interactions) |
| |
|
| Teil von |
|
|
|
|
|
|
|
|