 |
| Titel |
Solar and magnetospheric forcing of the low latitude thermospheric mass density as observed by CHAMP |
| VerfasserIn |
S. Müller, H. Lühr, S. Rentz |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 5 ; Nr. 27, no. 5 (2009-05-06), S.2087-2099 |
| Datensatznummer |
250016527
|
| Publikation (Nr.) |
 copernicus.org/angeo-27-2087-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| We have studied the dependence of the thermospheric mass density at
equatorial latitudes on the influence of various drivers. This
statistical study is based on CHAMP accelerometer measurements. Our aim is to
delineate the influences of the different contributions. For the
isolation of the effects we make use of a dedicated data selection procedure
and/or removal of disturbing effects. In a first step all readings are
normalised to an altitude of 400 km. For the investigation of the
solar influences only magnetically quiet days (Ap≤15) are considered.
The dependence on solar flux can well be described by a linear relation
within the flux range F10.7=80–240. The slope is twice as steep on the
day side as on the night side. The air density exhibits clear annual and
semi-annual variations with maxima at the equinoxes and a pronounced minimum
around June solstice. The thermosphere maintains during quiet days a day
to night mass density ratio very close to 2, which is independent of solar
flux level or season. The magnetospheric input causing
thermospheric density enhancement can well be parameterised by the am
activity index. The low latitude density responds with a delay to changes of
the index by about 3 h on the dayside and 4–5 h
on the night side. The magnetospheric forcing causes an additive
contribution to the quiet-time density, which is linearly correlated with the
am index. The slopes of density increases are the same on the day and
night sides. We present quantitative expressions for all the dependences.
Our results suggest that all the studied forcing terms can be treated as
linear combinations of the respective contribution. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|