 |
| Titel |
On the relationship between auroral absorption, electrojet currents and plasma convection |
| VerfasserIn |
A. C. Kellerman, R. A. Makarevich, F. Honary, T. L. Hansen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-02), S.473-486 |
| Datensatznummer |
250016388
|
| Publikation (Nr.) |
 copernicus.org/angeo-27-473-2009.pdf |
|
|
|
|
|
| Zusammenfassung |
| In this study, the relationship between auroral absorption, electrojet
currents, and ionospheric plasma convection velocity is investigated using a
series of new methods where temporal correlations are calculated and analysed
for different events and MLT sectors. We employ cosmic noise absorption (CNA)
observations obtained by the Imaging Riometer for Ionospheric Studies (IRIS)
system in Kilpisjärvi, Finland, plasma convection measurements by the
European Incoherent Scatter (EISCAT) radar, and estimates of the electrojet
currents derived from the Tromsø magnetometer data. The IRIS absorption
and EISCAT plasma convection measurements are used as a proxy for the
particle precipitation component of the Hall conductance and ionospheric
electric field, respectively. It is shown that the electrojet currents are
affected by both enhanced conductance and electric field but with the
relative importance of these two factors varying with magnetic local time
(MLT). The correlation between the current and electric field (absorption) is
the highest at 12:00–15:00 MLT (00:00–03:00 MLT). It is demonstrated that the
electric-field-dominant region is asymmetric with respect to
magnetic-noon-midnight meridian extending from 09:00 to 21:00 MLT. This may be
related to the recently reported absence of mirror-symmetry between the
effects of positive and negative IMF By on the high-latitude plasma
convection pattern. The conductivity-dominant region is somewhat wider than
previously thought extending from 21:00 to 09:00 MLT with correlation slowly
declining from midnight towards the morning, which is interpreted as being in
part due to high-energy electron clouds gradually depleting and drifting from
midnight towards the morning sector. The conductivity-dominant region is
further investigated using the extensive IRIS riometer and Tromsø
magnetometer datasets with results showing a distinct seasonal dependence.
The region of high current-absorption correlation extends from 21:00 to 06:00 MLT
near both equinoxes, however, it is narrower and rotated towards the morning
(02:00–07:00 MLT) in summer, while in winter the correlation shows much greater
variability with MLT. During periods of high current-electric-field
correlation, the relationship between electric field and absorption can be
described as an inverse proportionality, which can be explained by limitation
of the electrojet current by the magnetospheric generator. Possible cases of
electron heating absorption are also investigated with absorption showing no
obvious dependence on the ion velocity or electron temperature. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|