 |
| Titel |
CUTLASS/IMAGE observations of high-latitude convection features during substorms |
| VerfasserIn |
T. K. Yeoman, H. Lühr |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 15, no. 6 ; Nr. 15, no. 6, S.692-702 |
| Datensatznummer |
250012829
|
| Publikation (Nr.) |
 copernicus.org/angeo-15-692-1997.pdf |
|
|
|
|
|
| Zusammenfassung |
| The CUTLASS Finland HF radar has been
operational since February 1995. The radar frequently observes backscatter
during the midnight sector from a latitude range 70–75° geographic, latitudes
often associated with the polar cap. These intervals of backscatter occur during
intervals of substorm activity, predominantly in periods of relatively quiet
magnetospheric activity, with Kp during the interval under
study being 2- and ΣKp for the day being only 8-.
During August 1995 the radar ran in a high time resolution mode, allowing
measurements of line-of-sight convection velocities along a single beam with a
temporal resolution of 14 s, and measurement of a full spatial scan of
line-of-sight convection velocities every four minutes. Data from such scans
reveal the radar to be measuring return flow convection during the interval of
substorm activity. For three intervals during the period under study, a
reduction in the spatial extent of radar backscatter occurred. This is a
consequence of D region HF absorption and its limited extent in the
present study is probably a consequence of the high latitude of the substorm
activity, with the electrojet centre lying between 67° and 71° geomagnetic
latitude. The high time resolution beam of the radar additionally demonstrates
that the convection is highly time dependent. Pulses of equatorward flow
exceeding ~600 m s–1 are observed with a duration of ~5 min and
a repetition period of ~8 min. Their spatial extent in the CUTLASS field of
view was 400–500 km in longitude, and 300–400 km in latitude. Each pulse of
enhanced equatorward flow was preceded by an interval of suppressed flow and
enhanced ionospheric Hall conductance. The transient features are interpreted as
being due to ionospheric current vortices associated with field aligned current
pairs. The relationship between these observations and substorm phenomena in the
magnetotail is discussed. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|