 |
| Titel |
Simultaneous optical, CUTLASS HF radar, and FAST spacecraft observations: signatures of boundary layer processes in the cusp |
| VerfasserIn |
K. Oksavik, F. Søraas, J. Moen, R. Pfaff, J. A. Davies, Mark Lester |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 22, no. 2 ; Nr. 22, no. 2 (2004-01-01), S.511-525 |
| Datensatznummer |
250014779
|
| Publikation (Nr.) |
 copernicus.org/angeo-22-511-2004.pdf |
|
|
|
|
|
| Zusammenfassung |
In this paper we discuss counterstreaming electrons, electric
field turbulence, HF radar spectral width enhancements, and
field-aligned currents in the southward IMF cusp region. Electric
field and particle observations from the FAST spacecraft are
compared with CUTLASS Finland spectral width enhancements and
ground-based optical data from Svalbard during a meridional
crossing of the cusp. The observed 630nm rayed arc (Type-1 cusp
aurora) is associated with stepped cusp ion signatures.
Simultaneous counterstreaming low-energy electrons on open
magnetic field lines lead us to propose that such electrons may be
an important source for rayed red arcs through pitch angle
scattering in collisions with the upper atmosphere. The observed
particle precipitation and electric field turbulence are found to
be nearly collocated with the equatorward edge of the optical
cusp, in a region where CUTLASS Finland also observed enhanced
spectral width. The electric field turbulence is observed to
extend far poleward of the optical cusp. The broad-band electric
field turbulence corresponds to spatial scale lengths down to 5m.
Therefore, we suggest that electric field irregularities are
directly responsible for the formation of HF radar backscatter
targets and may also explain the observed wide spectra. FAST also
encountered two narrow highly structured field-aligned current
pairs flowing near the edges of cusp ion steps.
Key words. Ionosphere (electric fields and currents). Magnetosphere
physics (magnetopause, cusp, and boundary layers;
auroral phenomena) |
| |
|
| Teil von |
|
|
|
|
|
|
|
|