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| Titel |
A study of fine structure of diffuse aurora with ALIS-FAST measurements |
| VerfasserIn |
T. Sergienko, I. Sandahl, B. Gustavsson, L. Andersson, U. Brandstrom, Å. Steen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 26, no. 11 ; Nr. 26, no. 11 (2008-10-21), S.3185-3195 |
| Datensatznummer |
250016264
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| Publikation (Nr.) |
 copernicus.org/angeo-26-3185-2008.pdf |
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| Zusammenfassung |
| We present results of an investigation of the fine structure of the night
sector diffuse auroral zone, observed simultaneously with optical instruments
(ALIS) from the ground and the FAST electron spectrometer from space 16
February 1997. Both the optical and particle data show that the diffuse
auroral zone consisted of two regions. The equatorward part of the diffuse
aurora was occupied by a pattern of regular, parallel auroral stripes. The
auroral stripes were significantly brighter than the background luminosity,
had widths of approximately 5 km and moved southward with a velocity of about
100 m/s. The second region, located between the region with auroral stripes
and the discrete auroral arcs to the north, was filled with weak and almost
homogeneous luminosity, against which short-lived auroral rays and small
patches appeared chaotically. From analysis of the electron differential
fluxes corresponding to the different regions of the diffuse aurora and based
on existing theories of the scattering process we conclude the following:
Strong pitch angle diffusion by electron cyclotron harmonic waves (ECH) of
plasma sheet electrons in the energy range from a few hundred eV to 3–4 keV
was responsible for the electron precipitation, that produced the background
luminosity within the whole diffuse zone. The fine structure, represented by
the auroral stripes, was created by precipitation of electrons above 3–4 keV
as a result of pitch angle diffusion into the loss cone by whistler mode
waves. A so called "internal gravity wave" (Safargaleev and Maltsev, 1986) may explain the
formation of the regular spatial pattern formed by the auroral stripes in the
equatorward part of the diffuse auroral zone. |
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