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| Titel |
The dynamic cusp aurora on 30 November 1997: response to southward turning of the IMF |
| VerfasserIn |
P. E. Sandholt, C. J. Farrugia, B. Lybekk |
| 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 ; 17, no. 9 ; Nr. 17, no. 9, S.1155-1165 |
| Datensatznummer |
250013808
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1155-1999.pdf |
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| Zusammenfassung |
We document the detailed dynamics of the
dayside aurora in the \sim1200-1600 MLT sector in response to a sharp southward
turning of the interplanetary magnetic field (IMF) under negative IMF By
conditions. Features not documented in previous work are elucidated by using two
meridan scanning photometers (separated by 2 h) and an all-sky auroral imager in
Ny Ålesund, Svalbard (75.5°MLAT) in combination with magnetograms
from stations on Svalbard, covering the latitude range 71°75°MLAT.
The initial auroral response may be divided into three phases consisting of: (1)
intensification of both the red (630.0 nm) and green (557.7 nm) line emissions
in the cusp aurora near 1200 MLT and ~100 km equatorward shift of its
equatorward boundary, at ~75°MLAT, (2)
eastward and poleward expansions of the cusp aurora, reaching the 1430 MLT
meridian after 5-6 min, and (3) east-west expansion of the higher-latitude
aurora (at ~77°78°MLAT)
in the postnoon sector. The associated magnetic disturbance is characterized by
an initial positive deflection of the X-component at stations located 100-400 km
south of the aurora, corresponding to enhanced Sunward return flow associated
with the merging convection cell in the post-noon sector. The sequence of partly
overlapping poleward moving auroral forms (PMAFs) during the first 15 min,
accompanied by corresponding pulsations in the convection current, was followed
by a strong westward contraction of the cusp aurora when the ground magnetograms
indicated a temporary return to the pre-onset level. These observations are
discussed in relation to the Cowley-Lockwood model of ionospheric response to
pulsed magnetopause reconnection.
Key words. Mangetospheric physics (magnetopause · cusp
and boundary layers; solar wind-magnetosphere interactions; auroral phenomena) |
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