|
Titel |
SABRE observations of Pi2 pulsations: case studies |
VerfasserIn |
E. G. Bradshaw, Mark Lester |
Medientyp |
Artikel
|
Sprache |
Englisch
|
ISSN |
0992-7689
|
Digitales Dokument |
URL |
Erschienen |
In: Annales Geophysicae ; 15, no. 1 ; Nr. 15, no. 1, S.40-53 |
Datensatznummer |
250012572
|
Publikation (Nr.) |
copernicus.org/angeo-15-40-1997.pdf |
|
|
|
Zusammenfassung |
The characteristics of substorm-associated
Pi2 pulsations observed by the SABRE coherent radar system during three separate
case studies are presented. The SABRE field of view is well positioned to
observe the differences between the auroral zone pulsation signature and that
observed at mid-latitudes. During the first case study the SABRE field of view
is initially in the eastward electrojet, equatorward and to the west of the
substorm-enhanced electrojet current. As the interval progresses, the western,
upward field-aligned current of the substorm current wedge moves westward across
the longitudes of the radar field of view. The westward motion of the wedge is
apparent in the spatial and temporal signatures of the associated Pi2 pulsation
spectra and polarisation sense. During the second case study, the complex
field-aligned and ionospheric currents associated with the pulsation generation
region move equatorward into the SABRE field of view and then poleward out of it
again after the third pulsation in the series. The spectral content of the four
pulsations during the interval indicate different auroral zone and mid-latitude
signatures. The final case study is from a period of low magnetic activity when
SABRE observes a Pi2 pulsation signature from regions equatorward of the
enhanced substorm currents. There is an apparent mode change between the
signature observed by SABRE in the ionosphere and that on the ground by
magnetometers at latitudes slightly equatorward of the radar field of view. The
observations are discussed in terms of published theories of the generation
mechanisms for this type of pulsation. Different signatures are observed by
SABRE depending on the level of magnetic activity and the position of the SABRE
field of view relative to the pulsation generation region. A twin source model
for Pi2 pulsation generation provides the clearest explanation of the signatures
observed. |
|
|
Teil von |
|
|
|
|
|
|