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| Titel |
Association of Pi2 pulsations and pulsed reconnection: ground and Cluster observations in the tail lobe at 16 RE |
| VerfasserIn |
A. Keiling, M. Fujimoto, H. Hasegawa, F. Honary, V. Sergeev, V. S. Semenov, H. U. Frey, O. Amm, H. Rème, I. Dandouras, E. Lucek |
| 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 ; 24, no. 12 ; Nr. 24, no. 12 (2006-12-21), S.3433-3449 |
| Datensatznummer |
250015716
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| Publikation (Nr.) |
 copernicus.org/angeo-24-3433-2006.pdf |
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| Zusammenfassung |
| Simultaneous measurements from the Cluster spacecraft and
several ground stations (SAMNET, IMAGE, Kakioka, Hermanus) provide evidence
for an association of Pi2 pulsations and pulsed reconnection in the
magnetotail. On 8 September 2002, substorm-related Pi2 pulsations were
recorded with the same waveform (same frequency) in the tail lobe at 16 RE
and time-delayed on the ground (both nightside and dayside) spanning L values
from 1.23 to 6.11. The tail lobe Pi2 pulsations were a series of nightside
flux transfer event (NFTE) pulses propagating at a speed of 600–800 km/s
towards Earth, which for the first time relates these two magnetospheric
phenomena. NFTEs have previously been considered as the remote signature of
tail reconnection. The first ground onset of the Pi2 pulsations occurred at
high- and midlatitude ground stations with a time delay of ~30 s with respect
to the tail lobe Pi2, followed by lower latitude ground stations. The
largest pulsations were observed at high latitude (ten times larger than at
low latitude) near the polar cap boundary. The polarization pattern of the
ground Pi2s in the H-D plane was consistent with a periodically driven
field-aligned current (FAC) system. In addition, fast mode waves must have
also played a role in the inner magnetosphere because of propagation effects
among ground stations and because of the simultaneous occurrence of dayside
low-latitude Pi2. Auroral brightening occurred in the region of upflowing
FAC, and the auroral electrojet expanded poleward together with the auroral
bulge both of which are typical substorm signatures. Hence, we conclude that
the substorm-related Pi2 pulsations in space at 16 RE and on the ground were
remotely driven by pulsed reconnection in the magnetotail, that is,
reconnection not only provided the energy but its temporal variations also
determined the characteristic Pi2 frequency. Scenarios are discussed that
address the connection of pulsed reconnection and the driven current system
in the ionosphere. These results show that reconnection can be coupled to
the ionosphere through what is phenomenologically known as Pi2 pulsations.
As a corollary, it is shown that the time history of events fits within the
modified NENL model of substorms. |
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