Observation of polar cap patches and calculation of gradient drift instability growth times: A Swarm case study
The Swarm mission represents a strong new tool to survey polar cap patches and plasma structuring inside the polar cap. In the early commissioning phase, the three Swarm satellites were operated in a pearls‐on‐a‐string configuration making noon‐midnight transpolar passes. This provides an unparallel...
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Published in | Geophysical research letters Vol. 42; no. 2; pp. 201 - 206 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Washington
Blackwell Publishing Ltd
28.01.2015
John Wiley & Sons, Inc |
Subjects | |
Online Access | Get full text |
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Summary: | The Swarm mission represents a strong new tool to survey polar cap patches and plasma structuring inside the polar cap. In the early commissioning phase, the three Swarm satellites were operated in a pearls‐on‐a‐string configuration making noon‐midnight transpolar passes. This provides an unparalleled opportunity to examine the potential role of the gradient drift instability (GDI) process on polar cap patches by systematically calculating GDI growth times during their transit across the pole from day to night. Steep kilometer‐scale gradients appeared in this study as initial structures that persisted during the approximate 90 min it took a patch to cross the polar cap. The GDI growth times were calculated for a selection of the steep density gradients on both the dayside and the nightside. The values ranged from 23 s to 147 s, which is consistent with recent rocket measurements in the cusp auroral region and provides a template for future studies. Growth times of the order of 1 min found both on the dayside and on the nightside support the existing view that the GDI may play a dominant role in the generation of radio wave scintillation irregularities as the patches transit the polar cap from day to night.
Key Points
New technique to assess GDI/polar cap plasma structuring using Swarm
Internal kilometer‐scale structures persist as patches convect across the polar cap
The GDI can act quickly on several kilometer‐scale gradients within polar cap patches |
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Bibliography: | International Cooperation in Education (SiU) - No. NNA-2012/10999 istex:E26965D127CC4E3E5C47CB6694442E66B2AAE478 Research Council of Norway - No. 230935 Research Council of Norway - No. 230996 ArticleID:GRL52468 ark:/67375/WNG-3X1FXHQR-Q ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0094-8276 1944-8007 1944-8007 |
DOI: | 10.1002/2014GL062590 |