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Probing the magnetic structure of a pair of transpolar arcs with a solar wind pressure step

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journal contribution
posted on 2020-05-11, 08:27 authored by Stephen E Milan, Jennifer Alyson Carter, Benoit Hubert
We present observations of the Northern Hemisphere auroras taken with the far ultraviolet cameras onboard the Imager for Magnetopause‐to‐Aurora Global Exploration spacecraft during a compression of the magnetosphere by a solar wind pressure step on 30 December 2001. The compression occurs during a period of northward interplanetary magnetic field which has given rise to the presence of a pair of transpolar arcs (TPAs) near the dawnside oval. The compression causes a brightening of the oval, from dayside to nightside over the course of 10 min, followed by a brightening of the midnight sector oval and TPAs from nightside to dayside, again over 10 min. We suggest that the brightening is caused by pitch angle scattering of particles trapped on closed magnetic field lines and that the sequence of the brightening tracks the solar wind pressure step as it progresses along the length of the magnetotail. Traveling at 600 km s , the step reaches up to 90 down‐tail over the period of brightening, suggesting that the magnetic field lines which map to the TPAs are closed and stretch almost this length down‐tail.

Funding

S. E. M. and J. A. C. are supported by the Science and Technology Facilities Council (STFC), UK, Grant ST/N000749/1. B. H. is supported by the Belgian National Fund for Scientific Research (FNRS). We acknowledge use of NASA/GSFC's Space Physics Data Facility's CDAWeb service (at http://cdaweb.gsfc.nasa.gov), and OMNI data. The OMNI data, including solar wind parameters and geomagnetic indices, and the IMAGE WIC and SI12 data were obtained from CDAWeb. SuperDARN data are available through the SuperDARN portal at Virginia Tech (at http://vt.superdarn.org). The SuperDARN data used in this study were processed as part of the ECLAT project, funded by the European Union Framework 7 Programme Grant 263325, and was accessed through the ESA Cluster Science Archive (at https://www.cosmos.esa.int/web/csa).

History

Citation

Journal of Geophysical Research: Space Physics Volume 125, Issue 2, February 2020, e2019JA027196

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Space Physics

Volume

125

Issue

2

Pagination

e2019JA027196

Publisher

American Geophysical Union (AGU), Wiley

eissn

2169-9402

Acceptance date

2020-02-01

Copyright date

2020

Available date

2020-02-06

Publisher version

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JA027196

Language

en

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