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Direct observations of the full Dungey convection cycle in the polar ionosphere for southward interplanetary magnetic field conditions
journal contributionposted on 2015-07-23, 11:33 authored by Q-H Zhang, M Lockwood, JC Foster, S-R Zhang, B-C Zhang, IW Mccrea, J Moen, M Lester, JM Ruohoniemi
Tracking the formation and full evolution of polar cap ionization patches in the polar ionosphere, we directly observe the full Dungey convection cycle for southward interplanetary magnetic field (IMF) conditions. This enables us to study how the Dungey cycle influences the patches' evolution. The patches were initially segmented from the dayside storm enhanced density plume at the equatorward edge of the cusp, by the expansion and contraction of the polar cap boundary due to pulsed dayside magnetopause reconnection, as indicated by in situ Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. Convection led to the patches entering the polar cap and being transported antisunward, while being continuously monitored by the globally distributed arrays of GPS receivers and Super Dual Auroral Radar Network radars. Changes in convection over time resulted in the patches following a range of trajectories, each of which differed somewhat from the classical twin-cell convection streamlines. Pulsed nightside reconnection, occurring as part of the magnetospheric substorm cycle, modulated the exit of the patches from the polar cap, as confirmed by coordinated observations of the magnetometer at Tromsø and European Incoherent Scatter Tromsø UHF radar. After exiting the polar cap, the patches broke up into a number of plasma blobs and returned sunward in the auroral return flow of the dawn and/or dusk convection cell. The full circulation time was about 3h.
This work is supported by the National Basic Research Program of China (grant 2012CB825603), the National Natural Science Foundation of China (grants 41274149, 41104091, 41031064, and 41274148), the International Collaboration Supporting Project, Chinese Arctic and Antarctic Administration (IC201112), and the Shandong Provincial Natural Science Foundation (grant JQ201412). J. Moen is supported by the Research Council of Norway grant 230996. M. Lester is supported by NERC grant NE/K011766/ 1. J. Foster and S.-R. Zhang receive partial support from NSF cooperative agreement ATM-0733510. We thank the MIT Haystack Observatory for generating GPS TEC data and making them available through the Madrigal Database (http://madrigal.haystack. mit.edu/), and the NASA CDAWeb site for the solar wind and IMF data from the ACE spacecraft. J. M. Ruohoniemi is supported by NSF grant AGS-1243070. SuperDARN is a collection of radars funded by national scientific funding agencies of Australia, Canada, China, France, Japan, South Africa, United Kingdom, and United States of America.
CitationJournal of Geophysical Research: Space Physics June 2015. 120(6), 4519–4530
Author affiliation/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy
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