Variations in the polar cap area during two substorm cycles
| Autor: | R. A. Greenwald, Mitchell J. Brittnacher, Jean-Paul Villain, Kjellmar Oksavik, Steve Milan, Mark Lester, George J. Sofko, Stanley W. H. Cowley |
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| Přispěvatelé: | EGU, Publication, Department of Physics and Astronomy [Leicester], University of Leicester, Department of Physics, Okayama University, University of Washington [Seattle], Johns Hopkins University (JHU), Institute of Space and Atmospheric Studies [Saskatoon] (ISAS), Department of Physics and Engineering Physics [Saskatoon], University of Saskatchewan [Saskatoon] (U of S)-University of Saskatchewan [Saskatoon] (U of S), CNRS, Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Atmospheric Science
010504 meteorology & atmospheric sciences Field line Magnetosphere [SDU.STU]Sciences of the Universe [physics]/Earth Sciences 01 natural sciences 0103 physical sciences Substorm Earth and Planetary Sciences (miscellaneous) lcsh:Science 010303 astronomy & astrophysics 0105 earth and related environmental sciences [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.OCEAN] Sciences of the Universe [physics]/Ocean Atmosphere lcsh:QC801-809 Defense Meteorological Satellite Program Geology Astronomy and Astrophysics Magnetic reconnection Geophysics lcsh:QC1-999 lcsh:Geophysics. Cosmic physics 13. Climate action Space and Planetary Science Physics::Space Physics [SDU.STU] Sciences of the Universe [physics]/Earth Sciences Magnetopause Polar lcsh:Q Ionosphere lcsh:Physics |
| Zdroj: | Annales Geophysicae Annales Geophysicae, European Geosciences Union, 2003, 21 (5), pp.1121-1140 Scopus-Elsevier Annales Geophysicae, Vol 21, Pp 1121-1140 (2003) Annales Geophysicae, Vol 21, Iss 5, Pp 1121-1140 (0000) |
| ISSN: | 1432-0576 0992-7689 |
| Popis: | This study employs observations from several sources to determine the location of the polar cap boundary, or open/closed field line boundary, at all local times, allowing the amount of open flux in the magnetosphere to be quantified. These data sources include global auroral images from the Ultraviolet Imager (UVI) instrument on board the Polar spacecraft, SuperDARN HF radar measurements of the convection flow, and low altitude particle measurements from Defense Meteorological Satellite Program (DMSP) and National Oceanographic and Atmospheric Administration (NOAA) satellites, and the Fast Auroral SnapshoT (FAST) spacecraft. Changes in the open flux content of the magnetosphere are related to the rate of magnetic reconnection occurring at the magnetopause and in the magnetotail, allowing us to estimate the day- and nightside reconnection voltages during two substorm cycles. Specifically, increases in the polar cap area are found to be consistent with open flux being created when the IMF is oriented southwards and low-latitude magnetopause reconnection is ongoing, and decreases in area correspond to open flux being destroyed at substorm breakup. The polar cap area can continue to decrease for 100 min following the onset of substorm breakup, continuing even after substorm-associated auroral features have died away. An estimate of the dayside reconnection voltage, determined from plasma drift measurements in the ionosphere, indicates that reconnection can take place at all local times along the dayside portion of the polar cap boundary, and hence presumably across the majority of the dayside magnetopause. The observation of ionospheric signatures of bursty reconnection over a wide extent of local times supports this finding.Key words. Ionosphere (plasma convection; polar ionosphere) – Magnetospheric physics (magnetospheric configuration and dynamics) |
| Databáze: | OpenAIRE |
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