Journal article
Two-step evolution of auroral acceleration at substorm onset
Journal of geophysical research. Space physics, Vol.115(A11), p.n/a
11/2010
DOI: 10.1029/2010JA015361
Abstract
The sudden formation of parallel electric fields in the magnetosphere-ionosphere (M-I) coupling system is essential to complete substorm onset. From this standpoint, we focus substorm ignition on field-aligned acceleration by studying the dynamical behavior of auroral kilometric radiation. Field-aligned auroral acceleration shows a distinct two-step evolution at substorm onset: the activation of low-altitude acceleration (h similar to 4000-5000 km) which corresponds to auroral initial brightening and the subsequent abrupt breakout of high-altitude acceleration (h similar to 6000-12,000 km) which corresponds to auroral breakup. Cases when only low-altitude acceleration (first-step evolution) is activated are pseudosubstorms. This indicates that the second evolution of field-aligned acceleration divides full substorm from pseudosubstorm. The statistical relationship between the plasma flow burst in the plasma sheet and its response to the M-I coupling region shows that about 65% of flow bursts cause pseudobreakup/initial brightening (low-altitude acceleration) and one third of them develops into full substorm (low-altitude and high-altitude accelerations), while the magnitude of flow velocity does not necessarily distinguish between pseudobreakup and full substorm. This suggests that some plasma flow bursts originate field-aligned current which first enhance low-altitude acceleration, and the increasing field-aligned current induces second acceleration above the preexisting low-altitude acceleration as a consequence of current/current-driven instabilities. In this sense, the substorm is finally ignited in the auroral M-I coupling region.
Details
- Title: Subtitle
- Two-step evolution of auroral acceleration at substorm onset
- Creators
- A. Morioka - Tohoku UniversityY. Miyoshi - Nagoya UniversityY. Miyashita - Nagoya UniversityY. Kasaba - Tohoku UniversityH. Misawa - Tohoku UniversityF. Tsuchiya - Tohoku UniversityR. Kataoka - Tokyo Institute of TechnologyA. Kadokura - National Institute of Polar ResearchT. Mukai - Japan Aerospace Exploration AgencyK. Yumoto - Kyushu UniversityD. J. Menietti - University of IowaG. Parks - University of California, BerkeleyK. Liou - Johns Hopkins University Applied Physics LaboratoryF. Honary - Lancaster UniversityE. Donovan - University of CalgaryJohn D Menietti - Physics and Astronomy
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.115(A11), p.n/a
- Publisher
- Amer Geophysical Union
- DOI
- 10.1029/2010JA015361
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 21
- Grant note
- ST/F003005/1 / STFC; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) ST/F003005/1 / Science and Technology Facilities Council; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) 22340145 / Grants-in-Aid for Scientific Research; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Japan Society for the Promotion of Science; Grants-in-Aid for Scientific Research (KAKENHI) STFC; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) Canadian Space Agency
- Language
- English
- Date published
- 11/2010
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984627304702771
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