Journal article
AKR breakup and auroral particle acceleration at substorm onset
Journal of geophysical research. Space physics, Vol.113(A9), pp.A09213-n/a
09/2008
DOI: 10.1029/2008JA013322
Abstract
The dynamical behavior of auroral kilometric radiation (AKR) is investigated in connection with auroral particle acceleration at substorm onsets using high-time-resolution wave spectrograms provided by Polar/PWI electric field observations. AKR develops explosively at altitudes above a preexisting low-altitude AKR source at substorm onsets. This "AKR breakup'' suggests an abrupt formation of a new field-aligned acceleration region above the preexisting acceleration region. The formation of the new acceleration region is completed in a very short time (amplitude increases 10,000 times in 30 seconds), suggesting that the explosive development is confined to a localized region. AKR breakups are usually preceded (1-3 minutes) by the appearance and/or gradual enhancement of the low-altitude AKR. This means that the explosive formation of the high-altitude electric field takes place in the course of the growing low-altitude acceleration. The development of the low-altitude acceleration region is thus a necessary condition for the ignition of the high-altitude bursty acceleration. The dH/dt component from a search-coil magnetometer at ground shows that a few minutes prior to substorm onsets, the quasi-DC component begins a negative excursion that is nearly synchronized with the start of the gradual enhancement of the low-altitude AKR, indicating a precursor-like behavior for the substorm. This negative variation of dH/dt suggests an exponentially increasing ionospheric current induced by the upward field-aligned current. At substorm onsets, the decrease in the quasi-DC variation of dH/dt further accelerates, indicating a sudden reinforcement of the field-aligned current.
Details
- Title: Subtitle
- AKR breakup and auroral particle acceleration at substorm onset
- Creators
- A. Morioka - Tohoku UniversityY. Miyoshi - Nagoya UniversityF. Tsuchiya - Tohoku UniversityH. Misawa - Tohoku UniversityK. Yumoto - Kyushu UniversityG. K. Parks - University of California, BerkeleyR. R. Anderson - University of IowaJ. D. Menietti - University of IowaE. F. Donovan - University of CalgaryF. Honary - Lancaster UniversityE. Spanswick - University of Calgary
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.113(A9), pp.A09213-n/a
- Publisher
- Amer Geophysical Union
- DOI
- 10.1029/2008JA013322
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 14
- Grant note
- ST/F003005/1 / STFC; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC) 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)
- Language
- English
- Date published
- 09/2008
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984627199202771
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