Journal article
Magnetopause expansions for quasi‐radial interplanetary magnetic field: THEMIS and Geotail observations
Journal of Geophysical Research: Space Physics, Vol.115(A10), A10216
10/2010
DOI: 10.1029/2010JA015404
Abstract
We report Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geotail observations of prolonged magnetopause (MP) expansions during long‐lasting intervals of quasi‐radial interplanetary magnetic field (IMF) and nearly constant solar wind dynamic pressure. The expansions were global: The magnetopause was located more than 3 RE and ∼7 RE outside its nominal dayside and magnetotail locations, respectively. The expanded states persisted several hours, just as long as the quasi‐radial IMF conditions, indicating steady state situations. For an observed solar wind pressure of ∼1.1–1.3 nPa, the new equilibrium subsolar MP position lay at ∼14.5 RE, far beyond its expected location. The equilibrium position was affected by geomagnetic activity. The magnetopause expansions result from significant decreases in the total pressure of the high‐β magnetosheath, which we term the low‐pressure magnetosheath (LPM) mode. A prominent LPM mode was observed for upstream conditions characterized by IMF cone angles less than 20°–25°, high Mach numbers and proton plasma β ≤ 1.3. The minimum value for the total pressure observed by THEMIS in the magnetosheath adjacent to the magnetopause was 0.16 nPa and the fraction of the solar wind pressure applied to the magnetopause was therefore 0.2, extremely small. The equilibrium location of the magnetopause was modulated by a nearly continuous wavy motion over a wide range of time and space scales.
Details
- Title: Subtitle
- Magnetopause expansions for quasi‐radial interplanetary magnetic field: THEMIS and Geotail observations
- Creators
- A. V Suvorova - Moscow State UniversityJ.‐H Shue - National Central UniversityA. V Dmitriev - Moscow State UniversityD. G Sibeck - NASA Goddard Space Flight CenterJ. P McFadden - University of CaliforniaH Hasegawa - Institute of Space and Astronautical Science, JAXAK Ackerson - University of Iowa, Physics and AstronomyK Jelínek - Charles UniversityJ Šafránková - Charles UniversityZ Němeček - Charles University
- Resource Type
- Journal article
- Publication Details
- Journal of Geophysical Research: Space Physics, Vol.115(A10), A10216
- DOI
- 10.1029/2010JA015404
- ISSN
- 0148-0227
- eISSN
- 2156-2202
- Number of pages
- 16
- Language
- English
- Date published
- 10/2010
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984130701102771
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