Journal article
The dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of EMIC waves observed by the Van Allen Probes
Journal of geophysical research. Space physics, Vol.121(5), pp.4362-4377
05/2016
DOI: 10.1002/2016JA022523
Abstract
A statistical examination on the spatial distributions of electromagnetic ion cyclotron (EMIC) waves observed by the Van Allen Probes against varying levels of geomagnetic activity (i.e., AE and SYM‐H) and dynamic pressure has been performed. Measurements taken by the Electric and Magnetic Field Instrument Suite and Integrated Science for the first full magnetic local time (MLT) precession of the Van Allen Probes (September 2012–June 2014) are used to identify over 700 EMIC wave events. Spatial distributions of EMIC waves are found to vary depending on the level of geomagnetic activity and solar wind dynamic pressure. EMIC wave events were observed under quiet (AE ≤ 100 nT, 325 wave events), moderate (100 nT < AE ≤ 300 nT, 218 wave events), and disturbed (AE > 300 nT, 228 wave events) geomagnetic conditions and are primarily observed in the prenoon sector (~800 < MLT ≤ ~1100) at L ≈ 5.5 during quiet activity times. As AE increases to disturbed levels, the peak occurrence rates shift to the afternoon sector (1200 < MLT ≤ 1800) between L = 4 and L = 6. A majority of EMIC wave events (~56%) were observed during nonstorm times (defined by SYM‐H). Consistent with the quiet AE levels, nonstorm EMIC waves are observed in the prenoon sector. EMIC waves observed through the duration of a geomagnetic storm are primarily located in the afternoon sector. High solar wind pressure (Pdyn > 3 nPa) correlates to mostly afternoon EMIC wave observations.
Key Points
EMIC waves are examined with varying levels of dynamic pressure and geomagnetic indices
During quiet (AE ≤ 100 nT) activity levels, the prenoon sector features high occurrence rates
For active periods (storms or substorms), the afternoon sector displays highest occurrence rates
Details
- Title: Subtitle
- The dependence on geomagnetic conditions and solar wind dynamic pressure of the spatial distributions of EMIC waves observed by the Van Allen Probes
- Creators
- A. A Saikin - University of New HampshireJ.‐C Zhang - University of New HampshireC. W Smith - University of New HampshireH. E Spence - University of New HampshireR. B Torbert - University of New HampshireC. A Kletzing - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.121(5), pp.4362-4377
- DOI
- 10.1002/2016JA022523
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 16
- Grant note
- NASA (NNX11AO82G; NNX15AF66G)
- Language
- English
- Date published
- 05/2016
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984200040702771
Metrics
6 Record Views