Superposed Epoch Analysis of Plasmaspheric Electron Density
Abstract
We perform statistical superposed epoch analysis of multiple years of electron density data and obtain the first global empirical characterization of plasmaspheric density that explicitly includes plumes produced during stormtime erosion. It is well established that the plasmaspheric density distribution evolves in phases (analogous to storm phases), in which the formation and subsequent development of plumes follow epochs divided by changes in the relative strength of convection. Plasmaspheric (plume) phases are an obvious and consistent feature in single-event case studies. Statistical analysis requires a superposed epoch analysis to reveal phases, but this approach requires a very large amount of data to provide anything but a very crude empirical characterization of global density structure versus epoch and geomagnetic activity. Density data are derived from plasma wave measurements from four missions: (1) Imager for Magnetopause-to-Aurora Global Exploration (IMAGE), years 2001 through 2005; (2) Polar, years 1996 and 1997; (3) International Sun-Earth Explorer 1 (ISEE-1), years 1977 through 1987; and (4) Combined Release and Radiation Effects Satellite (CRRES), years 1990 and 1991. Superposed epoch analysis reveals clear evidence of plume phases, and yields a global model for plume density versus epoch time, something not achieved by previous empirical global density (and plasmapause location) models that have employed ranges of values of geomagnetic indices (Kp, Dst, and AE) to organize plasmaspheric data. Quantitative analysis of sub-global density structure will also be presented, showing the evolution versus epoch of density structure at various sub-global spatial scales, and its empirical (epoch-based) characterization.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMSM32A..06C
- Keywords:
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- 2730 MAGNETOSPHERIC PHYSICS / Magnetosphere: inner;
- 2768 MAGNETOSPHERIC PHYSICS / Plasmasphere