Application of multivariate Maxwellian mixture model to plasma velocity distribution function

Citation
G. Ueno et al., Application of multivariate Maxwellian mixture model to plasma velocity distribution function, J GEO R-S P, 106(A11), 2001, pp. 25655-25672
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
ISSN journal
2169-9380 → ACNP
Volume
106
Issue
A11
Year of publication
2001
Pages
25655 - 25672
Database
ISI
SICI code
0148-0227(20011101)106:A11<25655:AOMMMM>2.0.ZU;2-G
Abstract
Recent space plasma observations have provided us with three-dimensional ve locity distributions having multiple peaks. We propose a method for analyzi ng such velocity distributions via a multivariate Maxwellian mixture model where each component of the model represents each of the multiple peaks. Th e parameters of the model are determined through an iterative nonlinear opt imization technique, specifically the expectation-maximization (EM) algorit hm. For the automatic judgment of the preferable number of components in th e mixture model, we introduce a method of examining the number of extrema o f a resulting mixture model. We show applications of our method to ion obse rvations in the plasma sheet boundary layer (PSBL) and in the central plasm a sheet (CPS) of the Earth's magnetotail. From an analysis of the PSBL and CPS, low-energy ions that have properties similar to those of lobe ions wer e detected also in the PSBL and CPS. In the PSBL, middle-energy ion compone nt which is flowing dawnward and directed the neutral sheet was extracted. We suggested that magnetic field fluctuations in the PSBL can be explained only when the two ion components were properly treated.