Maha Ashour-Abdalla

Plasma Physics on Auroral Field Lines: The formation of Ion Conic Distributions

Auroral field lines near 1 RE altitude exhibit rich and complex plasma physics phenomena. These include the precipitation of energetic electrons, electrostatic shocks, potential double layers, electrostatic hydrogen cyclotron waves, and upward streaming ions (Mozer et al., 1980). Figure 1 is an attempt to illustrate schematically our present understanding of the phenomena of auroral field lines in the dusk sector. At high altitudes the observations are consistent with double layers and the associated parallel electric fields. These field aligned potential differences can produce beams of both downward electrons and upward ions with fluxes peaked in energy and enhanced in the direction parallel to the magnetic field. The visible discrete auroral arcs result from the precipitation of 1 -10 keV electrons which carry an upward field aligned current. In order to maintain charge neutrality the ionosphere must respond by sending an outflow of cold electrons which carry downward field aligned currents. Particle observations indicate that ion beams are not the only distribution which are observed. At altitudes ≈ 1500 km, measurements from the ISIS-1 and ISIS-2 satellites report the existence of ion distributions with enhanced particle fluxes at pitch angles between 90–130 degrees (Klumpar, 1979; Ungstrup et al., 1979). Such distributions are commonly termed ion conic distributions.

Ion dynamics associated with substorm dipolarization fronts

We report where and how ions are accelerated in the proximity of earthward propagating dipolarization fronts (DFs) in the magnetotail during a magnetospheric substorm on February 15, 2008. Two DFs were observed by multiple THEMIS spacecraft in the near-Earth magnetotail (∼−10 Re). We studied the ion dynamics associated with these DFs by comparing observed results with large scale kinetic (LSK) simulation results. The LSK simulation reproduced the sudden ion energy flux enhancement concurrent with the arrival of the DF at the satellite locations. We found that ions can be accelerated to more than 100 keV energy at the DF. These ions were initially non-adiabatically accelerated near magnetic reconnection site and then still non-adiabatically accelerated at the DF structure.

“Interactive Multimedia Education at a Distance-Linear Algebra (IMED-LA)”: Its Present Status and Special Features of Its Content

The IMED-LA or Interactive Multimedia Education at a Distance — Linear Algebra is the ongoing international joint project by the collaboration of the Japan Team currently consisting of five members and the Center for Digital Innovation (CDI) of the University of California at Los Angeles (UCLA) headed by Director Maha Ashour-Abdalla. The project started in July, 1999. Its goal is the production of virtual university content in linear algebra, intended primarily for graduate students and working students who need a fast-paced study of the basic facts from linear algebra; hence the content can also effectively be used by the beginning college students under a proper guidance from the teacher. Our partially completed content is already available on the Internet at the following URL: http://www.cdi.ucla.edu/linearalgebra.