The upper atmospheres of the Sun, stars, and many other astrophysical plasma besides, are sufficiently tenuous that the plasma is not efficiently equilibrated by particle collisions. In such cases, plasma waves can play a crucial, if not dominant role in the dynamical behavior. For example, the ionization balance of various elements in the solar wind (measured in situ) when compared with that in their solar coronal source regions (measured spectroscopically, e.g., with instruments onboard the SOHO mission) reveals an electron heating process that is presumably related to the acceleration mechanisms of the solar wind itself. Further, element abundances in the solar corona and wind can be different to those in the underlying photosphere-suggesting a fractionation process as a result of plasma waves. In this program, we analyze spectroscopic data of the solar corona and wind to study particle heating and acceleration, and pursue a program of modeling to better understand and constrain plasma physics.

We also study such processes in a wider variety of astrophysical environments using high-quality data sets obtained by Chandra and XMM-Newton satellites. Particle heating and acceleration at the shock waves of supernova remnants provide an interesting contrast to the solar wind while element abundance anomalies in late type stellar coronae can extend and challenge models of the solar chemical fractionation.

 

key words

Atomic physics; Plasma physics; Shock waves; Solar physics; Solar wind; Spectroscopy;

Citizenship:  Open to U.S. citizens and permanent residents

Level:  Open to Postdoctoral applicants