Ferdinand Coroniti - US grants

The proposed research is on the plasma kinetic processes in the earth's geomagnetic tail. The approach to be used is a combination of analytical an numerical methods. The research topics to be studied are new theories of slow shock in the distant tail region. Additional theoretical work includes study of broadband electrostatic noise (BEN) associated with slow shocks and electromagnetic instabilities in the plasma sheet.

This project will utilize magnetohydrodynamic (MHD) simulations of the magnetosphere-ionosphere system to examine the sensitivity of MHD simulations to variability of the solar wind driver. The work will compare the variability induced by intrinsic, internal magnetospheric dynamics with the variability caused by both temporal and spatial variability in the solar wind. Case studies will be done with real events to allow for comparisons of the simulations with realistic conditions. This work will provide a mechanism for determining the accuracy with which MHD models might in the future be able to predict space weather conditions.

The magnetospheric substorm constitutes the largest energy dissipation process in the magnetosphere, and the explication of the nature of substorm onset is the key to understanding the complex dynamics of the magnetotail. Preliminary 3-D particle-in-cell (PIC) simulations have suggested that an interchange mode driven by a positive tailward gradient in the equatorial magnetic field may be the underlying mechanism for triggering substorms. This mode is driven by the need to return magnetic flux to the dayside region; since this flux transfer must occur over large scales in the magnetotail, the Bz interchange is potentially a stronger and more dynamic instability than the standard interchange. This project will carry out a detailed, fully kinetic investigation of ballooning/interchange modes in configurations characteristic of the coupled magnetosphere-ionosphere system. The primary tool will be state-of-the-art, large-scale, 3-D PIC simulations carried out on massively parallel computers. These new simulations will overcome the previous limitations associated with a small ion to electron mass ratio, limited spatial extent in the east-west direction, and a too strong convection electric field. The conditions that lead to growth, the saturation mechanism and level, and the effect of ionospheric boundary conditions will be determined. The simulations will also determine whether or not an external trigger such as a northward turning of the IMF can directly excite the nonlinear interchange. It is possible that both types of interchange may occur simultaneously. This could lead to the creation of a magnetic neutral region magnetic reconnection can take place under the continued driving by the convection electric field. The project will provide a decisive determination of whether the interchange mode scenario is a viable solution to the substorm onset conundrum. The project will provide training for a graduate student in the rapidly evolving field of computational plasma physics. In addition, the research personnel will collaborate with the Los Angeles Physics Teachers Alliance Group (LAPTAG) to develop an outreach presentation on the use of computers in scientific research. This presentation, to be offered on several Saturdays during the year, will aim at demonstrating to local high school students the exciting opportunities in science made possible by advances in computing power and encouraging them to further their education in science.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This award supports the REU site at the University of California - Los Angeles. The main objective of the program is to encourage students, including women, underrepresented minorities, and students from institutions with limited research facilities to pursue careers in physics, astrophysics, and science in general. The program is aimed at a geographically and culturally diverse group and thus students are recruited nationally and special effort is made to target 4-year institutions, historically black colleges and traditional women's colleges. The program's activities include at its core a 10-week research project under the supervision of a UCLA faculty member. The projects span the various fields represented in the department (including plasma physics, condensed matter physics, accelerator physics, high energy physics, nuclear physics, astrophysics, astroparticle physics, and biophysics), and vary from year to year as different faculty members volunteer their time. The intellectual merit of this program is rooted in the close student-faculty interactions as they work together on one of a rich selection of cutting-edge projects. These research experiences have been supplemented by other auxiliary training such as a machine shop workshop, an ethics workshop, a Physics GRE prep course, and a weekly faculty seminar series.