CAREER: Magnetosphere-Ionosphere Coupling-Nonlinear Alfven Waves and Particle Acceleration

University Of Texas At Arlington, Arlington TX

Investigators

Abstract

The categorization of auroras into three distinct types of acceleration regions is well established: an upward current region; a downward current region; and an Alfvenic acceleration region. This investigation is focused particular on the Alfvenic region. An understanding of Alfven wave properties, energy transfer, and particle acceleration is critical in studying M-I coupling (Magnetosphere-Ionosphere Coupling). The specific objectives of this project are to answer the following questions: (1) What is the occurrence distribution of low-frequency electromagnetic fluctuations in the auroral oval? What is the relationship between the particle acceleration and wave energy? (2) What is the source mechanism of electron acceleration associated with Earth-based S-bursts? Can Alfven waves generate an unstable electron ring distribution? (3) How does a large-amplitude Alfven wave break down (cascade) into smaller wave numbers? What are the nonlinear Alfven wave properties? (4) How do observations compare with both linear and nonlinear Alfven wave theories/simulations? The systematic data analysis will be primarily based on observations from the FAST satellite. The data of Alfvenic fluctuations will be sorted according to field magnitude, magnetic local time, invariant latitude, geomagnetic activity, interplanetary magnetic field, and solar wind conditions. Particle measurements will also be analyzed to compare with the wave power. The space-based observations and data analysis effort will provide guidance for the theoretical and numerical framework. A linear gyrofluid model with a test particle method will be used to compare with the observed Earth-based S-bursts. It is our goal to understand the source mechanism of electron acceleration associated with S-bursts. A multi-dimensional gyrokinetic code will be developed to study nonlinear Alfven wave properties in the geomagnetic environment. It will first be tested in a homogeneous background, and then extended to an inhomogeneous background. The simulation results will ultimately be compared with satellite observations in order to identify which signatures can be understood by the linear theory, and which signatures must be addressed by nonlinear theories. The code that is developed in this undertaking will be used both in future research projects as well as in educational projects. The project is to be led by a female principal investigator, and many of the students who will be involved will be women. The physics department at the University of Texas at Arlington has one of the highest percentages (approximately 40%) of women graduate students among physics institutions of higher learning in the United States.