Charles F. Kennel - 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 proposal is for numerical studies of the magnetosphere with a focus on the properties of intermediate shock waves, the dynamics of the magnetosheath and magnetopause, reconnection and convection in the geomagnetic tail, and auroral electron acceleration by lower-hybrid wave turbulence. Scaling behavior of intermediate shocks will be handled through magnetohydrodynamics (MHD) followed by hybrid simulations extended to the high ion beta case (beta is the ratio of plasma to field energy density). MHD studies of the magnetopause will be pursued along with hybrid models to study magnetopause structure. 3D global simulations will be done including all the large-scale dynamics of the magnetosphere to test the effects of magnetosheath and magnetopause boundary conditions. Response of the magnetosphere to these inputs will be analyzed through studies of collisionless reconnection in the near- Earth plasma sheet, extended to cover more general aspects of convection and to consider the structure and stability of more distant parts of the tail current sheet. A new high beta drift- kinetic simulation code will be developed including some kinetic effects for the electrons as well as ions. This code will be used to test the hypothesis that chaotization of electron orbits can restore the universal ion tearing mode - a fundamental question for the reconnection process in space plasmas. Resonant electron acceleration by ion wave turbulence will be studied and the results compared with observations of auroral electron spectra and the structure of auroral arcs.

Numerical simulations are important tools for the study of space plasma physics. This grant is for continued research support to study the properties of shock waves and discontinuities in dissipative MHD and kinetic theory, the dynamics of the magnetosphere, and collisionless tearing instability in the magnetotail. Hybrid and implicit particle simulations will be used to study the kinetic properties of intermediate shocks and the possible role of such structures in dayside reconnection in the Earth's magnetotail will be investigated using increasingly realistic models of the near Earth plasma sheet. The principal aim will be to understand how and when a new neutral line forms within the pre-existing closed field lines of the plasma sheet.

Present theories of magnetic reconnection fail to account for magnetospheric substorms. Recent measurements of impulsive, short duration, high velocity flow bursts directed towards the Earth also do not conform to the standard picture of magnetospheric convection at quiet times. This grant is for support to study observationally and theoretically the small scale dynamics of the plasma sheet prior to substorm breakup. The observational part will characterize individual flow bursts using AMPTE satellite measurements so as to deduce information that might lead to a better understanding of the their dynamics. The theoretical objective will be to develop a one-dimensional nonlinear travelling wave model of an individual flow burst incorporating the effects of non-adiabaticity in the ion dynamics.

Alfven wave chaos is examined in two related studies. The first effort examines the driven Burgers equation, which has only one kind of shock wave, and is easier to solve than the more complex DLNSB equation. Using this equation it is possible to examine the essential dependencies of the onset of chaos on the number of harmonics and their growth rates. The second problem explores the analytic and numerical properties of oblique Alfven shock trains via the driven Korteweg- deVries-Burgers equation.

This project develops the Digital Crust, an online workspace where the geosciences community can contribute data and knowledge, visualize, explore, synthesize and test multiple hypotheses across space-time and themes, and derive 4D data product from multiple data.The platform can serve as a resource to bring together geoscientists working on separate aspects of the Earth system, by bringing their data/ideas together and by providing an environment to view the Earth from different perspectives. It will also be a "one-stop shop" for Earth science educators to expose the growing minds to the multi-faceted nature of Earth science problems and to see data and knowledge gaps which are powerful motivators for the young (not all problems have been solved ? there is a place for me to contribute).

The Digital Crust platform prototype will demonstrate technology that has the potential to transform the way geoscientists conduct research and learning, by (1) linking existing data repositories on all aspects of the Earth?s crust created by all disciplines of geosciences, communities as well as individuals, (2) creating a multi-context environment (e.g., tectonics, structural geology, stratigraphy, sedimentology, geomorphology, paleontology, archeology, mineralogy, geochemistry, soil science, hydrology, terrestrial ecology) at any given space (xyz) and time (t) for synthesis-type explorations, hypothesis-testing or learning, (3) allowing for multi-scale (e.g., outcrop to continent) data extractions and downloads for all research and learning applications, and (4) exposing data-knowledge gaps to identify the most rewarding future investments. Hosting multiple data types and sometimes conflicting interpretations and hypotheses of Earth processes will promote community discussion and debate on Earth processes that will foster interaction, collaboration, and data/idea sharing among scientists who might otherwise never have met. From the CI perspective, Digital Crust leverages and links with existing Building Blocks, explores the application of "loose-schema", noSQL databases to allow the flexibility necessary in a geoscience research database, and utilizes a modular software design to facilitate long-term maintenance and evolution of the platform.