National Aeronautics and Space Administration (NASA) Grant NAG 5-2346 from Goddard Space Flight Center (GSFC) supports the data reduction and analysis effort at The University of Iowa for the ISTP/GGS GEOTAIL Multi-Channel Analyzer (MCA) which is a part of the GEOTAIL Plasma Wave Instrument (PWI). The International Solar Terrestrial Physics / Global Geospace Science (ISTP/GGS) program began as the Origin of Plasma in the Earth's Neighborhood (OPEN). The goals of the program include identifying, studying, and understanding the source, movement, and dissipation of plasma mass, momentum, and energy between the Sun and the Earth. The GEOTAIL spacecraft was built by the Japanese Institute of Space and Astronautical Science and has provided extensive measurements of entry, storage, acceleration, and transport in the geomagnetic tail. GEOTAIL began its scientific mission with eighteen extensions into the deep-tail region with apogees ranging from around 60 Re to more than 208 Re in the period up to late 1994. Due to the nature of the GEOTAIL trajectory which kept the spacecraft passing into the deep tail, GEOTAIL also made "magnetopause skimming passes" which allowed measurements in the outer magnetosphere, magnetopause, magnetosheath, bow shock, and upstream solar wind regions as well as in the lobe, magnetosheath, boundary layers, and central plasma sheet regions of the tail. In late 1994, after spending nearly 30 months primarily traversing the deep tail region, GEOTAIL began its near-Earth phase. Perigee was reduced to 10 Re and apogee first to 50 Re and finally to 30 Re in early 1995. In 1997 perigee was further reduced to 9 Re to shorten the long shadows. These orbits provide many more opportunities for GEOTAIL to explore the upstream solar wind, bow shock, magnetosheath, magnetopause, and outer magnetosphere as well as the near-Earth tail regions. The WIND spacecraft was launched on November 1, 1994 and the POLAR spacecraft was launched on February 24, 1996. EQUATOR-S was launched on December 2, 1997. These successful launches have dramatically increased the opportunities for GEOTAIL and the GGS spacecraft to be used to conduct the global research for which the ISTP program was designed.
The measurement and study of plasma waves have made and will continue to make significant contributions to reaching the ISTP/GGS goals and solving the significant problems of sun-earth connections. Plasma waves are involved in the energization and de-energization of plasma and energetic particles via numerous wave-particle interaction processes. Plasma waves in many instances are the source for the heating or cooling of the particles. They can cause particle precipitation by scattering particles into the loss cone. They move particles across boundaries in mass and energy dependent ways. Identifying the waves and the instabilities which produce them are thus crucial for understanding the plasma processes. Wave particle interaction processes are especially important at various boundaries between the different regions of geospace including the bow shock, magnetopause, and interfaces in the geomagnetic tail between the magnetosheath, lobe, plasmasheet, boundary layers, and neutral sheet. In addition to identifying the characteristics of the instabilities and generation mechanisms encountered, plasma wave measurements are used in conjunction with other fields and particle measurements to identify the region of space the spacecraft is in or the boundary that is being crossed. Plasma wave emissions can also be used to quantify the plasma density as well. Observations of Auroral Kilometric Radiation (AKR) provide a remote indicator of the timing and strengths of geomagnetic storms and substorms. Observations of electromagnetic escaping continuum radiation can provide remote tracking of the movement of injected plasmas during geomagnetic storms and substorms.
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