This is a 3-year project to determine the effects and implications of plasmaspheric material being eroded from the plasmasphere and subsequently being convected to the dayside reconnection site. Specifically, the project seeks to answer the following science questions: (1) how plasmaspheric losses are partitioned during magnetic storms between downward flow into the ionosphere and transport to the dayside boundary layers and (2) whether transport of plasmaspheric material to the dayside magnetopause slows magnetic reconnection as manifested in a possible systematic reduction in the polar cap potential at these times. Global images of the plasmasphere from the EUV instrument onboard the IMAGE spacecraft; cold plasma density and flow data from geosynchronous spacecraft; density and total flux tube content derived from ground-based measurements of whistlers and cross polar cap potential measured by the SuperDARN radar will be combined to address these questions.
The project will have significant broader impacts in a number of ways. It will support the research career of a female scientist, who will act as the science PI on the project. Undergraduate students will participate in the research project through an established REU program. Finally, magnetic reconnection is a universal process and observational verification that reconnection is reduced in the presence of cold plasma would be a result that would have implications for numerous other plasma- and astrophysical studies.
The plasmasphere is a vast toroidal region of low energy ionized gas or plasma that encircles the Earth and extends from the top of the ionized upper atmosphere at altitudes of about 1000 km out to equatorial altitudes ranging from about 10,000 to 40,000 km. The structure and dynamics of the plasmasphere are highly sensitive to geomagnetic disturbance activity in the near-Earth space environment, which is ultimately driven by the sun. The plasmasphere is host to many of the complex interactions among charged particle populations and electromagnetic ?elds in near-Earth space, and knowledge of its dynamics on a global scale is therefore fundamental to our understanding of the ?ow of mass and energy within the solar-terrestrial environment. During geomagnetic storms, large-scale solar wind-driven electric fields massively redistribute the cold plasma comprising the plasmasphere. This large-scale redistribution profoundly effects the generation and propagation of plasma waves and the interaction of these waves with the higher energetic particles that co-exist in the near-Earth space environment. Cyclotron resonant interactions between plasma waves and energetic ions or electrons are significant mechanism by which energy is transferred in the magnetosphere, and the location of the cold plasma boundary determines what types of wave modes can grow and the resonant energy for wave-particle interactions. Thus, as the plasmasphere evolves during storms, the regions favorable for the growth of various wave modes also evolve. This NSF-funded research project has led to advanced understanding of how the evolving shape of the plasmasphere dictates the regions favorable for wave growth and wave-particle interactions. As the plasmasphere is distorted during storms and cold plasma density piles up in specific regions, a specific class of wave mode, called electromagnetic ion cyclotron (EMIC) waves, is more favorably generated. Small-scaled density irregularities within the cold plasma also act to further improve wave-generation and propagation. In other regions of space, the cold plasma density is depleted during storms, and this leads to favorable conditions for another type of plasma wave, known as whistler-mode chorus. Once generated both EMIC and chorus waves strongly influence the behavior of the much higher energy particles and ultimately the distribution of energy in the near-Earth space environment.
