AGS-PRF: Probing the Relationship Between Radiation Belt Electron Precipitation and Electromagnetic Ion Cyclotron (EMIC) Waves

Blum Lauren W, San Francisco CA

Investigators

Abstract

Just as in the ocean and the atmosphere, waves exist in space plasmas. In these plasmas, where collisions between charged particles are rare, energy can be transferred to a charged particle from a plasma wave (analogous to a surfer on an ocean wave). As a result, plasma waves are a major means of transferring energy from one charged particle population to another, and for energizing a small portion of the population to very high energies. There are many types of plasma waves. Microphysics tells us that plasma waves, called electromagnetic ion cyclotron waves (EMIC), are able to scatter electrons formerly trapped in the radiation belts into the atmosphere where they are lost. However, the relative importance of EMIC waves to the global variability of the radiation belts has been a subject of intense scientific debate for the past 50 years. The main goal of the research is to resolve this debate by combining multi-point conjugate measurements of particles and fields in space with electron precipitation. The capability for making these measurements was recently expanded by the Van Allen Probes and BARREL balloons missions. The grant will support the further training and development of a promising female early-career scientist. The resulting global maps of relativistic electron precipitation will be useful to the broader space physics and aeronomy communities, to researchers studying the chemistry of the middle atmosphere, and for space environment applications, such as active mitigation techniques for both natural and artificial radiation in space. To address the open questions raised above, the methodology is to construct large-scale maps of plasma and wave fields in space and correlated maps of high-energy electrons precipitating into the atmosphere from multiple satellites both at high- and low-Earth orbit. At issue is how long radiation belt electrons actually travel through regions occupied by EMIC waves as they move along closed drift path in the radiation belts. The longer they interact with the EMIC waves the more likely they will be scattered out of their closed drift paths and be lost. If the waves exist only in limited regions that are sparsely distributed throughout the radiation belts, or turn on and off rapidly, their cumulative effects may be insignificant. Comparing these maps not only provides information about the global distribution of plasma waves but also about whether the relationships between the mapped quantities are consistent with EMIC waves. Even if these maps are not consistent with EMIC wave interactions with the energetic particles and cold plasmas, they provide clues to, and place constraints on, other mechanisms..