This project will add important new features to the PI's model for entry of magnetosheath ions and electrons into the magnetosphere in the cusp. The improved model will have more realistic magnetic and electric field parameters. It will also utilize recent magneto-hydrodynamics (MHD) simulations of the magnetosheath to more accurately characterize the sheath. The third major improvement will be to incorporate wave-particle interactions that result in energization of the particles. The project will utilize data from the Defense Meteorological Satellite Program (DMSP) satellites and the Polar satellite (NASA International Solar Terrestrial Program mission).
After the model improvements have been implemented, the model will be used in conjunction with the satellite data to investigate two important topics concerning the cusp. The first topic is the understanding of the processes that limit the spatial size of the cusp, both in latitude and longitude. The second topic is to determine to what extent wave-particle interactions heat the particles and alter their distributions.
The project is relevant to the Geospace Environment Modeling (GEM) Focus Group on cusp physics. The results are expected to also have impacts in other areas of space physics where particle energization by waves is thought to be important.
Intellectual merits of the proposed activity: We advanced a sophisticated APL open-field line particle precipitation model to study wave-particle interactions in the Earth magnetosphere. In addition, we also used DMSP and ACE satellite observations to provide inputs to the model and to verify model results. The study has illuminated (1) the plasma transport from solar wind to magnetosphere-ionosphere and (2) charged-particles energization in the magnetosphere and ionosphere. The following are the key outcomes: 1. In addition to waves, the field-aligned current, parallel electric field, and particle precipitation play important roles in particle energization in the cusp. 2. The anomalous parallel electric field in the polar rain can be explained by the evolution of the shocked solar wind particle in the magnetosheath, field-aligned current, and the velocity shear at the magnetopause boundary layer. 3. Low frequency waves such as Alfven waves can heat the ions in the direction perpendicular to the magnetic field. Subsequent pitch angle scattering by high frequency whistler and ion cyclotron waves can pitch angle scatter the heated ions, which can then precipitate into the ionosphere. Thus, both low and high frequency waves are needed to explain the heated ions observed by the DMSP satellites. 4. The APL open-field line particle precipitation model will contribute greatly to the development of a global magnetosphere model that is the overarching goal of the NSF GEM program. 5. A new method to estimate the electron path from the magnetotail X-line to the ionosphere was developed with the help of APL open-field line particle precipitation model. 6. Different waves can be associated with different types of electron precipitation in the ionosphere. For example, Whistler mode waves can be associated with diffuse electrons while Alfven wave can be associated with broadband electrons. 7. We observationally confirmed the predicted parallel electric field in the APL open-field line particle precipitation model. Broader impacts of the proposed activity: The following outlines broader impacts. 1. Simon Wing (PI) trained summer high school, undergraduate, and first year graduate students on space physics analysis technique and scientific programming. The proposed project is rich with topics that are suitable for a beginning graduate or an upper undergraduate student. These topics included data mining, data fitting, modeling, electricity and magnetism, thermodynamics etc. The student learned advanced scientific programming with IDL, C, and Fortran in LINUX and Window environments. As a result of his internship and with plenty of Simon Wing’s encouragement, Michael Kerns is now enrolled in a graduate program in electro-optics program at University of Dayton. Simon Wing also encouraged and wrote a strong letter of recommendation for another intern, Conor Francois, to pursue a graduate study. As a result, Conor is now pursuing a PhD in astrophysics at ETH in Switzerland. 2. Jay Johnson mentored Scott Keller, an undergraduate at Rutgers who participated in the Science Undergraduate Laboratory Internship program at PPPL, in the area of ion cyclotron waves, which can be important for pitch angle scattering. Scott Keller has subsequently been admitted to the Princeton University Graduate program. 3. Simon Wing (PI) has been instrumental in serving the DMSP SSJ4 data and spectrogram online to the community. 4. Simon Wing also has lectured to Middle School students on Space Physics. 5. Simon Wing and Jay Johnson organized meetings and convened special sessions at international meetings/conferences on the topic covered by the grant.
