Joint Astrophysics/Space Physics Seminar

October 9, 2018 - 12:30pm
309 VAN

"Characteristics of Reflected Ions and Ultra-Low Frequency Waves in the Lunar Plasma Environment” by Ms. Stephanie Howard, Department of Physics & Astronomy, The University of Iowa

Abstract:  A variety of plasma waves have been observed in the lunar plasma environment. These include ultra-low frequency waves near the ion cyclotron frequency.  Both left-hand and right-hand polarization is displayed by these waves in the spacecraft frame. One generating mechanism for such waves is resonant interactions with ions reflected from localized crustal magnetic fields on the lunar surface. We study the characteristics of these waves and the conditions under which they occur. Using over five years of observational data from the ARTEMIS spacecraft, we look for simultaneous observations of ultra-low frequency waves and non-solar wind ions. We use an ion tracing program to simulate trajectories and velocities of reflected ions for given ambient solar wind and interplanetary magnetic field (IMF) conditions, such as the conditions present during the observed events. By combining the cyclotron resonance condition with the Doppler shift due to the solar wind, the intrinsic properties of waves generated by a range of ion velocities can be determined.  Ion velocity distributions generated from the ion tracing program for times when waves are detected show a preference for velocities in a range that indicates intrinsically right-hand polarized waves. Additionally, we compare the IMF and solar wind parameter distributions during the observed events to the parameter distributions from accumulated ARTEMIS data. The times when ultra-low frequency waves and non-solar wind ions are observed show a preference for lower solar wind speed and a Parker spiral IMF direction.

 

“Bifocal: A Next-Generation Electron Instrument” by Mr. Gian Anderone, Department of Physics & Astronomy, The University of Iowa

Abstract:  The electron velocity distribution function (EVDF) gives valuable information about space plasma environments. Large scale measurements of the distribution provide routine density and temperature measurements, while small scale measurements provide detailed information of the plasma environment, such as magnetic field topology and small-scale heating. However, stringent mass and power constraints for space physics instruments often force electron instruments to take either exclusively coarse or fine scale measurements of the electron population. Bifocal is a next-generation electron instrument which is capable of making both coarse- and fine- measurements of the EVDF. In this talk, I will give the theory behind Bifocal, as well as an overview of its specific characteristics. The inaugural flight for Bifocal will be on a sounding rocket to study precipitating electrons in earth’s magnetic cusp (ICI-5). I will give a brief overview of this mission, emphasizing Bifocal’s role.