Normal-mode Magnetoseismology as a Virtual Instrument for the Plasma Mass Density in the Inner Magneotsphere: MMS Observations during Magnetic Storms
Abstract
Previous studies have demonstrated that the electric and magnetic field measurements on closed field lines can detect harmonic frequencies of field line resonance (FLR) and infer the plasma mass density distribution in the inner magnetosphere. This normal-mode magnetoseismology technique can act as a virtual instrument for spacecraft with a magnetometer and/or an electric field instrument, and it can convert the electromagnetic measurements to knowledge about the plasma mass, of which the dominant low-energy core is difficult to detect directly due to the spacecraft potential. The additional measurement of the upper hybrid frequency by the plasma wave instrument can well constrain the oxygen content in the plasma. In this study, we use field line resonance (FLR) frequencies observed by the Magnetospheric Multiscale (MMS) satellites to estimate the plasma mass density during magnetic storms. At FLR frequencies, the phase difference between the azimuthal magnetic perturbation and the radial electric perturbation is approximately ±90°, which is consistent with the characteristic of standing waves. During the magnetic storm in October 2015, the FLR observations indicate a clear enhancement in the plasma mass density on the first day of the recovery phase, but the added plasma was quickly removed on the following day. We will compare with the FLR observations by other operating satellites such as the Van Allen Probes and GOES to examine the spatial variations of the plasma mass density in the magnetosphere. Also discussed are how the spacing in harmonic frequencies can infer the distribution of plasma mass density along the field line as well as its implications.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMSM21B..11C
- Keywords:
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- 2720 Energetic particles: trapped;
- MAGNETOSPHERIC PHYSICS;
- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS;
- 2740 Magnetospheric configuration and dynamics;
- MAGNETOSPHERIC PHYSICS;
- 2760 Plasma convection;
- MAGNETOSPHERIC PHYSICS