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Faculty Mentor

Mark J. Engebretson, PhD


Earth’s atmosphere becomes increasingly thin with increasing altitude. Above 100 miles charged particles such as electrons and charged atoms called ions begin to fill the atmosphere. The atmosphere gradually transitions into the thin plasmas that make up the ionosphere, the magnetosphere, and finally interplanetary space. Plasmas are notoriously unstable, and can generate more than a dozen different kinds of waves, many of them not well understood yet. I studied one particular class of plasma waves called electromagnetic ion cyclotron (EMIC) waves using data from one of NASA’s most recent scientific satellite missions, Magnetospheric Multiscale (MMS). The frequency range of EMIC waves is 0.1 – 5 Hz. The MMS mission consists of four closely spaced (down to ≈7 km) spacecraft in a highly elliptical orbit with their apogee from 12 to 25 Earth radii. Magnetic field measurements are provided by the MMS Fluxgate Magnetometer (FGM). My research centered around determining the scale size of EMIC waves, which has never been done accurately before as it is hard to estimate the size of these EMIC waves using only one satellite. What is unique about the MMS mission is that there are four satellites flown in close proximity to each other. Having only one spacecraft flying next to an EMIC wave event provides only one dimension, compared to multiple spacecraft which provide measurements in more than one dimension. Using two methods I concluded that the spatial scale size of EMIC waves is on the order of a few gyroradii of the protons that generated them.

Publication Date



EMIC waves, charged particles, plasma, Magnetospheric Multiscale


Astrophysics and Astronomy

Determining Spatial Scale Size of EMIC Waves