Plasma Wave Observations During Geomagnetic Storms with MMS
During magnetic storms, the Earth’s atmosphere loses enhanced amounts of oxygen which escapes to the magnetosphere. In space, governed by the Earth’s magnetic field, these oxygen ions gyrate around magnetic field lines and generate electromagnetic plasma waves at frequencies around the oxygen cyclotron frequency. These waves could indicate elevated oxygen levels, which can be observed for a few consecutive days from storm onset during the recovery phase of the storm. This project surveys data from NASA’s Magnetospheric MultiScale mission (MMS) in the inner magnetosphere from September 2015 to April 2016. These dates were chosen due to a large number of geomagnetic storms. We also took advantage of high-resolution measurements and looked at higher frequency plasma waves observed at the vicinity of electron cyclotron frequencies. Surprisingly, over certain intervals of these events, there is a clear modulation of high-frequency wave packets with low-frequency ion cyclotron waves. Though the mechanism for this modulation is yet to be investigated, these observations suggest a cross-frequency relationship between plasma processes happening at ion and electron scales which may be important for the magnetospheric dynamics. Additionally, we accidentally found ion cyclotron waves with unusual properties that have never been reported before.
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