Identifying and Quantifying Wave Cross-scale Coupling in the Earth’s Magnetosphere and the Solar Wind

We present observations of modulation of higher frequency waves (lower hybrid, whistler mode, magnetosonic, ion acoustic) by lower frequency waves (electromagnetic ion cyclotron, ultra-low frequency) in the Earth’s magnetosphere including the radiation belts, plasma sheet boundary layer, and magnetotail, as well as in the solar wind. This cross-scale coupling links the vastly different ion and electron temporal and spatial scales, and can have dramatic effects on wave-particle interactions. Such modulations can have a significant impact on the formation and depletion of Earth’s radiation belts, and the mechanisms that control the heat flux in the solar wind.

We have recently developed a new automated technique to identify modulations in the RBSP data using the filterbank data products, and found that such modulation is considerably more common than previously understood.  Similar modulations were observed in MMS measurements taken in the radiation belts and elsewhere in the magnetosphere, as well as PSP measurements in the solar wind.  We use these data sets to automatically detect modulated wave events. This database of modulated events and characteristics of the waves and plasma environment, including geomagnetic conditions for magnetospheric observations, allows us to determine the prevalence of this process and under which conditions it can occur.

We will present the results of applying our algorithm across the entire RBSP dataset, including the location and prevalence of modulations across the range of frequencies and geomagnetic conditions. Observations from MMS will be added to this database. We also present comparative studies between events at Earth and those observed in the solar wind by PSP to provide insights into the coupling process.