Persistent EMIC Wave Activity Across the Nightside Inner Magnetosphere

Abstract

Electromagnetic ion cyclotron (EMIC) waves can act as a loss process for both ring current ions and radiation belt electrons, and the spatial and temporal characteristics of these waves are important for quantifying their effects on energetic particles. Here we utilize observations from multiple spacecraft to constrain the azimuthal and radial dimensions as well as the duration of an EMIC wave event occurring on the nightside of the inner magnetosphere on 7 July 2013. These combined observations reveal waves limited to a narrow radial extent but persisting ~10+ hr and spanning ~12 hr in local time. The solar wind conditions, geomagnetic activity, and plasma environment are also examined to better understand the conditions under which persistent nightside EMIC waves can occur. Relativistic electron phase space density profiles during this event reveal local minima concurrent with the wave activity, consistent with EMIC‐driven scattering and loss of radiation belt electrons.

Evidence of Sub‐MeV EMIC‐Driven Trapped Electron Flux Dropouts From GPS Observations

“…As we have based our zero-epoch on the timing of the precipitation triggers seen by POES, our epochs are based on when the POES satellites happen to fly through the event region. As has been observed in previous studies, EMIC events may last for many hours (e.g., Blum et al, 2020;Engebretson et al, 2015), and our POES triggers may occur anywhere within these events (e.g., Hendry et al, 2016). This likely explains why we typically see the flux levels drop just before the zero-epoch.…”

Energetic Electron Precipitation Observed by FIREBIRD‐II Potentially Driven by EMIC Waves: Location, Extent, and Energy Range From a Multievent Analysis

“…Similar to previous studies (e.g., Capannolo et al, 2019a;Shekhar et al, 2017;Woodger et al 2018), EMIC-driven precipitation occurs on localized radial scales. This is probably because EMIC waves are excited only within a few L-shells (Blum et al, 2017Blum, Remya, Denton, & Schiller, 2020). However, for most selected conjunction events, precipitation was observed during multiple UT periods within the same FIREBIRD pass, with short temporal and radial scales between the various precipitation intervals.…”

Application of Cold and Hot Plasma Composition Measurements to Investigate Impacts on Dusk‐Side Electromagnetic Ion Cyclotron Waves

“…Tu et al, 2019; and references therein). Blum et al (2020) discussed the occurrence of persistent EMIC waves above Ω He+ in Earth's premidnight inner magnetosphere during storm recovery that were associated with a decrease in radiation belt electron phase space density. Trends have shown the presence of warm plasma and lower plasma density in the premidnight sector (e.g.…”