Determining the Global Coherence of Plasmaspheric Hiss Waves in the Magnetosphere

Abstract:

Plasmaspheric hiss waves are a fundamental component of radiation belt dynamics, proving key acceleration and loss mechanisms for relativistic electrons. Hiss is thought to be coherent across large distances inside the plasmapause, acting on radiation belt electrons throughout their drift trajectories. In this study, we investigate both the spatial and temporal coherence of plasmaspheric hiss between the two Van Allen probes during 2012-2015. We find ~2000 events where we can determine the correlation of wave amplitudes as a function of both spatial separation and time lag in order to study the spatial and temporal coherence of plasmaspheric hiss. The statistical results show that, with the increase of L-shell, both the spatial and temporal correlation of plasmaspheric hiss are clearly reduced, and close to 0 at L > ~4.5. When L < ~4.5, we find the plasmaspheric hiss become incoherent when separation > ~1435.6 km and time lag > ~10 min. We investigate how the spatial and temporal coherence of plasmaspheric hiss depends on geomagnetic indices (AL*) and magnetic local time (MLT). We discuss the ramifications of our results with relevance to understanding the global characteristics of plasmaspheric hiss waves and their role in radiation belt dynamics.