Cherenkov Whistler Emission by Electron Holes

Abstract:

Electron holes (EHs) are nonlinear, electrostatic, Debye scale, plasma waves where self-consistent electron trapping results in a localized positive potential. They are formed by various instabilities related to electron beams such as the Buneman and electron two stream instability. As such they are ubiquitous in most space plasmas, and have been found for example, in the solar wind, at Earth's magnetopause, and in Earth's auroral acceleration region.
Simulations and recent spacecraft observations have shown that EHs propagating with speeds approaching half the electron Alfvén speed act as antennas radiating whistler waves via the classic Cherenkov mechanism. In a simulation of magnetic reconnection, the radiated whistlers were found to affect the reconnection process.
Since the Cherenkov mechanism is independent of the particle distribution function, the waves may be generated in a plasma where they are damped, leading to strong wave-particle interaction.
We present and discuss MMS data showing evidence of EHs Cherenkov radiating whistler waves in the Earth's magnetotail during ongoing magnetic reconnection. We also discuss how this process can be important in different regions of the heliosphere.