Investigation of plasma irregularity sources associated with charged dust in the earth’s mesosphere

Abstract

Noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs) are two phenomena at the forefront of near earth space science. NLCs are high altitude clouds in the earth’s mesosphere that are formed from aerosol particles. The increase in the occurence of NLCs over time is believed to have profound implications on global climate change. PMSEs are believed to be related to NLCs and are strong radar echoes from mesospheric turbulence in the 50 MHz to 1.3 GHz range. Currently, there is no universally accepted explanation for the irregularities thought to produce PMSEs. Recent simultaneous sounding rocket, radar, and lidar observations of NLCs and PMSEs have provided a more detailed description of the electrodynamics and plasma configuration inside NLCs and the relationship to PMSEs. Particularly important is the simultaneous observation of charged aerosols, electron depletions, and small-scale electric field irregularities in the PMSE generation region. This work considers the consequences of the recent experimental observations on ultimately understanding the generation mechanism for PMSEs and the relationship to NLCs. A model for the electrodynamics and plasma configuration in the charged aerosol boundary layer will be described that indicates that plasma flows are expected to exist in the equilibrium. The possible role of these plasma flows in producing electron turbulence and irregularities in the charged aerosol boundary layer that may ultimately result in PMSEs is discussed.