Electron temperature enhancement effects on plasma irregularities associated with charged dust in the Earth's mesosphere

Abstract

Recently, experimental observations have shown that Polar Mesospheric Summer Echoes (PMSE) may be modulated by radio wave heating the irregularity source region with a ground‐based ionospheric heating facility. It is clear from these past investigations that the temporal behavior of PMSE during ionospheric heating shows promise as a diagnostic for the associated dust layer. To investigate the temporal behavior of plasma irregularities thought to produce PMSE, this work describes a new model that incorporates both finite diffusion time effects as well as dust charging. The hybrid model utilizes fluid ions described by continuity and momentum equations, electrons whose behavior is determined from quasi‐neutrality, and charged dust described by the standard Particle‐In‐Cell (PIC) method. The model has been used to investigate the temporal behavior of charged dust associated electron irregularities during electron temperature enhancement associated with radio wave heating. The model predicts that the temporal behavior of the irregularities depends on the ratio of the electron‐ion ambipolar diffusion time to the dust particle charging time τdif/τchg. The results indicate that typically for τdif/τchg ≪ 1, an enhancement in electron irregularity amplitude occurs for a period after turn‐off of the radio wave heating. The work also predicts that for τdif/τchg ≫ 1, an enhancement in electron irregularity amplitude occurs for a time period after the turn‐on of the radio wave heating. Owing to the dependence of τdif on irregularity scale size, these results have important implications for observations of PMSE modification at different radar frequencies. Therefore new possibilities may exist for diagnosing the dust layer with radio wave heating which are discussed.