Dusty space plasma diagnosis using temporal behavior of polar mesospheric summer echoes during solar proton event

Natural dusty plasma formed by disintegration of meteors appears in the atmosphere's mesosphere region between 50 and 80 km altitude. Climate change and human activity have caused decreasing mesospheric temperatures and increasing water vapor content via increased methane concentration. Noctilucent clouds (NLC) occur in cold polar summer mesopause and are the direct visual manifestation of freezing of water vapor on the dust particles and formation of ice-coated meteoric dust particles. In-situ measurements using sounding rockets have shown deep depletion of electron density due to charging on mesospheric dust particles (Rapp, 2009; Robertson et al., 2009). Accumulation of free electrons on the ice particles produces electron density structures, which cause the reflection of radar waves. Polar Mesospheric Summer Echoes PMSE are strong coherent radar echoes produced by electron density fluctuations in the vicinity of polar mesopause and at the half the radar wavelength (Rapp and Lubken, 2004). The first VHF radar echoes from the high-latitude mesosphere were observed using the Poker Flat radar in Alaska (location 65.120 N, 147.430 W) (Ecklund and Balsley, 1981; Balsley et al., 1983).We have investigated the behavior of polar Mesospheric summer echoes (PMSE) during solar proton event (SPE) including dusty plasma effects for the first time. The observational data recorded using the VHF (224 MHz) radar at the European Incoherent SCATter Scientific Association (EISCAT) on July 10 and 11, 2012 will be presented. The observed radar echoes show correlation and anti-correlation with the elevated background electron density variation. The experimental observations are compared with the numerical simulations of the temporal evolution of PMSE with different background dusty plasma parameters during SPE. Specifically, the effect of dust radius, dust density, and electron density on the behavior of PMSE layer and the associated dust charging process in the course of electron precipitation events is studied. It has been indicated that the ratio of electron density fluctuation amplitude _ne to the plasma density (ne), dust density and dust radius, recombination/photoionization rates play a critical role in appearance (and disappearance) of the layer. Possibilities of ice particles charging by mesospheric electrons will be discussed. The condensation of nuclei of the ice particles such as proton hydrate clusters (H+(H2O)n) or meteoric smoke particles (MSP) can be determined by employing microphysical simulations. This can resolve the discrepancy in the description of the observed phenomena. The possibilities of combining the Virginia Tech dusty plasma model with NCAR WACCM/CARMA (Whole Atmosphere Community Climate Model/ Community Aerosol and Radiation Model) to develop a large aperture radar simulator for the dusty space plasma in the near-Earth space environment will be discussed. - Balsley, B. B., Ecklund, W. L., and Fritts, D. C.: VHF echoes from the high-latitude mesosphere and lower thermosphere: observations and interpretations, J. Atmos. Sci., 40, 2451-2466, 1983.- Ecklund, W. L. and Balsley, B. B.: Long-term observations of the arctic mesosphere with the MST radar at Poker Flat, Alaska, J. Geophys. Res., 86, 7775-7780, 1981.- Rapp, M. and F.J. Lubken (2004), Polar mesosphere summer echoes (PMSE): Review of observations and current understanding, Atmos. Chem. Phys., 4, 2601-2633.- Rapp, M., Charging of mesospheric aerosol particles: the role of photodetachment and photoionization from meteoric smoke and ice particles, Annales Geophys. 27, 2417-2422, 2009.- Robertson, S., et al. (2009), Mass analysis of charged aerosol particles in NLC and PMSE during the ECOMA/MASS campaign, Ann. Geophys., 27, 1213-1232.- Mahmoudian, A., W. A. Scales, A. Senior, M. Kosch, Dusty space plasma diagnosis using temporal behavior of polar mesospheric summer echoes during solar proton event, to be submitted to GRL.