Plasma Irregularity Sources Associated with Charged Dust in the Polar Summer Mesosphere

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The explanation of Polar Mesospheric Summer Echoes (PMSEs) has become one of the central challenges in near earth space science. These radar echoes are often observed in conjunction with high altitude noctilucent clouds (NLCs), which consist of charged dust particles. Since NLCs may provide evidence of global climate change on earth and are an indicator of the evolution and dynamics of the near earth space environment, a quantitative understanding of the relationship between PMSEs and NLCs has also become a forefront issue. PMSEs are believed to be produced by small-scale electron density irregularities in the NLC source layer. Recent simultaneous sounding rocket and radar measurements have produced the most complete picture to date of the plasma configuration inside NLCs and the relationship to PMSEs. These measurements provide strong evidence that PMSEs are enhanced in the boundary layer between the charged dust cloud and the background mesospheric plasma where plasma irregularities are also observed to be enhanced. Funding is requested to make an important and substantial advance in the quantitative understanding of the source of electron density irregularities believed to produce PMSEs. Consistent with the recent experimental evidence, a new model will be developed to consider the NLC boundary layer as a primary source region for PMSE generation. This investigation will provide a new methodology and approach to gaining fundamental insight into the importance of NLC boundary layers in producing PMSEs.The proposed activity will have broad impact by establishing infrastructure and collaboration between academic departments at the principal investigator's home institution. The activity will also sustain long term collaboration between the principal investigator and government research laboratories. The activity will allow collaborations to be furthered between the atmospheric science and international plasma communities. Finally, a minority PI and graduate student education will be supported by this work.