Global Thunderstorm Activity and its Effects on the Radiation Belts and the Lower Ionosphere

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The project proposes an experimental study of thunderstorm coupling to the radiation belts, characterization of lightning flashes which lead to upward electrodynamic coupling, ionospheric variability and parameters, and global lightning and climatology. Newly discovered precipitation of radiation belt particles by magnetospherically reflecting whistler waves launched by lightning discharges will be measured via the associated localized and transient disturbances of the lower ionosphere. The latter disturbances are sensed remotely by means of their effect on the phase and amplitude of very low frequency (VLF) signals propagating in the nearby earth-ionosphere waveguide. Broadband ELF/VLF radio atmospherics measurements at the Antarctic base Palmer are proposed for the measurement of characteristics waveforms of sferics associated with upward electrodynamic coupling phenomena such as sprites. Recent results indicate that such measurements can be unique and used as a proxy measure for occurrences of intense upward coupling phenomena on a global scale. The unique location of Palmer station facilitates the measurements of sferics originating in lightning discharges over large regions of the globe, including the Americas, Africa, and the Atlantic and Pacific oceans. When used together with space-borne measurements, the highly accurate determinations of occurrence time and arrival bearings of sferics as measured at Palmer constitute a powerful new tool for assessment of global lightning activity. VLF observations at Palmer will provide crucial support to a separately funded (by the NSF/OPP) program, operating a VLF beacon transmitter at South Pole. Reception of the beacon signal at Palmer Station will allow the continuous measurement of relativistic electron precipitation from the outer radiation belts, an important component of worldwide efforts to assess "space weather". The proposed program is a part of the international collaboration with Stanford observations at Palmer (PA), complemented by and coordinated with observations at the British station Rothera, the Brazilian base Commandante Ferraz on King George Island (through the collaboration with the Centro de Radio-Astronomia e Aplicacoes Espaciais of Brazil), and at Negev Desert in Israel supported by the University of Tel Aviv. The proposed program complements similar observations carried by Stanford University in the northern hemisphere under the support from the NSF Atmospheric Sciences Division. Coordinated measurements in both the northern and southern hemispheres are needed to study the geomagnetic conjugacy of the phenomena under investigation.