Solar Variability Linkages to Atmospheric Processes

Project Description
Short Title: Solar Variability Linkages to Atmospheric Processes
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Solar variability influences the atmosphere, particularly the global electric circuit and ozone. We propose an IPY cluster to quantify solar variability linkages to weather, climate and ozone.

The geoelectric circuit links weather and solar activity. It remains an open and a scientifically achievable goal to determine whether or not this linkage is passive or involves active coupling i.e., whether the global circuit merely responds to both meteorological and solar variations, or whether there is an active input to weather and climate via electrically induced changes in cloud microphysics. Present research indicates that the best place to measure the global circuit is the Antarctic plateau (high, dry, relatively meteorologically stable). The Greenland plateau provides an ideal northern hemisphere site. We propose making simultaneous vertical electric field and air-earth current measurements at a range of polar sites (plans presently envisage measurements at Vostok, South Pole and Concordia, 78S 24W, 84S 26W and 75S 70W). We encourage and seek to promote development of further sites, particularly in the northern polar regions.

A model of the global circuit is being developed that incorporates spatially and temporally varying global ion production due to the solar wind modulation of galactic cosmic rays, globally varying tropospheric and stratospheric aerosol concentrations and ion production in the stratosphere from relativistic electron precipitation and solar energetic particle events. It is also planned to insert the polar-cap potential distribution driven by solar wind-magnetosphere-ionosphere coupling into this model. We propose to compare the model and measurements to quantify limits on the hypothesis that the geoelectric circuit provides a viable path for a sun-weather linkage. Measurements indicate that the geoelectric circuit is sustained by both thunderstorm activity and electrified clouds. Published evidence exists that global thunderstorm activity has a multiplicative dependency on equatorial surface temperatures. Simultaneous measurements of the DC circuit and of power in the Schumann resonance bands may provide sensitive independent proxy monitors for both an equatorially-weighted, global temperature and rainfall. Our team includes a scientist making mid-latitude ELF/VLF measurements recording global lightning activity. We encourage measurements of Schumann resonance power and VLF-lightning data. We propose to determine how accurately our measurements can be used as proxy monitors, and to provide an accurate reference measurement of the geoelectric circuit in the IPY era.

Ground-based geoelectric instrumentation on the Antarctic Plateau has recently been used to confirm that broad-scale polar ionospheric convection potentials can be measured independent of the existence of small scale ionospheric irregularities. Our multiple polar-plateau geoelectric field measurements will contribute to understanding and monitoring polar-cap ionospheric convection.

The circumpolar vortex surrounding Antarctica is typical of the southern polar regions under winter conditions. This strong circumpolar vortex blocks lower latitude, ozone-rich air from reaching central Antarctica. In combination with the lack of solar insolation in winter, the total ozone content above the southern polar regions decreases dramatically. The depth of the so-called ozone hole and its rate of filling in spring depends on the previous state of the atmosphere and has been shown to be affected by external influences related to solar activity. The relative effects of the influences of short-term changes in cosmic ray intensity, variations of the interplanetary electric field on atmospheric parameters (temperature and pressure) in the southern winter polar regions, the dynamics of the ozone layer, the effects of solar UV radiation and the role of the global electric circuit on winter-spring Antarctic ozone concentrations will be examined. A study of pulsed cosmophysical signals in the Arctic (Barentzburg) and in Antarctica (Novolazarevskaya) is proposed. Measurments at Novolazarevskaya have revealed the regular occurrence of pulsed signals in the solar spectrum. The most pronounced pulses have been detected 4 days ahead of solar flare proton events (SPE). Results of the analysis of the spatial-temporal anisotropy of the cosmological signals will be used for derivation of an empirical model and to study the solar sources and mechanism of the pulsed irradiation. Study of the effects of the pulsed radiation on biological and technogenic systems is also planned.Most of our team are actively involved in enthusing students and educating the public. The geoelectric circuit with its link to thunderstorms, sprites, climate change and a sun-weather hypothesis provides considerable scope for such activities. Polar convection studies additionally provide a neat link of this proposed IPY activity with the geophysical focus of the IGY.