Measurement of Solar Plasma Electric Fields

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This proposal is to observe solar electric fields. Solar plasma electric fields have received relatively little attention considering the central importance of such fields in energy release, and in plasma and energetic particle acceleration in the solar atmosphere. This proposal is to carry out ground-based measurements of such fields to validate the promising "electrograph" technique of electric field remote sensing. This is based on measurement of the transverse Stark effect in solar hydrogen lines. The PI plans to upgrade the SPO instrument to increase its sensitivity to 1 volt cm1, and test this sensitivity by observing the motional electric field (due to random cross-B particle motions in any magnetized plasma) which should become detectable in the sunspot chromosphere at this sensitivity level. More broadly, they plan to operate the electrograph on a daily basis to study the intensity, geometry, and spatial and time behavior of electric fields associated with flares, eruptive filaments, sunspots and faculae. They also plan to extend the electrograph technique farther into the infrared, to include promising hydrogen lines out to beyond 10 . This IR work will be carried out with the FTS and with the main McMath spectrograph at Kitt Peak. The results of thes investigations will be compared to the discharge and reconnection models of flares, to models of post-flare loops, filament eruptions, and also to recent ideas on solar abundance variations. They experience in these ground- based observations will be also used to determine the optimum wavelengths of electrograph operation in the infrared, and to investigate whether important advantages in electric field measurements on the disc and at the limb might be achieved with an electrograph flown on a balloon, on the Shuttle or on a satellite.