Moran, T. | Search NASA

NASA NTRS1997

SUMER observations detecting downward propagating waves in the solar transition region

The O IV density sensitive emission lines around 1400 A, using the solar ultraviolet measurement of emitted radiation (SUMER) instrument onboard the Solar and Heliospheric Observatory (SOHO), are reported on. The data for the quiet sun, obtained close to the disk center and the solar limb were acquired. A systematic correlation between a density sensitive emission line ratio and Doppler shift across the same emission profiles was obtained. The correlation is such that the density is higher in the downflowing than in the upflowing plasma. The results are in good agreement with the simulations of downward propagating waves.

Wikstol, O.↗

NASA NTRS1991

An electrograph for measurement of macroscopic electric fields in prominences and flares

An 'electrograph' instrument designed for measurement of macroscopic electric fields in solar plasmas is described, using the polarization dependence of line width in Stark-broadened hydrogen Paschen emission lines. Observations of quiescent prominences and limb chromosphere with the electrograph at the NSO/Sac Peak Evans Coronal Facility provide upper limits of 5-10 V/cm for transverse macroscopic electric fields in these structures, averaged over an area of about 5 x 7 arcsec. Random thermal motions of hydrogen ions across magnetic field lines generate a quasi-static electric field, which should be distinguishable from pressure broadening in the intensely magnetized chromosphere over a sunspot, given an electrograph sensitivity a factor 2-3 better than that achieved here. Future electrograph measurements of limb flares, post-flare loops, and eruptive prominences, even at 5-V/cm sensitivity, could provide a useful new test of reconnection and discharge effects in such dynamic structures.

Moran, T.↗