Evidence for mass outflow in the low solar corona over a large sunspot

Details Evidence for mass outflow in the low solar corona over a large sunspot Evidence for mass outflow in the low solar corona over a large sunspot

Jun 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992apj...392l..95n&link_type=abstract

Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 392, no. 2, June 20, 1992, p. L95-L98.

Astronomy and Astrophysics

Astrophysics

18

Extreme Ultraviolet Radiation, Magnetohydrodynamic Flow, Solar Corona, Solar Wind, Sunspots, Ultraviolet Radiation, Interplanetary Medium, Iron, Line Of Sight, Magnesium, Solar Activity

Scientific paper

Spatially resolved EUV coronal emission-line profiles have been obtained in a solar active region, including a large sunspot, using an EUV imaging spectrograph. Relative Doppler velocities were measured in the lines of Mg IX, Fe XV, and Fe XVI with a sensitivity of 2-3 km/s at 350 A. The only significant Doppler shift occurred over the umbra of the large sunspot, in the emission line of Mg IX (at Te of about 1.1 x 10 exp 6 K). The maximum shift corresponded to a peak velocity toward the observer of 14 +/- 3 km/s relative to the mean of measurements in this emission line made elsewhere over the active region. The magnetic field in the low corona was aligned to within 10 deg of the line of sight at the location of maximum Doppler shift. Depending on the closure of the field, such a mass flow could either contribute to the solar wind or reappear as a downflow of material in distant regions on the solar surface. The site of the source, near a major photospheric field boundary, was consistent with origins of low-speed solar wind typically inferred from interplanetary plasma observations.

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