Evidence of mass outflow in the low corona over a large sunspot

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

Apr 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994adspr..14...61n&link_type=abstract

Advances in Space Research, vol. 14, no. 4, p. (4)61-(4)64

Astronomy and Astrophysics

Astronomy

2

Emission Spectra, Line Spectra, Solar Corona, Solar Magnetic Field, Solar Spectra, Solar Wind, Sunspots, Doppler Effect, Extreme Ultraviolet Radiation, Imaging Spectrometers, Interplanetary Magnetic Fields, Satellite Observation, Solar Physics, Spaceborne Astronomy, Space, Exploration, Venus, Probes, Balloons, Atmosphere, Altitude, Design, Mission Planning, Parameters, Technical Aspects, Temperature, Thermal Effects, Calculations, Alloys, Titanium, Equipment

Scientific paper

An extreme ultraviolet (EUV) imaging spectrograph designed for sounding rocket flight has been used to search for velocity fields in the low solar corona. During a flight in May, 1989, we obtained emission line profile measurements along a chord through an active region on the Sun. Relative Doppler velocities were measured in emission lines of Mg IX, Fe XV, and Fe XVI with a sensitivity of 2-3 km/s at 350 A. The only Doppler shift appreciably greater than this level was observed in the line of Mg IX at 368.1 A over the umbra of the large sunspot. The maximum shift measured at that location corresponded to a velocity toward the observer of 14 plus or minus 3 km/s relative to the mean of measurements in that 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 magnetic field geometry, this mass outflow could either re-appear as a downflow of material in distant footprints of closed coronal loops or, if along open field lines, could contribute to the solar wind. The site of the sunspot was near a major photospheric magnetic field boundary. Such boundaries have been associated with low-speed solar winds as observed in interplanetary plasmas.

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