A determination of the outflow speeds in the lower solar wind
G.M. Simnett and
Received 12 January 1999 / Accepted 19 July 1999
The acceleration of the low-latitude solar wind, which comes from regions of the corona above large, closed magnetic loops, is a theoretical challenge. Until recently we have lacked direct measurements close to the Sun with which to constrain the theory. When a series of high-resolution coronagraph images is viewed in the form of a movie the continuous outflow of matter from the Sun is very obvious. We report here the results of a correlation analysis of the LASCO coronagraph images from the SOHO spacecraft which we have used to estimate the low-latitude solar wind speed from 3-27 . Acceleration occurs to the outer parts of this radial range, by which time the solar wind has approached its measured speed at 1AU, implying little acceleration beyond 30 . A very significant result is the detection of a component flowing out at speeds up to 1500 km s-1, which is energetically very important and possibly dominant.
Key words: Sun: solar wind Sun: corona
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Correspondence to: S.J. Tappin (firstname.lastname@example.org)
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© European Southern Observatory (ESO) 1999
Online publication: September 24, 1999