Large scale evolution of solar wind and solar coronal rotation determined by multi-satellite observations at the ecliptic
Abstract
We examine the large-scale structure and development of solar wind in the late declining phase of solar cycle 23 and in the subsequent solar minimum using Wind and STEREO solar wind speed data from 2007 until mid-2010. We use auto- and cross correlation on 27-day time windows to determine the degree of large-scale spatial coherence at the three spacecraft and the temporal evolution of solar wind recurrence. Solar wind speed is used in this study because it shows higher correlation and smaller frequency of fluctuations than other solar wind parameters. Correlation is found to remain fairly high until April 2009, when the new solar cycle begins. In order to better determine the spatial coherence in solar wind, we studied the two solar hemispheres separately and found a systematic bias towards higher correlation in the northern hemisphere. Using autocorrelation we defined the optimum solar wind recurrence period near the 27-day rotation period. We found that, on an average, recurrence period declined through most of the studied period. Large fluctuations were observed during the early ascending phase of solar cycle 24. We also found a systematic difference between the two hemispheres with faster rotation in the northern hemisphere. We discuss the results obtained between the different correlation methods and compare them with solar rotation rates defined by other solar photospheric and coronal features such as sunspots and coronal holes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMSH21B1912K
- Keywords:
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- 2164 INTERPLANETARY PHYSICS / Solar wind plasma;
- 2199 INTERPLANETARY PHYSICS / General or miscellaneous