The ACE (Advanced Composition Explorer) satellite detected a steady increase, over a period of roughly one day on the 28th of August, of the solar wind speed from 400 to 600 km/s (yellow curve in plot underneath). This gradual but significant change of the wind speed indicates that the Earth is experiencing the solar wind originating from a different region of the sun, namely a coronal hole.
The solar wind of 600 km /s that we see now, had taken about 70 hours to travel the sun-earth distance. The source of this fast wind on the sun should then be coming from near the solar disk center on the 24th of August.
The images above are from the instrument SXT (Soft X-Ray Telescope) on board the Yohkoh satellite and show the solar corona on three different days. The colour table has been reversed (so dark means higher intensity). Notice the elongated coronal hole (bright region in northern hemisphere towards equator) passing the solar disk.
