A vast coronal hole stretching more than a million kilometers across the sun’s northern hemisphere is facing Earth. A stream of solar wind flowing from this coronal hole (NOAA CH 575) should reach Earth on July 19-20, 2013 so increased geomagnetic activity levels will be possible under the influence of the high speed coronal hole stream.
The Earth is still inside the fast speed stream due to the low-latitude coronal hole in the northern hemisphere. At the moment the solar wind speed is about 600 km/s and the interplanetary magnetic field (IMF) is rather stable with the magnitude of about 6 nT, blowing southward.
The combined impact of the CME and the incoming solar wind stream could cause some geomagnetic disturbance around Earth in the days ahead. NOAA forecasters estimate a 65% chance of polar geomagnetic storms on July 19-20, 2013.
Composite imagery showing SDO’s AIA 193, combined AIA 304, 211 and 171, combined AIA 094, 335 and 193 and AIA 211 (Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams/TheWatchers)
Coronal holes are places in the sun’s upper atmosphere where the magnetic field opens up and allows solar wind to escape. A broad stream of solar wind flowing from this particular coronal hole should reach Earth in the next 24 hours.
Source and read more at : The Watchers