How the Sun spent its time in August 2011: an overview
posted: Sept 6, 2011
Solar Activity
The Sun is shifting to an even higher activity level compared to the previous month. The higher values of the International Sunspot Number and the 10cm flux translated into a series of events: a sequel of Earth-directed CME's and flares, the up to now strongest flare of the current cycle and a proton event.
The Sun had two periods with remarkable strong solar activity during the first part of the month, from Aug 2 until Aug 4 and from Aug 8 to Aug 9.
During the first period, a sequence of 3 M-flares and associated CME's was spread over 3 days. Each flare was stronger then the previous one. The same holds for the plasma clouds: the speed of each CME was estimated to be faster then the previous one.
Read more in the weekly bulletin

The flare of the second period with strong solar activity was press-worthy: the X6.9 flare in the morning of Aug 09 is up to now the largest flare of the present solar cycle. The source region was located at N18W80. The event triggered a proton storm but the associated CME could not reach the Earth.
More to read in the weekly bulletin or the news item.
Further flaring in August was situated in the C-level.
5 coronal holes (CH) populated the solar disk in August. We list them and indicate when the first part touches the central meridian.
Aug 04, small southern CH Aug 11, long stretched equatorial CH Aug 17, small southern CH, between 20S and 40S, 20 wide, Aug 19, near the solar equator, diagonal between 10S and 20N, Aug 24, main part between 20N and 40N with a small extension towards the north pole.

Geomagnetic Activity
The event of August occurred on Aug 5-6 when a CME cannibal arrived: the geomagnetic disturbance was the strongest measured this solar cycle.
The consequences for Earth of the solar activity were the strongest on Aug 5 and 6 when two CME's bundled together and arrived as one. Aurora was seen in places with latitudes comparable to Belgium.
Read more in the weekly bulletin

The plasma eruption linked with the X6.9 flare did not blow over our magnetosphere, there was not even a glancing blow. The source region was located near the west limb.
The solar wind emanating from the Aug 04 CH peaked on Aug 8-9. The arrival of the co-rotating interaction region is masqueraded by the arrival on Aug 5 and aftermath of the cannibal CME. The geomagnetic conditions became only unsettled.
The solar wind speed curve profile from late Aug 13 until Aug 16-17 matches the length of the Aug 11 CH. The planetary geomagnetic conditions became unsettled, we had one period of active conditions early Aug 15.
The solar wind emanating from the Aug 17 CH could hardly overrun the background solar wind, while the solar wind of the Aug 19 CH left a clear ACE signature from Aug 23 until Aug 25. The arrival of the co-rotating interaction region linked with this hole is however vague, but the magnetically compressed region followed by a fast solar wind is easily recognised (a bump in the curve). The planetary geomagnetic response was limited: unsettled conditions and one active period late Aug 23.
The influence of the Aug 24 CH was also limited: unsettled conditions on Aug 29.