Solar Terrestrial Activity Report

Last major update issued on August 5, 2011 at 06:25 UTC. Minor update posted at 21:50 UTC

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update August 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 2, 2011)]

[POES auroral activity level since October 2009 - updated August 5, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2110 [May-June 2011] - 2111 [June-July 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on August 4. Solar wind speed ranged between 305 and 481 km/s. A weak solar wind shock was recorded at SOHO at 21:11 UTC, most likely the arrival of the CME observed on August 2.

Solar flux measured at 20h UTC on 2.8 GHz was 116.3 (increasing 30.5 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 10001213 (planetary), 10101213 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 6 spotted regions.

Region 11260 decayed slowly and quietly. The region will rotate over the northwest limb today.
Region 11261 decayed quickly following the major M9 event early in the day. The flare caused a total disintegration of the magnetic delta structure where the flare had its origin. While another M class flare is still possible, the region appears to have lost most of its flare potential. There's no longer penumbra on the positive polarity spots. Flares:  C1.7 at 01:09, C3.2 at 02:23, major M9.3/2B at 03:57 (associated with a fast full halo CME), C3.5 at 08:05, C2.5 at 09:00, C1.6 at 10:12, C1.0 at 14:17, C3.2 at 21:15 UTC
Region 11263 did not display any major changes and remains capable of producing a major flare. Flares: C2.1 at 13:07, C1.8 at 14:38 UTC
New region 11266 emerged in the northeast quadrant on August 2 and was numbered 2 days later by SWPC.

Spotted regions not numbered by NOAA/SWPC:
[S1153] emerged in the southeast quadrant on August 4. Location at midnight: S17E41
[S1154] emerged on August 4 close to the trailing spots of region 11263. Location at midnight: N17W11

Minor update added at 21:50 UTC on August 5: A solar wind shock was observed at ACE near 17:20 UTC, likely the arrival of the CME observed on August 3. Initially this seemed like a moderate storm, however, both solar wind speed and the total field of the IMF increased quickly an hour later. It is not yet certain if this change in solar wind parameters were caused be the CME which arrived a little earlier or by the larger and faster CME observed on August 4. Anyway, the IMF has been generally strongly to very strongly southwards after 18:30 UTC. This caused very severe geomagnetic storm conditions after 20h UTC with the planetary A index reaching 207 (= KP 8) for the 18-21h UTC intervals. Boulder (according to USAF) recorded K 9 for the 20-21h interval but strangely SWPC settled on K 5 for the 18-21h interval.

Coronal mass ejections (CMEs)

August 2: An Earth directed CME was observed in LASCO and STEREO images after the LDE in region 11261 peaking at 06:19 UTC.
August 3: A full halo CME was observed in LASCO and STEREO images following the M6 event in region 11261 at 13:48 UTC. The CME could reach Earth on August 5.
August 4: A full halo CME was observed in LASCO images after the M9 event in region 11261 at 03:57 UTC. This is a fast CME and could reach Earth late on August 5 or early on August 6.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH469) will be in an Earth facing position on August 3-4. A poorly defined coronal hole (CH470) was Earth facing on August 2-3.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.


Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor to fair.


The geomagnetic field is expected to be quiet to minor storm on August 5 and quiet to major storm on August 6 due to CME effects. A high speed stream from CH469 could contribute to the disturbance from sometime on August 6. Quiet to active conditions are likely on August 7 becoming quiet to unsettled on August 8.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

(Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with polarity overlay
11260 2011.07.24 2 3 N19W78 0260 DHO CSO

location: N18W80

area: 0230

11261 2011.07.25
19 21 N15W49 0380 DAI CSI


location: N15W50

area: 0160

S1136 2011.07.26     S24W43           plage
11264 2011.07.27


location: S33W38

S1142 2011.07.27     S17W46           plage
11263 2011.07.27
17 24 N17W18 0720 EKC DHC


location: N17W17

area: 0600

11266 2011.08.02
3 7 N18E38 0020 CRO BXO formerly region S1148

location: N18E40

S1151 2011.08.03     S19W66         plage
S1152 2011.08.03     S07E53         plage
S1153 2011.08.04   6 S17E41 0010   BXO    
S1154 2011.08.04   4 N17W11 0010   BXO    
Total spot count: 41 65  
Sunspot number: 81 125  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 69 85  (Sum of raw spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 49 41  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
2010.05 73.8 8.7 15.5 (+1.5) 9.18 / 8.15
2010.06 72.5 13.6 16.4 (+0.9) 8.17 / 6.85
2010.07 79.8 16.1 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 (33.6 predicted, +2.6) 5.41 / 6.44
2011.03 115.0 56.2 (36.6 predicted, +3.0) 7.79 / 8.18
2011.04 112.6 54.4 (39.4 predicted, +2.8) 9.71 / 8.83
2011.05 95.8 41.6 (42.7 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (46.5 predicted, +3.8) 8.96
2011.07 94.2 43.9 (50.6 predicted, +4.1) 9.14
2011.08 120.7 (1) 12.1 (2A) / 93.8 (2B) (54.8 predicted, +4.2) (4.78)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.