Solar Terrestrial Activity Report

Last major update issued on July 27, 2011 at 06:10 UTC. Minor update posted at 16:20 UTC

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

[POES auroral activity level charts since October 2009 - updated July 26, 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 on July 26. Solar wind speed ranged between 426 and 562 km/s under the decreasing influence of a high speed stream associated with CH467.

Solar flux measured at 20h UTC on 2.8 GHz was 93.5 (increasing 6.2 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.1). Three hour interval K indices: 22211111 (planetary), 22212111 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight UTC the visible solar disk had 8 spotted regions.

Region 11259 was quiet and stable.
Region 11260 developed slowly and has a minor magnetic delta structure in a central penumbra. Further C class flaring is likely. Flares: C1.2 at 03:39 and C3.8 at 22:41 UTC.
New region 11261 rotated partly into view at the nortrheast limb on July 25 and was numbered the next day by NOAA/SWPC. This is a complex and compact region which has M class flare potential. Two magnetic delta structures are evident.

Spotted regions not numbered by NOAA/SWPC:
[S1131] reemerged with a tiny spot on July 26. Location at midnight: S16W06
[S1133] emerged in the northeast quadrant on July 24 and has since been developing slowly. Polarities are mixed. Location at midnight: N17W23
[S1135] rotated into view at the southeast limb on July 26. Location at midnight: S23E75
[S1136] rotated into view at the southeast limb on July 26. Location at midnight: S28E70
[S1137] emerged in the northeast quadrant on July 26. Location at midnight: N07E17

Minor update added at 16:20 UTC on July 27: Region 11260 produced an M1.1 flare at 16:07 UTC. Several new regions have emerged today and there is a larger region about to rotate into view at the northeast limb. The latest high resolution CHARMAP.

Coronal mass ejections (CMEs)

July 24-26: No obviously earth directed CMEs were observed.

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 well defined recurrent coronal hole (CH468) in the northern hemisphere will rotate into an Earth facing position on July 26-27. CH468 may be too far to the north to cause a geomagnetic disturbance. A poorly defined trans equatorial coronal hole will be Earth facing on July 26-27.

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.

Propagation

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.

Forecast

The geomagnetic field is expected to be quiet on July 27-28. Late on July 28 or early on July 29 effects from CH468 are possible with a chance of unsettled and active intervals. A trans equatorial coronal hole could contribute to the disturbance.

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
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
11259 2011.07.17
2011.07.18
  1 N25W36 0000   AXX

location: N23W37

S1126 2011.07.21     N23W59           plage
S1127 2011.07.22     N05W03         plage
S1129 2011.07.23     N11W07           plage
S1130 2011.07.23     N27W13           plage
S1131 2011.07.23   1 S16W06 0000   AXX    
S1132 2011.07.23     S17W21           plage
11260 2011.07.24 8 26 N20E45 0120 DAO DSI beta-gamma-delta

location: N18E46

S1133 2011.07.24   9 N17W23 0010   CRO beta-gamma
11261 2011.07.25
2011.07.26
2 18 N16W74 0200 DHO DKC beta-gamma-delta

formerly region S1134

area: 0450

location: N15E76

S1135 2011.07.26   1 S23E75 0000   AXX    
S1136 2011.07.26   1 S28E70 0000   AXX    
S1137 2011.07.26   3 N07E17 0000   AXX    
Total spot count: 10 60  
Sunspot number: 30 140  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 25 78  (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): 18 46  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
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.04 75.9 8.0 14.0 (+1.7) 10.22 / 10.24
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 (30.6 predicted, +1.8) 4.32 / 5.51
2011.02 94.6 29.4 (32.6 predicted, +2.0) 5.41 / 6.44
2011.03 115.0 56.2 (35.2 predicted, +2.6) 7.79 / 8.18
2011.04 112.6 54.4 (38.1 predicted, +2.9) 9.71 / 8.83
2011.05 95.8 41.6 (41.4 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (45.2 predicted, +3.8) 8.96
2011.07 91.1 (1) 52.4 (2A) / 62.4 (2B) (49.4 predicted, +4.1) (9.50)

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.