Solar Terrestrial Activity Report

Last major update issued on July 24, 2011 at 06:05 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 19, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2110 [May-June 2011] - 2111 [June-July 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on July 23. Solar wind speed ranged between 460 and 588 km/s under the influence of a high speed stream from CH466. The stream appeared to be ending near 16h UTC as SOHO observed a significant decrease in solar wind speed then.

Solar flux measured at 20h UTC on 2.8 GHz was 88.2 (decreasing 1.9 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.3). Three hour interval K indices: 33221122 (planetary), 33332112 (Boulder).

The background x-ray flux is at the class B1 level.

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

Region 11251 was quiet and stable. The region is rotating out of view at the northwest limb.
Region 11254 decayed quickly losing all penumbra.
Region 11259 decayed and was quiet.

Spotted regions not numbered by NOAA/SWPC:
[S1127] emerged in the northeast quadrant on July 22. Location at midnight: N05E37
[S1129] emerged in the northeast quadrant on July 23. Location at midnight: N11E33
[S1130] emerged in the northeast quadrant on July 23. Location at midnight: N28E25
[S1131] emerged in the southeast quadrant on July 23. Location at midnight: S17E34
[S1132] emerged in the southeast quadrant on July 23. Location at midnight: S17E18

Coronal mass ejections (CMEs)

July 21-23: 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 small trans equatorial coronal hole was observed on July 21-22 and rotated to an Earth facing position late on July 22. However, this coronal hole closed while Earth facing. Minor geomagnetic effects are possible on July 26. A well defined coronal hole has rotated into view in the northeast quadrant. It currently appears to be too far to the north to cause a geomagnetic disturbance.

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 fair.

Forecast

The geomagnetic field is expected to be quiet on July 24-26.

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
11251 2011.07.10
2011.07.11
1 1 N17W88 0060 HAX HSX

location: N18W85

11255 2011.07.12
2011.07.14
    N18W76           plage
11252 2011.07.12
2011.07.13
    N25W64          

plage

11254 2011.07.13
2011.07.14
7 9 S23W54 0060 CAO BXO

location: S23W53

area: 0010

11256 2011.07.14
2011.07.15
    N10W77          

plage

S1121 2011.07.16     N18W47           plage
11259 2011.07.17
2011.07.18
3 9 N25E02 0040 CAO CRO

location: N23E04

area: 0010

S1123 2011.07.17     N10W37           plage
S1125 2011.07.19     S17W40           plage
S1126 2011.07.21     N23W20           plage
S1127 2011.07.22   4 N05E37 0000   BXO  
S1128 2011.07.22     N07W40         plage
S1129 2011.07.23   2 N11E33 0000   BXO    
S1130 2011.07.23   3 N28E25 0010   BXO    
S1131 2011.07.23   1 S17E34 0000   AXX    
S1132 2011.07.23   1 S17E18 0000   AXX    
Total spot count: 11 30  
Sunspot number: 41 110  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 26 38  (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): 25 36  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 91.4 (1) 48.6 (2A) / 65.6 (2B) (49.4 predicted, +4.1) (9.81)

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.