Solar Terrestrial Activity Report

Last major update issued on August 1, 2011 at 04:20 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 since October 2009 - updated July 29, 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 July 31. Solar wind speed ranged between 506 and 652 km/s under the influence of a high speed stream from CH468.

Solar flux measured at 20h UTC on 2.8 GHz was 118.6 (increasing 33.6 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 32211223 (planetary), 33322333 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight UTC the visible solar disk had 5 spotted regions.

Region 11260 was quiet and stable.
Region 11261 has many spots with a high degree of polarity intermixing and several small magnetic delta structures. M class flares are possible. Flare:  C3.8 at 02:54 UTC.
Region 11263 increased in complexity due to the development of opposite polarity spots in the northern part of the trailing penumbra. This region could produce a major flare, maybe even an X class flare. Flares: C1.1 at 18:10, C1.4 at 18:50, C1.9 at 20:47, C1.0 at 23:40 UTC
Region 11265 was mostly unchanged. Flare:  C1.7 at 19:09 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S1136] reemerged with several spots on July 30 and decayed slowly on July 31. Note that for unknown reasons SWPC is now using region number 11264 for this region even if region 11264 is currently spotless and 7 degrees further south. The magnetic fields are clearly separate. Location at midnight: S26E10

Coronal mass ejections (CMEs)

July 29-31: 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 was in an Earth facing position 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 fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 1 due to effects from CH468. Quiet conditions are likely on August 2-3.

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
11260 2011.07.24 21 22 N19W22 0300 EHI EHO

beta-gamma

area: 0400

location: N18W24

11261 2011.07.25
2011.07.26
35 61 N16E05 0350 EKI EKC

gamma-delta

location: N15E07

S1136 2011.07.26   2 S26E10 0000   BXO  
S1137 2011.07.26     N07W48           plage
11264 2011.07.27
2011.07.28
2   S23E07 0010 BXO     spotless

location: S33E14

11265 2011.07.27
2011.07.30
3 6 N18W54 0010 BXO CRO area: 0020
S1142 2011.07.27     S17E06           plage
11263 2011.07.27
2011.07.28
17 25 N18E34 0460 DKI DKC

beta-gamma-delta

location: N17E35

area: 0700

S1145 2011.07.28     N30W59           plage
S1146 2011.07.29     S22W09           plage
S1147 2011.07.29     S24W43           plage
Total spot count: 78 116  
Sunspot number: 128 166  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 108 149  (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): 77 55  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 94.2 (1) 67.0 (2A) & (2B) (49.4 predicted, +4.1) (9.14)

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.