Solar Terrestrial Activity Report

Activity chart

Last major update issued on July 22, 2012 at 05:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update June 2, 2012)] [Cycle 24 progress NEW]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update June 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update June 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update July 1, 2012)]

[POES auroral activity level since October 2009 - updated July 17, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on July 21. Solar wind speed at SOHO ranged between 391 and 507 km/s. What was probably a weak solar wind shock was observed at SOHO at 15:24 UTC (and by ACE at about the same time). The interplanetary magnetic field was northwards afterwards and only a minor increase in geomagnetic activity was observed.

Solar flux measured at 20h UTC on 2.8 GHz was 89.9 (increasing 4.6 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 32211332 (planetary), 32322432 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight UTC the visible solar disk had 4 spotted active regions (in 2K resolution SDO images).

Region 11525 [S20W03] was quiet and stable.
Region 11526 [S18E55] was mostly quiet and stable producing a single C flare late in the day.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
New region S1810 [N19W59] emerged with small spots.
New region S1809 [S11E22] emerged with a tiny spot.

Several active regions behind the northeast and southeast limbs will rotate into view over the next 2-3 days.

Coronal mass ejections (CMEs)

July 20-21: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
July 19: While the core of the full halo CME observed after the M7.7 event in AR 11520 won't reach Earth, there's at least a 50% chance of a flank impact on July 22.

Coronal holes

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

A coronal hole (CH524) in the southern hemisphere was in an Earth facing position on July 19-20, but could be too far to the south to become geoeffective. A recurrent trans equatorial coronal hole (CH525) could rotate into an Earth facing position on July 25-27. CH525 appears to have become smaller over the last solar rotation.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs 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 unsettled on July 22-24. CME effects are possible on July 22 and could cause an increase to active levels. Additionally on July 22-23 there's a chance of weak effects from CH524.

Coronal holes (1) Coronal mass ejection (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 magnetic polarity overlay
2K 1K
11523 2012.07.11
1     S27W87 0000 AXX    

rotated out of view

S1797 2012.07.14       N09W45           plage
11524 2012.07.15
3     S17W01 0010 AXX     spotless
11525 2012.07.16
3 15 9 S20W05 0040 CSO CAO

area: 0080

S1801 2012.07.16       S15W54           plage
S1803 2012.07.17       N10W57           plage
S1804 2012.07.18       S33W05           plage
11526 2012.07.19
3 5 2 S18E52 0010 BXO BXO  
S1806 2012.07.19       N16E12         plage
S1807 2012.07.19       S01W14           plage
S1808 2012.07.20       S25E06         plage
S1809 2012.07.20       S24W16         plage
S1810 2012.07.21   4 1 N19W59 0000   BXO    
S1811 2012.07.21   1   S11E22 0000   AXX    
Total spot count: 10 25 12  
Sunspot number: 50 65 42  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 15 30 17  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 30 23 23 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

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
2011.04 112.6 54.4 41.8 (+4.9) 8.83
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 (65.0 projected, +1.6) 7.15
2012.02 106.5 33.1 (66.5 projected, +1.5) 8.81
2012.03 114.7 64.2 (67.2 projected, +0.7) 16.08
2012.04 113.0 55.2 (66.5 projected, -0.7) 10.10
2012.05 121.5 69.0 (64.8 projected, -1.7) 7.06
2012.06 119.6 64.5 (64.0 projected, -0.8) 10.08
2012.07 141.9 (1) 72.2 (2A) / 112.0 (2B) (65.0 projected, +1.0) (19.43)

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 quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC 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.