Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 9, 2012 at 04:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 5, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to active on May 8. Solar wind speed at SOHO ranged between 285 and 461 km/s. A high speed stream associated with CH515 became the dominant solar wind source after 18h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 122.8 (increasing 29.6 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.4). Three hour interval K indices: 23122224 (planetary), 12123323 (Boulder).

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

At midnight UTC the visible solar disk had 13 spotted active regions (in 2K resolution SDO images).

Region 11470 [S17W67] decayed slowly and quietly.
Region 11471 [S22W63] decayed slowly and quietly.
Region 11474 [N14W10] decayed slowly and quietly.
Region 11475 [N12W02] lost the southernmost spot and gained a spot in the northern part of the same polarity area.
Region 11476 [N10E33] has developed slowly with a strong magnetic delta structure forming in the southern part of the huge leading penumbra. Another strong delta with nearly no distance between opposite polarity umbrae is in a penumbra in the northern central part of the region. A major flare will become likely if the current development continues. Flares: M1.4/1F at 13:08 as well as a few C1 events.
New region 11477 [S22E74] rotated into view at the southeast limb on May 7 and was numbered the next day by SWPC.

Spotted active regions not numbered by NOAA/SWPC:
New region S1635 [S24E83] rotated into view at the southeast limb as a single symmetrical penumbra.
New region S1636 [S17E32] emerged with a tiny spot.
New region S1637 [N23W02] emerged with a single spot.
New region S1638 [S21W06] emerged with 2 spots.
New region S1639 [S16W18] emerged with a tiny spot.
New region S1640 [S16W33] emerged with a single spot.
New region S1641 [N11W27] emerged with a single spot.

Coronal mass ejections (CMEs)

May 6: No obviously Earth directed CMEs were observed in STEREO imagery.
May 7: The M1.9 event in region 11471 may have had a weak Earth directed component. The most interesting CME of the day was observed after a filament erupted in the southeast quadrant  beginning near 21:15 UTC. STEREO-B displays a CME late on May 7 and early on May 8 which could easily be Earth directed, neither STEREO-A nor LASCO imagery from the relevant time is currently available.
May 8: A filament eruption beginning at 09:45 UTC near AR 11474 across the central meridian was the source of a small CME observed in both STEREO-A and B imagery after 11h UTC. While most of the ejected material was over the northern limbs, it appears that a part of the CME is Earth directed.

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 recurrent trans equatorial coronal hole (CH515) was in an Earth facing position on May 5-7. Another recurrent trans equatorial coronal hole (CH516) will become Earth facing on May 9-10.

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 fair to good.


The geomagnetic field is expected to be unsettled to minor storm on May 9-10 due to a high speed stream from CH515 becoming quiet to active on May 11. quiet initially on May 8. The CME observed late on May 7 could reach Earth on May 10 and contribute to the ongoing disturbance. The CME observed on May 8 could reach Earth on May 11. Starting late on May 12 or early on May 13 a high speed stream from CH516 could cause quiet to active conditions until May 14.

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
11471 2012.04.27
3 7 1 S22W60 0120 CSO CSO

location: S22W63

11470 2012.04.27
2 1 1 S19W68 0030 CRO AXX location: S17W67
11472 2012.04.29       S28W80           plage

location: S30W71

11474 2012.05.01
1 2 1 N14W13 0010 AXX BXO location: N14W10
11475 2012.05.02   1   N05W05 0000   AXX location: N12W02
S1626 2012.05.02       S28W54           plage
11476 2012.05.04
33 78 47 N11E35 0940 FKC FKC beta-gamma-delta

area: 1400

location: N10E33

S1629 2012.05.04       S16W26           plage
S1630 2012.05.04       N27W43           plage
S1631 2012.05.04       S24E01           plage
S1633 2012.05.06       N12E12         plage
11477 2012.05.07
1 1 1 S22E73 0060 HSX HSX  
S1635 2012.05.08   1 1 S24E83 0090   HSX    
S1636 2012.05.08   1 1 S17E32 0000   AXX    
S1637 2012.05.08   1   N23W03 0000   AXX    
S1638 2012.05.08   2 1 S21W06 0000   BXO    
S1639 2012.05.08   1   S16W18 0000   AXX    
S1640 2012.05.08   1 1 S16W33 0000   AXX    
S1641 2012.05.08   1   N11W27 0000   AXX    
Total spot count: 40 98 55  
Sunspot number: 90 228 145  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 63 123 80  (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): 54 80 80 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
2011.02 94.6 29.4 33.4 (+2.4)  6.44
2011.03 115.0 56.2 36.9 (+3.5) 8.18
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 (61.2 projected, +1.3) 5.55
2011.12 141.3 73.0 (63.9 projected, +2.7) 3.78
2012.01 132.5 58.3 (67.4 projected, +3.5) 7.15
2012.02 106.5 33.1 (71.4 projected, +4.0) 8.81
2012.03 114.7 64.2 (73.5 projected, +2.1) 16.08
2012.04 113.0 55.2 (74.5 projected, +1.0) 10.10
2012.05 116.4 (1) 25.1 (2A) / 97.1 (2B) (75.8 projected, +1.3) (6.19)

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.