Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 27, 2012 at 05:45 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 26, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on May 26. Solar wind speed at SOHO ranged between 347 and 460 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 110.0 (decreasing 6.0 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 31111000 (planetary), 21121211 (Boulder).

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

At midnight UTC the visible solar disk had 15 spotted active regions (in 2K resolution SDO images).

Region 11486 [N17W38] was quiet and stable.
Region 11488 [N11E02] was quiet and stable.
Region 11489 [S23E03] was quiet and stable.
Region 11490 [S12E32] added a few spots and has minor polarity intermixing.
Region 11491 [N23W42] was mostly quiet and stable.
Region 11492 [S14E60] produced a couple of minor C class events and has M class flare potential.

Spotted active regions not numbered by NOAA/SWPC:
S1671
[S19W11] was quiet and stable.
S1682 [S22E62] was quiet and stable.
S1684 [N21E06] was quet and stable.
New region S1686 [S18E13] emerged with small spots.
New region S1687 [S28E18] emerged with tiny spots.
New region S1688 [N31W08] emerged with tiny spots in an old plage area.
New region S1689 [N17W65] emerged with a single spot.
New region S1690 [S07E47] emerged with reversed polarities.
New region S1691 [S26E40] emerged with a tiny spot.

The most significant event of the day occurred at 20:45 UTC in AR 11476 several days behind the west limb. This major event was associated with a full halo CME and a noticable increase in the above 10 MeV proton flux.

Coronal mass ejections (CMEs)

May 24-26: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.

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 poorly defined southern hemisphere coronal hole (CH519) was Earth facing on May 23-24.

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.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 27-28 due to possible weak effects from CH519 and quiet on May 28-29.

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
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
S1659 2012.05.15       N14W49           plage
11486 2012.05.17
2012.05.18
1 5 3 N22W33 0090 CSO CSO area: 0220

location: N17W38

Maybe SWPC used a trainee to prepare their SRS product? Location far off target for several ARs. Classification CSO impossible with just one spot

S1667 2012.05.19       N04W36           plage
11489 2012.05.21
2012.05.22
  4 2 S30W02 0000   AXX location: S23E03
S1671 2012.05.21   4   S19W11 0000   BXO  
11488 2012.05.21
2012.05.22
6 22 9 N12W00 0060 DSO BXI location: N11E02

area: 0020

S1674 2012.05.22       S21E02           plage
11490 2012.05.23
2012.05.24
4 23 10 S26E15 0040 DSO DRI beta-gamma

location: S12E32

area: 0060

S1676 2012.05.23       S10W05           plage
S1677 2012.05.23       N06W29           plage
11491 2012.05.23
2012.05.25
4 13 6 N27W38 0060 DSO DRI  
S1679 2012.05.23       N12W44           plage
S1680 2012.05.24       N12W29           plage
11492 2012.05.24
2012.05.25
5 16 11 S40E31 0160 DSO DKO

area: 0370

location: S14E60

S1682 2012.05.25   1   S22E62 0000   AXX  
S1683 2012.05.25       N01E17         plage
S1684 2012.05.25   2   N21E06 0000   AXX  
S1685 2012.05.25       S12W30         plage
S1686 2012.05.26   2 1 S18E13 0010   AXX    
S1687 2012.05.26   2 1 S28E18 0000   BXO    
S1688 2012.05.26   2 1 N31W08 0000   AXX    
S1689 2012.05.26   1   N17W65 0000   AXX    
S1690 2012.05.26   1   S07E47 0000   AXX    
S1691 2012.05.26   1   S26E40 0000   AXX    
Total spot count: 20 99 44  
Sunspot number: 70 249 134  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 45 120 65  (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): 42 87 74 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
(3)
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
2012.05 123.5 (1) 86.4 (2A) / 103.0 (2B) (75.8 projected, +1.3) (8.90)

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.