Solar Terrestrial Activity Report

Last major update issued on June 1, 2011 at 04:35 UTC. Minor update added at 18:50 UTC,

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update June 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update June 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update June 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 1, 2011)]

[POES auroral activity level charts since October 2009 - updated June 1, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2108 [March-April 2011] - 2109 [April-May 2011]
[Solar polar fields vs solar cycles - updated May 26, 2011] NEW

Recent activity

The geomagnetic field was quiet to unsettled on May 31. Solar wind speed ranged between 551 and 615 km/s under the influence of a high speed stream from CH451.

Solar flux measured at 20h UTC on 2.8 GHz was 112.0 (increasing 6.0 over the last solar rotation). The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 13.4). Three hour interval K indices: 33332233 (planetary), 32443333 (Boulder).

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

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

Region 11224 decayed further losing most spots.
Region 11225 was quiet and stable.
Region 11226 decayed further and lost all penumbra on the trailing spots. The largest penumbra split into smaller penumbrae. There's only minor polarity intermixing. Flares: C1.7 at 05:53 UTC.
Region 11227 is probably two regions as both the trailing and leading penumbrae are the same polarity. Flare: C1.8 at 04:43 UTC.
Region 11228 developed slowly and quietly.
Region 11229 developed slowly and quietly.
New region 11230 rotated into view at the northeast limb on May 30 and was numbered the next day by NOAA/SWPC.

Spotted regions not numbered by NOAA/SWPC:
[S1042] rotated partly into view at the northeast limb on May 31. Location at midnight: N07E86.

Minor update added at 18:50 UTC on June 1: Region 11226 was the source of a C4.1 long duration event peaking at 17:08 UTC. This event was associated with a northwards fast moving wave and likely a CME. A CME from the current position of 11226 could easily be Earth directed and cause major geomagnetic storming.

Coronal mass ejections (CMEs)

May 29-31: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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

The southernmost extension of a large coronal hole (CH452) in the northern hemisphere was in an Earth facing position on May 30-31.

The above coronal hole map is based on a new method to detect coronal holes 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 to good.

Forecast

The geomagnetic field is expected to be quiet to unsettled on June 1 due to effects from CH451. A high speed stream from CH452 could reach Earth on June 2 or 3 and cause unsettled to minor storm conditions.

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
11222 2011.05.20
2011.05.25
1   N17W98 0030 AXX     rotated out of view
11219 2011.05.21     N15W69           plage
11223 2011.05.21
2011.05.26
    S17W50           plage
S1026 2011.05.25     N10W34           plage
11225 2011.05.25
2011.05.27
1 4 N16E04 0030 HSX CSO  
S1028 2011.05.25     S22W58           plage
11224 2011.05.26
2011.05.27
8 4 N21W68 0050 CSI BXO area: 0010
11226 2011.05.27 18 40 S22E27 0330 DKC CSI beta-gamma
S1033 2011.05.28     S18W04           plage
11228 2011.05.28
2011.05.29
8 15 N17E50 0110 CSO CSO

location: N16E45

11227 2011.05.28
2011.05.29
7 12 S18E40 0190 DSI CSO

beta-gamma

location: S20E40

S1037 2011.05.28     N00W37           plage
S1038 2011.05.28     N30W32           plage
11229 2011.05.29
2011.05.30
6 14 N16E24 0040 CSO CSO  
S1040 2011.05.29     N12W51           plage
11230 2011.05.30
2011.05.31
3 5 N19E58 0030 BXO BXO formerly region S1041

area: 0010

S1042 2011.05.31   1 N07E86 0050   HSX    
Total spot count: 52 95  
Sunspot number: 132 175  

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
2010.02 84.7 18.8 10.6 (+1.3) 4.15 / 4.61
2010.03 83.4 15.4 12.3 (+1.7) 4.58 / 4.65
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 (26.9 predicted, +3.7) 4.80 / 5.50
2010.12 84.2 14.4 (30.1 predicted, +3.2) 3.41 / 4.35
2011.01 83.6 19.1 (33.1 predicted, +3.0) 4.32 / 5.51
2011.02 94.6 29.4 (35.6 predicted, +2.5) 5.41 / 6.44
2011.03 115.0 56.2 (37.9 predicted, +2.3) 7.79
2011.04 112.6 54.4 (40.8 predicted, +2.9) 9.71
2011.05 95.8 (1) 61.8 (2A/2B) (44.1 predicted, +3.3) (9.18)

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.