Solar Terrestrial Activity Report

Last major update issued on May 31, 2011 at 04:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 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 May 27, 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 30. Solar wind speed ranged between 460 and 723 km/s under the influence of a high speed stream from CH451.

Solar flux measured at 20h UTC on 2.8 GHz was 111.9 (increasing 4.9 over the last solar rotation). The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.4). Three hour interval K indices: 32132223 (planetary), 22242222 (Boulder).

The background x-ray flux is at the class B4 level.

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

Region 11222 developed further and is rotating over the northwest limb.
Region 11224 decayed signigicantly and could soon loose all penumbra. Flare: C3.2 at 02:52 UTC.
Region 11225 was quiet and stable.
Region 11226 decayed slowly but could still produce C flares and minor M class flares. Flares: C3.5 at 05:49, C7.0 at 06:05 UTC.
Region 11227 is probably two regions as both the main trailing and leading penumbrae are the same polarity. What is now the trailing penumbra is probably the leading penumbra of a separate region (with a tiny trailing spot emerging). Flare: C2.8 at 11:01 UTC.
Region 11228 was quiet and stable.
New region 11229 emerged in the northeast quadrant on May 29 and was numbered the next day by NOAA/SWPC.

Spotted regions not numbered by NOAA/SWPC:
[S1041] rotated into view at the northeast quadrant on May 30. Location at midnight: N18E72.

Coronal mass ejections (CMEs)

May 28-30: 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 will rotate into an Earth facing position on May 30-31.

The darkest areas on the solar disk are likely coronal holes.

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 May 31 due to effects from CH451 and quiet on June 1. Effects 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
3 6 N16W83 0150 DSO DAI  
11219 2011.05.21     N15W55            
11223 2011.05.21
2011.05.26
    S17W36         plage
S1024 2011.05.24     N29W50           plage
S1026 2011.05.25     N10W21           plage
11225 2011.05.25
2011.05.27
1 2 N17E18 0040 HSX CSO  
S1028 2011.05.25     S22W45           plage
11224 2011.05.26
2011.05.27
9 19 N20W56 0140 DSO CAI area: 0060

location: N21W54

11226 2011.05.27 11 34 S21E42 0360 DKI DHC beta-gamma
S1033 2011.05.28     S18E09           plage
11228 2011.05.28
2011.05.29
1 3 N17E55 0110 HSX CSO

 

11227 2011.05.28
2011.05.29
6 13 S18E54 0170 DSI DSI

location: S20E54

S1037 2011.05.28     N00W24           plage
S1038 2011.05.28     N30W19           plage
11229 2011.05.29
2011.05.30
4 7 N16E38 0030 CAO CSO formerly region S1039
S1040 2011.05.29     N12W38         plage
S1041 2011.05.30   2 N18E72 0010   BXO   plage
Total spot count: 35 86  
Sunspot number: 105 166  

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 95.3 (1) 57.5 (2A) / 59.5 (2B) (44.1 predicted, +3.3) (9.04)

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.