Solar Terrestrial Activity Report

Last major update issued on March 27, 2011 at 06:05 UTC. Minor update posted at 11:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2011)]

[POES auroral activity level charts since October 2009 - updated March 23, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011] NEW

Recent activity

The geomagnetic field was very quiet on March 26. Solar wind speed ranged between 350-431 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 114.5 (increasing 24.1 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 00012111 (planetary), 00112211 (Boulder).

The background x-ray flux is at the class B5 level. A long duration C2 (estimated) event peaked in the morning during a GOES-15 data dropout. This event was associated with a large CME from a source behind the east limb.

At midnight UTC the visible solar disk had 7 spotted regions.

Region 11176 added quite a few tiny spots in the large trailing polarity area. At midnight the westernmost spot was at E07 while the easternmost spot was at E37. It is rare that a region spans 30 degrees longitudinally. There's a weak magnetic delta structure in the southern central part of the region. M class flaring is likely Flare: C1.0 at 00:58 UTC.
Region 11177 was quiet and stable.
Region 11178 developed during the first half of the day adding penumbra on both polarities, slow decay was observed later in the day.
Region 11180 added a few small trailing spots.
Region 11181 was quiet and stable.

Spotted regions not numbered by NOAA/SWPC:
[S921] became visible at the northeast limb before noon on March 26. Early on March 27 trailing spots are becoming visible and the classification is changing to EAO. Location at midnight: N15E77
[S922] tiny spots emerged late on March 26. Location at midnight: N23E24.

Minor update added at 11:20 UTC on March 27: Not much activity of interest during the first half of the day. Regions S915 and S919 have reemerged with spots while region S921 has rotated fully into view and currently has an EAI classification. Region 11176 could be splitting into two regions with the leading penumbra and some nearby opposite polarity spots becoming a new region. The latest STAR CHARMAP.

Coronal mass ejections (CMEs)

March 25-26: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
March 24: A small partial halo CME was observed in association with an M1 flare in region 11176.

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

No obvious coronal holes are currently in or near Earth facing positions.

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

Forecast

The geomagnetic field is expected to be quiet on March 27 and 29. On March 28 there's a chance of unsettled and active intervals if the CME observed on March 24 reaches Earth.

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
11176 2011.03.21 28 66 S16E16 0420 FKI FKI beta-gamma-delta
11179 2011.03.21
2011.03.24
2   N08W61 0010 BXO     plage
11177 2011.03.21
2011.03.23
5 14 N20E11 0030 CRO BXI location: N20E14
S915 2011.03.22     S15W49           plage
11178 2011.03.24 7 16 S15E43 0130 DAI DAO

 

11181 2011.03.24
2011.03.25
1 1 S25E55 0010 AXX HRX location: S27E57
11180 2011.03.24
2011.03.25
1 5 N25E53 0070 HSX CSO

location: N24E55

S919 2011.03.24     N13E16           plage
S920 2011.03.25     S24E42         plage
S921 2011.03.26   2 N15E77 0050   HSX    
S922 2011.03.26   2 N23E24 0000   BXO    
Total spot count: 44 106  
Sunspot number: 104 176  

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
2009.12 76.7 10.8 8.3 (+0.7) 1.41 / 1.92
2010.01 81.1 13.2 9.3 (+1.0) 2.93 / 3.07
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 16.8 (+0.4) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.6) 8.49 / 7.77
2010.09 81.1 25.2 (19.1 predicted, +1.7) 5.33 / 5.45
2010.10 81.6 23.5 (21.7 predicted, +2.6) 6.07 / 6.27
2010.11 82.5 21.6 (24.5 predicted, +2.8) 4.80 / 5.50
2010.12 84.2 14.5 (26.9 predicted, +2.4) 3.41 / 4.35
2011.01 83.6 19.1 (29.0 predicted, +2.1) 4.32
2011.02 94.6 29.4 (31.1 predicted, +2.1) 5.41
2011.03 114.7 (1) 64.6 (2A) / 77.0 (2B) (33.0 predicted, +1.9) (8.63)

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.