Solar Terrestrial Activity Report

Last major update issued on March 25, 2011 at 04:15 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 quiet on March 24. Solar wind speed ranged between 405-482 km/s under the influence of a weak coronal hole stream from CH441/442.

Solar flux measured at 20h UTC on 2.8 GHz was 107.6 (increasing 19.4 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6). Three hour interval K indices: 10112111 (planetary), 10211111 (Boulder).

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

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

Region 11176 developed as quite a few new spots emerged, there's a lot of polarity intermixing. A major flare is possible. Flares: M1.0 at 12:07, C1.6 at 15:37, C9.1 at 17:06, C1.3 at 18:57, C1.4 at 20:57 UTC.
Region 11177 was quiet and stable.
New region 11178 emerged near the southeast limb early in the day.
New region 11179 emerged in the northeast quadrant on March 21 and was detected by NOAA/SWPC 3 days later.

Spotted regions not numbered by NOAA/SWPC:
[S917] rotated into view at the southeast limb on March 24. Location at midnight: S26E81
[S918] rotated into view at the northeast limb on March 24. Location at midnight: N23E79
[S919] emerged in the northeast quadrant on March 24. Location at midnight: N13E42

Coronal mass ejections (CMEs)

March 22-24: 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

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

Forecast

The geomagnetic field is expected to be quiet on March 25-27.

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
11173 2011.03.15
2011.03.16
    S29W66           plage
S911 2011.03.18     S22W42           plage
11176 2011.03.21 25 49 S16E44 0380 EKI EKI gamma
11179 2011.03.21
2011.03.24
4 6 N09W32 0010 BXO BXO formerly region S912
11177 2011.03.21
2011.03.23
3 8 N21E37 0010 BXO BXO location: N20E39
S915 2011.03.22     S15W23           plage
11178 2011.03.24 1 5 S13E68 0000 AXX CRO   location: S16E69

area: 0020

S917 2011.03.24   1 S26E81 0010   HRX    
S918 2011.03.24   1 N23E79 0030   HSX    
S919 2011.03.24   2 N13E42 0000   BXO    
Total spot count: 33 72  
Sunspot number: 73 142  

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
2011.03 114.8 (1) 57.9 (2A) / 74.8 (2B) (33.0 predicted, +1.9) (9.16)

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.