Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 28, 2013 at 04:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update February 1, 2013)] [Cycle 24 progress (last update February 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 3, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated February 3, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on February 27. Solar wind speed at SOHO ranged between 291 and 336 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 102.0 (decreasing 0.7 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.4). Three hour interval K indices: 11211001 (planetary), 12211211 (Boulder).

The background x-ray flux was at the class B2 level.

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11680 [S29E13] decayed slowly and quietly.
Region 11681 [N17E36] decayed slowly and quietly.
Region 11682 [S19W16] gained spots but is still magnetically fairly simple structured.
New region 11683 [S17E82] rotated into view.

Spotted regions not numbered by SWPC:
S2253 [N30W22] reemerged with penumbra spots.
S2259
[S13E24] decayed slowly and quietly.
New region S2261 [S10E50] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

February 25-27: No obviously Earth directed CMEs were observed in LASCO and 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 recurrent trans equatorial coronal hole (CH556) was in an Earth facing position on February 26-28. A northern hemisphere coronal hole (CH557) will rotate into a potentially geoeffective position on March 1.

Coronal hole map

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 February 28. Quiet to active conditions are possible on March 1-5 due to effects from CH556 and CH557.

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 2K resolution) Compare to the previous day's image. 0.5k image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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
11676 2013.02.16       S18W67           plage
11677 2013.02.16
2013.02.17
      S28W72          

plage

11679 2013.02.17       S10W62           plage
11682 2013.02.21
2013.02.25
13 33 19 S18W17 0110 DAI DAC area: 0250
S2248 2013.02.22       S18W33           plage
11680 2013.02.24
2013.02.25
4 6 3 S29E11 0010 BXO CRO area: 0025
11681 2013.02.24
2013.02.25
3 9 5 N17E33 0040 CSO CRO  
S2253 2013.02.24   2 1 N30W22 0006   AXX    
S2255 2013.02.25       S28E02           plage
S2257 2013.02.25       N03W38           plage
S2258 2013.02.25       S08W22           plage
S2259 2013.02.26   1   S13E24 0002   AXX  
S2260 2013.02.26       N15W31         plage
11683 2013.02.27 1 3 2 S17E79 0090 HSX DHO   area: 0380
S2261 2013.02.27   1   S10E50 0001   AXX    
Total spot count: 21 55 30  
Sunspot number: 61 125 80  (total spot count + 10 * number of spotted regions)
Weighted SN: 36 76 51  (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): 37 44 44 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 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)
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 (cycle max) 96.7 (cycle max) 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 65.5 (+2.1) 7.15
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
8.81
2012.03 114.7 64.3 66.8 (-0.1) 16.08
2012.04 113.0 55.2 64.6 (-2.2) 10.10
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.7 (-1.2) 13.90
2012.08 115.4 63.0 (58.6 projected, +0.9) 7.96
2012.09 122.9 61.4 (58.7 projected, +0.1) 8.07
2012.10 123.3 53.3 (58.1 projected, -0.6) 9.97
2012.11 121.3 61.4 (57.4 projected, -0.7) 7.08
2012.12 108.6 40.8 (56.7 projected, -0.7) 3.44
2013.01 127.1 62.9 (56.0 projected, -0.7) 4.69
2013.02 104.3 (1) 57.8 (2A) / 60.0 (2B) / 40.8 (2C) (55.0 projected, -1.0) (5.44)

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) Boulder SN current month average to date. 2C) STAR SDO 1K Wolf number 30 day average.
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.