Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 11, 2013 at 05:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update May 1, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 6, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated March 24, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on May 10. Solar wind speed at SOHO ranged between 412 and 461 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 124.8 (decreasing 0.3 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: 11111000 (planetary), 11222311 (Boulder).

The background x-ray flux was at the class B6 level.

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11734 [S18W76] was quiet and stable
Region 11736 [S07W82] rotated partly out of view and was mostly quiet.
Region 11738 [N17W28] decayed slowly and quietly.
Region 11739 [N12W23] developed slowly and quietly.
Region 11740 [S21W13] was quiet and stable.
Region 11741 [S22E10] added several penumbra spots.
Region 11742 [N29E37] was quiet and stable.
Region 11743 [N24E44] decayed slowly and quietly.
Region 11744 [N03E59] was mostly quiet and stable.
New region 11745 [N13E80] rotated into view with one large penumbra. Further M class flares are possible. C5+ flares: M3.9 at 00:57, M1.3 at 12:56 UTC.

Spotted regions not numbered by SWPC:
New region S2407 [S28E77] rotated into view early in the day.
New region S2408 [S04W01] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

May 8-10: 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 poorly defined trans equatorial coronal hole (CH569) was in an Earth facing position on May 9-10.

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 May 11. Quiet to unsettled is possible on May 12-13 du to weak coronal hole effects.

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
11734 2013.04.28
2013.04.29
2 3 2 S18W76 0310 HKX CKO

 

11736 2013.04.30
2013.05.01
10 4 3 S08W85 0240 DAI HAX

 

11737 2013.04.30
2013.05.03
      N16W63           plage
11738 2013.05.03 7 5 4 N17W33 0030 CAI HRX

location: N17W28

11739 2013.05.03 5 14 9 N12W25 0020 CAO CRO location: N11W11

area: 0040

11740 2013.05.03 4 6 2 S21W15 0010 BXO CRO

location: S21W13

S2397 2013.05.04       N11W38           plage
11741 2013.05.05
2013.05.06
2 18 6 S20E05 0010 BXOo BXI area: 0035

location: S22E10

11742 2013.05.07
2013.05.09
6 9 2 N30E36 0100 DAO DAO  
S2402 2013.05.07       S29W40           plage
S2403 2013.05.07       N07W40           plage
11743 2013.05.08
2013.05.09
5 8 2 N24E43 0020 CAO CRO  
11744 2013.05.08
2013.05.09
7 14 4 N04E56 0030 DAO EAO

location: N03E59

S2406 2013.05.08       N16E07           plage
11745 2013.05.10 1 5 2 N11E73 0120 HRX DHO   area: 0600

location: N13E80

S2407 2013.05.10   1 1 S28E77 0150   HSX    
S2408 2013.05.10   1   S04W01 0002   AXX    
Total spot count: 49 88 37  
Sunspot number: 149 208 147  (total spot count + 10 * number of spotted regions)
Weighted SN: 92 140 89  (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): 89 73 81 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)
2011.11 153.5 (cycle max) 96.7 (cycle max) 61.1 (+1.2) 5.55
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 58.1 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.0) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 (59.1 projected, +0.5) 7.08
2012.12 108.6 40.8 (58.4 projected, -0.7) 3.44
2013.01 127.1 62.9 (58.0 projected, -0.4) 4.69
2013.02 104.3 38.0 (58.2 projected, +0.5) 6.11
2013.03 111.3 57.9 (57.8 projected, -0.4) 10.56
2013.04 124.8 72.4 (57.4 projected, -0.4) 5.40
2013.05 137.5 (1) 42.5 (2A) / 131.7 (2B) / 71.3 (2C) (57.5 projected, +0.1) (8.13)

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.