Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 2, 2013 at 05:00 UTC.

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

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated July 28, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on August 1. Solar wind speed at SOHO ranged between 286 and 374 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 112.1 (decreasing 28.7 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 21111201 (planetary), 12012211 (Boulder).

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

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

Region 11801 [N19W48] was quiet and stable.
Region 11806 [S15W05] developed as new flux emerged.
Region 11807 [N28W56] decayed slowly and quietly.
Region 11808 [N14E14] decayed slowly and quietly.
Region 11809 [N12E54] decayed slightly and was quiet.
Region 11810 [S26E58] was quiet and stable.
New region 11811 [N06E27] emerged on July 31 and was numbered by SWPC the next day as the region began to decay.

Spotted regions not numbered by SWPC:
S2570 [S13W47] reemerged with penumbra spots.
S2574 [S09E17] developed slowly and quietly.
S2578 [S17W24] reemerged with penumbra spots.
New region S2583 [N07E21] emerged with several spots to the west of AR 11811.
New region S2584 [S15E15] emerged with a few spots.

Coronal mass ejections (CMEs)

July 30 - August 1: 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 northern hemisphere coronal hole (CH577) rotated across the central meridian on July 31-August 1 and could become marginally geoeffective.

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 August 2. On August 3-4 there's a chance of unsettled and active intervals due to effects from CH577.

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
11801 2013.07.22
2013.07.23
1 1 1 N20W50 0060 HSX HSX  
S2570 2013.07.25   2   S13W47 0006   BXO    
11806 2013.07.26
2013.07.27
7 28 10 S15W05 0030 DAO DAI area: 0100
S2573 2013.07.27       S18W59           plage
S2574 2013.07.28   18 3 S09E17 0028   BXO  
11807 2013.07.28
2013.07.29
3 5 2 N28W56 0020 CRO BXO  
S2577 2013.07.28       S23W00           plage
11808 2013.07.29 1 8 1 N15E14 0060 HSX CSO area: 0110
11809 2013.07.30 3 10 5 N12E52 0160 DSO DAO

area: 0230

S2578 2013.07.30   2   S17W24 0003   BXO    
S2579 2013.07.30       N21W17           plage
11810 2013.07.31 1 3 1 S26E59 0040 HSX HSX  
S2580 2013.07.31       S13E40         plage
S2581 2013.07.31       S11E54         plage
11811 2013.07.31
2013.08.01
2 6 3 N06E27 0010 CRO BXO  
S2583 2013.08.01   9 4 N07E21 0025   DRO    
S2584 2013.08.01   4 1 S15E15 0010   BXO    
Total spot count: 18 96 31  
Sunspot number: 88 216 131  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 124 59  (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): 53 76 72 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 peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
possible cycle 24 max
8.81
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 57.8 (-1.1) 13.90
2012.08 115.4 63.0 58.2 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.1) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 38.0 (57.8 projected, -0.9) 6.11
2013.03 111.3 57.9 (57.3 projected, -0.5) 10.56
2013.04 124.8 72.4 (57.3 projected, 0.0) 5.40
2013.05 131.4 78.7 (57.3 projected, 0.0) 9.73
2013.06 110.1 52.5 (57.6 projected, +0.3) 12.60
2013.07 115.5 57.0 (57.7 projected, +0.1) 9.33
2013.08 112.1 (1) 2.8 (2A) / 88.0 (2B) / 55.2 (2C) (57.6 projected, -0.1) (4.3)

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 the 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.