Solar Terrestrial Activity Report

Activity chart

Last major update issued on July 31, 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 July 1, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update July 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update July 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 July 30. Solar wind speed at SOHO ranged between 334 and 407 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 113.1 (decreasing 11.4 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.3). Three hour interval K indices: 11112112 (planetary), 12222212 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11801 [N19W22] was quiet and stable.
Region 11805 [S06W71] was quiet and stable.
Region 11806 [S15E24] was quiet and stable.
Region 11807 [N28W29] was quiet and stable.
Region 11808 [N14E41] matured and was quiet.
New region 11809 [N13E79] rotated into view.

Spotted regions not numbered by SWPC:
S2570 [S13W18] was quiet and stable.
S2574 [S09E45] was quiet and stable.
New region S2578 [S18W02] emerged with penumbra spots.
New region S2579 [N21E09] emerged with a penumbra spot near the edge of CH577.

Coronal mass ejections (CMEs)

July 28-30: 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) could rotate into a marginally geoeffective position on July 31-August 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 poor. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be quiet on July 31 and August 1-2. 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
11800 2013.07.17
2013.07.18
1     S07W95 0030 HSX    

rotated out of view

11803 2013.07.18
2013.07.23
      S09W87           plage
11801 2013.07.22
2013.07.23
1 3 1 N19W23 0060 HSX CSO  
S2567 2013.07.23       N22W59           plage
11805 2013.07.24
2013.07.25
9 8 4 S07W71 0150 DAO DAO

area: 0200

S2570 2013.07.25   4   S13W18 0008   BXO  
11806 2013.07.26
2013.07.27
11 17 7 S15E20 0060 DAO DRI location: S15E24
S2573 2013.07.27       S18W33         plage
S2574 2013.07.28   8 1 S09E45 0014   BXO  
11807 2013.07.28
2013.07.29
6 17 7 N28W31 0050 CAO DRI  
S2576 2013.07.28       N35W36         plage
S2577 2013.07.28       S23E26           plage
11808 2013.07.29 6 9 3 N15E41 0080 DSO CAO  
11809 2013.07.30 1 3 2 N14E79 0060 HSX CAO   area: 0130
S2578 2013.07.30   2 1 S18W02 0006   AXX    
S2579 2013.07.30   1   N21E09 0002   AXX    
Total spot count: 35 72 26  
Sunspot number: 105 172 106  (total spot count + 10 * number of spotted regions)
Weighted SN: 65 98 52  (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): 63 60 58 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
2012.04 113.0 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 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 (58.7 projected, -0.9) 4.69
2013.02 104.3 38.0 (58.3 projected, -0.4) 6.11
2013.03 111.3 57.9 (57.9 projected, -0.4) 10.56
2013.04 124.8 72.4 (57.5 projected, -0.4) 5.40
2013.05 131.4 78.7 (57.6 projected, +0.1) 9.73
2013.06 110.1 52.5 (57.9 projected, +0.3) 12.60
2013.07 115.8 (1) 83.2 (2A) / 85.9 (2B) / 55.3 (2C) (58.0 projected, +0.1) (9.52)

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.