Solar Terrestrial Activity Report

Activity chart

Last major update issued on August 24, 2012 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update August 6, 2012)] [Cycle 24 progress (last update August 2, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update August 6, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update August 6, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update August 5, 2012)]

[POES auroral activity level since October 2009 - updated August 5, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on August 23. Solar wind speed at SOHO ranged between 347 and 422 km/s, likely under the influence of a weak low speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 96.7 (decreasing 26.6 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.9). Three hour interval K indices: 323332231 (planetary), 23333321 (Boulder).

The background x-ray flux is at the class B1 level.

At 20h UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11546 [N15W20] decayed slowly and quietly.
Region 11548 [N17E07] decayed slowly and quietly.
Region 11552 [S18E30] added some tiny spots.
New region 11553 [S21E62] rotated into view on August 22 and was numbered by SWPC the next day.

Spotted regions not numbered by NOAA/SWPC:
S1872 [S21W28] lost the trailing polarity spots and gained a leader spot.
New region S1873 [N15E27] emerged quickly and could produce C flares.

Coronal mass ejections (CMEs)

August 21-23: 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 (CH530) was in an Earth facing position on August 22-23.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

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 fair.

Forecast

The geomagnetic field is expected to be mostly quiet on August 24. A high speed stream from CH530 could cause unsettled to active conditions on August 25-26 with a chance of minor storm intervals.

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 higher resolution image) Compare to the previous day's image. 0.5k image [NEW]

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 magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11546 2012.08.15
2012.08.16
1 1 1 N16W21 0020 HSX HSX  
11547 2012.08.16
2012.08.17
      N05W56           plage
S1861 2012.08.16       N23W55           plage
11548 2012.08.17
2012.08.18
6 10 4 N18E04 0030 CSO CRO area: 0010
11549 2012.08.18
2012.08.19
      S18W85           plage
11551 2012.08.19
2012.08.21
      N13W41         plage
11552 2012.08.20
2012.08.21
1 9 3 S18E27 0030 HSX HSX location: S18E30
S1870 2012.08.21       S00W30           plage
11553 2012.08.22
2012.08.23
1 1 1 S23E50 0150 HSX HSX location: S21E62
S1872 2012.08.22   1   S21W28 0000   AXX  
S1873 2012.08.23   11 7 N15E27 0050   DRI    
Total spot count: 9 33 16  
Sunspot number: 49 93 66  (total spot count + 10 * number of spotted regions)
Weighted SN: 29 54 37  (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): 29 33 36 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)
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 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 (67.4 projected, +1.9) 8.81
2012.03 114.7 64.3 (68.1 projected, +0.7) 16.08
2012.04 113.0 55.2 (67.5 projected, -0.6) 10.10
2012.05 121.5 69.0 (65.8 projected, -1.7) 7.06
2012.06 119.6 64.5 (65.0 projected, -0.8) 10.08
2012.07 133.9 66.5 (66.0 projected, +1.0) 13.90
2012.08 115.4 (1) 62.4 (2A) / 84.0 (2B) (68.6 projected, +2.6) (8.55)

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 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.