Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 19, 2012 at 05:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update October 3, 2012)] [Cycle 24 progress (last update October 1, 2012) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 1, 2012)]

[POES auroral activity level since October 2009 - updated October 7, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on October 18. Solar wind speed at SOHO ranged between 479 and 704 km/s under the influence of a high speed stream from CH541.

Solar flux measured at 20h UTC on 2.8 GHz was 137.6 (increasing 20.7 over the last solar rotation). The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.9). Three hour interval K indices: 31121111 (planetary), 21012321 (Boulder).

The background x-ray flux was at the class B4 level.

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

Region 11586 [S13W82] rotated quietly to the southwest limb.
Region 11589 [N12W45] decayed slowly and quietly.
Region 11590 [S30W28] decayed slowly and quietly.
Region 11591 [N07W06] was quiet and stable.
Region 11592  [N23W31] was quiet and stable.
Region 11593 [N15E37] developed slowly and quietly.
Region 11594 [S27E24] decayed slowly and quietly.
New region 11596 [N06E74] rotated fully into view as the largest region on the visible disk. C flares are possible and there is a minor chance of an M class event.
New region 11597 [S22W30] emerged on October 17 and was numbered the next day by SWPC. Slow development was observed during the day.

Spotted regions not numbered by NOAA/SWPC:
New region S1993 [N18E02] decayed slowly and quietly.
New region S1997 [N09E31] emerged with tiny spots.
New region S1998 [S16W02] emerged with tiny spots.

Coronal mass ejections (CMEs)

October 16-18: 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 (CH542) was in an Earth facing position on October 17-18.

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 fair. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on October 19-20 becoming quiet to unsettled on October 21 due to effects from CH542

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

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
11586 2012.10.06
2012.10.07
1 1 1 S13W80 0050 HSX HSX  
11589 2012.10.09 13 24 11 N12W45 0020 BXI BXI

 

11590 2012.10.10
2012.10.11
2 3 2 S30W29 0010 BXO BXO  
11591 2012.10.11
2012.10.12
1 12 4 N08W08 0170 HSX CHO

area: 0260

11595 2012.10.11
2012.10.17
      S14W55         plage
11592 2012.10.12
2012.10.14
  1   N24W34 0000   AXX  
11594 2012.10.14
2012.10.15
4 20 10 S27E23 0040 CRO  BXO  
S1984 2012.10.14       N03W39           plage
11593 2012.10.15 3 8 5 N18E36 0030 HAX CAO  
S1986 2012.10.15       N22W02           plage
S1987 2012.10.15       N08E33           plage
S1988 2012.10.15       S12W20           plage
S1989 2012.10.15       S25W44           plage
S1990 2012.10.16       N20W15           plage
11596 2012.10.17
2012.10.18
4 10 4 N11E73 0300 EAO EKO location: N06E74

area: 0470

S1992 2012.10.17       S16E23         plage
S1993 2012.10.17   3   N18E02 0000   BXO  
11597 2012.10.17
2012.10.18
4 14 6 S21W30 0020 DRO DRO  
S1995 2012.10.17       S12W71         plage
S1996 2012.10.17       N41W60         plage
S1997 2012.10.18   6 2 N09E31 0010   AXX    
S1998 2012.10.18   3 1 S16W02 0000   AXX    
Total spot count: 32 105 46  
Sunspot number: 112 225 146  (total spot count + 10 * number of spotted regions)
Weighted SN: 58 138 79  (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): 67 79 80 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)
2011.08 101.7 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 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 (64.7 projected, -2.1) 10.10
2012.05 121.5 69.0 (61.8 projected, -2.9) 7.06
2012.06 119.6 64.5 (59.9 projected, -1.9) 10.08
2012.07 133.9 66.5 (60.0 projected, +0.1) 13.90
2012.08 115.4 63.1 (62.0 projected, +2.0) 7.96
2012.09 122.9 61.5 (63.6 projected, +1.6) 8.07
2012.10 118.6 (1) 43.1 (2A) / 74.3 (2B) / 57.4 (2C) (63.5 projected, -0.1) (16.53)

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.