Solar Terrestrial Activity Report

Activity chart

Last major update issued on October 28, 2012 at 05:50 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 on October 27. Solar wind speed at SOHO ranged between 288 and 396 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 121.7 (decreasing 13.9 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: 4.0). Three hour interval K indices: 21111001 (planetary), 12211211 (Boulder).

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

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11596 [N08W51] decayed slowly and quietly.
Region 11598 [S11W10] decayed slowly and quietly.
Region 11599 [S11E17] was quiet and stable.
Region 11600 [N09W27] decayed slowly and quietly

Spotted regions not numbered by NOAA/SWPC:
S2007 [S33W40] reemerged with a tiny spot.
S2010
[S12E35] developed slightly and was quiet.
New region S2014 [S02W03] emerged with tiny spots.
New region S2015 [S24W05] emerged with tiny spots.

Coronal mass ejections (CMEs)

October 25-26: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
October 27: A filament eruption across the equator near AR 11600 began near 14h UTC and reached its most intense level 2 hours later. A CME was observed in STEREO-B at 16:25 UTC and in STEREO-B when imagery resumed a couple of hours later. This CME is likely to have Earth directed components and could reach Earth on October 30.

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

No obvious coronal holes are currently in or near potentially geoeffective positions.

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 28-29. A CME could cause unsettled to minor storm conditions on October 30-31.

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
11596 2012.10.17
2012.10.18
5 11 5 N08W48 0170 DAO CAO

area: 0320

location: N08W51

11598 2012.10.20 11 23 10 S11W10 0330 DKC DKC

area: 0420

S2004 2012.10.21       N20W58           plage
S2005 2012.10.21       N08W55           plage
11599 2012.10.22
2012.10.23
1 4 2 S11E17 0110 HSX HSX area: 0180
S2007 2012.10.22   1   S33W40 0000   AXX    
11600 2012.10.24
2012.10.26
2 5 3 N09W28 0020 CRO BXO  
S2010 2012.10.25   3 2 S12E37 0010   AXX  
S2012 2012.10.25       S09W43           plage
S2014 2012.10.27   2 1 S02W03 0010   AXX    
S2015 2012.10.27   4   S24W05 0000   BXO    
Total spot count: 19 53 23  
Sunspot number: 59 133 83  (total spot count + 10 * number of spotted regions)
Weighted SN: 42 73 43  (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): 35 47 46 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
2012.10 125.4 (1) 66.8 (2A) / 76.7 (2B) / 53.7 (2C) (63.5 projected, -0.1) (11.42)

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.