Solar Terrestrial Activity Report

Last major update issued on October 21, 2011 at 07:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update October 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update October 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update October 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update October 1, 2011)]

[POES auroral activity level since October 2009 - updated October 12, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on October 20. Solar wind speed ranged between 354 and 413 km/s under the influence of a weak coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 159 (increasing 0.8 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 21002222 (planetary), 21102221 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight UTC the visible solar disk had 16 spotted regions (in 2K resolution SDO images).

Region 11314 [N28W69] was quiet and stable.
Region 11316 [S12W63] decayed slowly and quietly.
Region 11317 [S26W48] was quiet and stable.
Region 11319 [N10W66] was quiet and has M class flare potential.
Region 11321 [S15W18] was quiet and stable.
Region 11323 [N23E13] was quiet and stable.
Region 11324 [N13E43] has many spots, is compact and has a magnetic delta structure in a central penumbra. M flares are possible. Flares: C1.5 at 02:03, C5.4 at 15:39 UTC
Region 11325 [N15E71] was quiet and stable.
New region 11326 [N16W34] emerged in the northwest quadrant.
New region 11327 [S20E13] emerged in the southeast quadrant on October 17 and was noticed by SWPC 3 days later. The region developed quickly on October 20 and could produce C flares.
New region 11328 [N19E23] emerged in the northeast quadrant on October but was then regarded as part of region 11323.

Spotted regions not reported by NOAA/SWPC:
[S1281] emerged in the southwest quadrant on October 19. Location at midnight: S16W73
[S1282] emerged in the southwest quadrant on October 20 and could soon develop C class flare potential. Location at midnight: S30W26
[S1283] emerged in the southeast quadrant on October 20. Location at midnight: S06E15
[S1284] emerged in the northwest quadrant on October 20. Location at midnight: N27W34
[S1285] emerged near the southwest limb on October 20. Location at midnight: S08W85

Region 11318 behind the northwest limb was the source of an M1.6 flare at 03:25 UTC.

Coronal mass ejections (CMEs)

October 18-20: No obviously Earth directed CMEs observed.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A small coronal hole (CH480)  in the northern hemisphere was in an Earth facing position on October 19-20.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, 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 the new method, the extent and intensity of both holes 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 to fair. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on October 21. Weak effects from CH480 are possible on October 22-23.

Coronal holes (1) Coronal mass ejections (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

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 polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
11314 2011.10.08
2011.10.09
1 1 N29W69 0210 HSX HHX

location: N28W69

area: 0320

11317 2011.10.10
2011.10.11
1 2 S26W51 0060 HSX CSO location: S26W48
11316 2011.10.10
2011.10.11
6 6 S12W62 0060 DSO CRO

area: 0020

11319 2011.10.10
2011.10.12
10 26 N11W66 0330 EHO EKO  
11321 2011.10.14
2011.10.15
4 6 S14W18 0010 BXO BXO  
S1273 2011.10.14     N12W40           plage
11323 2011.10.16
2011.10.17
  1 N24E14 0000   AXX

location: N23E15

11324 2011.10.17 27 58 N11E40 0360 EKC EKC beta-gamma-delta
11327 2011.10.17
2011.10.20
5 16 S22E10 0010 BXI DAI location: S20E13

area: 0150

S1280 2011.10.17     S15E01           plage
11325 2011.10.19 4 11 N14E67 0270 DKO DKO area: 0400

location: N15E71

S1281 2011.10.19   1 S16W73 0000   AXX  
11326 2011.10.20 2 5 N16W36 0010 CSO CRO    
11328 2011.10.20 1 7 N18E23 0010 BXO BXO    
S1282 2011.10.20   10 S30W26 0030   DRO    
S1283 2011.10.20   2 S06E15 0000   AXX    
S1284 2011.10.20   1 N27W34 0000   AXX    
S1285 2011.10.20   1 S08W85 0010   AXX    
Total spot count: 61 154  
Sunspot number: 161 314  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 111 213  (Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 97 104  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.07 79.8 16.1 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 31.0 (+2.2) 4.32 / 5.51
2011.02 94.6 29.4 33.4 (+2.4) 5.41 / 6.44
2011.03 115.0 56.2 36.9 (+3.5) 7.79 / 8.18
2011.04 112.6 54.4 (41.1 predicted, +4.2) 9.71 / 8.83
2011.05 95.8 41.6 (45.2 predicted, +4.1) 9.18 / 8.94
2011.06 95.8 37.0 (49.2 predicted, +4.0) 8.96
2011.07 94.2 43.9 (53.1 predicted, +3.9) 9.14
2011.08 101.7 50.6 (57.2 predicted, +4.1) 8.16
2011.09 133.8 78.0 (60.3 predicted, +3.1) 12.80
2011.10 134.9 (1) 77.6 (2A) / 120.4 (2B) (61.8 predicted, +1.5) (7.08)

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 preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.