Solar Terrestrial Activity Report

Last major update issued on October 31, 2011 at 04:45 UTC. Minor update posted at 17:55 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 30, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2114 [August-September 2011] - 2115 [September-October 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on October 30. Solar wind speed ranged between 269 and 419 km/s. A weak solar wind shock was observed at SOHO at 08:55 UTC. This was likely the arrival of the CME observed early on October 27 following a filament eruption to the north of AR 11330.

Solar flux measured at 20h UTC on 2.8 GHz was 126.7 (decreasing 2.2 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.5). Three hour interval K indices: 10012312 (planetary), 01022422 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight UTC the visible solar disk had 9 spotted regions (in 2K resolution SDO images).

Region 11324 [N13W84] decayed slowly and quietly with only the easternmost spot visible at the northwest limb.
Region 11330 [N07W40] lost all penumbra on the trailing spots. There's still minor polarity intermixing and there's a small chance of an M class flare. Flares: C2.4 at 09:39, C1.9 at 17:12 UTC.
Region 11332 [N32W01] was quiet and stable.
Region 11333 [N15W31] was quiet and stable.
New region 11334 [N12E25] emerged in the northeast quadrant on October 29 and was numbered by SWPC the next day. The region developed quickly on October 30 and could soon become capable of producing an M class flare. Flares: C2.1 at 10:10, C1.5 at 14:49, C1.5 at 20:52, C1.5 at 21:16, C1.4 at 21:43, C1.2 at 22:50 UTC.

Spotted regions not reported by NOAA/SWPC:
[S1296] reemerged with a single tiny spot on October 30. Location at midnight: N17W03
[S1298] reemerged with several spots on October 30. Location at midnight: N18E30
[S1300] rotated into view at the northeast limb on October 29. The region decayed slowly on October 30. Location at midnight: N13E68
[S1302] rotated into view at the northeast limb on October 30. Location at midnight: N17E80

Minor update added at 17:55 UTC on October 31: A region at the northeast limb was the source of an M1.1 flare at 15:10 UTC. Further M class flaring is likely from this source. A filament eruption was observed starting in the northeast quadrant at 13:56 UTC, no significant CME seems to have been produced.

Coronal mass ejections (CMEs)

October 28-30: 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 (CH482) in the northern hemisphere will likely rotate into an Earth facing position on November 1-2. CH482 became smaller on October 30 due to the development of region 11334.

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 fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on October 31 and quiet on November 1-2.

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
11324 2011.10.17 2 1 N13W83 0020 CSO AXX  
11325 2011.10.19     N17W66          

spotless

11330 2011.10.21
2011.10.22
16 33 N08W35 0380 EHI CKI

beta-gamma

location: N07W40

11333 2011.10.23
2011.10.27
2 7 N15W32 0010 CRO CRO  
11332 2011.10.23
2011.10.24
1 2 N30W02 0020 HSX CRO location: N32W01
S1295 2011.10.25     S20W40         plage
S1296 2011.10.27   1 N17W03 0000   AXX    
S1298 2011.10.28   3 N18E30 0030   DRO    
S1299 2011.10.28     N16W10           plage
S1300 2011.10.29   2 N13E68 0000   AXX  
11334 2011.10.29
2011.10.30
9 23 N13E25 0070 CSO DAI  
S1302 2011.10.30   1 N17E80 0000   AXX    
Total spot count: 30 73  
Sunspot number: 80 163  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 58 97  (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): 48 54  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 / 8.06
2011.07 94.2 43.9 (53.1 predicted, +3.9) 9.14 / 8.16
2011.08 101.7 50.6 (57.2 predicted, +4.1) 8.16 / 7.26
2011.09 133.8 78.0 (60.3 predicted, +3.1) 12.80 / 12.27
2011.10 137.2 (1) 113.6 (2A) / 117.4 (2B) (61.8 predicted, +1.5) (7.51)

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.