Solar Terrestrial Activity Report

Last major update issued on October 12, 2011 at 04:20 UTC. Minor update posted at 15:10 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 10, 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 11. Solar wind speed ranged between 304 and 372 km/s.

Solar flux measured at 23h UTC on 2.8 GHz was 130.1 (decreasing 12.5 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.9). Three hour interval K indices: 00102211 (planetary), 00101321 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted regions (in 2K resolution SDO images).

Region 11309 [N23W49] decayed slowly and quietly.
Region 11311 [S12W77] rotated quietly to the southwest limb.
Region 11312 [N23W15] was quiet and stable.
Region 11313 [S14W12] has minor polarity intermixing, however, opposite polarity spots are not closely spaced and the region was quiet.
Region 11314 [N27E48] was quiet and mostly unchanged. There's a small chance of a major flare.
Region 11315 [N20W05] decayed quickly and was quiet.
New region 11316 [S12E57] emerged near the southeast limb on October 10 and was numbered the next day by SWPC. The region developed fairly quickly and is currently the most complex region on the visible disk. There's a weak magnetic delta structure at the eastern edge of the main penumbra and some polarity intermixing elsewhere in this fairly compact region. Further C flares are possible and if the region develops further there'll be a chance of minor M class flares. Flare: C1.1 at 23:23 UTC.
New region 11317 [S26E68] rotated into view at the southeast limb on October 10 and was assigned a number by SWPC the following day.

Spotted regions not reported by NOAA/SWPC:
[S1267] emerged near the northeast limb on October 10 and developed on October 11. The region has polarity intermixing. Location at midnight: N10E57
[S1270] emerged in the northeast quadrant on October 11. Polarities are intermixed. Location at midnight: N22E10

Minor update added at 15:10 UTC on October 12: Regions 11316 and S1267 have developed further with both becoming capable of producing minor M class flares. Flare activity has increased significantly today because of the development in these two regions. The latest high resolution CHARMAP.

Coronal mass ejections (CMEs)

October 9-11: 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 trans equatorial coronal hole (CH479) will rotate into an Earth facing position on October 12-13.

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 12-14. Quiet to active with a chance of minor storm intervals is possible on October 15-16 due to effects from CH479.

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
11308 2011.09.30
2011.10.01
    S25W83           plage
11309 2011.10.01
2011.10.02
1 2 N23W51 0040 HSX HSX

area: 0080

location: N23W49

S1251 2011.10.03     S20W46           plage
11311 2011.10.03
2011.10.04
1 1 S12W77 0030 HSX AXX area: 0000
11312 2011.10.03
2011.10.04
1 4 N22W16 0210 HSX CHO

area: 0320

location: N23W15

11313 2011.10.04
2011.10.05
18 30 S15W13 0120 DAI EAI beta-gamma

location: S14W12

S1255 2011.10.06     S14W39           plage
S1257 2011.10.07     N11E20           plage
S1258 2011.10.07     S26W30           plage
S1259 2011.10.07     N19W36           plage
11314 2011.10.08
2011.10.09
2 3 N27E45 0250 CHO CHO

area: 0450

location: N27E48

11315 2011.10.09
2011.10.10
6 8 N20W06 0040 DAO CRO

area: 0020

S1264 2011.10.09     N33W09           plage
11317 2011.10.10
2011.10.11
1 1 S26E68 0090 HSX HSX formerly region S1265
11316 2011.10.10
2011.10.11
3 14 S12E56 0060 DAI DSI beta-gamma-delta

formerly region S1266

area: 0140

S1267 2011.10.10   7 N10E57 0030   CRO beta-gamma
S1268 2011.10.10     N18E55          
S1269 2011.10.10     N18W22         plage
S1270 2011.10.11   6 N22E10 0010   BXO   beta-gamma
Total spot count: 33 76  
Sunspot number: 113 176  (total spot count + 10 * number of spotted regions)
Classification adjusted SN: 78 122  (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): 68 58  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
2011.10 126.9 (1) 33.3 (2A) / 93.8 (2B) (61.8 predicted, +1.5) (8.42)

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) 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.