Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 12, 2012 at 06:30 UTC. Minor update posted at 13:25 UTC

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update February 2, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 5, 2012)]

[POES auroral activity level since October 2009 - updated February 10, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2117 [November-December 2011] - 2118 [December 2011 - January 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet on February 11. Solar wind speed ranged between 322 and 410 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 112.3 (decreasing 21.2 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6). Three hour interval K indices: 21101111 (planetary), 31111211 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight UTC the visible solar disk had 4 spotted regions (in 2K resolution SDO images).

Region 11416 [S18W03] matured and lost a few spots in the central part. Although the region has been mostly quiet so far and is fairly simple magnetically, there's a chance of a minor M class flare. Flare: C1.5 at 10:44 UTC
Region 11417 [N17E47] was quiet and stable.

Spotted regions not reported by NOAA/SWPC:
[S1469] emerged in the southeast quadrant on February 10. Location at midnight: S23E28
[S1471] emerged in the northwest quadrant on February 11. Location at midnight: N15W37

A region just behind the northeast limb was quite active during the day producing many C flares. The leading penumbra is becoming visible at the limb early on February 12. Flares: C1.4 at 08:55, C7.9 at 10:44, C2.7 at 16:05, C7.7 at 18:54, C5.3 at 19:12, C2.7 at 20:44, C2.7 at 23:33 UTC.

Minor update posted at 13:25 UTC: Regions S1474 (N28E81 at noon) and S1473 (N11E85 at noon) have rotated into view (see this high resolution map) while the trailing penumbra in region 11416 appears to be splitting into 2 smaller penumbrae. Region S1469 is developing and has added several spots. A low speed stream associated with CH500 arrived at ACE near 06h UTC.

Coronal mass ejections (CMEs)

February 10-11: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
February 9: A filament eruption near region 11417 late in the day produced a large partial halo CME with nearly all material observed off the east limb. There were faint traces of ejecta over parts of the northwest limb. While the core of the CME will not reach Earth there's a chance of a weak flanking impact on February 12 or 13.

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 recurrent trans equatorial coronal hole (CH500) was Earth facing on February 8-9. A trans equatorial coronal hole (CH501) will likely rotate into an Earth facing position on February 15-16.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 12 due to weak coronal hole effects. Quiet conditions are likely on February 13-14, with a chance of a few unsettled intervals due to a possible flank CME impact.

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 magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
S1461 2012.02.07       N07W51         plage
11416 2012.02.08
2012.02.09
27 24 11 S19W02 0400 DHI EKO area: 0700

location: S18W03

S1464 2012.02.08       S21E24           plage
11417 2012.02.09
2012.02.10
3 6 3 N16E44 0020 CRO DRO location: N17E47
S1466 2012.02.09       N16E24           plage
S1467 2012.02.09       N29W13           plage
S1468 2012.02.09       N11W40           plage
S1469 2012.02.10   1   S23E28 0000   AXX  
S1471 2012.02.11   1   N15W37 0000   AXX    
Total spot count: 30 32 14  
Sunspot number: 50 72 34  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 43 45 27  (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): 30 32    k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1, 2011) for STAR SDO 2K

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
2010.11 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 41.8 (+4.9) 9.71 / 8.83
2011.05 95.8 41.6 47.6 (+5.8) 9.18 / 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.96 / 8.06
2011.07 94.2 43.9 57.2 (+4.0) 9.14 / 8.16
2011.08 101.7 50.6 (60.4 projected, +3.2) 8.16 / 7.26
2011.09 133.8 78.0 (63.1 projected, +2.7) 12.80 / 12.27
2011.10 137.3 88.0 (65.8 projected, +2.7) 7.52 / 8.28
2011.11 153.5 96.7 (69.1 projected, +3.3) 4.58 / 5.55
2011.12 141.3 73.0 (73.9 projected, +4.8) 3.32
2012.01 132.5 58.3 (79.3 projected, +5.4) 6.59
2012.02 107.7 (1) 16.9 (2A) / 44.6 (2B) (82.4 projected, +3.1) (7.18)

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.