Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 6, 2013 at 05:00 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update February 1, 2013)] [Cycle 24 progress (last update February 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update February 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update February 3, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated February 3, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was very quiet on February 5. Solar wind speed at SOHO ranged between 297 and 361 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 105.1 (decreasing 64.2 over the last solar rotation). The Potsdam WDC planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 11100000 (planetary), 11210100 (Boulder).

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

At midnight UTC the visible solar disk had 5 spotted active regions (in 2K resolution SDO images).

Region 11665 [N12W28] was quiet and stable.
Region 11667 [N22E17] was quiet and stable. A C8.7 event peaking at 00:21 UTC on February 6 had its origin in this region. This event was associated with a type II radio sweep. It's too early to tell if there was a potentially Earth directed CME. The flare apparently triggered a filament eruption to the east of the region, this was recorded as a long duration C1.2 event peaking between 03-04 UTC.
New region 11669 [N08E52] emerged on February 4, was numbered by SWPC the next day, and developed slowly on Feb.5. The region was the source of the only C flare of the day, a C6.3 event at 08:19 UTC.

Spotted regions not numbered by SWPC:
S2208 [S22E01] reemerged with a few penumbra spots.
New region S2211 [N18E55] emerged with one spot.

Coronal mass ejections (CMEs)

February 3-5: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

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 small coronal hole (CH553) in the southern hemisphere rotated across the central meridian on February 5.

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.

Forecast

The geomagnetic field is expected to be mostly quiet on February 6-9. On February 8-9 there's a chance of a few unsettled intervals due to effects from CH553.

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 2K resolution) 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
11666 2013.01.28
2013.01.29
      S24W34         plage

 

11665 2013.01.28
2013.01.29
1 11 5 N10W31 0120 HSX CSO area: 0230

location: N12W28

S2205 2013.01.29       N11W40           plage
11667 2013.01.31
2013.02.01
6 8 6 N22E14 0080 DSO DSO

area: 0130

S2208 2013.02.01   3 1 S22E01 0014   AXX    
11668 2013.02.02
2013.02.03
      N12W44         plage
11669 2013.02.04
2013.02.05
4 7 3 N08E52 0010 BXO BXO location: N08E55

area: 0040

S2211 2013.02.05   1   N18E55 0002   AXX    
Total spot count: 11 30 15  
Sunspot number: 41 80 55  (total spot count + 10 * number of spotted regions)
Weighted SN: 21 40 25  (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): 25 28 30 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)
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 (cycle max) 96.7 (cycle max) 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 64.6 (-2.2) 10.10
2012.05 121.5 69.0 61.7 (-2.9) 7.06
2012.06 119.6 64.5 58.9 (-2.8) 10.08
2012.07 133.9 66.5 57.7 (-1.2) 13.90
2012.08 115.4 63.0 (58.6 projected, +0.9) 7.96
2012.09 122.9 61.4 (58.7 projected, +0.1) 8.07
2012.10 123.3 53.3 (58.1 projected, -0.6) 9.97
2012.11 121.3 61.4 (57.4 projected, -0.7) 7.08
2012.12 108.6 40.8 (56.7 projected, -0.7) 3.44
2013.01 127.1 62.9 (56.0 projected, -0.7) 4.49
2013.02 107.7 (1) 9.6 (2A) / 53.8 (2B) / 55.3 (2C) (55.0 projected, -1.0) (4.55)

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.