Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 4, 2013 at 05:50 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) - NEW]

Recent activity

The geomagnetic field was quiet on February 3. Solar wind speed at SOHO ranged between 374 and 491 km/s, weakly under the influence of a moderately high speed stream from CH551.

Solar flux measured at 20h UTC on 2.8 GHz was 111.1 (decreasing 38.6 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.8). Three hour interval K indices: 20011101 (planetary), 21122111 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11662 [N27W77] decayed slowly and quietly.
Region 11663 [S09W65] was quiet and stable.
Region 11665 [N11W02] was quiet and stable.
Region 11666 [S25W00] reemerged with penumbra spots.
Region 11667 [N22E42] developed early in the day, then lost some of its complexity and decayed slowly during the latter half of the day. C5+ flare: C8.4 at 06:10 UTC.
New region 11668 [N12W16] emerged quickly on February 2 and was numbered by SWPC the next day. The region decayed quickly on February 3.

Spotted regions not numbered by SWPC:
S2208 [S22E38] decayed retaining only a single penumbra spot.

Coronal mass ejections (CMEs)

February 1-3: 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 large northern hemisphere coronal hole is probably too far to the north to cause a geomagnetic disturbance, other than that there are no obvious coronal holes in or near Earth facing positions.

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

Forecast

The geomagnetic field is expected to be quiet on February 4-6.

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
11662 2013.01.22
2013.01.23
2 1 1 N27W79 0020 HSX HRX  
11663 2013.01.25
2013.01.26
1 1 1 S09W65 0000 AXX HRX area: 0012
S2196 2013.01.26       S30W53           plage
S2199 2013.01.26       N13W58         plage
11666 2013.01.28
2013.01.29
  4   S24W06         location: S25W00

count includes one spot outside of image

11665 2013.01.28
2013.01.29
5 8 4 N10W04 0190 CSO CSO area: 0240
S2205 2013.01.29       N11W14           plage
11667 2013.01.31
2013.02.01
14 17 9 N22E42 0160 DSI DSC

 

S2207 2013.01.31       N28W54           plage
S2208 2013.02.01   1 1 S22E25 0006   AXX  
11668 2013.02.02
2013.02.03
7 5 3 N12W16 0030 DAO BXO  
Total spot count: 29 37 19  
Sunspot number: 79 107 79  (total spot count + 10 * number of spotted regions)
Weighted SN: 49 53 35  (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): 47 37 43 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 63.1 (58.6 projected, +0.9) 7.96
2012.09 122.9 61.5 (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
2013.02 108.9 (1) 7.1 (2A) / 66.0 (2B) / 60.2 (2C) (55.0 projected, -1.0) (5.5)

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.