Solar Terrestrial Activity Report

Activity chart

Last major update issued on February 2, 2012 at 06:20 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 January 5, 2012)]

[POES auroral activity level since October 2009 - updated January 31, 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 to unsettled on February 1. Solar wind speed ranged between 343 and 399 km/s. Early on February 2 solar wind speed and temperature has increased and it appears a weak disturbance associated with CH498 is in progress.

Solar flux measured at 20h UTC on 2.8 GHz was 117.5 (decreasing 23.8 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.3). Three hour interval K indices: 22223111 (planetary), 22233111 (Boulder).

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

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

Region 11408 [N08W77] decayed slowly and quietly as it rotated to the northwest limb.
Region 11410 [N19W03] lost a few small spots and was quiet.
Region 11411 [S25W42] was quiet and stable.
Region 11413 [N10W05] developed slowly and could produce C flares.

Spotted regions not reported by NOAA/SWPC:
[S1446] rotated into view at the southeast limb on January 24. Location at midnight: S17W31
[S1453] reemerged with a single tiny spot on February 1. Location at midnight: N19W13
[S1454] emerged in the northwest quadrant on January 30. The region developed further on January 31 and February 1. Location at midnight: N15W74
[S1455] emerged in the southeast quadrant on February 1. Location at midnight: S17E43
[S1456] emerged in the northeast quadrant on February 1. Location at midnight: N13E10

Coronal mass ejections (CMEs)

January 31-February 2: 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 trans equatorial coronal hole (CH498) was in an Earth facing position on January 30-February 2.

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 to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on February 2-5 due to weak effects from CH498. Occasional active intervals are possible.

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
11408 2012.01.20
2012.01.21
1 1 1 N07W79 0070 HSX HRX area: 0010
S1441 2012.01.22       S18W49           plage
S1446 2012.01.24   3 2 S17W31 0010   AXX  
11410 2012.01.26 13 12 4 N18W00 0240 CSO CHO

area: 0280

location: N19W03

11411 2012.01.26
2012.01.28
7 15 5 S28W41 0010 BXO CRI location: S25W42
11413 2012.01.27
2012.01.29
24 23 11 N08W07 0100 CSI DAI

location: N10W05

11412 2012.01.28
2012.01.29
      S16W81           plage
S1453 2012.01.29   1   N19W13 0000   AXX    
S1454 2012.01.30   6 3 N15W74 0030   DRO  
S1455 2012.02.01   2   S17E43 0000   BXO    
S1456 2012.02.01   1   N13E10 0000   AXX    
Total spot count: 45 64 26  
Sunspot number: 85 154 86  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 60 93 50  (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): 51 69    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
2012.02 117.5 (1) 2.9 (2A) / 85.0 (2B) (82.4 projected, +3.1) (6.25)

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.