Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 24, 2013 at 04:05 UTC.

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

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated September 24, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet on September 23. Solar wind speed at SOHO ranged between 333 and 373 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 107.8 (decreasing 1.9 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 113.9. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5). Three hour interval K indices: 12100021 (planetary), 13112222 (Boulder).

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

At the time of counting spots (see image time) spots were observed for 8 active regions in 2K resolution (SN: 147) and 7 active regions in 1K resolution (SN: 91) SDO images on the visible solar disk.

Region 11845 [S17W14] decayed slowly and quietly.
Region 11846 [S18W02] was quiet and stable.
Region 11849 [N19W25] decayed slowly and quietly.
Region 11850 [N08E24] developed slowly as new flux emerged near the leader spots. The region currently has weak polarity intermixing.
Region 11851 [S18E59] was quiet and stable, weak polarity intermixing was observed.
New region 11852 [S20W26] emerged on September 21 and was numbered by SWPC 2 days later.

Spotted regions not numbered by SWPC:
S2707 [N16E27] was quiet and stable.
New region S2709 [S13E28] formed penumbra spots in an old plage area.

Coronal mass ejections (CMEs)

September 21-23: 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

No obvious coronal holes are currently in or near Earth facing positions.

Coronal hole map

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

Forecast

The geomagnetic field is expected to be quiet on September 24-27.

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 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
11848 2013.09.16
2013.09.19
      S11W19           plage
11845 2013.09.16
2013.09.17
  6 1 S17W19 0012   BXO location: S17W14
11847 2013.09.16
2013.09.17
      N11W15           plage
11843 2013.09.16
2013.09.17
      N03W76         plage

location: N00W76

11846 2013.09.17 1 5 2 S18W04 0150 HSX CSO area: 0230

location: S18W02

S2692 2013.09.17       N22W53           plage
S2694 2013.09.17       N06W50           plage
S2699 2013.09.18       S20W55           plage
11849 2013.09.19 8 16 5 N19W24 0080 DSO DAO  
11850 2013.09.19 4 18 8 N08E24 0040 CSO CAO beta-gamma
S2704 2013.09.21       S09E24           plage
11852 2013.09.21
2013.09.23
1 5 2 S21W28 0010 AXX BXO  
11851 2013.09.22 1 7 2 S16E55 0010 AXX CRO beta-gamma

location: S18E59

S2707 2013.09.22   8 1 N16E27 0015   BXO  
S2708 2013.09.22       S19W53         plage
S2709 2013.09.23   2   S13E28 0003   AXX    
Total spot count: 15 67 21  
Sunspot number: 65 147 91  (total spot count + 10 * number of spotted regions)
Weighted SN: 30 85 39  (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): 39 51 50 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)
2011.11 153.5 (cycle peak) 96.7 (cycle peak) 61.1 (+1.2) 5.55
2012.02 106.5 32.9 66.9 (+1.4)
likely cycle 24 max
8.81
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 57.8 (-1.1) 13.90
2012.08 115.4 63.0 58.2 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.1) 8.07
2012.10 123.3 53.3 58.6 (+0.5) 9.97
2012.11 121.3 61.8 59.7 (+1.1) 7.08
2012.12 108.6 40.8 59.6 (-0.1) 3.44
2013.01 127.1 62.9 58.7 (-0.9) 4.69
2013.02 104.3 38.0 58.4 (-0.3) 6.11
2013.03 111.3 57.9 (58.2 projected, -0.2) 10.56
2013.04 124.8 72.4 (57.9 projected, -0.3) 5.40
2013.05 131.4 78.7 (58.0 projected, +0.1) 9.73
2013.06 110.1 52.5 (58.3 projected, +0.3) 12.60
2013.07 115.5 57.0 (58.3 projected, 0.0) 9.47
2013.08 114.6 66.0 (58.2 projected, -0.1) 8.27
2013.09 101.1 (1) 42.7 (2A) / 55.7 (2B) / 36.6 (2C) (57.8 projected, -0.4) (5.85)

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 the 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.