Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 26, 2013 at 03:55 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 to unsettled on September 25. Solar wind speed at SOHO ranged between 344 and 436 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 111.1 (increasing 2.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 114.0. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 32200001 (planetary), 12211211 (Boulder).

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

At the time of counting spots (see image time) spots were observed in 10 active regions in 2K resolution (SN: 173) and 7 active regions in 1K resolution (SN: 96) SDO images on the visible solar disk.

Region 11845 [S17W41] was quiet and stable.
Region 11846 [S18W29] was quiet and stable.
Region 11847 [N10W35] reemerged with penumbra spots.
Region 11849 [N18W53] was quiet and stable.
Region 11850 [N09W03] developed further and could produce C and minr M class flares.
Region 11851 [S18E32] was quiet and stable.

Spotted regions not numbered by SWPC:
S2710 [N20E43] was quiet and stable.
S2715 [N18W62] was quiet and stable.
New region S2716 [N03W07] emerged with penumbra spots.
New region S2717 [S09W68] emerged with a few spots.

Coronal mass ejections (CMEs)

September 23-25: 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 recurrent trans equatorial coronal hole (CH588) will likely rotate into an Earth facing position on September 28.

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

Forecast

The geomagnetic field is expected to be quiet on September 26-30. On October 1 there's a chance of unsettled intervals due to effects from CH588.

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
      S11W47           plage
11845 2013.09.16
2013.09.17
  2   S17W47 0003   BXO location: S17W41
11847 2013.09.16
2013.09.17
  3   N11W43 0003   BXO   location: N10W35
11846 2013.09.17 1 2 1 S17W31 0160 HSX CSO area: 0210

location: S18W29

11849 2013.09.19 5 6 2 N21W53 0030 EAO BXO location: N18W53
11850 2013.09.19 14 44 19 N08W03 0070 DAO DAC images/AR_11850_20130924_2345.png beta-gamma-delta

area: 0270

S2704 2013.09.21       S09W02           plage
11852 2013.09.21
2013.09.23
      S21W56           plage
11851 2013.09.22 1 6 1 S20E30 0010 AXX BXO

location: S18E32

S2709 2013.09.23       S15E05         plage
S2710 2013.09.24   3 1 N20E43 0011   BXO  
S2711 2013.09.24       S12W00         plage
S2712 2013.09.24       S16E17         plage
S2713 2013.09.24       S05E10         plage
S2714 2013.09.24       S26W29         plage
S2715 2013.09.24   3 1 N18W62 0008   BXO  
S2716 2013.09.25   2   N03W07 0006   BXO    
S2717 2013.09.25   2 1 S09W68 0011   CRO    
Total spot count: 21 73 26  
Sunspot number: 61 173 96  (total spot count + 10 * number of spotted regions)
Weighted SN: 36 86 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): 37 61 53 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
2013.09 101.9 (1) 46.6 (2A) / 55.9 (2B) / 37.7 (2C) (57.8 projected, -0.4) (6.03)

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.