Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 2, 2013 at 04:45 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 August 4, 2013)]

[POES auroral activity level since October 2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated August 20, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]

Recent activity

The geomagnetic field was quiet to unsettled on September 1. Solar wind speed at SOHO ranged between 389 and 561 km/s. Solar wind speed increased after 06h and peaked between 07 and 14h UTC, probably due to a high speed coronal hole stream.

Solar flux measured at 20h UTC on 2.8 GHz was 103.8 (decreasing 0.5 over the last solar rotation). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.8). Three hour interval K indices: 32213222 (planetary), 32322322 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11834 [N12W35] developed slowly and has polarity intermixing.
Region 11835 [S09W26] decayed slowly and quietly.
Region 11836 [N11E05] decayed in the trailing spot section.

Spotted regions not numbered by SWPC:
S2639 [S13W37] reemerged with several spots.
S2646 [S13E38] reemerged with a penumbra spot.
S2650 [S17W06] developed further and has several positive polarity umbrae.
New region S2651 [N20E42] emerged with penumbra spots.
New region S2652 [S22W13] emerged with a penumbra spot.
New region S2653 [N10W07] emerged with a penumbra spot.
New region S2654 [N07W29] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

August 31 - September 1: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
August 30: An asymmetric full halo CME was observed after the LDE in AR 11836 early in the day. The CME will likely reach Earth early on September 2.

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 (CH583) was in an Earth facing position on August 31 and September 1.

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

Forecast

The geomagnetic field is expected to be quiet to minor storm on September 2 due to CME effects. Quiet to unsettled conditions are likely on September 3-4 under the influence of a high speed stream from CH583.

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
11834 2013.08.23
2013.08.24
18 32 16 N12W34 0060 EAI DRI

beta-gamma

11835 2013.08.24 11 12 7 S11W26 0110 CSO CSO

location: S09W26

area: 0220

S2633 2013.08.24       S10W34           plage
11836 2013.08.26
2013.08.27
12 23 10 N11E04 0150 ESO ESO  
S2638 2013.08.26       S20W55           plage
S2639 2013.08.26   4 1 S13W37 0014   CRO      
S2643 2013.08.27       N03W40           plage
S2645 2013.08.29       N33E09           plage
S2646 2013.08.30   1   S13E38 0001   AXX    
S2647 2013.08.30       S13E04         plaage
S2648 2013.08.30       N42E34           plage
S2649 2013.08.31       S04E17         plage
S2650 2013.08.31   12 5 S17W06 0045   CRO  
S2651 2013.09.01   2   N20E42 0005   BXO    
S2652 2013.09.01   1   S22W13 0003   AXX    
S2653 2013.09.01   1   N10W07 0002   AXX    
S2654 2013.09.01   1   N07W29 0002   AXX    
Total spot count: 41 89 39  
Sunspot number: 71 189 89  (total spot count + 10 * number of spotted regions)
Weighted SN: 56 108 57  (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): 43 66 49 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) 7.86
2013.09 103.8 (1) 2.4 (2A) / 71 (2B) / 57.8 (2C) (57.8 projected, -0.4) (8.8)

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.