Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 15, 2013 at 04:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2013)] [Cycle 24 progress (last update April 7, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 4, 2013)]

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

Recent activity

The geomagnetic field was quiet to unsettled on April 14. Solar wind speed at SOHO ranged between 494 and 541 km/s under the influence of weak CME effects.

Solar flux measured at 20h UTC on 2.8 GHz was 116.8 (decreasing 0.8 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: 9.1). Three hour interval K indices: 23322212 (planetary), 23332322 (Boulder).

The background x-ray flux was at the class B3 level.

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

Region 11718 [N20W70] is disintegrating and has only small umbrae in the leading polarity in addition to fairly large penumbra spots.
Region 11719 [N08W37] decayed slowly and quietly.
Region 11721 [S19W22] decayed slowly and quietly.
Region 11722 [S22W12] was quiet and stable.
Region 11723 [S19E35] developed gaining penumbral area.
Region 11724 [S27E59] was quiet and stable.

Spotted regions not numbered by SWPC:
S2349 [S11W53] reemerged with a penumbra spot.
S2353 [N17W05] decayed slowly and quietly.
S2354 [N09E17] was quiet and stable.
New region S2355 [S05W16] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

April 12-14: 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 small trans equatorial coronal hole (CH565) was in an Earth facing position on April 14, CH565 decreased in size on April 13-14 and has almost closed.

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.

Forecast

The geomagnetic field is expected to be quiet on April 15-17 possibly becoming quiet to unsettled on April 18 due to weak effects from CH565.

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
11717 2013.04.05       S12W57          

plage

11718 2013.04.05 12 11 6 N20W70 0260 DKC CRO

area: 0090

11719 2013.04.05 11 12 4 N10W41 0120 DAO DSO beta-gamma

location: N08W37

 

11721 2013.04.09
2013.04.10
13 22 10 S19W21 0180 DSO DSO  

 

11722 2013.04.09
2013.04.10
4 4 4 S22W11 0020 CRO CRO  
S2348 2013.04.10       N07W53           plage
S2349 2013.04.10   1   S11W53 0004       plage
S2350 2013.04.11       S24E33           plage
11724 2013.04.12
2013.04.13
3 4 3 S27E58 0050 HAX HAX  
11723 2013.04.12
2013.04.13
8 16 5 S18E36 0080 DAC DAO area: 0180
S2353 2013.04.12   1   N17W05 0001   AXX  
S2354 2013.04.13   3   N09E17 0007   BXO  
S2355 2013.04.14   1 1 S05W16 0004   BXO    
Total spot count: 51 75 33  
Sunspot number: 111 175 103  (total spot count + 10 * number of spotted regions)
Weighted SN: 84 101 59  (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): 67 61 57 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 max) 96.7 (cycle max) 61.1 (+1.2) 5.55
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 63.0 58.1 (+0.4) 7.96
2012.09 122.9 61.4 58.1 (-0.0) 8.07
2012.10 123.3 53.3 (57.6 projected, -0.5) 9.97
2012.11 121.3 61.8 (56.9 projected, -0.7) 7.08
2012.12 108.6 40.8 (55.7 projected, -1.2) 3.44
2013.01 127.1 62.9 (54.3 projected, -1.4) 4.69
2013.02 104.3 38.0 (53.3 projected, -1.0) 6.11
2013.03 111.3 57.9 (52.2 projected, -1.1) 10.56
2013.04 132.6 (1) 59.0 (2A) / 126.5 (2B) / 58.7 (2C) (51.0 projected, -1.2) (3.98)

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.