Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 7, 2013 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update May 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 May 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 6, 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 on May 6. Solar wind speed at SOHO ranged between 411 and 601 km/s under the nfluence of a high speed stream from CH568.

Solar flux measured at 20h UTC on 2.8 GHz was 130.7 (decreasing 15.8 over the last solar rotation). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.9). Three hour interval K indices: 11222222 (planetary), 113322-- (Boulder).

The background x-ray flux was at the class B5 level.

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

Region 11732 [S17W47] decayed slowly and quietly.
Region 11734 [S18W22] decayed slowly and quietly.
Region 11736 [S08W30] remeerged with several spots.
Region 11737 [N27E07] lost the leader spots.
Region 11738 [N17E23] was quiet and stable.
Region 11739 [N12E30] decayed significantly losing spots and penumbral area as well and has a much simpler magnetic layout than during the previous days.
Region 11740 [S20E39] developed slowly and quietly.
New region 11741 [S20E63] rotated into view on May 5 and developed slowly on May 6 when it was numbered by SWPC.

Spotted regions not numbered by SWPC:
New region S2400 [S31W33] emerged with a penumbra spot.

Coronal mass ejections (CMEs)

May 4-6: 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 (CH568) was Earth facing on May 2-3.

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 fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 7 due to coronal hole effects and quiet on May 8-9.

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
11731 2013.04.24
2013.04.25
1     N09W85 0010 AXX    

rotated out of view

location: N09W91

11732 2013.04.26
2013.04.27
4 8 4 S17W49 0090 DSO CAO

area: 0140

11734 2013.04.28
2013.04.29
17 33 13 S18W23 0370 EKI DKI

area: 0670

S2387 2013.04.29       N17W56           plage
11736 2013.04.30
2013.05.01
3 10 5 S07W39 0010 BXO DRO   area: 0040

location: S08W30

S2389 2013.04.30       S22W30           plage
S2390 2013.04.30       S34W28           plage
11737 2013.04.30
2013.05.03
  2   N16W07 0003   AXX location: N27E07
S2392 2013.04.30       N23W26         plage
S2394 2013.05.02       N15W51           plage
11738 2013.05.03 5 15 6 N15E20 0050 CAO CSI area: 0090

location: N17E23

11739 2013.05.03 7 19 7 N12E30 0110 DAI DSI beta-gamma
11740 2013.05.03 3 9 4 S20E39 0020 CAO DAO beta-gamma

area: 0060

S2397 2013.05.04       N11E14           plage
11741 2013.05.05
2013.05.06
2 7 4 S20E59 0010 BXO DRO area: 0025
S2399 2013.05.05       N13W42         plage
S2400 2013.05.06   1   S31W33 0002   AXX    
Total spot count: 42 104 43  
Sunspot number: 122 194 113  (total spot count + 10 * number of spotted regions)
Weighted SN: 72 140 79  (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): 73 68 62 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
2012.02 106.5 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 58.6 (+0.5) 9.97
2012.11 121.3 61.8 (59.1 projected, +0.5) 7.08
2012.12 108.6 40.8 (58.4 projected, -0.7) 3.44
2013.01 127.1 62.9 (58.0 projected, -0.4) 4.69
2013.02 104.3 38.0 (58.2 projected, +0.5) 6.11
2013.03 111.3 57.9 (57.8 projected, -0.4) 10.56
2013.04 124.8 72.4 (57.4 projected, -0.4) 5.40
2013.05 144.3 (1) 25.3 (2A) / 130.7 (2B) / 71.3 (2C) (57.5 projected, +0.1) (10.17)

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.