Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 5, 2013 at 05:00 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 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 on May 4. Solar wind speed at SOHO ranged between 346 and 408 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 141.6 (increasing 3.8 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 11111111 (planetary), 11221312 (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 11731 [N09W60] produced a few low level C flares and continued to simplify and lose spots.
Region 11732 [S17W20] was quiet and stable.
Region 11734 [S18E05] gained spots and has polarity intermixing. C and M flars are possible.
Region 11737 [N20E23] gained penumbra spots and was quiet.
Region 11738 [N16E48] developed slowly and quietly.
Region 11739 [N13E59] developed with a magnetic delta structure forming centrally. There's significant polarity intermixing. C and M flares are possible. C5+ flare: C5.6 at 12:36 UTC.
New region 11740 [S20E67] rotated into view on May 3 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2392 [N22W02] was quiet and stable.
New region S2397 [N11E40] emerged with penumbra spots.

Coronal mass ejections (CMEs)

May 3-4: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
May 2: The CME associated with the M1 event in AR 11731 may have had a faint Earth directed component. A very weak glancing blow is possible on May 5.

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 with a chance of active intervals on May 5-6 due to effects from CH568. Quiet conditions are likely on May 7.

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
11728 2013.04.22
2013.04.23
2     N20W85 0010 BXO    

spotless

11730 2013.04.24 1     S16W93 0080 HSX    

rotated out of view

11731 2013.04.24
2013.04.25
20 17 8 N10W43 0090 EAI FAI beta-gamma

area: 0070

 

11732 2013.04.26
2013.04.27
12 22 6 S17W22 0150 DSO CAO

area: 0210

11734 2013.04.28
2013.04.29
22 57 21 S17E04 0590 EKI EHI

beta-gamma

area: 0800

S2386 2013.04.29       N25W43           plage
S2387 2013.04.29       N17W30           plage
11736 2013.04.30
2013.05.01
      S07W10           plage
S2389 2013.04.30       S22W04           plage
S2390 2013.04.30       S34W02           plage
11737 2013.04.30
2013.05.03
1 13 2 N16E21 0010 AXX BXO location: N20E23
S2392 2013.04.30   4 2 W22W02 0011   AXX  
S2394 2013.05.02       N15W25         plage
11738 2013.05.03 2 8 4 N15E47 0010 CSO CRO area: 0040
11739 2013.05.03 5 17 8 N13E57 0110 DAC DAC beta-gamma-delta

area: 0200

11740 2013.05.03 1 1 1 S20E64 0030 HSX HSX  
S2396 2013.05.03       N43W35          
S2397 2013.05.04   2 1 N11E40 0007   AXX    
Total spot count: 66 141 53  
Sunspot number: 156 231 143  (total spot count + 10 * number of spotted regions)
Weighted SN: 106 174 86  (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): 94 81 79 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) 5.45
2013.05 149.5 (1) 18.0 (2A) / 139.8 (2B) / 71.8 (2C) (57.5 projected, +0.1) (11.81)

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.