Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 2, 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 unsettled to minor storm on May 1. Solar wind speed at SOHO ranged between 323 and 473 km/s. Near 08h UTC a disturbance likely related to a high speed stream from CH567 began. There was some overlap with the disturbance noted the day before.

Solar flux measured at 20h UTC on 2.8 GHz was 159.2 (increasing 30.7 over the last solar rotation). The Potsdam WDC planetary A index was 27 (STAR Ap - based on the mean of three hour interval ap indices: 27.0). Three hour interval K indices: 33545353 (planetary), 23454333 (Boulder).

The background x-ray flux was at the class B7 level.

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

Region 11728 [N22W36] was quiet and stable.
Region 11730 [S16W53] produced several C flares and decayed significantly. C5+ flares: C9.6 at 01:26, C5.5 at 07:29 UTC.
Region 11731 [N09W17] decayed losing spots and penumbral area. There are still minor magnetic delta structures in the trailing and central spot sections.C and minor M class flares are possible. C5+ flare: C5.5 at 07:29 UTC.
Region 11732 [S17E18] was quiet and stable.
Region 11734 [S18E45] was mostly quiet and stable. M flares are possible.
Region 11735 [S17W78] decayed further and was quiet.
New region 11736 [S07E36] emerged on April 30 and was numbered by SWPC the next day.

Spotted regions not numbered by SWPC:
S2391 [N17E62] was quiet and stable.
S2392 [N22E38] was quiet with barely visible penumbra spots.

Coronal mass ejections (CMEs)

April 29 - May 1: 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 northern hemisphere coronal hole (CH567) was in an Earth facing position on April 28-30. A recurrent trans equatorial coronal hole (CH568) could become Earth facing on May 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 to good.

Forecast

The geomagnetic field is expected to be quiet to unsettled with a chance of active intervals on May 2-3 due to effects from CH567. Quiet conditions are likely on May 4 becoming quiet to unsettled on May 5-6 due to effects from CH568.

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
11735 2013.04.20
2013.04.29
1 1 1 S17W76 0010 AXX HRX location: S17W78
11728 2013.04.22
2013.04.23
1 5 2 N19W44 0010 AXX CRO

location: N22W36

S2374 2013.04.23       N16W55           plage
11730 2013.04.24 12 20 13 S18W48 0100 EAI DSI beta-gamma

location: S16W53

11731 2013.04.24
2013.04.25
36 76 34 N09W17 0350 EKC EAC beta-gamma-delta

area: 0500

 

11732 2013.04.26
2013.04.27
10 26 10 S17E12 0180 DSI DSO

area: 0230

location: S17E18

S2378 2013.04.26       N45W12           plage
11733 2013.04.26
2013.04.27
1     S17W84 0010 AXX     spotless
11734 2013.04.28
2013.04.29
6 20 8 S19E37 0550 DKO EKO

area: 0950

location: S18E45

S2386 2013.04.29       N25W04           plage
S2387 2013.04.29       N17E09           plage
11736 2013.04.30
2013.05.01
4 6 5 S07E34 0010 BXO BXO  
S2389 2013.04.30       S22E35         plage
S2390 2013.04.30       S34E37         plage
S2391 2013.04.30   2 1 N17E62 0007   AXX  
S2392 2013.04.30   2   N22E38 0002   AXX  
S2393 2013.04.30       S09W25         plage
Total spot count: 71 158 74  
Sunspot number: 151 248 154  (total spot count + 10 * number of spotted regions)
Weighted SN: 101 189 105  (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): 91 87 85 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
2013.05 159.2 (1) 4.9 (2A) / 151.0 (2B) / 71.9 (2C) (57.5 projected, +0.1) (27.0)

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.