Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 4, 2013 at 03:20 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 3. Solar wind speed at SOHO ranged between 351 and 479 km/s, slowly decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 147.9 (increasing 10.9 over the last solar rotation). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 22111121 (planetary), 22211321 (Boulder).

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

At midnight UTC the visible solar disk had 12 spotted active regions (in 2K resolution SDO images).

Region 11728 [N21W64] was quiet and stable.
Region 11730 [S17W82] was quiet and stable.
Region 11731 [N10W43] decayed further with few umbrae remaining and only rudimentary penumbra. There's polarity intermixing, particularly in the trailing spot section. C5+ flare: M1.3/2N at 16:55 UTC.
Region 11732 [S18W08] developed slowly and quietly.
Region 11734 [S18E18] was mostly quiet and stable.
New region 11737 [N12E33] emerged with one spot.
New region 11738 [N15E62] emerged with a few spots.
New region 11739 [N13E74] rotated into view and had several spots emerging during the day. There's significant polarity intermixing. C and M flares are possible. C5+ flare: major M5.7 at 17:32 UTC. This event was associated with a fast CME off the east limb.

Spotted regions not numbered by SWPC:
S2392 [N19E07] reemerged with penumbra spots.
S2394 [N15W12] decayed slowly and quietly.
New region S2395 [S19E80] rotated into view with a single spot.
New region S2396 [N43W22] emerged with a penumbra spot at a high latitude.

Coronal mass ejections (CMEs)

May 1, 3: 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 northern hemisphere coronal hole (CH567) was in an Earth facing position on April 28-30. A recurrent trans equatorial coronal hole (CH568) will become 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 poor to fair.

Forecast

The geomagnetic field is expected to be quiet on May 4 becoming quiet to unsettled with a chance of active intervals 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
11728 2013.04.22
2013.04.23
1 3 1 N19W72 0010 AXX BXO

location: N21W49

11730 2013.04.24 1 1 1 S16W81 0100 HSX HSX

 

11731 2013.04.24
2013.04.25
31 48 17 N10W43 0150 EAC ERI beta-gamma

area: 0100

 

11732 2013.04.26
2013.04.27
7 23 13 S17W15 0160 DSO DAI

area: 0220

location: S18W08

S2378 2013.04.26       N45W38           plage
11734 2013.04.28
2013.04.29
15 36 13 S19E10 0550 EKO EKO

beta-gamma

area: 0850

location: S18E18

S2386 2013.04.29       N25W30           plage
S2387 2013.04.29       N17W17           plage
11736 2013.04.30
2013.05.01
      S07E05           plage
S2389 2013.04.30       S22E09           plage
S2390 2013.04.30       S34E11           plage
11737 2013.04.30
2013.05.03
1 1 1 N19E35 0010 AXX HRX   location: N12E33
S2392 2013.04.30   3 1 N19E07 0008   BXO    
S2393 2013.04.30       S09W51           plage
S2394 2013.05.02   1   N15W12 0001   AXX  
11738 2013.05.03 1 2 1 N16E63 0030 HSX BXO   area: 0010
11739 2013.05.03 13 9 6 N13E75 0150 DAC CAI    
S2395 2013.05.03   1 1 S19E80 0050   HSX    
S2396 2013.05.03   1   N43W22 0001   AXX    
Total spot count: 70 129 55  
Sunspot number: 150 249 155  (total spot count + 10 * number of spotted regions)
Weighted SN: 105 165 91  (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): 90 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
2013.05 152.2 (1) 13.0 (2A) / 134.3 (2B) / 72.1 (2C) (57.5 projected, +0.1) (14.29)

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.