Last major update issued on May 3, 2013 at 04:50 UTC.
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[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)]
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[POES auroral activity level since October
2009 - updated January 26, 2013]
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[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to active on May 2. Solar wind speed at SOHO ranged between 428 and 551 km/s under the influence of a high speed stream from CH567.
Solar flux measured at 20h UTC on 2.8 GHz was 149.4 (increasing 15.0 over the last solar rotation). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.5). Three hour interval K indices: 44221132 (planetary), 44322322 (Boulder).
The background x-ray flux was at the class B8 level.
At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).
Region 11728 [N22W49] decayed slowly and quietly.
Region 11730 [S16W69] decayed quickly and quietly.
Region 11731 [N09W32] decayed further losing penumbral area. There are still many spots, however, most of them are small. The magnetic delta structures disappeared. C5+ flare: M1.1 at 05:10 UTC. This event was associated with a type II radio sweep and a fairly narrow northwards directed CME.
Region 11732 [S17E07] was quiet and stable.
Region 11734 [S18E31] developed slowly and has polarity intermixing.C and M flares are possible.
Spotted regions not numbered by SWPC:
New region S2394 [N14W01] emerged next to CH568.
April 30 - May 1: No obviously Earth directed CMEs were observed in LASCO
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 hole history (since October
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.
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.
The geomagnetic field is expected to be quiet to unsettled on May 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
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.
(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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
|Total spot count:||52||145||70|
|Sunspot number:||102||205||110||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||82||170||95||(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):||61||72||61||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K|
|Month||Average measured solar flux||International sunspot number (SIDC)||Smoothed sunspot number||Average ap
|2011.11||153.5 (cycle max)||96.7 (cycle max)||61.1 (+1.2)||5.55|
possible cycle 24 max
|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||154.3 (1)||8.2 (2A) / 126.5 (2B) / 71.8 (2C)||(57.5 projected, +0.1)||(19.0)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
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.