Last major update issued on May 2, 2013 at 05:00 UTC.
[Solar and geomagnetic data - last month (updated
[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)]
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.
April 29 - May 1: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
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) could become Earth facing on May 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 to good.
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
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:||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|
|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||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
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.