Last major update issued on March 21, 2013 at 05:05 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update March 1, 2013)] [Cycle 24 progress (last update March 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 1, 2013)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2013)]
[POES auroral activity level since October
2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated February 3, 2013]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to unsettled on March 20. Solar wind speed at SOHO ranged between 352 and 637 km/s. Although there was no distinct solar wind shock, wind speed increased quickly from 12:18 UTC at SOHO as the CME observed on March 17 arrived. While initially there was only a minor increase in geomagnetic activity, minor storm levels have been observed early on March 21.
Solar flux measured at 20h UTC on 2.8 GHz was 107.6 (increasing 0.6 over the last solar rotation). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.3). Three hour interval K indices: 23212323 (planetary), 13212323 (Boulder).
The background x-ray flux was at the class B3 level.
At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).
Region 11692 [N08W69] developed slowly and has polarity intermixing.
There's a chance of an M class flare.
Region 11694 [N13W60] developed slowly and quietly. SWPC has renumbered this region as AR 11701.
Region 11695 [N09W47] was quiet and stable.
Region 11700 [S13E16] decayed slowly and quietly.
Spotted regions not numbered by SWPC:
S2292 [S27W13] reemerged with penumbra spots.
S2306 [N08W53] was quiet and stable.
S2307 [S24W33] was quiet and stable.
New region S2308 [N08W08] emerged with a penumbra spot.
March 18-20: 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 small southern hemisphere coronal hole (CH561) was in an Earth facing position on March 18.
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 minor storm on March 21 due to CME effects and quiet to unsettled on March 22 due to effects from CH561. Quiet conditions are likely on March 23-24.
|Coronal holes (1)||Coronal mass ejection (2)||M and X class flares (3)|
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
|S2306||2013.03.18||1||1||N08W53||0020||HRX||split off from AR 11695|
|11701||2013.03.20||5||N14W59||0020||CRO||see AR 11694|
|Total spot count:||20||28||15|
|Sunspot number:||70||108||75||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||41||49||36||(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):||42||38||41||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
|2012.09||122.9||61.4||(57.9 projected, -0.2)||8.07|
|2012.10||123.3||53.3||(57.0 projected, -0.9)||9.97|
|2012.11||121.3||61.4||(56.1 projected, -0.9)||7.08|
|2012.12||108.6||40.8||(54.9 projected, -1.2)||3.44|
|2013.01||127.1||62.9||(53.6 projected, -1.3)||4.69|
|2013.02||104.3||38.0||(52.5 projected, -1.1)||6.11|
|2013.03||117.3 (1)||61.0 (2A) / 94.6 (2B) / 52.6 (2C)||(51.5 projected, -1.0)||(9.89)|
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.