Last major update issued on February 2, 2013 at 08:10 UTC.
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[Solar cycles 23-24 (last update February 1, 2013)] [Cycle 24 progress (last update February 2, 2013) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update February 1, 2013)]
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[Archived reports since January 2003 (last update January 2, 2013)]
[POES auroral activity level since October
2009 - updated January 26, 2013]
[Solar polar fields vs solar cycles - updated January 8, 2013]
The geomagnetic field was quiet on February 1. Solar wind speed at SOHO ranged between 302 and 369 km/s. A low speed stream associated with CH551 arrived after noon and caused an increase in geomagnetic activity for the remainder of the day.
Solar flux measured at 20h UTC on 2.8 GHz was 103.7 (decreasing 41.4 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 10011112 (planetary), 10011202 (Boulder).
The background x-ray flux was at the class B2 level.
At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).
Region 11662 [N27W50] was quiet and stable.
Region 11663 [S09W37] decayed slowly and quietly.
Region 11665 [N11E25] developed slowly adding penumbra spots. C flares are possible.
Region 11666 [S24E23] was quiet and stable.
New region 11667 [N22E67] rotated into view on January 31 and was numbered by SWPC the next day.
Spotted regions not numbered by SWPC:
New region S2208 [S22E52] emerged with two spots, one of them with rudimentary penumbra.
January 30 - February 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 recurrent coronal hole (CH551) rotated over the central meridian on January 30-31.
The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.
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 February 2-5 due to weak coronal hole effects.
|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 (blue-green) 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:||15||40||19|
|Sunspot number:||65||100||79||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||38||68||47||(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):||39||35||38||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
|2012.08||115.4||63.1||(58.6 projected, +0.9)||7.96|
|2012.09||122.9||61.5||(58.7 projected, +0.1)||8.07|
|2012.10||123.3||53.3||(58.1 projected, -0.6)||9.97|
|2012.11||121.3||61.4||(57.4 projected, -0.7)||7.08|
|2012.12||108.6||40.8||(56.7 projected, -0.7)||3.44|
|2013.01||127.1||62.9||(56.0 projected, -0.7)||4.49|
|2013.02||103.7 (1)||2.3 (2A) / 65.0 (2B) / 63.5 (2C)||(55.0 projected, -1.0)||(4.0)|
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.