Last major update issued on May 13, 2012 at 06:15 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet to unsettled on May 12. Solar wind speed at SOHO ranged between 452 and 623 km/s. SOHO recorded what appears to be a solar wind shock at 13:13 UTC, this caused an increase in solar wind speed to above 600 km/s and a minor increase in geomagnetic activity. The event was observed in ACE at the same time as a sudden increase in the total field of the IMF. The source of the event was likely a small CME on May 9 or 10.
Solar flux measured at 20h UTC on 2.8 GHz was 129.5 (increasing 27.8 over the last solar rotation). The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.1). Three hour interval K indices: 32223233 (planetary), 32222323 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).
Region 11476 [N08W22] decayed significantly losing penumbral area and spots.
While there are still magnetic delta structures within the region, they are
smaller and weaker than they were a few days ago. M class flares are possible.
Region 11477 [S23E21] was quiet and stable.
Region 11478 [S24E30] was quiet and stable.
Region 11479 [N14E54] was quiet and stable. SWPC is including S1646 in this region, an interpretation which is not supportable by magnetic polarity analysis.
Region 11480 [S17W18] decayed and could soon become spotless.
Spotted active regions not numbered by NOAA/SWPC:
S1642 [S15W04] was quiet and stable.
S1646 [N15E64] was quiet and stable.
S1647 [N12E22] decayed slowly and quietly.
New region S1648 [S26E64] emerged early in the day near the southeast limb.
New region S1649 [S10E75] rotated into view at the southeast limb.
New region S1650 [N05W34] emerged to the southwest of AR 11476.
May 10: No obviously Earth directed significant CMEs were observed in STEREO imagery.
May 11: A filament eruption began after 18h UTC and involved a large area around the center of the disk, including the southern part of AR 11476, AR 11480 and extending towards the east. A CME was observed in STEREO-B at 23:54 UTC and in STEREO-A a couple of hours later when images resumed. LASCO displays a slow and small halo CME. The CME is likely Earth directed.
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 southern hemisphere coronal hole (CH516) was Earth facing on May 9-10.
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 to good.
The geomagnetic field is expected to be quiet to active on May 13 due to a high speed stream from CH516. Quiet to unsettled is likely on May 14. The CME observed late on May 11 / early on May 12 could reach Earth on May 15 and cause unsettled to active conditions.
|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 higher resolution image) Compare to the previous day's 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:||45||117||63|
|Sunspot number:||85||227||143||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||70||155||101||(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):||51||79||79||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) 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
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|2011.11||153.5||96.7||(61.2 projected, +1.3)||5.55|
|2011.12||141.3||73.0||(63.9 projected, +2.7)||3.78|
|2012.01||132.5||58.3||(67.4 projected, +3.5)||7.15|
|2012.02||106.5||33.1||(71.4 projected, +4.0)||8.81|
|2012.03||114.7||64.2||(73.5 projected, +2.1)||16.08|
|2012.04||113.0||55.2||(74.5 projected, +1.0)||10.10|
|2012.05||121.3 (1)||36.6 (2A) / 94.7 (2B)||(75.8 projected, +1.3)||(10.56)|
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) Month average to date.
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.