Last major update issued on April 12, 2012 at 04:10 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
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The geomagnetic field was quiet to unsettled on April 11. Solar wind speed at SOHO ranged between 283 and 353 km/s. A high speed stream associated with CH512 was observed arriving at ACE near 02h UTC on April 12.
Solar flux measured at 20h UTC on 2.8 GHz was 93.4 (decreasing 17.2 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.9). Three hour interval K indices: 22322113 (planetary), 11321112 (Boulder).
The background x-ray flux is at the class B1 level.
At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).
Region 11454 [S13E68] was quiet and stable.
New region 11455 [N07E08] emerged in the northeast quadrant on April 10 and got an SWPC number the next day. The region is developing slowly and has polarity intermixing. C flares are possible.
Spotted active regions not numbered by NOAA/SWPC:
S1573 [N25W13] reemerged with a single tiny spot.
S1577 [S28W02] was quiet and stable.
S1578 [S40E08] was quiet and stable.
S1579 [S16W41] was quiet and stable.
New region S1580 [S19W05] emerged in the southern hemisphere near the central meridian.
April 10-11: No obviously Earth directed CMEs were observed in LASCO and
April 9: A full halo CME became visible near noon after a C3 LDE in spotless AR 11451.
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 trans equatorial coronal hole (CH512) was in an Earth facing position on April 8-10. A small and poorly defined coronal hole (CH513) in the southern hemisphere could rotate into an Earth facing position on April 12-13.
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 minor storm on April 12-13 due to effects from CH512, isolated major storm intervals are possible. The CME observed on April 9 could reach Earth on April 12, however, in the presence of a strong high speed stream from CH512, what would likely have been a weak flanking impact will probably not be noticed. Quiet to unsettled conditions are likely on April 14. Weak effects from CH513 could be observed on April 15-16.
|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:||8||34||18|
|Sunspot number:||28||104||68||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||16||46||30||(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):||17||36||37||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)|
|2011.10||137.3||88.0||(60.1 projected, +0.6)||8.28|
|2011.11||153.5||96.7||(61.6 projected, +1.5)||5.55|
|2011.12||141.3||73.0||(64.3 projected, +2.7)||3.78|
|2012.01||132.5||58.3||(67.8 projected, +3.5)||7.15|
|2012.02||106.5||33.1||(71.8 projected, +4.0)||8.81|
|2012.03||114.7||64.2||(73.9 projected, +2.1)||16.08|
|2012.04||98.8 (1)||15.2 (2A) / 41.5 (2B)||(74.9 projected, +1.0)||(9.93)|
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 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.