Last major update issued on June 1, 2011 at 04:35 UTC. Minor update added at 18:50 UTC,
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The geomagnetic field was quiet to unsettled on May 31. Solar wind speed ranged between 551 and 615 km/s under the influence of a high speed stream from CH451.
Solar flux measured at 20h UTC on 2.8 GHz was 112.0 (increasing 6.0 over the last solar rotation). The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 13.4). Three hour interval K indices: 33332233 (planetary), 32443333 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 8 spotted regions.
Region 11224 decayed further losing most spots.
Region 11225 was quiet and stable.
Region 11226 decayed further and lost all penumbra on the trailing spots. The largest penumbra split into smaller penumbrae. There's only minor polarity intermixing. Flares: C1.7 at 05:53 UTC.
Region 11227 is probably two regions as both the trailing and leading penumbrae are the same polarity. Flare: C1.8 at 04:43 UTC.
Region 11228 developed slowly and quietly.
Region 11229 developed slowly and quietly.
New region 11230 rotated into view at the northeast limb on May 30 and was numbered the next day by NOAA/SWPC.
Spotted regions not numbered by NOAA/SWPC:
[S1042] rotated partly into view at the northeast limb on May 31. Location at midnight: N07E86.
Minor update added at 18:50 UTC on June 1: Region 11226 was the source of a C4.1 long duration event peaking at 17:08 UTC. This event was associated with a northwards fast moving wave and likely a CME. A CME from the current position of 11226 could easily be Earth directed and cause major geomagnetic storming.
May 29-31: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since late October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
The southernmost extension of a large coronal hole (CH452) in the northern hemisphere was in an Earth facing position on May 30-31.
The above coronal hole map is based on a new method to detect coronal holes automatically. The method may need some fine tuning, however, 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 the new method, the extent and intensity of both holes 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 unsettled on June 1 due to effects from CH451. A high speed stream from CH452 could reach Earth on June 2 or 3 and cause unsettled to minor storm conditions.
|Coronal holes (1)||Coronal mass ejections (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 polarity overlay
|1||N17W98||0030||AXX||rotated out of view|
|3||5||N19E58||0030||BXO||BXO||formerly region S1041
|Total spot count:||52||95|
|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)|
|2010.02||84.7||18.8||10.6 (+1.3)||4.15 / 4.61|
|2010.03||83.4||15.4||12.3 (+1.7)||4.58 / 4.65|
|2010.04||75.9||8.0||14.0 (+1.7)||10.22 / 10.24|
|2010.05||73.8||8.7||15.5 (+1.5)||9.18 / 8.15|
|2010.06||72.5||13.6||16.4 (+0.9)||8.17 / 6.85|
|2010.07||79.8||16.1||16.7 (+0.3)||6.31 / 5.15|
|2010.08||79.2||19.6||17.4 (+0.7)||8.49 / 7.77|
|2010.09||81.1||25.2||19.6 (+2.2)||5.33 / 5.45|
|2010.10||81.6||23.5||23.2 (+3.6)||6.07 / 6.27|
|2010.11||82.5||21.5||(26.9 predicted, +3.7)||4.80 / 5.50|
|2010.12||84.2||14.4||(30.1 predicted, +3.2)||3.41 / 4.35|
|2011.01||83.6||19.1||(33.1 predicted, +3.0)||4.32 / 5.51|
|2011.02||94.6||29.4||(35.6 predicted, +2.5)||5.41 / 6.44|
|2011.03||115.0||56.2||(37.9 predicted, +2.3)||7.79|
|2011.04||112.6||54.4||(40.8 predicted, +2.9)||9.71|
|2011.05||95.8 (1)||61.8 (2A/2B)||(44.1 predicted, +3.3)||(9.18)|
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 preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.