Last major update issued on April 20, 2011 at 05:20 UTC.
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[POES auroral activity level charts since October
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Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011] NEW
The geomagnetic field was quiet to unsettled on April 19. Solar wind speed ranged between 346 and 426 km/s. A high speed stream associated with CH445 was observed beginning at about 20h UTC at ACE.
Solar flux measured at 20h UTC on 2.8 GHz was 110.9 (increasing 6.3 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 12112213 (planetary), 12112213 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight UTC the visible solar disk had 10 spotted regions.
Region 11190 decayed further and will be rotating over the northwest
Region 11191 was quiet and stable.
Region 11193 lost some penumbra in the trailing spot section and was otherwise mostly unchanged. A minor M class flare is possible.
New region 11195 rotated into view on April 18 and was numbered by NOAA/SWPC the next day.
Spotted regions not numbered by NOAA/SWPC:
[S950] reemerged on April 15. Location at midnight: S15W17
[S960] emerged in the northeast quadrant on April 18. Location at midnight: N10E18
[S961] rotated into view at the southeast limb late on April 19. Location at midnight: S23E83
[S962] rotated into view at the southeast limb late on April 19. Location at midnight: S17E82
[S963] emerged in the southeast quadrant on April 19. Location at midnight: S18E27
[S964] emerged in the southwest quadrant on April 19. Location a midnight: S25W13
April 17-19: 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
An extension (CH445) of the southern polar coronal hole was Earth facing on April 16-17.
The darkest areas on the solar disk are likely coronal holes.
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 minor storm on April 20 with a chance of a major storm interval and quiet to unsettled on April 21 due to coronal hole effects. Quiet conditions are likely on April 22.
|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||8||S16E68||0020||DAO||CAO||formerly region S959
|Total spot count:||36||83|
|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||(22.6 predicted, +3.0)||6.07 / 6.27|
|2010.11||82.5||21.5||(25.7 predicted, +3.1)||4.80 / 5.50|
|2010.12||84.2||14.4||(28.9 predicted, +3.2)||3.41 / 4.35|
|2011.01||83.6||19.1||(31.9 predicted, +3.0)||4.32 / 5.51|
|2011.02||94.6||29.4||(34.4 predicted, +2.5)||5.41 / 6.44|
|2011.03||115.0||56.2||(36.7 predicted, +2.3)||7.79|
|2011.04||112.5 (1)||53.9 (2A) / 85.1 (2B)||(39.6 predicted, +2.9)||(10.63)|
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.