Last major update issued on April 16, 2011 at 03:35 UTC.
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[POES auroral activity level charts since October
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Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011]
The geomagnetic field was quiet on April 15. Solar wind speed ranged between 346 and 406 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 129.4 (increasing 40.6 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 6.0). Three hour interval K indices: 22012221 (planetary), 22112212 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 13 spotted regions.
Region 11186 decayed slowly and quietly.
Region 11187 reemerged in the southwest quadrant.
Region 11189 added a few small spots and was quiet. [Note that SWPC has this region as 11185 with the real region 11185 having been renumbered 11189]
Region 11190 developed further as most of the spots in the leading and intermediate spot section merged into a single large penumbra. This penumbra is complex as positive polarity spots have invaded the eastern central part creating a strong magnetic delta structure. Further M class flares are likely and there's a chance of a major flare. Flares: C1.8 at 03:55, C1.3 at 04:41, C1.6 at 09:36, C2.8 at 13:50, C2.0 at 14:49, C1.6 at 16:14 and M1.3/1F at 17:12 UTC.
Region 11191 added several tiny spots in the trailing spot section.
Region 11192 decayed slowly and quietly.
Region 11193 decayed slowly and became less complex. There's still polarity intermixing and the region could produce an M class flare.
Region 11194 was quiet and stable.
Spotted regions not numbered by NOAA/SWPC:
[S950] reemerged with a single spot on April 15. Location at midnight: S16E31
[S951] reemerged with a few spots on April 15. Location at midnight: N28E17
[S952] emerged in the southern hemisphere near the central meridian on April 14. Location at midnight: S19W13
[S953] emerged in the northeast quadrant on April 14. Location at midnight: N21E13.
[S954] emerged near the northwest limb on April 15. Location at midnight: N29W82
A filament eruption in the southeast quadrant (traces captured on the AIA 193 image below) late in the day may be interesting (awaiting further analysis).
April 13-14: No obviously Earth directed CMEs were observed in LASCO
and STEREO imagery.
April 15: A slow moving CME was observed early in the day following a filament eruption in the southeast quadrant late on April 14. This CME could reach Earth on April 18 or 19.
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 will be Earth facing on April 16.
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 to fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be mostly quiet on April 16-18. On April 18 and 19 there's a chance of weak effects from a CME observed early on April 15. On April 19-20 a high speed coronal hole stream could reach Earth and cause some unsettled and active intervals.
|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||0010||AXX||SWPC data is for region 11189
|Total spot count:||54||124|
|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||112.1 (1)||43.6 (2A) / 87.3 (2B)||(39.6 predicted, +2.9)||(11.87)|
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.