Last major update issued on December 19, 2011 at 05:10 UTC.
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The geomagnetic field was quiet on December 18. Solar wind speed ranged between 270 and 313 km/s. A weak disturbance associated with CH489 appears to have arrived at ACE at 04h UTC on December 19.
Solar flux measured at 20h UTC on 2.8 GHz was 127.4 (decreasing 13.7 over the last solar rotation). The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.8). Three hour interval K indices: 00010011 (planetary), 10021012 (Boulder).
The background x-ray flux is at the class B3 level.
At midnight UTC the visible solar disk had 13 spotted regions (in 2K resolution SDO images).
Region 11374 [S17W64] was quiet and stable.
Region 11375 [N09W72] decayed slowly and quietly.
Region 11376 [N24W09] was quiet and stable.
Region 11377 [N15W12] decayed slowly and quietly.
Region 11378 [S19W30] decayed slowly and quietly.
Region 11379 [S28W33] was quiet and lost a few spots.
Region 11380 [S19E58] was quiet and stable.
New region 11381 [S16E24] emerged quickly in the southeast quadrant on December 17 and was assigned an SWPC number the next day. C flares are possible.
New region 11382 [S16E32] emerged in the southeast quadrant on December 16 and was numbered by SWPC 2 days later. The region developed quickly on Dec.18 and could produce C flares.
Spotted regions not reported by NOAA/SWPC:
[S1378] emerged in the northern hemisphere near the central meridian on December 17. Note that SWPC considers this to be region 11376. The region decayed on Dec.18.
[S1379] rotated into view at the northeast limb on December 18. Location at midnight: N04E83
[S1380] emerged in the northeast quadrant on December 18. Location at midnight: N13E18
[S1381] emerged inside CH489 in the northwest quadrant on December 18. Location at midnight: N13W30
December 16-18: No obviously Earth directed CMEs observed.
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A small recurrent coronal hole (CH489) in the northern hemisphere was in an Earth facing position on December 16-17.
The above coronal hole map is based on a new method where coronal holes are detected 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 fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to unsettled with a chance of active intervals on December 19 due to effects from CH489. Quiet to unsettled is likely on December 20 becoming quiet on December 21-22.
|Coronal holes (1)||Coronal mass ejections (2)||M and X class flares (3)|
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
note that SWPC has region S1378 as 11376
|Total spot count:||23||82|
|Sunspot number:||103||212||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||50||112||(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):||62||95||k * (sunspot number). k = 0.6 for SWPC. k = 0.45 (changed from 0.33 on Nov.1) for STAR SDO|
|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)|
|2010.10||81.6||23.5||23.2 (+3.6)||6.07 / 6.27|
|2010.11||82.5||21.5||26.5 (+3.3)||4.80 / 5.50|
|2010.12||84.2||14.4||28.8 (+2.3)||3.41 / 4.35|
|2011.01||83.6||19.1||31.0 (+2.2)||4.32 / 5.51|
|2011.02||94.6||29.4||33.4 (+2.4)||5.41 / 6.44|
|2011.03||115.0||56.2||36.9 (+3.5)||7.79 / 8.18|
|2011.04||112.6||54.4||41.8 (+4.9)||9.71 / 8.83|
|2011.05||95.8||41.6||47.6 (+5.8)||9.18 / 8.94|
|2011.06||95.8||37.0||(53.7 projected, +6.1)||8.96 / 8.06|
|2011.07||94.2||43.9||(60.0 projected, +6.3)||9.14 / 8.16|
|2011.08||101.7||50.6||(65.5 projected, +5.5)||8.16 / 7.26|
|2011.09||133.8||78.0||(68.8 projected, +3.3)||12.80 / 12.27|
|2011.10||137.3||88.0||(72.3 projected, +3.5)||7.52|
|2011.11||153.5||96.7||(76.6 projected, +4.3)||4.58|
|2011.12||141.5 (1)||60.9 (2A) / 104.9 (2B)||(82.1 projected, +5.5)||(3.43)|
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.