Last major update issued on October 21, 2011 at 07:05 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet on October 20. Solar wind speed ranged between 354 and 413 km/s under the influence of a weak coronal hole stream.
Solar flux measured at 20h UTC on 2.8 GHz was 159 (increasing 0.8 over the last solar rotation). The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 21002222 (planetary), 21102221 (Boulder).
The background x-ray flux is at the class C1 level.
At midnight UTC the visible solar disk had 16 spotted regions (in 2K resolution SDO images).
Region 11314 [N28W69] was quiet and stable.
Region 11316 [S12W63] decayed slowly and quietly.
Region 11317 [S26W48] was quiet and stable.
Region 11319 [N10W66] was quiet and has M class flare potential.
Region 11321 [S15W18] was quiet and stable.
Region 11323 [N23E13] was quiet and stable.
Region 11324 [N13E43] has many spots, is compact and has a magnetic delta structure in a central penumbra. M flares are possible. Flares: C1.5 at 02:03, C5.4 at 15:39 UTC
Region 11325 [N15E71] was quiet and stable.
New region 11326 [N16W34] emerged in the northwest quadrant.
New region 11327 [S20E13] emerged in the southeast quadrant on October 17 and was noticed by SWPC 3 days later. The region developed quickly on October 20 and could produce C flares.
New region 11328 [N19E23] emerged in the northeast quadrant on October but was then regarded as part of region 11323.
Spotted regions not reported by NOAA/SWPC:
[S1281] emerged in the southwest quadrant on October 19. Location at midnight: S16W73
[S1282] emerged in the southwest quadrant on October 20 and could soon develop C class flare potential. Location at midnight: S30W26
[S1283] emerged in the southeast quadrant on October 20. Location at midnight: S06E15
[S1284] emerged in the northwest quadrant on October 20. Location at midnight: N27W34
[S1285] emerged near the southwest limb on October 20. Location at midnight: S08W85
Region 11318 behind the northwest limb was the source of an M1.6 flare at 03:25 UTC.
October 18-20: No obviously Earth directed CMEs observed.
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
A small coronal hole (CH480) in the northern hemisphere was in an Earth facing position on October 19-20.
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 poor to fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet on October 21. Weak effects from CH480 are possible on October 22-23.
|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
|Total spot count:||61||154|
|Sunspot number:||161||314||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||111||213||(Sum of total spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)|
|Relative sunspot number (Wolf number):||97||104||k * (sunspot number). k = 0.6 for SWPC. k = 0.33 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)|
|2010.07||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||26.5 (+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||(41.1 predicted, +4.2)||9.71 / 8.83|
|2011.05||95.8||41.6||(45.2 predicted, +4.1)||9.18 / 8.94|
|2011.06||95.8||37.0||(49.2 predicted, +4.0)||8.96|
|2011.07||94.2||43.9||(53.1 predicted, +3.9)||9.14|
|2011.08||101.7||50.6||(57.2 predicted, +4.1)||8.16|
|2011.09||133.8||78.0||(60.3 predicted, +3.1)||12.80|
|2011.10||134.9 (1)||77.6 (2A) / 120.4 (2B)||(61.8 predicted, +1.5)||(7.08)|
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.