Last major update issued on September 20, 2011 at 03:05 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update September 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update September 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update September 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update September 1, 2011)]
[POES auroral activity level since October
2009 - updated September 15, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2112 [July 2011] - 2113 [July-August 2011]
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet on September 19. Solar wind speed ranged between 359 and 424 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 140.9 (increasing 37.2 over the last solar rotation). The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 2.8). Three hour interval K indices: 10101111 (planetary), 00101211 (Boulder).
The background x-ray flux is at the class B8 level.
At midnight UTC the visible solar disk had 6 spotted regions (in 2K resolution SDO images).
Region 11295 [N22W22] developed in the leading spot section while the
trailing spots displayed some decay. Polarities are intermixed. An M class flare is possible.
Region 11296 [N26W05] decayed slowly. Flares: C2.4 at 04:59, long duration C6.2 peaking at 07:37 (this event was associated with a partial halo CME with most of the ejected material observed off the eastern limbs) UTC.
Region 11298 [N14W23] decayed further and was quiet.
Region 11299 [S19W27] lost a few spots but gained penumbra on the trailing spots.
Region 11300 [N24W59] decayed slowly and quietly
Region 11301 [N20E67] has mixed polarities and could produce a minor M class flare. Flares: C6.9 at 15:41, C1.3 at 18:47 UTC.
September 17-18: No obviously Earth directed CMEs observed.
September 19: A partial halo CME was observed following an LDE in region 11296. There's a slight chance this CME could reach Earth on September 22.
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
No obvious coronal holes are currently in or near potentially geoeffective positions.
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 mostly quiet on September 20-22. There's a minor chance a weak CME could reach Earth on Sept.22 and cause a few unsettled to 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
rotated out of view
|Total spot count:||58||118|
|Sunspot number:||128||178||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||91||151||(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):||77||59||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)|
|2010.06||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||26.5 (+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||(36.2 predicted, +2.8)||7.79 / 8.18|
|2011.04||112.6||54.4||(39.1 predicted, +2.9)||9.71 / 8.83|
|2011.05||95.8||41.6||(42.4 predicted, +3.3)||9.18 / 8.94|
|2011.06||95.8||37.0||(46.1 predicted, +3.7)||8.96|
|2011.07||94.2||43.9||(50.3 predicted, +4.2)||9.14|
|2011.08||101.7||50.6||(54.4 predicted, +4.1)||8.16|
|2011.09||125.4 (1)||70.7 (2A) / 111.7 (2B)||(56.7 predicted, +2.3)||(11.71)|
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.