Last major update issued on October 2, 2011 at 05:30 UTC.
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Annotated geomagnetic activity charts - Carrington rotation 2113 [July-August 2011] - 2114 [August-September 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]
The geomagnetic field was quiet to unsettled on October 1. Solar wind speed ranged between 405 and 545 km/s. A weak disturbance associated with CH477 was observed arriving at ACE near 09h UTC..
Solar flux measured at 23h UTC on 2.8 GHz was 136.9 (increasing 17.5 over the last solar rotation). The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.0). Three hour interval K indices: 32331212 (planetary), 44222223 (Boulder).
The background x-ray flux is at the class B7 level.
At midnight UTC the visible solar disk had 8 spotted regions (in 2K resolution SDO images).
Region 11302 [N13W46] decayed slowly and was mostly quiet. There's a magnetic delta structure in
a penumbra just south of the main penumbra. Flares:
C4.1 at 04:50, C1.0 at 12:39 UTC
Region 11305 [N12W12] developed slowly with a magnetic delta structure forming in a new penumbra just south of the main penumbra. Further M class flares are possible. Flares: C1.3 at 03:56, M1.2/1N long duration event peaking at 09:59 UTC. The latter event was associated with an Earth directed CME. The region was the source of an M3.9/1N flare at 00:50 on October 2, again producing an Earth directed CME.
Region 11306 [N15E09] added a few tiny trailing spots and was quiet.
Region 11307 [N15E37] was quiet and stable.
New region 11308 [S26E58] rotated into view at the southeast limb on September 30 and got an SWPC number the next day.
Spotted regions not reported by NOAA/SWPC:
[S1240] reemerged with several spots on September 30 and decayed again on October 1. Location at midnight: N26W62
[S1246] rotated into view at the northeast limb on October 1. Location at midnight: N23E82
[S1247] emerged on October 1 in the northwest quadrant to the west of region 11305. Location at midnight: N08W22
September 29: No obviously Earth directed CMEs observed.
September 30: A small and slow CME was observed after an M1 event in region 11305. This CME could reach Earth on October 3.
October 1: An Earth directed CME was associated with the M1 event in region 11305. The CME will likely reach Earth sometime between late on October 3 and noon on October 4. A large full halo CME was observed later in the day both in STEREO-A and B, its origin an active region a couple of days behind the northeast limb.
October 2: Another apparently Earth directed CME was observed in STEREO images early in the day. This CME could reach Earth sometime between noon and midnight on October 4.
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 recurrent coronal hole (CH477) in the southern hemisphere was in an Earth facing position on September 28-29. A northern hemisphere coronal hole (CH478) will probably rotate into an Earth facing position on October 6.
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. Propagation on long distance northeast-southwest paths is fair.
The geomagnetic field is expected to be quiet to active on October 2-3 due to CME and coronal hole effects. Unsettled to major storm conditions are possible on October 4-5 due to several CMEs arriving.
|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||3||S25E55||0030||HSX||HRX||formerly region S1241
|Total spot count:||36||64|
|Sunspot number:||86||144||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||64||95||(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):||52||48||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||136.9 (1)||2.8 (2A) / 86.0 (2B)||(61.8 predicted, +1.5)||(9.0)|
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.