Last major update issued on October 1, 2011 at 05:50 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 active on September 30. Solar wind speed ranged between 427 and 564 km/s. Another disturbance was observed arriving at ACE near 14h UTC and caused active geomagnetic conditions after 18h UTC.
Solar flux measured at 23h UTC on 2.8 GHz was 138.1 (increasing 19.4 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.6). Three hour interval K indices: 10001144 (planetary), 21011223 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight UTC the visible solar disk had 11 spotted regions (in 2K resolution SDO images).
Region 11301 [N17W78] was quiet and stable as it rotated to the
Region 11302 [N13W32] decayed slowly and was mostly quiet. There's still a magnetic delta structure in the southern part of the main penumbra and a major flare is possible. Flares: C1.0 at 02:52, C1.1 at 20:42 UTC
Region 11305 [N12E02] developed further and could produce another M class flare. Flares: C7.7 at 04:00, M1.0/1F at 19:06. A small and slow CME was observed in STEREO-A after the M1 event.
Region 11306 [N14E22] was quiet and stable.
Region 11307 [N15E50] was mostly quiet. There's minor polarity intermixing in the leading spot section. Flare: C3.4 at 18:47 UTC.
Spotted regions not reported by NOAA/SWPC:
[S1240] reemerged with several spots on September 30. Location at midnight: N24W47
[S1241] rotated into view at the southeast limb on September 30. Location at midnight: S26E72
[S1242] emerged in the northeast quadrant on September 30. Location at midnight: N21E43
[S1243] emerged in the southeast quadrant on September 30. Location at midnight: S16E21
[S1244] emerged in the southeast quadrant on September 30. Location at midnight: S27E41
[S1245] emerged in the southeast quadrant on September 30. Location at midnight: S23E16
September 28-29: 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.
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.
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 1-4 due to CME and coronal hole effects.
|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:||39||85|
|Sunspot number:||89||195||(total spot count + 10 * number of spotted regions)|
|Classification adjusted SN:||69||113||(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):||53||64||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||133.8 (1)||106.8 (2A / 2B) SWPC
Wolf number: 64.1
|(56.7 predicted, +2.3)||(12.80)|
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.