Last major update issued on October 5, 2011 at 04:35 UTC. Minor update posted at 13:40 UTC
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2114 [August-September 2011]
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The geomagnetic field was quiet on October 4. Solar wind speed ranged between 326 and 371 km/s.
Solar flux measured at 23h UTC on 2.8 GHz was 130.5 (increasing 17.7 over the last solar rotation). The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.9). Three hour interval K indices: 20222221 (planetary), 11322211 (Boulder).
The background x-ray flux is at the class B5 level.
At midnight UTC the visible solar disk had 9 spotted regions (in 2K resolution SDO images).
Region 11302 [N14W85] decayed further as it rotated to the northwest
limb. Flare: C7.3 long duration event
peaking at 09:23 UTC
Region 11305 [N11W52] was quiet and stable.
Region 11306 [N14W33] was quiet and stable.
Region 11307 [N16E04] decayed slowly and quietly.
Region 11309 [N24E42] was quiet and stable.
Region 11310 [S33E04] developed early in the day, then began to decay
slowly.
New region 11311 [S12E22] emerged in the southeast quadrant on October 3
and was assigned an SWPC number the next day. The region developed slowly on
October 4.
New region 11312 [N23E75] rotated into view at the northeast limb on
October 3 and was numbered the next day by SWPC.
Spotted regions not reported by NOAA/SWPC:
[S1254] rotated into view at the southeast limb on October 4.
Location at midnight: S12E85
Minor update added at 13:40 UTC on October 5: A relatively weak solar wind shock was observed at SOHO at 06:55 UTC, likely the arrival of the CME observed on October 1. Quiet to active conditions are likely for the remainder of the day.
Region S1254 has developed very quickly today and has polarity intermixing. The region produced a C9.2 flare at 12:42 UTC and is currently the most likely region on the visible disk to produce an M class event.
October 1: An Earth directed CME was associated with the M1 event in
region 11305. 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: An apparently Earth directed CME was observed in STEREO
images early in the day (associated with the M3.9 event in region 11305).
October 3: No obviously Earth directed CMEs observed.
October 4: No obviously Earth directed CMEs observed. An impressive full
halo CME was observed in LASCO images following an eruption in a very active
backsided northern hemisphere region. This region will rotate into view in 3-4
days. Several filament eruptions were observed during the latter half of the day
in the southern hemisphere. It's unclear if any of these eruptions produced
small partially Earth directed CMEs.
Coronal hole history (since late October
2002)
Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
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 poor to fair.
The geomagnetic field is expected to be quiet to active on October 5 due to CME effects. Quiet to unsettled is likely on October 6-8 becoming quiet to active on October 9 due to effects from CH478.
| 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
green.
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 detected |
Spot count | Location at midnight | Area | Classification | SDO / HMI 4K continuum image with polarity overlay |
Comment | |||
|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | |||||
| 11302 | 2011.09.21 2011.09.22 |
7 | 5 | N13W85 | 0240 | DSO | CSO |
 |
 |
|
| 11305 | 2011.09.24 2011.09.25 |
10 | 8 | N11W49 | 0190 | CSI | CHO |
 |
 |
location: N11W52 area: 0270 |
| 11306 | 2011.09.25 2011.09.26 |
1 | 5 | N14W34 | 0030 | HSX | CRO |
 |
 |
area: 0020 |
| 11307 | 2011.09.27 2011.09.28 |
4 | 9 | N15W01 | 0010 | BXO | BXO |
 |
 |
location: N16E04 |
| S1239 | 2011.09.27 | S22W59 | plage | |||||||
| 11308 | 2011.09.30 2011.10.01 |
S25E15 |
 |
plage | ||||||
| S1242 | 2011.09.30 | N21W22 | plage | |||||||
| S1243 | 2011.09.30 | S16W44 | plage | |||||||
| S1244 | 2011.09.30 | S27W24 | plage | |||||||
| S1245 | 2011.09.30 | S23W38 | plage | |||||||
| 11309 | 2011.10.01 2011.10.02 |
6 | 6 | N24E42 | 0160 | DAO | CHO |
 |
 |
area: 0300 |
| 11310 | 2011.10.02 2011.10.03 |
8 | 12 | S32E02 | 0045 | DAO | DRO |
 |
 |
|
| S1249 | 2011.10.02 | N33E05 | plage | |||||||
| S1250 | 2011.10.02 | N27W08 | plage | |||||||
| S1251 | 2011.10.03 | S18E45 |
 |
plage | ||||||
| 11311 | 2011.10.03 2011.10.04 |
12 | 12 | S12E20 | 0070 | DAI | CSO |
 |
 |
formerly region S1252 |
| 11312 | 2011.10.03 2011.10.04 |
1 | 1 | N22E74 | 0210 | HSX | HHX |
 |
 |
area: 0350 |
| S1254 | 2011.10.04 | 1 | S12E85 | 0000 | AXX |
 |
||||
| Total spot count: | 49 | 59 | ||||||||
| Sunspot number: | 129 | 149 | (total spot count + 10 * number of spotted regions) | |||||||
| Classification adjusted SN: | 84 | 105 | (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 | 49 | 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 (3) |
|---|---|---|---|---|
| 2008.07 | 65.7 (SF minimum) | 0.5 | 2.8 (-0.4) | |
| 2008.12 | 69.2 | 0.8 | 1.7 (-) sunspot minimum |
3.25 |
| 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 | 131.8 (1) | 12.8 (2A) / 99.5 (2B) | (61.8 predicted, +1.5) | (8.01) |
1) Running average based on the daily 20:00 UTC observed solar flux value at
2800 MHz.
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.
