Last major update issued on September 25, 2013 at 04:25 UTC.
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daily)]
[Solar wind and
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[Solar cycles 23-24 (last update September 1, 2013)] [Cycle
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[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last
update September 1, 2013)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and
24 (last update September 1, 2013)]
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(last update April 5, 2007)]
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[Solar polar fields vs solar cycles - updated
September 24, 2013]
[Presentation
3rd
SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to active on September 24. Solar wind speed at SOHO ranged between 316 and 427 km/s. While there was no CME signature in ACE EPAM data, a sudden change in some solar wind parameters was observed at SOHO at 08:11 UTC. Wind density increased abruptly from 12 to 25 p/cm3. The geomagnetic disturbance lasted only approx. 9 hours and the most likely disturbance source is the large partial halo CME observed after a filament eruption in the northeast quadrant on September 21.
Solar flux measured at 20h UTC on 2.8 GHz was 110.2 (increasing 2.1 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 113.9. The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.0). Three hour interval K indices: 21144311 (planetary), 11133412 (Boulder).
The background x-ray flux was at the class B2 level.
At the time of counting spots (see image time) spots were observed in 12 active regions in 2K resolution (SN: 196) and 7 active regions in 1K resolution (SN: 103) SDO images on the visible solar disk.
Region 11845 [S17W26] decayed slowly and quietly.
Region 11846 [S18W16] was mostly quiet and stable.
Region 11849 [N19W38] decayed slowly and quietly.
Region 11850 [N09E09] developed quickly as new flux emerged. A magnetic
delta structure has formed and there is a chance of an M class flare.
Region 11851 [S20E47] decayed slowly and quietly.
Spotted regions not numbered by SWPC:
S2709 [S15E18] was quiet and stable.
New region S2710 [N22E58] emerged with a few spots.
New region S2711 [S12E13] emerged with a penumbra spot.
New region S2712 [S16E30] emerged with penumbra spots.
New region S2713 [S05E23] emerged with penumbra spots.
New region S2714 [S26W16] emerged with a penumbra spot.
New region S2715 [N17W48] was split off from AR
11849 as new trailing polarity flux emerged.
September 22-24: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since October
2002)
Compare today's report to the situation one solar rotation ago:
28 days ago
27 days ago
26 days ago
A recurrent trans equatorial coronal hole (CH588) will likely rotate into an Earth facing position on September 28.
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.
The geomagnetic field is expected to be quiet on September 25-27.
| Coronal holes (1) | Coronal mass ejection (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 2K resolution) Compare to the previous day's image. 0.5k image
When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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 magnetic polarity overlay |
Comment | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 11848 | 2013.09.16 2013.09.19 |
S11W33 | plage | ||||||||
| 11845 | 2013.09.16 2013.09.17 |
1 | S17W33 | 0003 | AXX |
 |
 |
location: S17W26 | |||
| 11847 | 2013.09.16 2013.09.17 |
N11W29 | plage | ||||||||
| 11846 | 2013.09.17 | 1 | 4 | 1 | S18W18 | 0150 | HSX | CSO |
 |
 |
area: 0230 location: S18W16 |
| 11849 | 2013.09.19 | 4 | 12 | 6 | N19W38 | 0030 | CRO | CRO |
 |
 |
|
| 11850 | 2013.09.19 | 10 | 43 | 21 | N08E10 | 0050 | CSO | DAC |
 |
 |
beta-gamma-delta location: N09E09 area: 0150 |
| S2704 | 2013.09.21 | S09E11 | plage | ||||||||
| 11852 | 2013.09.21 2013.09.23 |
S21W42 |
 |
plage | |||||||
| 11851 | 2013.09.22 | 1 | 2 | 1 | S19E41 | 0010 | AXX | CRO |
 |
 |
location: S20E47 |
| S2707 | 2013.09.22 | N16E14 |
 |
merged with AR 11850 | |||||||
| S2709 | 2013.09.23 | 3 | 1 | S15E18 | 0009 | AXX |
 |
 |
|||
| S2710 | 2013.09.24 | 3 | 1 | N22E58 | 0012 | HRX |
 |
||||
| S2711 | 2013.09.24 | 1 | S12E13 | 0003 | AXX |
 |
|||||
| S2712 | 2013.09.24 | 2 | S16E30 | 0002 | BXO |
 |
|||||
| S2713 | 2013.09.24 | 2 | S05E23 | 0002 | AXX |
 |
|||||
| S2714 | 2013.09.24 | 1 | S26W16 | 0001 | AXX |
 |
|||||
| S2715 | 2013.09.24 | 2 | 2 | N17W48 | 0008 | BXO |
 |
||||
| Total spot count: | 16 | 76 | 33 | ||||||||
| Sunspot number: | 56 | 196 | 103 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 29 | 100 | 57 | (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10) | |||||||
| Relative sunspot number (Wolf number): | 34 | 69 | 57 | k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for STAR SDO 2K, k = 0.55 for STAR SDO 1K | |||||||
| Month | Average measured solar flux | International sunspot number (SIDC) | Smoothed sunspot number | Average ap (3) |
|---|---|---|---|---|
| 2011.11 | 153.5 (cycle peak) | 96.7 (cycle peak) | 61.1 (+1.2) | 5.55 |
| 2012.02 | 106.5 | 32.9 | 66.9 (+1.4) likely cycle 24 max |
8.81 |
| 2012.05 | 121.5 | 69.0 | 61.7 (-2.9) | 7.06 |
| 2012.06 | 119.6 | 64.5 | 58.9 (-2.8) | 10.08 |
| 2012.07 | 133.9 | 66.5 | 57.8 (-1.1) | 13.90 |
| 2012.08 | 115.4 | 63.0 | 58.2 (+0.4) | 7.96 |
| 2012.09 | 122.9 | 61.4 | 58.1 (-0.1) | 8.07 |
| 2012.10 | 123.3 | 53.3 | 58.6 (+0.5) | 9.97 |
| 2012.11 | 121.3 | 61.8 | 59.7 (+1.1) | 7.08 |
| 2012.12 | 108.6 | 40.8 | 59.6 (-0.1) | 3.44 |
| 2013.01 | 127.1 | 62.9 | 58.7 (-0.9) | 4.69 |
| 2013.02 | 104.3 | 38.0 | 58.4 (-0.3) | 6.11 |
| 2013.03 | 111.3 | 57.9 | (58.2 projected, -0.2) | 10.56 |
| 2013.04 | 124.8 | 72.4 | (57.9 projected, -0.3) | 5.40 |
| 2013.05 | 131.4 | 78.7 | (58.0 projected, +0.1) | 9.73 |
| 2013.06 | 110.1 | 52.5 | (58.3 projected, +0.3) | 12.60 |
| 2013.07 | 115.5 | 57.0 | (58.3 projected, 0.0) | 9.47 |
| 2013.08 | 114.6 | 66.0 | (58.2 projected, -0.1) | 8.27 |
| 2013.09 | 101.5 (1) | 44.5 (2A) / 55.7 (2B) / 37.2 (2C) | (57.8 projected, -0.4) | (6.10) |
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)
Boulder SN current month
average to date. 2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices.
Values in red are based on the definitive
international Potsdam
WDC
ap indices.
This report has been prepared by Jan Alvestad. It is based on the 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.
