Last major update issued on April 26, 2013 at 04:00 UTC.
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SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to unsettled on April 25. Solar wind speed at SOHO ranged between 420 and 609 km/s under the influence of a high speed stream from CH566.
Solar flux measured at 20h UTC on 2.8 GHz was 119.2 (increasing 14.1 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5). Three hour interval K indices: 32122232 (planetary), 22232222 (Boulder).
The background x-ray flux was at the class B8 level.
At midnight UTC the visible solar disk had 9 spotted active regions (in 2K resolution SDO images).
Region 11726 [N13W76] still has the potential to produce a major flare
and will be rotating over the northwest limb today and tomorrow.
C5+ flares: C5.6 at 17:28, C5.8 at 19:40,
C5.7 at 22:02 UTC.
Region 11727 [N25W24] decayed slowly and quietly.
Region 11728 [N19E39] was quiet and stable.
Region 11729 [S15W34] decayed slowly and quietly.
Region 11730 [S18E33] matured and was mostly quiet.
New region 11731 [N08E64] rotated into view on April 24 and was numbered
the next day by SWPC. The region has polarity intermixing and could produce M
class flares.
Spotted regions not numbered by SWPC:
S2368 [S17E05] was quiet and stable.
S2369 [N17W07] was quiet and stable.
S2376 [N13W43] was quiet and stable.
April 23-25: 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 trans equatorial coronal hole (CH566) was Earth facing position on April 22-24. CH566 has decayed significantly during its transition of the visible disk.
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 to good.
The geomagnetic field is expected to be quiet to active on April 26 and quiet to unsettled on April 27 due to effects from CH566. Quiet conditions are likely on April 28.
| 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 | ||||||||||
| 11724 | 2013.04.12 2013.04.13 |
S26W88 | plage | ||||||||
| S2359 | 2013.04.17 | S15W28 | plage | ||||||||
| 11727 | 2013.04.18 2013.04.19 |
1 | 10 | 3 | N24W26 | 0030 | HRX | CRO |
 |
 |
|
| 11726 | 2013.04.19 | 17 | 13 | 10 | N13W85 | 1000 | FKC | FKI |
 |
 |
beta-gamma-delta |
| S2368 | 2013.04.20 | 8 | 1 | S17E05 | 0010 | AXX |
 |
 |
|||
| S2369 | 2013.04.21 | 4 | N17W07 | 0011 | AXX |
 |
 |
||||
| 11729 | 2013.04.21 2013.04.23 |
3 | 8 | 2 | S15W35 | 0040 | DSO | CRO |
 |
 |
|
| 11728 | 2013.04.22 2013.04.23 |
1 | 10 | 4 | N19E37 | 0050 | HSX | CSO |
 |
 |
beta-gamma |
| S2373 | 2013.04.23 | N08E17 | plage | ||||||||
| S2374 | 2013.04.23 | N16E23 |
 |
plage | |||||||
| 11730 | 2013.04.24 | 7 | 12 | 3 | S19E34 | 0060 | DAO | DSO |
 |
 |
area: 0130 |
| 11731 | 2013.04.24 2013.04.25 |
4 | 19 | 10 | N07E61 | 0270 | DKC | DKC |
 |
 |
beta-gamma location: N08E64 area: 0500 |
| S2376 | 2013.04.24 | 7 | 3 | N13W43 | 0018 | BXO |
 |
 |
|||
| Total spot count: | 33 | 91 | 36 | ||||||||
| Sunspot number: | 93 | 181 | 116 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 71 | 127 | 82 | (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): | 56 | 63 | 64 | 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 max) | 96.7 (cycle max) | 61.1 (+1.2) | 5.55 |
| 2012.01 | 132.5 | 58.3 | 65.5 (+2.1) | 7.15 |
| 2012.02 | 106.5 | 32.9 | 66.9 (+1.4) possible cycle 24 max |
8.81 |
| 2012.03 | 114.7 | 64.3 | 66.8 (-0.1) | 16.08 |
| 2012.04 | 113.0 | 55.2 | 64.6 (-2.2) | 10.10 |
| 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 | 57.7 (-1.2) | 13.90 |
| 2012.08 | 115.4 | 63.0 | 58.1 (+0.4) | 7.96 |
| 2012.09 | 122.9 | 61.4 | 58.1 (-0.0) | 8.07 |
| 2012.10 | 123.3 | 53.3 | (57.6 projected, -0.5) | 9.97 |
| 2012.11 | 121.3 | 61.8 | (56.9 projected, -0.7) | 7.08 |
| 2012.12 | 108.6 | 40.8 | (55.7 projected, -1.2) | 3.44 |
| 2013.01 | 127.1 | 62.9 | (54.3 projected, -1.4) | 4.69 |
| 2013.02 | 104.3 | 38.0 | (53.3 projected, -1.0) | 6.11 |
| 2013.03 | 111.3 | 57.9 | (52.2 projected, -1.1) | 10.56 |
| 2013.04 | 122.7 (1) | 92.8 (2A) / 111.3 (2B) / 65.2 (2C) | (51.0 projected, -1.2) | (5.12) |
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 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.
