Last major update issued on April 29, 2013 at 04:45 UTC.
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The geomagnetic field was quiet on April 28. Solar wind speed at SOHO ranged between 364 and 467 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 131.7 (increasing 12.6 over the last solar rotation). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 10022222 (planetary), 00022222 (Boulder).
The background x-ray flux was at the class B6 level.
At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).
Region 11728 [N22E03] developed slightly in the trailing spot section.
Region 11730 [S17W08] developed slowly and quietly. The region has polarity
intermixing and C flares are possible.
Region 11731 [N10E24] gained spots and has polarity intermixing. The
region was the most active on the visible disk and produced several low level C
flares. M class flares are possible.
Region 11732 [S16E57] was quiet and stable.
Region 11733 [S17W42] decayed slowly and was mostly quiet.
Spotted regions not numbered by SWPC:
S2368 [S17W33] reemerged with several spots.
S2384 [N13W70] decayed slowly and quietly.
New region S2385 [S18E81] rotated partly into view. The region could
produce M class flares.
April 26-28: 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 northern hemisphere coronal hole (CH567) will rotate into an Earth facing position on April 28-30.
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 on April 29 - May 1. Quiet to unsettled conditions with a chance of active intervals is possible on May 2-3 due to effects from CH567.
| 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 | ||||||||||
| 11727 | 2013.04.18 2013.04.19 |
N25W66 |
 |
plage | |||||||
| S2368 | 2013.04.20 | 9 | 2 | S17W33 | 0030 | CRO |
 |
||||
| S2369 | 2013.04.21 | N20W46 |
 |
plage | |||||||
| 11729 | 2013.04.21 2013.04.23 |
S15W77 |
 |
plage | |||||||
| 11728 | 2013.04.22 2013.04.23 |
1 | 10 | 7 | N19W02 | 0020 | HRX | CRO |
 |
 |
location: N22E03 |
| S2373 | 2013.04.23 | N08W22 | plage | ||||||||
| S2374 | 2013.04.23 | N16W16 | plage | ||||||||
| 11730 | 2013.04.24 | 18 | 42 | 28 | S18W07 | 0140 | DAI | EAI |
 |
 |
beta-gamma |
| 11731 | 2013.04.24 2013.04.25 |
25 | 73 | 31 | N09E25 | 0420 | DKC | EKC |
 |
 |
beta-gamma |
| 11732 | 2013.04.26 2013.04.27 |
1 | 2 | 1 | S17E54 | 0030 | HSX | HSX |
 |
 |
area: 0100 location: S16E57 |
| S2378 | 2013.04.26 | N45E27 | plage | ||||||||
| 11733 | 2013.04.26 2013.04.27 |
2 | 10 | 3 | S17W42 | 0030 | CSO | CRO |
 |
 |
|
| S2380 | 2013.04.26 | N36W33 | plage | ||||||||
| S2383 | 2013.04.27 | S42W53 |
 |
plage | |||||||
| S2384 | 2013.04.27 | 1 | 1 | N13W70 | 0004 | AXX |
 |
 |
|||
| S2385 | 2013.04.28 | 3 | 2 | S18E81 | 0380 | CKO |
 |
||||
| Total spot count: | 47 | 150 | 75 | ||||||||
| Sunspot number: | 97 | 230 | 155 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 75 | 189 | 114 | (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): | 58 | 81 | 85 | 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 | 123.1 (1) | 102.8 (2A) / 110.1 (2B) / 68.5 (2C) | (51.0 projected, -1.2) | (5.46) |
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.
