Last major update issued on September 20, 2012 at 05:15 UTC.
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The geomagnetic field was quiet to minor storm on September 19. Solar wind speed at SOHO ranged between 324 and 397 km/s. Wind speed and temperature increased slowly after about 14h UTC as another coronal hole stream became the dominant solar wind source. It is uncertain if this is the early arrival of the stream from CH536 or a higher latitude northern hemisphere coronal hole.
Solar flux measured at 20h UTC on 2.8 GHz was 109.5 (increasing 12.8 over the last solar rotation). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 15.1). Three hour interval K indices: 23122345 (planetary), 13122444 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).
Region 11569 [S12W56] was quiet and stable.
Region 11571 [S14W35] was quiet and stable.
Region 11573 [N17E28] was quiet and stable.
Region 11574 [S23W57] developed slowly and quietly.
Region 11575 [N07E64] was quiet but could produce a minor M class flare.
The region has weak polarity intermixing.
New region 11576 [S22E69] rotated into view on September 18 and was
numbered one day later by SWPC. The region produced the two small C flares
recorded during the day.
Spotted regions not numbered by NOAA/SWPC:
S1924 [S22E23] added tiny spots in an extensive old plage area.
New region S1927 [N20E80] rotated into view with a single small spot.
September 17-19: 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 (CH536) was in an Earth facing position on September 17-19.
The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs 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 September 20-22 due to effects from CH536.
| 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 higher resolution image) 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 (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 magnetic polarity overlay |
Comment | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | STAR SDO | SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 11569 | 2012.09.09 2012.09.10 |
2 | 5 | 1 | S14W55 | 0100 | CSO | CSO |
 |
 |
area: 0180 location: S12W56 |
| 11571 | 2012.09.10 2012.09.12 |
1 | 7 | 3 | S14W35 | 0030 | HSX | CSO |
 |
 |
area: 0060 |
| S1912 | 2012.09.12 | N14W13 |
 |
plage | |||||||
| S1913 | 2012.09.12 | N13W47 | plage | ||||||||
| S1914 | 2012.09.13 | N20W08 | plage | ||||||||
| S1915 | 2012.09.13 | N23W28 | plage | ||||||||
| S1920 | 2012.09.14 | S04W51 | plage | ||||||||
| 11573 | 2012.09.15 2012.09.16 |
6 | 1 | N19E22 | 0000 | BXO |
 |
 |
location: N17E28 | ||
| 11574 | 2012.09.16 | 1 | 5 | 4 | S25W57 | 0020 | HSX | DRO |
 |
 |
location: S23W57 |
| S1922 | 2012.09.16 | N15W26 | plage | ||||||||
| 11575 | 2012.09.17 2012.09.18 |
4 | 12 | 6 | N10E62 | 0220 | EAO | EKO |
 |
 |
beta-gamma location: N07E64 area: 0420 |
| S1924 | 2012.09.17 | 6 | 2 | S22E23 | 0000 | AXX |
 |
 |
|||
| S1925 | 2012.09.17 | S12E14 | plage | ||||||||
| 11576 | 2012.09.18 2012.09.19 |
4 | 6 | 4 | S22E62 | 0050 | DSO | DSO |
 |
 |
|
| S1927 | 2012.09.19 | 1 | N20E80 | 0000 | AXX |
 |
|||||
| Total spot count: | 12 | 48 | 21 | ||||||||
| Sunspot number: | 62 | 128 | 91 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 37 | 76 | 49 | (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): | 37 | 45 | 50 | 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) |
|---|---|---|---|---|
| 2011.05 | 95.8 | 41.5 | 47.6 (+5.8) | 8.94 |
| 2011.06 | 95.8 | 37.0 | 53.2 (+5.6) | 8.06 |
| 2011.07 | 94.2 | 43.8 | 57.2 (+4.0) | 8.16 |
| 2011.08 | 101.7 | 50.6 | 59.0 (+1.8) | 7.26 |
| 2011.09 | 133.8 | 78.0 | 59.5 (+0.5) | 12.27 |
| 2011.10 | 137.3 | 88.0 | 59.9 (+0.4) | 8.28 |
| 2011.11 | 153.5 | 96.7 | 61.1 (+1.2) | 5.55 |
| 2011.12 | 141.3 | 73.0 | 63.4 (+2.3) | 3.78 |
| 2012.01 | 132.5 | 58.3 | 65.5 (+2.1) | 7.15 |
| 2012.02 | 106.5 | 32.9 | 66.9 (+1.4) | 8.81 |
| 2012.03 | 114.7 | 64.3 | (67.3 projected, +0.4) | 16.08 |
| 2012.04 | 113.0 | 55.2 | (66.5 projected, -0.8) | 10.10 |
| 2012.05 | 121.5 | 69.0 | (64.4 projected, -2.1) | 7.06 |
| 2012.06 | 119.6 | 64.5 | (63.6 projected, -0.8) | 10.08 |
| 2012.07 | 133.9 | 66.5 | (64.6 projected, +1.0) | 13.90 |
| 2012.08 | 115.4 | 63.1 | (67.2 projected, +2.6) | 7.96 |
| 2012.09 | 117.7 (1) | 53.8 (2A) / 84.9 (2B) / 58.3 (2C) | (70.0 projected, +2.8) | (11.43) |
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. 2C) STAR SDO 1K Wolf number month to date.
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.
