Last major update issued on March 15, 2012 at 04:30 UTC. Minor update posted at 14:40 UTC
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The geomagnetic field was quiet to unsettled on March 14. Solar wind speed at SOHO ranged between 446 and 572 km/s.
Solar flux measured at 20h UTC on 2.8 GHz was 118.8 (increasing 15.6 over the last solar rotation). The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.1). Three hour interval K indices: 32012323 (planetary), 22222322 (Boulder).
The background x-ray flux is at the class B6 level.
At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).
Region 11429 [N18W79] decayed slowly as it rotated to the northwest
limb. Another major flare is possible while the region is transiting the limb.
Region 11432 [N15W00] displayed no significant changes. Flare: M2.8/1N at 15:21 UTC. This flare occurred along the inversion line between the trailing spots of region 11432 and the leader spots of region S1525. See this image during the early stages of the flare (location: N13E05):
Region 11433 [N13E24] lost a few spots and has weak polarity intermixing.
Region 11434 [S22E13] decayed slowly and quietly.
Spotted regions not reported by NOAA/SWPC:
[S1524] emerged in the southeast quadrant on March 11. Location at midnight: S25E03
[S1525] was split off from region 11432 on March 13. Location at midnight: N13E04
[S1526] emerged near the trailing spot of region 11434 on March 14. Location at midnight: S24E22
[S1527] emerged inside CH507 on March 14. Location at midnight: N10W16
Minor update added at 14:40 UTC: Regions 11432/S1525 again managed to produce an M class flare, M1.8/1F at 07:52 UTC. This time a weak type II radio burst was associated with the event. A small and apparently Earth directed CME was observed in STEREO imagery. It is very unusual for regions without mature penumbra to produce M class events, in this case it's interaction between opposite polarity fields in two nearby regions causing the events.
The CME observed on March 13 arrived some hours earlier than expected, solar wind speed and density increased quickly near 12:30 UTC at ACE. Active to major geomagnetic storming is possible for the remainder of the day and the first half of March 16. Interestingly solar wind speed had been increasing slowly since 05h UTC today, likely caused by the arrival of a high speed stream from CH507. The poorly defined solar wind shock is probably because of interaction between the high speed stream and the CME. Currently solar wind speed is above 700 km/s.
Two new active regions are visible as this is written. S1528 is rotating into view at the southeast limb (S13E83) and S1529 is emerging in the northeast quadrant (N16E47). The latest high res. CHARMAP.
March 12 and 14: No obviously Earth directed CMEs were observed in LASCO and
March 13: The M7 event in region 11429 was associated with a halo CME which could reach Earth late on March 15 or early on March 16.
Coronal hole history (since October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
A large recurrent trans equatorial coronal hole (CH507) was in an Earth facing position on March 13-14.
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 initially quiet to unsettled on March 15. Late in the day or early on March 16 the CME observed on March 13 is likely to arrive and cause unsettled to minor storm conditions, major storm intervals are possible. A high speed stream from CH507 in combination with the mentioned CME could cause unsettled to minor storm conditions on March 16-17.
|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
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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
SWPC includes region S1525
|S1525||2012.03.13||14||7||N13E04||0050||DSI||inversion line added in most recent image|
|Total spot count:||35||72||33|
|Sunspot number:||75||152||113||(total spot count + 10 * number of spotted regions)|
|Weighted penumbral SN:||60||103||64||(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):||45||53||62||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) 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
|2008.07||65.7 (SF minimum)||0.5||2.8 (-0.4)|
|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||41.8 (+4.9)||9.71 / 8.83|
|2011.05||95.8||41.6||47.6 (+5.8)||9.18 / 8.94|
|2011.06||95.8||37.0||53.2 (+5.6)||8.96 / 8.06|
|2011.07||94.2||43.9||57.2 (+4.0)||9.14 / 8.16|
|2011.08||101.7||50.6||59.0 (+1.8)||8.16 / 7.26|
|2011.09||133.8||78.0||(59.2 projected, +0.2)||12.80 / 12.27|
|2011.10||137.3||88.0||(59.4 projected, +0.2)||7.52 / 8.28|
|2011.11||153.5||96.7||(60.8 projected, +1.4)||4.58 / 5.55|
|2011.12||141.3||73.0||(63.6 projected, +2.8)||3.32|
|2012.01||132.5||58.3||(67.1 projected, +3.5)||6.59|
|2012.02||106.5||33.1||(71.0 projected, +3.9)||8.09|
|2012.03||127.2 (1)||35.6 (2A) / 78.9 (2B)||(73.2 projected, +2.2)||(23.92)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
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.