Last major update issued on April 20, 2014 at 05:50 UTC.
[Solar and geomagnetic data - last month (updated
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2014)] [Cycle 24 progress (last update April 1, 2014) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2014)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2014)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 2, 2014)]
[POES auroral activity level October
2009 - December 2012]
[Solar polar fields vs solar cycles - updated April 17, 2014]
[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet to active on April 20. Solar wind speed at SOHO ranged between 445 and 641 km/s.
Solar flux at 20h UTC on 2.8 GHz was 169.3 (increasing 12.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 153.6. The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.4). Three hour interval K indices: 43222331 (planetary), 34333321 (Boulder).
The background x-ray flux is at the class B8 level.
At the time of counting spots (see image time), spots were observed in 18 active regions in 2K resolution (SN: 408) and 17 active regions in 1K resolution (SN: 297) SDO images on the visible solar disk.
Region 12032 [N11W84] was mostly unchanged and
produced a few low level C flares.
Region 12033 [N11W70] was quiet and stable.
Region 12034 [N04W53] decayed slowly and was mostly quiet.
Region 12035 [S16W27] decayed slowly and was quiet.
Region 12036 [S17W54] has a weak magnetic delta structure in the central spot section. An M flare is possible.
Region 12037 [S09W53] decayed slowly and quietly.
Region 12038 [S11E09] merged with AR S3337 and was quiet.
Region 12039 [N23W41] decayed slowly and could soon become spotless.
Region 12040 [N15W27] developed slowly and quietly.
Region 12042 [N18E28] was quiet and stable.
New region 12044 [S20E53] rotated into view on April 18 and was numbered by SWPC the next day as the region developed slowly.
New region 12045 [S23E75] rotated partly into view on April 18 and produced a few low level C flares.
Spotted regions not numbered (or interpreted differently) by SWPC:
S3323 [S18W06] was quiet and stable.
S3330 [N10E08] was quiet and stable.
New region S3339 [N07E33] emerged with a few spots.
New region S3340 [S21W65] emerged early in the day with a penumbra spot and decayed slowly during the latter half of the day.
New region S3341 [S09E48] emerged with a penumbra spot.
New region S3342 [S03W12] emerged with a penumbra spot.
April 17, 19: No obviously Earth directed CMEs were observed in LASCO and
April 18: A filament eruption began just after 09h UTC to the south of AR 12036 and extended towards another center to the south of AR S3323 and appears to have been associated with a halo CME. The M8 flare after noon in AR 12036 was associated with a full halo CME which could reach Earth on April 20.
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
No obvious coronal holes are currently in or near Earth facing positions.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet to minor storm on April 20-21 due to CME effects and quiet on April 22.
|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
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: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% 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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
merged with AR S3337
|Total spot count:||139||238||147|
|Sunspot number:||259||408||297||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||207||294||203||(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):||155||143||163||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for MSN 2K, k = 0.55 for MSN 1K (MSN=Magnetic Sunspot Number)|
|Month||Average solar flux||International sunspot number
|Smoothed sunspot number||Average ap
|2013.10||132.1||131.2||85.6||(75.3 projected, +2.1)||7.71|
|2013.11||148.3||145.1||77.6||(76.3 projected, +1.0)||5.68|
|2013.12||147.7||143.1||90.3||(77.3 projected, +1.0)||4.68|
|2014.01||157.4||152.4||82.0||(78.3 projected, +1.0)||5.44|
|166.3||102.8 (cycle peak)||(78.1 projected, -0.2)||10.70|
|2014.03||149.9||148.5||92.2||(78.5 projected, +0.4)||4.88|
|2014.04||151.0 (1)||98.6 (2A) / 148.0 (2B) / 110.8 (2C)||(77.7 projected, -0.8)||(7.9)|
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 WDC-SILSO 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 GFZ 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.