Last major update issued on April 19, 2015 at 08:05 UT
[Solar and geomagnetic
data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2015)] [Cycle 24 progress (last update April 1, 2015) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2015)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2015)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2015)]
[Noon SDO sunspot count 1K Reference: 4K (large file) (updated daily)]
[POES auroral activity
level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated April 10, 2015]
[Presentations: 3rd SSN Workshop, Tucson, 2013 (pdf) / 4th SSN Workshop, Locarno, 2014]
The geomagnetic field was quiet to unsettled on April 18 under the decreasing influence of a high speed stream. Solar wind speed at SOHO ranged between 450 and 568 km/s.
Solar flux at 20h UTC on 2.8 GHz was 147.6 (increasing 25.2 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 127.6. The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.0). Three hour interval K indices: 22222232 (planetary), 22333322 (Boulder).
The background x-ray flux is at the class B5 level.
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 308) and 15 active regions using 1K resolution (SN: 234) SDO images on the visible solar disk.
Region 12321 [N11W26] decayed slowly and produced a
few C flares.
Region 12322 [N12W52] was quiet and stable.
Region 12324 [N19E08] decayed slowly and quietly.
Region 12325 [N04E17] was mostly unchanged and produced a C flare.
Region 12326 [N15W12] decayed slowly and quietly.
Region 12327 [S09E58] was quiet and stable.
New region 12328 [S02W68] emerged on April 17 and was numbered by SWPC the next day.
Spotted regions not numbered (or interpreted
differently) by SWPC:
S4367 [N08W17] decayed slowly and quietly.
S4380 [S18E10] was quiet and stable.
S4383 [S09E37] was quiet and stable.
S4385 [S19W27] decayed slowly and quietly.
S4391 [S08W32] developed slowly and quietly.
S4392 [N11W44] developed slowly and quietly.
New region S4394 [S08E19] emerged with a few spots.
New region S4395 [S15W24] emerged with penumbra spots.
New region S4396 [N14W47] emerged with a single spot.
|Magnitude||Peak time (UTC)||Location||AR||Recorded by||Comment|
April 16-18: No obviously Earth directed CMEs were observed.
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 southern hemisphere coronal hole (CH664) rotated across the central meridian on April 16-18.
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 unsettled on April 19-21. On April 19-20 there is a chance of occasional active intervals due to effects from CH664.
|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: 0-30% 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
|Total spot count:||44||148||84|
|Sunspot number:||114||308||234||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||69||196||132||(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):||68||108||129||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
|166.3||102.3 (cycle peak)||78.4 (+1.1)||10.70|
(likely solar max)
|2014.10||153.4||152.9||60.6||(67.3 projected, -3.6)||8.96|
|2014.11||154.8||151.4||70.1||(64.7 projected, -2.6)||9.33|
|2014.12||158.7||153.8||78.0||(62.4 projected, -2.3)||11.24|
|2015.01||141.9||137.3||67.0||(60.2 projected, -2.2)||9.46|
|2015.02||129.1||126.0||44.8||(58.4 projected, -1.8)||9.92|
|2015.03||125.9||124.6||38.4||(56.1 projected, -2.3)||16.14|
|2015.04||(128.8)||39.0 (2A) / 65.1 (2B) / 78.7 (2C)||(53.4 projected, -2.7)||(12.4)|
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.