|Charts (* = updated daily)||Data and archive|
|Solar wind (*)||Solar and geomagnetic data - last month (*)|
|Electron fluence (*)||Archived daily reports and monthly data since 2003.01 (April 2, 2018)|
|Solar cycle||Solar cycles 23-24 (April 2, 2018)||Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)|
|Cycle 24 progress (April 2, 2018) / Cycle 25 spots (April 9, 2018)||Noon SDO sunspot count 1K image / 4K (*)|
|Solar cycles 1-24 (July 17, 2015)||POES auroral activity level October 2009 - December 2012]|
|Comparison of cycles 21, 22, 23 and 24 (April 2, 2018)||3rd SSN Workshop, Tucson, 2013|
|Comparison of cycles 12, 13, 14, 16 and 24 (April 2, 2018)||4th SSN Workshop, Locarno, 2014|
|Solar polar fields vs. solar cycles (January 7, 2018)|
The geomagnetic field was quiet on April 26. Solar wind speed at SOHO ranged between
322 and 353
km/s. Solar wind speed increased slowly and solar wind temperature
indicated the presence of a very weak coronal hole stream
Solar flux at 20h UTC on 2.8 GHz was 69.4 (increasing 0.6 over the previous solar rotation). The average 90 day 10.7 flux at 1 AU was 69.2. The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5). Three hour interval K indices: 22110001 (planetary), 22221101 (Boulder)
The background x-ray flux is at the class A3 level.
At the time of counting spots (see image time), spots were observed in 1 active region using 2K resolution (SN: 25) and in 1 active region using 1K resolution (SN: 16) SDO images on the visible solar disk.
Region 12706 [N03W26] decayed slowly and quietly.
|Magnitude||Peak time (UT)||Location||AR||Recorded by||Comment|
April 24-26: No obviously Earth directed CMEs were observed in available LASCO 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]
An extension (CH862) of the northern polar
coronal hole was Earth facing on April 22.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet
to unsettled on April 26 due to weak effects from CH862. Quiet conditions are likely on April 27-28.
|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). 4K 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 overlays
|Total spot count:||4||15||6|
|Sunspot number:||14||25||16||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||7||18||9||(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):||15||14||13||k * (sunspot number)
As of May 7, 2016: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.80 for MSN 1K (MSN=Magnetic Sunspot Number)
|Month||Average solar flux||International sunspot number
|Smoothed sunspot number (4)||Average ap
|166.3||146.1 (cycle peak)||110.5||10.70|
|2014.04||143.9||144.8||112.5||116.4 (solar max)||7.88|
|2017.09||91.3||92.3||43.6||18.3 (-1.2)||18.22 (cycle peak)|
|2017.10||76.4||75.6||13.2||(16.5 projected, -1.8)||10.30|
|2017.11||72.2||70.6||5.7||(14.6 projected, -1.9)||10.06|
|2017.12||71.6||69.3||8.2||(13.3 projected, -1.3)||7.33|
|2018.01||69.9||67.7||6.7||(12.3 projected, -1.0)||5.53|
|2018.02||72.0||70.2||10.6||(10.5 projected, -1.8)||6.40|
|2018.03||68.3||67.6||2.5||(7.6 projected, -2.9)||7.91|
|2018.04||(70.0)||6.4 (2A) / 7.4 (2B) / 9.5 (2C)||(5.7 projected, -1.9)||(6.8)|
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).
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 Universal Time. Comments and suggestions are always welcome.
SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.