|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 1, 2020)|
|Solar cycle||Solar cycles 23-24 (April 1, 2020)||Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)|
|Cycle 24-25 progress (April 1, 2020)||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 1, 2020)||3rd SSN Workshop, Tucson, 2013|
|Comparison of cycles 12, 13, 14, 16 and 24 (April 1, 2020)||4th SSN Workshop, Locarno, 2014|
|Solar polar fields vs. solar cycles (March 18, 2020)||Cycle 25 spots (December 25, 2019)|
The geomagnetic field was very quiet on April 19. Solar wind speed at SOHO ranged between 288 and 332 km/sec. What appears to be a weak solar wind shock was observed at DSCOVR at 01:30 UT on April 20. The geomagnetic field has been quiet to unsettled afterwards.
Solar flux at 20h UT on 2.8 GHz was 68.6 (decreasing 1.8 over the previous solar rotation). The average 90 day 10.7 flux at 1 AU was 69.6 (Centered average 90 day SF at 1 AU: Minimum of 67.77 on December 9, 2018. Centered 1 year average SF at 1 AU: Minimum of 69.36 on October 19, 2019. Current: 69.36. Projected minimum in December 2019 at 68.9). The Potsdam WDC planetary A index was 1 (STAR Ap - based on the mean of three hour interval ap indices: 1.1). Three hour interval K indices: 00001000 (planetary), 00111310 (Boulder)
The background x-ray flux is at the class A1 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 1 active region using 2K resolution (SN: 11) and in 0 active regions using 1K resolution (SN: 0) SDO/HMI images.
Spotted regions not observed (or interpreted
differently) by SWPC:
New region S6422 [N03W31] emerged with a tiny spot.
|Magnitude||Peak time (UT)||Location||AR||Recorded by||Comment|
April 17-19: 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 (CH960) of the southern polar coronal hole was in an Earth facing position on April 16. A poorly defined trans equatorial coronal hole (CH961) rotated across the central meridian on April 18.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is poor to fair. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet to active on April 20 due to a disturbance which began early in the day. Quiet to unsettled is likely on April 21-22 due to weak coronal hole effects.
|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||SWPC date numbered
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlays
|Total spot count:||0||1||0|
|Sunspot number:||0||11||0||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||0||1||0||(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):||0||6||0||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||18.2 (-1.3)||18.22 (cycle peak)|
|2019.10||67.4||67.0||0.4||(2.7 projected, -0.4)
(solar minimum candidate)
|2019.11||70.2||68.7||0.5||(2.7 projected, 0.0)
(solar minimum candidate)
|2019.12||70.8||68.6||1.6||(3.0 projected, +0.3)||3.22|
|2020.01||72.2||69.9||6.4||(3.9 projected, +0.9)||4.39|
|2020.02||71.0||69.3||0.4||(4.9 projected, +1.0)||6.16|
|2020.03||70.2||69.5||1.5||(6.2 projected, +1.3)||5.63|
|2020.04||(69.7)||1.6 (2A) / 2.6 (2B) / 4.2 (2C)||(7.5 projected, +1.3)||(4.9)|
|2020.05||(9.1 projected, +1.6)|
|2020.06||(10.7 projected, +1.6)|
|2020.07||(12.0 projected, +1.3)|
|2020.08||(13.3 projected, +1.3)|
|2020.09||(15.3 projected, +2.0)|
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.
4) Source: SIDC-SILSO.
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.