|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 9, 2017)|
|Solar cycle||Solar cycles 23-24 (April 1, 2017)||Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)|
|Cycle 24 progress (April 1, 2017)||Noon SDO sunspot count 1K / 4K (*)|
|Solar cycles 1-24 (July 17, 2015)||POES auroral activity level October 2009 - December 2012N06W17]|
|Comparison of cycles 21, 22, 23 and 24 (April 1, 2017)||3rd SSN Workshop, Tucson, 2013|
|Comparison of cycles 12, 13, 14, 16 and 24 (April 1, 2017)||4th SSN Workshop, Locarno, 2014|
|Solar polar fields vs. solar cycles (April 17, 2017)|
The geomagnetic field was quiet to unsettled on April 18. Solar wind speed at SOHO ranged between 273 and 437 km/s. A low speed stream associated with CH801 arrived late in the day.
Solar flux at 17h UTC on 2.8 GHz was 76.7 (increasing 4.2 over the last solar rotation. The measurements at 20 and 23h UT were significantly enhanced by an LDE in AR 12651). The average 90 day 10.7 flux at 1 AU was 76.4. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 3.0). Three hour interval K indices: 21011123 (planetary), 10112223 (Boulder)
The background x-ray flux is at the class B1 level.
At the time of counting spots (see image time), spots were observed in 2 active regions using 2K resolution (SN: 31) and in 2 active regions using 1K resolution (SN: 26) SDO images on the visible solar disk.
New region 12651 [N11E71] rotated into view on April 17 and was numbered the next day by SWPC. The region has polarity intermixing and may be capable of producing a minor M class flare.
Spotted regions not numbered (or interpreted differently)
S5651 [N12W26] was quiet and stable.
|Magnitude||Peak time (UT)||Location||AR||Recorded by||Comment|
April 16-18: No obviously Earth directed CMEs were observed in available LASCO imagery.
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 recurrent trans equatorial coronal hole (CH801) was in an Earth facing position on April 13-16. Another recurrent trans equatorial coronal hole (CH802) will rotate across the central meridian on April 20-23.
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 19 due to effects from CH801 and quiet to unsettled on April 20-21. On April 22 or 23 a strong disturbance related to CH802 is likely to start.
|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:||2||11||6|
|Sunspot number:||12||31||26||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||7||16||11||(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):||13||17||21||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
|166.3||146.1 (cycle peak)||110.5 (+1.2)||10.70|
|2014.04||143.9||144.8||112.5||116.4 (+2.1) (solar max)||7.88|
|2016.10||86.1||85.6||33.6||(31.3 projected, -2.0)||15.33|
|2016.11||78.6||76.9||21.4||(29.4 projected, -1.9)||9.11|
|2016.12||75.1||72.8||18.9||(27.8 projected, -1.6)||9.34|
|2017.01||77.3||74.9||25.8||(27.0 projected, -0.8)||9.45|
|2017.02||76.8||75.0||26.1||(25.2 projected, -1.8)||9.58|
|2017.03||74.6||73.9||17.7||(22.6 projected, -2.6)||14.20|
|2017.04||(80.6)||17.3 (2A) / 28.8 (2B) / 27.3 (2C)||(20.6 projected, -2.0)||(8.0)|
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).
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) Updated to new data set from WDC-SILSO on July 1, 2015
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.