Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 25, 2019 at 03:20 UT.

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 (September 1, 2019)
Solar cycle Solar cycles 23-24 (September 1, 2019) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (September 1, 2019) / Cycle 25 spots (September 25, 2019) 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 (September 1, 2019) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (September 1, 2019) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (September 21, 2019)  

Recent activity

The geomagnetic field was quiet to active on September 24 under the influence of effects from CH937. Solar wind speed at SOHO ranged between 278 and 543 km/sec.

Solar flux at 20h UT on 2.8 GHz was 67.1 (increasing 1.2 over the previous solar rotation). The average 90 day 10.7 flux at 1 AU was 69.0 (The centered average 90 day SF at 1 AU reached a low of 67.77 on December 9, 2018. The centered 1 year average SF at 1 AU reached a minimum of 69.67 on March 24, 2019. The current 1 year average 1 AU SF is 69.67). The Potsdam WDC planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 11.9). Three hour interval K indices: 33213431 (planetary), 23213422 (Boulder)

The background x-ray flux is at the class A6 level.

At the time of counting spots (see image time), no spots were observed using 1K/2K resolution SDO/HMI images.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

Coronal mass ejections (CMEs)

September 22-24: No obviously Earth directed CMEs were observed in available LASCO imagery.

Coronal holes

[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]

A recurrent trans equatorial coronal hole (CH937) was Earth facing on September 20-21. Another recurrent trans equatorial coronal hole (CH938) will rotate across the central meridian on September 24-26.

Propagation

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.

Forecast

The geomagnetic field is expected to be quiet on September 25-26. Quiet to major storm conditions are possible on September 27-28 due to effects from CH938.

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.

Active solar regions


(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
STAR detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlays
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
S6257 2019.09.20       S13W53           likely cycle 25
S6258 2019.09.20       S50W23           cycle 25
S6259 2019.09.20       N09W41            
S6260 2019.09.22       N09W17            
S6261 2019.09.25       S34E27 @ 04:00 0002   BXO   cycle 25
S6262 2019.09.25       S27E34 @ 04:00 0003   AXX   cycle 25
Total spot count: 0 0 0  
Sunspot number: 0 0 0  (total spot count + 10 * number of spotted regions)
Weighted SN: 0 0 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 0 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)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
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)
2018.04 70.0 70.5 8.9 7.9 (-2.0) 6.80
2018.05 70.8 72.4 13.2 7.5 (-0.4) 7.16
2018.06 72.5 74.7 15.9 7.3 (-0.2) 6.83
2018.07 69.6 72.3 1.6 7.1 (-0.2) 5.38
2018.08 69.1 70.8 8.8 6.8 (-0.3) 8.98
2018.09 68.2 69.0 3.3 6.6 (-0.2) 8.91
2018.10 69.6 69.1 4.9 6.9 (+0.3) 6.49
2018.11 68.9 67.4 4.9 6.7 (-0.2) 5.78
2018.12 70.0 67.8 3.1 6.0 (-0.7) 6.10
2019.01 71.5 69.2 7.8 5.4 (-0.6) 5.89
2019.02 70.6 68.9 0.8 5.0 (-0.4) 6.88
2019.03 71.6 70.8 9.5 (4.7 projected, -0.3)
solar minimum candidate
6.12
2019.04 72.4 72.9 9.1 (4.9 projected, +0.2) 6.06
2019.05 71.3 72.8 10.1 (5.2 projected, +0.3) 6.98
2019.06 68.1 70.3 1.2 (5.7 projected, +0.5) 4.26
2019.07 67.1 69.3 0.9 (6.1 projected, +0.4) 5.36
2019.08 67.0 68.7 0.7 (6.9 projected, +0.8) 6.79
2019.09 (68.1)   0.8 (2A) / 1.0 (2B) / 2.9 (2C) (7.6 projected, +0.7) (9.2)
2019.10       (8.0 projected, +0.4)  
2019.11       (8.7 projected, +0.7)  
2019.12       (9.9 projected, +1.2)  
2020.01       (11.4 projected, +1.5)  
2020.02       (13.0 projected, +1.6)  

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.