Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 29, 2021 at 08:30 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 9, 2021)
Solar cycle Solar cycles 23-25 (August 2, 2021) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (August 2, 2021) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (June 1, 2020) POES auroral activity level October 2009 - December 2012]
  Comparison of cycles 21-25 (August 2, 2021) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (August 2, 2021) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (August 22, 2021) Cycle 25 spots (final update December 25, 2019)
  Solar cycles 24-25 transition using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing

Recent activity

The geomagnetic field was quiet to unsettled on September 28 under the influence of a high speed stream associated with CH1033. The high latitude magnetometer at Andenes recorded quiet to minor storm conditions.

Solar flux density measured at 20h UT on 2.8 GHz was 88.9 - increasing 4.7 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 79.40). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.5). Three hour interval K indices: 12222233 (planetary), 12332233 (Boulder), 22222255 (Andenes).

The background x-ray flux is at the class B1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 10 active regions using 2K resolution (SN: 174) and in 7 active regions using 1K resolution (SN: 106) SDO/HMI images.

Region 12871 [S29W52] decayed slowly. A long duration C1.6 event peaking at 06:34 UT was associated with a partial halo (only a section of the northeast quadrant was not covered) CME. The CME could reach Earth on September 30 or October 1.
Region 12877 [S17W27] developed further and was quiet.
Region 12878 [S22E11] decayed slowly and quietly.
New region 12880 [N30E54] emerged on September 27 and was numbered the next day by SWPC as the region developed further.
New region 12881 [N16W20] emerged with a few tiny spots.

Spotted regions not observed (or interpreted differently) by SWPC:
S7101 [N18W05] was quiet and stable.
S7106
[N26W39] was quiet and stable.
New region S7108 [S17E47] was observed with a tiny spot in an old plage area.
New region S7109 [N25E79] rotated into view with tiny spots.
New region S7110 [N25E52] was observed with a tiny spot in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

Coronal mass ejections (CMEs)

September 26-27: No obviously Earth directed CMEs were observed in available LASCO imagery.
September 28: A partial halo CME was observed after a C1 LDE in AR 12871 at 06:34. The CME could reach Earth late on September 30 or on October 1 and cause unsettled to minor storm conditions.

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 northern hemisphere coronal hole (CH1033) rotated across the central meridian on September 23-24.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is poor. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on September 29-30. Late on September 30 or on October 1 the September 28 CME is likely to arrive and cause unsettled to minor storm conditions.

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 officially numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC, all other regions are numbered sequentially as they emerge using the STAR spot number. 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. SWPC data considered to be not sufficiently precise (location, area, classification) are red colored.

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/
USAF
Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12871 2021.09.18 1 6 4 S28W54 0030 HRX CRO location: S29W52

area: 0040

12872 2021.09.19
2021.09.20
      N16W67        

location: N13W64

S7091 2021.09.21       N17W25            
S7095 2021.09.22       N21W53            
12877 2021.09.22
2021.09.26
10 28 15 S18W27 0030 CRO DRI area: 0090
S7097 2021.09.23       N17W28            
S7098 2021.09.23       N17W21            
12876 2021.09.24
2021.09.24
      S22W52            
12878 2021.09.24
2021.09.26
  4   S22E07 0004   AXX  
S7101 2021.09.24   4 1 N18W05 0007   AXX  
S7102 2021.09.24       N23W04            
S7103 2021.09.25       S18W09            
S7104 2021.09.26       N12W44            
12880 2021.09.27
2021.09.28
5 21 10 N30E54 0010 CRO DRI area: 0110
S7106 2021.09.27   4 3 N26W39 0010   BXO  
12881 2021.09.28
2021.09.28
1 3 2 N16W20 0010 AXX HRX   was AR S7107
S7108 2021.09.28   1   S17E47 0002   AXX    
S7109 2021.09.28   2 1 N25E79 0008   AXX    
S7110 2021.09.28   1   N25E52 0001   AXX    
Total spot count: 17 74 36  
Sunspot number: 57 174 106  (total spot count + 10 * number of spotted regions)
Weighted SN: 26 86 48  (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): 63 96 85  

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)
2019.11 70.2 68.7 0.5 2.0 (-0.6)
(Solar minimum using 365d smoothing:
November 17, 2019)
4.19
2019.12 70.8 68.6 1.6 1.8 (-0.2)
(ISN 13 months smoothed
solar minimum)
3.22
2020.03 70.2 69.5 1.5 3.0 (+0.3) 5.63
2020.04 69.5 70.0 5.4 3.6 (+0.6) 5.32
2020.05 69.0 70.6 0.2 5.6 (+2.0) 3.80
2020.06 69.5 71.7 5.8 7.9 (+2.3) 3.75
2020.07 69.5 71.8 6.3 9.0 (+1.1) 4.28
2020.08 71.6 73.4 7.6 9.5 (+0.5) 5.68
2020.09 70.7 71.4 0.7 10.5 (+1.0) 8.59
2020.10 74.6 74.2 14.6 11.9 (+1.4) 6.13
2020.11 89.9 88.0 34.5 13.6 (+1.7) 4.77
2020.12 86.9 84.2 23.1 15.3 (+1.7) 4.72
2021.01 76.0 73.6 10.4 17.3 (+2.0) 4.39
2021.02 74.3 72.4 8.3 19.1 (+1.8) 9.50
2021.03 76.0 75.2 17.3 (21.4 projected, +2.3) 10.17
2021.04 75.9 76.4 24.5 (25.0 projected, +3.6) 8.40
2021.05 75.3 77.1 21.2 (27.7 projected, +2.7) 6.50
2021.06 79.4 81.8 25.3 (30.9 projected, +3.2) 5.52
2021.07 81.0 83.6 34.4 (35.5 projected, +4.6) 5.51
2021.08 77.7 79.7 22.4 (40.2 projected, +4.7) 6.19
2021.09 86.2 (1)   47.9 (2A) / 51.4 (2B) / 57.8 (2C) (45.9 projected, +5.7) (6.7)
2021.10       (50.3 projected, +4.4)  
2021.11       (54.9 projected, +4.6)  
2021.12       (60.7 projected, +5.8)  
2022.01       (64.3 projected, +3.6)  
2022.02       (69.1 projected, +4.8)  

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz and any corrections applied to that measurement.
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.

Solar cycles 24-25

Smoothed SF and sunspot numbers

 

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.