Solar Terrestrial Activity Report

Activity chart

Last major update issued on September 6, 2021 at 06:30 UT. (Update covering September 4)

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 (August 2, 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 using 365d smoothing Research: Solar Cycle 25 Started on November 17, 2019 with 365 Days Smoothing

Recent activity

The geomagnetic field was quiet on September 4. The high latitude magnetometer at Andenes recorded quiet to minor storm conditions.

Solar flux density measured at 20h UT on 2.8 GHz was 86.5 - increasing 13.0 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 78.32). The Potsdam WDC planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.3). Three hour interval K indices: 21121012 (planetary), ******** (Boulder), 51021125 (Andenes).

The background x-ray flux is at the class B2 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 6 active regions using 2K resolution (SN: 132) and in 6 active regions using 1K resolution (SN: 102) SDO/HMI images.

Region 12863 [S16E01] decayed slowly and quietly.
Region 12864 [N23E09] developed gaining spots and area. C flares are possible.
New region 12865 [N21E26] emerged on September 3 and was numbered the next day by SWPC.
New region 12866 [S18E63] emerged on September 3 and developed further on September 4 when it was numbered by SWPC.
New region 12867 [S18W71] emerged with a few spots.

Spotted regions not observed (or interpreted differently) by SWPC:
S7063 [S21E47] developed gaining spots and area.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

Coronal mass ejections (CMEs)

September 2-4: 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 southern hemisphere coronal hole (CH1028) was Earth facing on September 1-2.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet to active on September 5-6 due to effects from CH1028 and quiet on September 7.

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
12861 2021.08.25
2021.08.26
      N16W64            
S7054 2021.08.29       N24W51            
S7057 2021.08.31       N27E29          
12863 2021.09.01
2021.09.02
5 15 7 S16E02 0090 CSO CSO area: 0120
12864 2021.09.02
2021.09.03
7 22 15 N24E10 0050 DAO DAI

area: 0200

12865 2021.09.03
2021.09.04
3 5 3 N22E25 0010 BXO CRO  
S7061 2021.09.03       N23W06          
S7062 2021.09.03       N15E39          
S7063 2021.09.03   10 6 S21E47 0050   DRO  
12866 2021.09.03
2021.09.04
2 15 8 S18E63 0040 BXO DAI area: 0100
12867 2021.09.04
2021.09.04
1 5 3 S18W74 0010 AXX CRO   was AR S7065
Total spot count: 18 72 42  
Sunspot number: 68 132 102  (total spot count + 10 * number of spotted regions)
Weighted SN: 28 96 66  (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): 75 73 82  

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) 6.0
2021.09 85.1 (1)   5.6 (2A) / 42.3 (2B) / 32.8 (2C) (45.9 projected, +5.7) (4.7)
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 transition

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.