Solar Terrestrial Activity Report

Activity chart

Last major update issued on March 18, 2023 at 12:00 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 (March 3, 2023)
Solar cycle Solar cycles 23-25 (March 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (March 1, 2023) Noon SDO sunspot count 1K image / 4K (*)
  Solar cycles 1-24 (July 1, 2020) POES auroral activity level [October 2009 - December 2012]
  Comparison of cycles 21-25 (March 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (March 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (January 21, 2023) 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 March 17. Solar wind speed at SOHO ranged between 379 and 470 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 134.2. (Centered 1 year average SF at 1 AU - 183 days ago: 137.35). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.4). Three hour interval K indices: 31122002 (planetary), 11234212 (Boulder), 12122005 (Andenes).

The background x-ray flux was at the class B6 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 10 active regions using 2K resolution (SN: 139) and in 7 active regions using 1K resolution (SN: 85) SDO/HMI images.

Region 13247 [S23W70] decayed slowly and quietly.
Region 13250 [S18W59] decayed slowly and was mostly quiet.
Region 13251 [S13W33] was quiet and stable.
Region 13252 [N12W33] decayed slowly and quietly.
New region 13256 [S21E73] rotated into view and could produce M flares.

Spotted regions not observed (or interpreted differently) by SWPC:
S8360 [N24W12] was quiet and stable.
S8365 [S18E08] was quiet and stable.
S8366 [S19E29] was quiet and stable.
S8367 [S29E11] was quiet and stable.
S8370 [N24E49] was quiet and stable.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment

Coronal mass ejections (CMEs)

March 15-16: No obviously Earth directed CMEs were observed.
March 17: A large number of CMEs were observed during the day, the most impressive was a bright CME off the southwest limb during the evening hours. Its source was likely behind the limb, like several of the other CMEs. A large filament eruption unfolded in the southwest quadrant during the first half of the day, the associated CME may have an Earth directed component.

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 southern hemisphere coronal hole (CH1135) rotated across the central meridian on March 16-17. Another southern hemisphere coronal hole (CH1136) will likely become Earth facing on March 20-21.

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.

Forecast

Mostly quiet conditions are expected for March 18-19. Quiet to active is likely on March 20-21 due to effects from CH1135 with a possibility of minor storm intervals if the March 17 CME reaches Earth.

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 colored red.

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
13247 2023.03.05
2023.03.06
1 7 4 S24W78 0010 AXX BXO location: S23W70

area: 0020

SWPC consider this to be 2 regions

13249 2023.03.07
2023.03.07
      S11W57           location: S10W55
13251 2023.03.08
2023.03.09
1 5 1 S13W35 0040 HSX CSO

location: S13W33

13252 2023.03.09
2023.03.10
1 3 1 N13W35 0010 AXX AXX

location: N12W33

13250 2023.03.09
2023.03.09
  2 2 S18W61 0005   BXO location: S18W59
13253 2023.03.11
2023.03.12
      S29W72           location: S29W64
S8360 2023.03.11   6 1 N24W12 0010   BXO  
S8362 2023.03.13       N08W08            
S8363 2023.03.13       S09W22            
13254 2023.03.14 4     S24W69           ref. AR S13247
13255 2023.03.14
2023.03.14
      S05W04            
S8365 2023.03.14   4 3 S18E08 0010   AXX  
S8366 2023.03.15   2   S19E29 0003   AXX  
S8367 2023.03.16   4   S29E11 0007   BXO  
S8368 2023.03.16       S00W26          
13256 2023.03.16
2023.03.17
1 5 3 S21E73 0060 HSX FKO area: 0410
S8370 2023.03.17   1   N24E49 0001   AXX    
Total spot count: 8 39 15  
Sunspot number: 58 139 85  (total spot count + 10 * number of spotted regions)
Weighted SN: 18 54 30  (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): 64 76 68  

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 (SC24 peak) 110.5 10.70
2014.04 143.9 144.8 112.5 116.4 (SC24 solar max) 7.88
2017.09 91.3 92.3 43.6 18.2 (-1.3) 18.22
(SC24 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
2021.08 77.7 79.7 22.0 35.4 (+4.0) 6.19
2021.09 87.0 88.2 51.3 40.2 (+4.8) 6.33
2021.10 88.9 88.3 37.4 45.2 (+5.0) 7.38
2021.11 86.2 84.4 34.8 50.8 (+5.6) 9.83
2021.12 103.0 99.8 67.5 55.9 (+5.1) 6.40
2022.01 103.8 100.5 55.3 60.1 (+4.2) 8.92
2022.02 109.1 106.5 60.9 64.7 (+4.6) 10.46
2022.03 117.0 115.8 78.6 68.7 (+4.0) 10.20
2022.04 130.8 131.7 84.0 73.0 (+4.3) 11.79
2022.05 133.8 136.8 96.5 77.2 (+4.2) 7.48
2022.06 116.1 119.8 70.3 80.9 (+3.7) 8.20
2022.07 125.4 129.5 91.4 86.5 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.3 (+5.8) 10.92
2022.09 135.1 136.5 96.0 (97.0 projected, +4.7) 12.18
2022.10 133.5 132.7 95.4 (100.2 projected, +3.2) 11.16
2022.11 123.4 120.7 77.6 (103.0 projected, +2.8) 9.33
2022.12 147.9 143.4 113.1 (107.8 projected, +4.8) 10.99
2023.01 182.4 176.6 143.6 (113.8 projected, +6.0) 8.73
2023.02 167.2 163.2 110.9 (118.9 projected, +5.1) 14.48
(current
SC25 peak)
2023.03 161.3 (1)   67.8 (2A) / 116.8 (2B) / 136.4 (2C) (122.0 projected, +3.1) (11.8)
2023.04       (127.4 projected, +5.4)  
2023.05       (133.2 projected, +5.8)  
2023.06       (136.4 projected, +3.2)  
2023.07       (135.9 projected, -0.5)  
2023.08       (136.9 projected, +1.0)  
2023.11       (142.5 projected max SC25)  

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.