Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 8, 2023 at 06:55 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 (April 1, 2023)
Solar cycle Solar cycles 23-25 (April 1, 2023) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (April 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 (April 1, 2023) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (April 1, 2023) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 5, 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 April 7. Solar wind speed at SOHO ranged between 361 and 441 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 136.3 - decreasing 21.1 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 138.60). The Potsdam WDC planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.4). Three hour interval K indices: 33222012 (planetary), 23312312 (Boulder), 54322125 (Andenes).

The background x-ray flux is at the class B8 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 7 active regions using 2K resolution (SN: 135) and in 5 active regions using 1K resolution (SN: 82) SDO/HMI images.

Region 13266 [N09W78] decayed slowly and was mostly quiet. C1 flares: C1.0 @ 12:12 UT
Region 13269 [S28W12] was quiet and stable.
Region 13270 [S23W71] decayed further and was mostly quiet. C1 flares: C1.3 @ 02:49 UT
Region 13272 [S21E64] has polarity intermixing and produced a number of small C flares. An M2.9 flare was recorded at 01:46 UT on April 8. Another M class flare is obviously possible. C1 flares: C1.4 @ 06:27, C1.3 @ 07:10, C1.0 @ 10:12, C1.0 @ 10:50, C1.1 @ 16:37, C1.5 @ 18:40, C1.1 @ 19:22, C1.7 @ 20:22, C1.2 @ 21:47 UT

Spotted regions not observed (or interpreted differently) by SWPC:
S8429 [S23E15] was quiet and stable.
S8437 [S11E12] was quiet and stable.
New region S8439 [S23E37] was observed with a tiny spot in an old plage area.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.5 20:42 S18E62 13272 GOES16  
C5.8 23:34   13272 GOES16  
C5.1 23:43   13272 GOES16  

Coronal mass ejections (CMEs)

April 5-6: No obviously Earth directed CMEs were observed.
April 7: A filament eruption across AR 13269 began at 07:34 in SDO/AIA imagery and peaked just after 09h UT. Coronal dimming was observed, however, no obvious CME was seen in subsequent LASCO C2 imagery. Several CMEs were observed during the day, however, most of them appears to be backsided.

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 northern hemisphere coronal hole (CH1140) will be Earth facing on April 7-8.

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 to fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

Mostly quiet conditions are likely on April 8-9. Quiet to active conditions are possible on April 10-11 due to effects from CH1140.

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
13266 2023.03.26
2023.03.29
  1   N09W80 0001   AXX location: N09W78
13267 2023.03.27
2023.03.29
      S17W78         location: S18W75
S8408 2023.03.28       N13W51          
13269 2023.03.30
2023.04.02
  5 2 S25W28 0010   BXO location: S28W12
S8418 2023.04.01       S11W37          
13270 2023.04.02 6 10 6 S24W73 0120 EAO EAO

location: S23W71

area: 0230

13271 2023.04.02
2023.04.04
      S16W61           location: S17W58
S8423 2023.04.02       S32W35            
S8426 2023.04.03       N33W30          
S8427 2023.04.04       N10W34          
S8428 2023.04.04       N19W16            
S8429 2023.04.04   11 2 S23E15 0017   BXO  
S8430 2023.04.05       N28E24            
S8431 2023.04.05       S21W27            
S8432 2023.04.05       S14W05            
13272 2023.04.05
2023.04.06
12 36 21 S22E63 0180 EAI EAI area: 0360

location: S21E64

S8434 2023.04.05       S07E43            
S8435 2023.04.06       S27E09          
S8437 2023.04.06   1   S11E12 0002   AXX  
S8438 2023.04.06       N14E16          
S8439 2023.04.07   1 1 S23E37 0003   AXX    
Total spot count: 18 65 32  
Sunspot number: 38 135 82  (total spot count + 10 * number of spotted regions)
Weighted SN: 28 75 42  (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): 42 74 66  

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
2021.09 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 77.4 (+4.4) 7.48
2022.06 116.1 119.8 70.3 81.1 (+3.7) 8.20
2022.07 125.4 129.5 91.4 86.7 (+5.6) 9.51
2022.08 114.2 117.1 74.6 92.5 (+5.8) 10.92
2022.09 135.1 136.5 96.0 96.4 (+3.9) 12.18
2022.10 133.5 132.7 95.5 (99.0 projected, +2.6) 11.16
2022.11 123.4 120.7 80.5 (102.0 projected, +3.0) 9.33
2022.12 147.9 143.4 112.8 (106.8 projected, +4.8) 10.99
2023.01 182.4 176.6 143.6 (112.9 projected, +6.1) 8.73
2023.02 167.2 163.2 110.9 (117.9 projected, +5.0) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 122.6 (121.0 projected, +3.1) 14.42
2023.04 133.1 (1)   9.5 (2A) / 40.7 (2B) / 123.7 (2C) (126.4 projected, +5.4) (11.0)
2023.05       (132.1 projected, +5.7)  
2023.06       (135.2 projected, +3.1)  
2023.07       (134.7 projected, -0.5)  
2023.08       (135.7 projected, +1.0)  
2023.09       (139.2 projected, +3.5)  
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.