Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 28, 2023 at 06:20 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 (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 unsettled to active on April 27 under the influence of effects from CH1142. Solar wind speed at SOHO ranged between 570 and 707 km/sec. The high latitude magnetometer at Andenes recorded active to major storm levels.

Solar flux density measured at 20h UT on 2.8 GHz was 140.8 - increasing 11.2 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.51. In comparison SC24 peaked on June 28, 2014 at 145.50). The Potsdam WDC planetary A index was 23 (STAR Ap - based on the mean of three hour interval ap indices: 22.8). Three hour interval K indices: 44334433 (planetary), 45333432 (Boulder), 56444565 (Andenes).

The background x-ray flux is at the class C1 level (GOES 16).

At the time of counting spots (see image time), spots were observed in 14 active regions using 2K resolution (SN: 288) and in 12 active regions using 1K resolution (SN: 195) SDO/HMI images.

Region 13285 [S17W11] decayed slowly and quietly.
Region 13286 [S11W00] was quiet and stable.
Region 13287 [S25E29] was quiet and stable.
Region 13288 [S22W05] developed further as magnetic delta in the central spot section enlarged. M class flares are possible. C1. flares: C1.1 @ 08:53, C1.0 @ 09:21, C1.1 @ 09:44, C1.3 @ 10:32, C1.7 @ 16:16, C1.0 @ 18:34, C1.0 @ 22:44 UT
Region 13289 [N19E52] decayed slowly. There is a small magnetic delta in a northern penumbra. An M class flare is possible. C1 flare: C1.4 @ 19:36 UT
Region 13290 [N25W58] decayed slowly and quietly.
Region 13291 [N09W00] developed slowly and quietly.
New region 13292 [N15E58] rotated into view on April 25 and was numbered by SWPC 2 days later.

Spotted regions not observed (or interpreted differently) by SWPC:
S8489 [N18W14] was quiet and stable.
S8492 [N16W25] was quiet and stable.
S8497 [S17E18] was quiet and stable.
New region S8501 [N17E26] emerged with tiny spots.
New region S8502 [N13W24] emerged with a tiny spot.
New region S8503 [S15W27] emerged with tiny spots.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.7 00:04   13288 GOES16  
C3.0 00:59   13289 GOES16  
C2.5 02:49   13289 GOES16 LDE
M1.8 11:14 S23E04 13288 GOES16  
C2.5 19:48   13288 GOES16  
C2.4 23:26   13288 GOES16  

Coronal mass ejections (CMEs)

April 25-26: No obviously Earth directed CMEs were observed.
April 27: A CME was observed after a filament eruption near AR 13289 early in the day. There's a slight chance effects from this CME could reach Earth late on April 29 or on April 30.

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 (CH1142) was Earth facing on April 23-26. A northern hemisphere coronal hole (CH1143) will rotate across the central meridian on April 27-28.

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

Quiet to active conditions are likely on April 28-29 due to effects from CH1142. On April 30-May 1 quiet to unsettled conditions are likely due to effects from CH1143.

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
13284 2023.04.17
2023.04.17
      S08W67        

location: S08W64

S8475 2023.04.19       N26W59            
S8479 2023.04.20       N06W54            
13285 2023.04.20
2023.04.21
5 19 11 S19W10 0240 CAO CAO location: S17W11
S8482 2023.04.21       S23W53            
13286 2023.04.21
2023.04.24
3 18 9 S11W02 0010 BXO CRO area: 0025
S8485 2023.04.22       N16W37            
S8486 2023.04.22       N27W29          
13287 2023.04.23
2023.04.24
  3   S25E21 0003   BXO location: S25E29
S8488 2023.04.23       S26W09            
S8489 2023.04.23   9 2 N18W14 0015   BXO  
13288 2023.04.24
2023.04.25
29 43 28 S23W07 0380 EKI EKI beta-gamma-delta

area: 0460

location: S22W05

S8492 2023.04.24   1 1 N16W25 0004   AXX  
S8493 2023.04.24       S21W28          
13289 2023.04.25
2023.04.25
5 18 4 N20E51 0180 DAO DAC

beta-delta

location: N19E52

13290 2023.04.25
2023.04.26
3 2 2 N24W59 0010 BXO BXO area: 0005
13291 2023.04.25
2023.04.26
20 24 13 N09W02 0030 CRO DAI area : 0110
S8497 2023.04.25   3   S17E18 0008   BXO  
13292 2023.04.25
2023.04.27
1 1 1 N14E62 0010 HRX HAX area: 0020
S8499 2023.04.25       S27W24            
S8500 2023.04.26       N12E07          
S8501 2023.04.27   2 1 N17E26 0005   BXO    
S8502 2023.04.27   1 1 N13W24 0003   AXX    
S8503 2023.04.27   4 2 S15W27 0008   BXO    
Total spot count: 66 148 75  
Sunspot number: 136 288 195  (total spot count + 10 * number of spotted regions)
Weighted SN: 92 181 108  (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): 150 158 156  

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
2023.04 144.5 (1)   82.3 (2A) / 91.4 (2B) / 137.4 (2C) (126.4 projected, +5.4) (13.0)
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.