Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 14, 2023 at 05:50 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 on April 13. Solar wind speed at SOHO ranged between 361 and 424 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 159.5 - increasing 25.3 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 139.33). The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6). Three hour interval K indices: 22000212 (planetary), 22101421 (Boulder), 33000345 (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 19 active regions using 2K resolution (SN: 466) and in 14 active regions using 1K resolution (SN: 280) SDO/HMI images.

Region 13272 [S20W16] decayed slowly and has only one spot with mature penumbra left. and was much less active than during the previous days. The region still has many small spots and weak polarity intermixing. There's a small chance of a minor M class flare. C1 flares: C1.4 @ 02:50 UT
Region 13273 [N09W29] decayed slowly and quietly.
Region 13274 [S07W43] decayed slowly and quietly.
Region 13275 [N19E22] was quiet and stable.
Region 13276 [S22E34] was quiet and stable.
Region 13277 [N10W05] decayed slowly and quietly.
Region 13278 [N12W48] decayed slowly and quietly.
Region 13279 [S20E50] has M class flare potential and produced several C flares during the day. C1 flares: C1.9 @ 17:38 UT
New region 13280 [S08W28] emerged on April 11 and was numbered by SWPC 2 days later. The region has lots of small spots, polarity intermixing, and a weak magnetic delta in a southern penumbra. M class flaring is possible. C1 flares: C1.9 @ 05:40, C1.8 @ 23:44 UT
New region 13281 [S24E68] rotated into view on April 12 and was numbered by SWPC the next day. C1 flares: C1.5 @ 03:35, C1.9 @ 12:47, C1.5 @ 14:37 UT

Spotted regions not observed (or interpreted differently) by SWPC:
S8429 [S24W58] reemerged with tiny spots.
S8445 [N26W06] was quiet and stable.
S8455 [N25E12] reemerged with tiny spots.
S8459 [N09E06] decayed slowly and quietly.
New region S8462 [N11E58] emerged before noon and developed quickly after noon. C and minor M class flaring is possible. SWPC has assigned 13282 to this region.
New region S8463 [N17E68] emerged with tiny spots.
New region S8464 [S14E39] emerged with tiny spots.
New region S8465 [S23E82] rotated into view with a tiny spot. C1 flares: C1.9 @ 16:02 UT
New region S8466 [S19E84] rotated into view with a tiny spot.

C2+ flares:

Magnitude Peak time (UT) Location Source Recorded by Comment
C4.0 00:53   13272 GOES16  
C3.3 01:06 S19E62 13279 GOES16  
C3.7 01:23 S19E62 13279 GOES16  
C2.5 02:24 S19E62 13279 GOES16  
C2.2 04:07   13280 GOES16 simultaneous flare in AR 13279
C2.0 04:34   13272 GOES16 simultaneous flare in AR 13281
C2.3 04:58   13279 GOES18  
C2.2 06:07   13279 GOES16  
C2.0 06:17   13279 GOES16  
C3.9 07:59 S20E56 13279 GOES16  
C3.8 08:20 S23E75 13281 GOES16  
C2.0 10:00   13279 GOES16  
C8.4 10:43 S19W08 13272 GOES16  
C6.7 10:56 S20E54 13279 GOES16  
C4.3 11:56 S20E53 13279 GOES16  
C2.2 18:57   13281 GOES16  
C2.1 20:36 N10E68 S8463 GOES16  

Coronal mass ejections (CMEs)

April 11-13: No obviously Earth directed CMEs were observed.

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 couple of positive polarity coronal holes have recently rotated across the central meridian, they are both likely to be too far north and south to cause a geomagnetic disturbance.

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.

Forecast

Quiet conditions are likely on April 14-16.

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
S8429 2023.04.04   4   S24W58 0004   BXO    
13272 2023.04.05
2023.04.06
22 74 40 S22W14 0150 FAI FAI beta-gamma

location: S20W16

S8434 2023.04.05       S07W35            
S8439 2023.04.07       S29W45          
13274 2023.04.08
2023.04.10
  1   S07W47 0002   AXX location: S07W43
13278 2023.04.08
2023.04.12
1 5 1 N12W46 0010 AXX BXO area: 0007
13273 2023.04.09
2023.04.09
3 12 3 N09W29 0070 CSO CAO

 

13275 2023.04.09
2023.04.10
1 5 2 N19E22 0020 HSX HSX area: 0050
S8445 2023.04.09   6 2 N26W06 0008   BXO  
S8446 2023.04.09       N27W28            
S8447 2023.04.09       S09W19            
13276 2023.04.10
2023.04.10
1 2 1 S22E34 0020 HSX HRX  
13277 2023.04.10
2023.04.11
  3 2 N10W05 0006   BXO  
S8451 2023.04.10       N29W54            
13279 2023.04.10
2023.04.12
15 50 27 S20E51 0230 DAI EAI beta-gamma

location: S20E50

S8454 2023.04.10       S01W48            
S8455 2023.04.10   3   N25E12 0006   BXO    
S8456 2023.04.10       S09W02            
S8457 2023.04.10       S33W37            
S8459 2023.04.11   1 1 N09E06 0003   AXX  
13280 2023.04.11
2023.04.13
8 71 40 S09W27 0060 DAO DRI beta-gamma-delta

location: S08W28

 

area: 0200

13281 2023.04.12
2023.04.13
3 19 10 S23E71 0220 DAO EKO location: S24E68

area: 0470

13282
S8462
2023.04.13
2023.04.13
  11 7 N11E68 0120   DAO    
S8463 2023.04.13   2 1 N17E68 0004   AXX    
S8464 2023.04.13   5 3 S14E39 0012   BXO    
S8465 2023.04.13   1   S23E82 0003   AXX    
S8466 2023.04.13   1   S19E84 0003   AXX    
Total spot count: 54 276 140  
Sunspot number: 134 466 280  (total spot count + 10 * number of spotted regions)
Weighted SN: 89 317 181  (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): 147 256 224  

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
2023.04 138.8 (1)   28.1 (2A) / 64.8 (2B) / 127.1 (2C) (126.4 projected, +5.4) (8.6)
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.