Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 18, 2024 at 11:50 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 (May 1, 2024)
Solar cycle Solar cycles 23-25 (May 1, 2024) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24-25 progress (May 1, 2024) 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 (May 1, 2024) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12-14, 16, 24-25 (May 1, 2024) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (March 3, 2024) 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
Calculating the Strength of Solar Cycle 25 Using 365-day Smoothing

Recent activity

The geomagnetic field was at quiet to major storm levels on May 17 due to CME effects. The high latitude magnetometer at Andenes recorded quiet to major storm levels. The above 10 MeV proton flux was at 0.8 pfu at the end of the day.

Solar flux density measured at 20h UT on 2.8 GHz was 204.1 - decreasing 5.4 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 160.58. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 160.58 on November 17, 2023). The Potsdam WDC planetary A index was 30 (STAR Ap - based on the mean of three hour interval ap indices: 29.6). Three hour interval K indices: 22223565 (planetary), 22214544 (Boulder), 23123566 (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: 382) and in 16 active regions using 1K resolution (SN: 254) SDO/HMI images.

Region 13671 [N20W72] decayed slowly and quietly.
Region 13672 [N19W44] was quiet and stable.
Region 13673 [S09W24] was quiet and stable.
Region 13674 [S14W14] was mostly quiet and stable.
Region 13676 [S20W58] decayed slowly and quietly.
Region 13679 [S09E06] produced several C flares and has minor polarity intermixing.
Region 13680 [N17E04] was quiet and stable.
Region 13682 [N14E22] gained some tiny trailing spots and produced a few flares.
Region 13683 [S24W31] developed slowly and produced a few flares.
Region 13684 [S06E40] was quiet and stable.
Region 13685 [S14E57] has weak polarity intermixing and could produce further M class flares. C1 flares: C1.9 @ 10:46 UT
New region 13686 [S07E67] rotated into view on May 16 and was numbered the next day by SWPC.

Spotted regions not observed (or interpreted differently) by SWPC/USAF:
S9689 [S15W34] was quiet and stable.
S9692 [N22W78] decayed slowly producing a few flares.
S9708 [N18W22] was quiet and stable.
S9716 [N27W02] was quiet and stable.
S9718 [S19W67] was quiet and stable.
New region S9721 [S22E28] was observed with tiny spots in an old plage area.
New region S9722 [S22W41] emerged with tiny spots.

C2+ flares

Magnitude Peak time (UT) Location Source Recorded by Comment
C2.9 00:31   13679 GOES16  
C2.8 01:06   13679 GOES16  
C8.7/1N 01:46 S07E12 13679 GOES16  
C3.9 02:37   13683 GOES16  
C2.1 03:39   13679 GOES16  
C2.1 04:03   13679 GOES16  
C3.1 05:08   13679 GOES16  
C2.2 06:48   13679 GOES16  
C2.2 07:07   13674 GOES16  
C2.5 07:21   13685 GOES16  
C2.2 08:05   S9692 GOES16  
C2.1 08:43   13679 GOES16  
C2.1 09:45   13685 GOES16  
C3.7 12:21   S9715 GOES16 incorrectly attributed to AR 13671 by SWPC
C4.8 12:47 N22W67 S9692 GOES16  
C3.1 13:27   13679 GOES16  
C2.7 13:55   13683 GOES16  
C2.1 15:28   13682 GOES16  
C2.1 15:43   13683 GOES16  
C2.3 16:04   13683 GOES16  
C2.6 18:46   13683 GOES16  
C2.8 19:56   13686 GOES16 incorrectly attributed to AR 13683 by SWPC
C2.7 20:15 S10E58 13685 GOES16  
M7.2/2B 21:08 S12E62 13685 GOES16 moderate type II and IV radio sweeps
C5.2 23:30   13686 GOES16  

Coronal mass ejections (CMEs)

May 17: A partial halo CME was observed after the M7 flare in AR 13685. There's a chance of weak geomagnetic effects from this CME on May 20-21.
May 16
: A partial halo CME was observed in LASCO imagery following a filament eruption in the northwest quadrant after 15h UT. There is a minor chance components of this CME could reach Earth on May 19.
May 15
: No obviously Earth directed CME 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]

No obvious coronal holes are currently in or near Earth facing positions.

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

The geomagnetic field is expected to be at quiet to unsettled levels on May 18-20.

Coronal holes (1) Coronal mass ejections (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
13670 2024.05.05
2024.05.06
2     N21W76 0010 BXO      

location: N14W77

spotless

SWPC has moved AR 13670 to the position of AR 13671 and AR 13671 to the position of AR S9692. What a mess!

13671 2024.05.06
2024.05.09
2 3 2 N21W78 0010 BXO CRO

location: N20W72

SWPC location on May 10 was N19E17, then they changed that to the location of AR S9692

13672 2024.05.08
2024.05.09
1 4 3 N18W51 0040 HSX HRX

location: N19W44

SWPC location is way off

S9689 2024.05.08   4   S15W34 0007   AXX  
13673 2024.05.09
2024.05.11
1 3 2 S08W28 0020 HSX CRO

location: S09W24

S9692 2024.05.09   2 1 N22W78 0007   BXO  
13676 2024.05.10
2024.05.12
1 4 2 S20W61 0100 HAX HAX

location: S20W58

area: 0160

13674 2024.05.10 8 25 17 S12W17 0120 CSO DSI beta-gamma

area: 0200

location: S14W14

13683 2024.05.11
2024.05.15
8 34 21 S23W35 0060 DSO DRI beta-gamma

area: 0170

location: S24W31

13678 2024.05.11
2024.05.12
      N09W06         location: N08W04
13681 2024.05.11
2024.05.13
      S07W79            
S9705 2024.05.11       S24W38            
13679 2024.05.12 13 22 17 S10E04 0230 ESO ESI beta-gamma

area: 0340

location: S09E06

13680 2024.05.12
2024.05.13
2 15 4 N18E08 0010 AXX CRO area: 0030

location: N17E04

13682 2024.05.12
2024.05.14
1 27 3 N16E16 0010 AXX CRO beta-gamma

location: N14E22

area: 0040

S9708 2024.05.12   6 2 N18W22 0010   AXX  
S9711 2024.05.14       N27W43            
13684 2024.05.15
2024.05.16
  4 3 S06E36 0012   BXO location: S06E40
13685 2024.05.15
2024.05.16
7 19 11 S13E50 0220 DSO EKI beta-gamma

location: S14E57

area: 0650

SWPC location is way off

S9715 2024.05.15       N19E18          
S9716 2024.05.15   10 3 N27W02 0030   BXO  
13686 2024.05.16
2024.05.17
2 2 2 S07E66 0190 HAX HKX area: 0340

location: S07E67

S9718 2024.05.16   2   S19W67 0002   BXO  
S9719 2024.05.16       S16W37          
S9720 2024.05.16       S30E41          
S9721 2024.05.17   4   S22E28 0006   BXO    
S9722 2024.05.17   2 1 S22W41 0004   BXO    
Total spot count: 48 192 94  
Sunspot number: 168 382 254  (total spot count + 10 * number of spotted regions)
Weighted SN: 88 245 147  (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): 185 210 203  

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
2022.10 133.5 132.7 95.5 98.9 (+2.4) 11.16
2022.11 123.4 120.7 80.5 101.2 (+2.3) 9.33
2022.12 147.9 143.4 112.8 106.7 (+5.5) 10.99
2023.01 182.4 176.6 144.4 113.3 (+6.6) 8.73
2023.02 167.2 163.2 111.3 117.8 (+3.5) 14.48
(current
SC25 peak)
2023.03 157.2 155.6 123.3 121.1 (+3.3) 14.42
2023.04 145.4 146.4 97.6 122.9 (+1.8) 13.40
2023.05 155.6 159.2 137.4 124.2 (+1.3) 10.67
2023.06 161.7 166.8 160.5 125.3 (+1.1)
(SC25 solar max candidate)
8.95
2023.07  176.4 182.2 160.0 124.4 (-0.9) 8.15
2023.08  153.7 157.6 114.8 124.1 (-0.3) 7.19
2023.09  154.4 156.0 134.2 123.9 (-0.2) 14.26
2023.10  142.8 141.9 99.4 124.8 (+0.9) 8.16
2023.11 153.5 150.2 105.4 (125.2 projected, +0.4) 12.20
2023.12 151.1 146.4 114.2 (121.9 projected, -3.3) 9.60
2024.01 164.6 159.3 123.0 (118.5 projected, -3.4) 5.46
2024.02 172.5 168.3 124.7 (117.7 projected, -0.8) 5.31
2024.03 154.4 152.9 104.9 (117.1 projected, -0.6) 11.03
2024.04 161.3 162.6 136.5 (117.1 projected, -0.0) 9.69
2024.05 196.1 (1)   86.2 (2A) / 157.2 (2B) / 208.2 (2C) (118.3 projected, +1.2) (38.5)
2024.06       (117.4 projected, -0.9)  
2024.07       (115.7 projected, -1.7)  
2024.08       (113.8 projected, -1.9)  
2024.09       (112.5 projected, -1.3)  
2024.10       (111.1 projected, -1.4)  
2024.11       (108.6 projected, -2.5)  

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: WDC-SILSO, Royal Observatory Of Belgium, Brussels

Solar cycles 24-25

Smoothed SF and sunspot numbers

Update on the progress of solar cycle 25 as of April 28, 2024

The big increase in sunspot counts during the April 14-27 interval caused a major uptick in the smoothed SNs and solar flux. It's not yet clear when the next peak will be, anytime between October 28 and December 20, 2023 looks possible. The 365d smoothed solar flux exceeded the June 27 peak on October 28, while the 365d smoothed ISN and NOAA SN both exceeded the June 2023 peak in late October 2023. It should be noted that the current peak using 13-month smoothing is still in June 2023.

--------------------------------------------------------------------------------------

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.