The geomagnetic field was unsettled to major storm on March 23 under the influence of effects from CH1207 most of the day. At 17:29 UT there was a sudden increase in solar wind temperature and solar wind speed at DSCOVR, possibly due to a CME combining with the coronal holehigh speed stream. Solar wind speed at SOHO ranged between 341 and 513 km/sec. The high latitude magnetometer at Andenes recorded quiet to minor storm levels. The above 10 MeV proton flux was at 294 pfu at the end of the day having peaked at 956 pfu at 18:20 UT and is likely to stay at moderate levels until the arrival of the March 23 CME late in the day or early on March 25.
Solar flux density measured at 20h UT on 2.8 GHz was 210.7 - increasing 29.9 over the previous solar rotation. (Centered 1 year average SF at 1 AU - 183 days ago: 156.84. In comparison SC24 peaked on June 28, 2014 at 145.50. Current SC25 peak: 158.71 on June 27, 2023). The Potsdam WDC planetary A index was 32 (STAR Ap - based on the mean of three hour interval ap indices: 32.5). Three hour interval K indices: 35444456 (planetary), 25434544 (Boulder), 15433555 (Andenes).
The background x-ray flux is at the class C2 level (GOES 16).
At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 299) and in 10 active regions using 1K resolution (SN: 190) SDO/HMI images.
Region 13614 [N17W07] decayed slowly losing
area and spots. Apart from the major X1 flare early in the day, the region
was mostly quiet.
Region 13615 [S12E01] developed further in the southern spot section.
Fairly long neutral lines between opposite polarity spot sections have
formed and an X class flare would be no surprise.
Region 13617 [S13E31] decayed slowly and was mostly quiet.
Region 13618 [S20W83] rotated mostly out of view and was quiet.
Region 13619 [N18E30] was mostly quiet and stable.
Region 13620 [S09E60] was mostly quiet and stable.
New region 13621 [N17W40] emerged on March 20 and was was numbered by
SWPC 3 days later as the spot group began to decay.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
S9528 [N19E48] was quiet and stable.
S9529 [S19W09] reemerged with tiny spots.
New region S9536 [N19E77] rotated into view with a few spots.
New region S9537 [S10E13] emerged with tiny
spots.
New region S9538 [S28E23] emerged with a tiny spot.
Minor update posted at 15:30 UT: The leading edge of the March 23 CME was observed at DSCOVR at approximately 14:02 UT, a transit time of just over 36 hours. Solar wind speed has reached 800 km/sec. The Bz component of the interplanetary magnetic field is currently very strongly southwards. K index intervals peaking at 8 or 9 are possible.
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| C4.9 | 00:22 | 13615 | GOES16 | ||
| C4.9 | 00:48 | 13621 | GOES16 | ||
| X1.1/2F | 01:33 | N27E08 | 13614 | GOES16 | LDE, moderate type II radio sweep asymmetrical full halo CME |
| M5.0 | 02:36 | 13615 | GOES16 | ||
| M1.4 | 04:27 | 13615 | GOES16 | ||
| M1.5 | 04:54 | 13615 | GOES18 | ||
| C8.9/1F | 05:38 | 13615 | GOES18 | ||
| M1.1 | 06:55 | S13E04 | 13615 | GOES16 | |
| M2.4/1B | 07:09 | 13615 | GOES16 | ||
| M3.1 | 07:38 | 13615 | GOES16 | ||
| M1.1 | 08:18 | 13615 | GOES16 | ||
| C7.2 | 08:58 | 13615 | GOES16 | ||
| C8.0 | 09:07 | 13615 | GOES16 | ||
| C8.0 | 09:12 | 13615 | GOES16 | ||
| C4.1 | 10:11 | 13615 | GOES16 | ||
| C4.7 | 10:28 | 13617 | GOES16 | ||
| C5.2 | 11:01 | 13615 | GOES16 | ||
| C6.7 | 11:18 | S15E05 | 13615 | GOES16 | |
| M1.0 | 11:29 | 13615 | GOES16 | ||
| C5.9 | 12:03 | 13615 | GOES16 | ||
| C5.8 | 12:15 | 13615 | GOES16 | simultaneous flare behind the southwest limb | |
| M1.3 | 12:47 | 13615 | GOES16 | ||
| M1.1 | 13:11 | 13615 | GOES16 | ||
| M1.9 | 13:37 | 13615 | GOES16 | ||
| M5.3/1B | 14:02 | 13615 | GOES16 | ||
| M1.8 | 14:33 | 13615 | GOES16 | ||
| M1.5 | 14:53 | 13615 | GOES16 | ||
| M3.8 | 15:13 | 13615 | GOES16 | ||
| M2.8 | 16:51 | 13615 | GOES16 | ||
| C3.9 | 17:48 | 13615 | GOES16 | ||
| C4.2 | 18:20 | 13615 | GOES16 | ||
| C9.9 | 18:57 | 13615 | GOES16 | ||
| C9.0 | 19:42 | 13615 | GOES16 | ||
| C8.5 | 20:08 | 13615 | GOES16 | ||
| C9.9 | 20:21 | 13615 | GOES16 | ||
| C9.3 | 20:28 | 13615 | GOES16 | ||
| C6.4 | 20:56 | 13615 | GOES16 | ||
| C6.1 | 21:05 | 13615 | GOES16 | ||
| C6.2 | 21:25 | S9536 | GOES16 | ||
| C6.1 | 21:32 | 13615 | GOES16 | ||
| C5.1 | 22:26 | 13615 | GOES16 | ||
| C4.2 | 22:39 | 13615 | GOES16 | ||
| C5.8 | 22:50 | 13615 | GOES16 | ||
| C7.9 | 22:59 | 13615 | GOES16 | ||
| M2.4/2N | 23:49 | S12E01 | 13615 | GOES16 |
March 21-22: No obviously Earth directed CMEs were observed.
March 23: An asymmetrical full halo CME was
observed after the X1.1 flare in AR 13614 early in the day. The CME could
reach Earth sometime between late on March 24 and noon on March 25 and cause
active to severe storm conditions.
[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 negative polarity southern hemisphere coronal hole (CH1207) rotated across the central meridian on March 20-22.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle and high latitudes is very poor. Propagation on long distance northeast-southwest paths is poor.
The geomagnetic field is expected to be quiet to minor storm on March 24 until the arrival of the March 23 CME. Active to severe storm conditions are likely from the onset of the CME disturbance until March 26.
| 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.
(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 | ||||||||||
| 13610 | 2024.03.12 2024.03.13 |
S16W71 | location: S15W59 | ||||||||
| 13611 | 2024.03.13 2024.03.14 |
N28W60 |
location: N29W53 |
||||||||
| 13614 | 2024.03.16 2024.03.17 |
5 | 28 | 8 | N17W07 | 0170 | DSO | DSO |
 |
 |
area: 0260 |
| 13615 | 2024.03.17 2024.03.18 |
53 | 100 | 59 | S13W01 | 0730 | FKC | FKC |
 |
 |
beta-gamma-delta area: 1760 location: S12E01 |
| S9514 | 2024.03.17 | S30W49 | |||||||||
| S9515 | 2024.03.17 | N09W07 | |||||||||
| S9519 | 2024.03.18 | N09W32 | |||||||||
| 13618 | 2024.03.19 2024.03.21 |
4 | 1 | 1 | S18W90 | 0120 | CAO | AXX |
 |
 |
location: S20W83 area: 0004 |
| 13617 | 2024.03.19 2024.03.20 |
4 | 13 | 7 | S14E29 | 0090 | CAO | CAO |
 |
 |
location: S13E31 |
| 13621 | 2024.03.20 2024.03.23 |
4 | 5 | 2 | N17W38 | 0020 | CRO | CAO |
 |
 |
location: N17W40 area: 0040 |
| 13619 | 2024.03.20 2024.03.21 |
3 | 15 | 5 | N19E31 | 0120 | CAO | CAO |
 |
 |
location: N18E30 area: 0160 |
| S9528 | 2024.03.21 | 2 | 1 | N19E48 | 0005 | AXX |
 |
 |
|||
| S9529 | 2024.03.21 | 5 | 3 | S19W09 | 0020 | CRO |
 |
||||
| S9530 | 2024.03.21 | N37W20 | |||||||||
| S9531 | 2024.03.22 | N09W14 |
 |
||||||||
| 13620 | 2024.03.22 2024.03.22 |
3 | 3 | 2 | S10E61 | 0030 | HRX | CAO |
 |
 |
area: 0050 |
| S9533 | 2024.03.22 | N05W22 |
 |
was AR S9527 | |||||||
| S9534 | 2024.03.22 | S04W27 |
 |
||||||||
| S9535 | 2024.03.22 | S08E13 |
 |
||||||||
| S9536 | 2024.03.23 | 4 | 2 | N19E77 | 0110 | HAX |
 |
||||
| S9537 | 2024.03.23 | 2 | S10E13 | 0002 | AXX |
 |
|||||
| S9538 | 2024.03.23 | 1 | S28E23 | 0001 | AXX |
 |
|||||
| Total spot count: | 76 | 179 | 90 | ||||||||
| Sunspot number: | 146 | 299 | 190 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 112 | 222 | 133 | (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): | 161 | 164 | 152 | ||||||||
| 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 |
| 2022.08 | 114.2 | 117.1 | 74.6 | 92.6 (+5.9) | 10.92 |
| 2022.09 | 135.1 | 136.5 | 96.0 | 96.5 (+3.9) | 12.18 |
| 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 | 124.1 (+1.2) | 10.67 |
| 2023.06 | 161.7 | 166.8 | 160.5 | 125.2 (+1.1) (SC25 solar max candidate) |
8.95 |
| 2023.07 | 176.4 | 182.2 | 160.0 | 124.3 (-0.9) | 8.15 |
| 2023.08 | 153.7 | 157.6 | 114.8 | 124.0 (-0.3) | 7.19 |
| 2023.09 | 154.4 | 156.0 | 134.2 | (124.2 projected, +0.2) | 14.26 |
| 2023.10 | 142.8 | 141.9 | 99.4 | (125.0 projected, +0.8) | 8.16 |
| 2023.11 | 153.5 | 150.2 | 105.4 | (125.0 projected, -0.0) | 12.20 |
| 2023.12 | 151.1 | 146.4 | 114.2 | (121.7 projected, -3.3) | 9.60 |
| 2024.01 | 164.6 | 159.3 | 123.0 | (118.3 projected, -3.4) | 5.46 |
| 2024.02 | 172.5 | 168.3 | 124.6 | (117.5 projected, -0.8) | 5.31 |
| 2024.03 | 149.3 (1) | 75.8 (2A) / 102.2 (2B) / 127.3 (2C) | (116.9 projected, -0.6) | (9.2) | |
| 2024.04 | (116.9 projected, -0.0) | ||||
| 2024.05 | (118.1 projected, +1.2) | ||||
| 2024.06 | (117.3 projected, -0.8) | ||||
| 2024.07 | (115.6 projected, -1.7) | ||||
| 2024.08 | (113.7 projected, -1.9) | ||||
| 2024.09 | (112.0 projected, -1.7) | ||||
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 activity saw a significant decrease during the latter half of February and the first part of March. While there is still a chance that there could be another and higher peak in October or November 2023, chances that June 2023 was solar max has increased. After November 2023 there is currently no other obvious candidate solar max month. Taking into account the state of the solar polar fields another major peak during SC25 is becoming less likely.
--------------------------------------------------------------------------------------
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.
