The geomagnetic field was at quiet levels, weakly under influence of effects associated with CH1366. Solar wind speed at SOHO ranged between 521 and 732 km/sec, averaging 630 km/sec (-46 km/sec compared to the previous day). The high latitude magnetometer at Andenes was at quiet to active levels. The above 10 MeV proton flux was at background levels all day.
Solar flux density measured at 20h UT on 2.8 GHz was 103.7 - decreasing 1.4 over the previous solar rotation.
The 365 day average solar flux at 1 AU was 140.19 (183 days ago). The 81 day average solar flux at 1 AU was 125.3 (41 days ago, this is 35.6% of the total SC25 solar flux range from the max 81 day average peak on September 4, 2024 at 227.3 and an average 81 day flux of 69 at solar minimum). SC25 365d peak: 195.9 on October 13, 2024.
The Potsdam WDC planetary A index was 7 (STAR Ap - based on the average of three hour interval ap indices: 7.0). Three hour interval K indices: 22222222 (planetary), 23232222 (Boulder), 44434243 (Andenes).
The background x-ray flux is at the class B3 level (GOES 19).
At the time of counting spots (see image time), spots were observed in 8 active regions using 2K resolution (SN: 136) and in 7 active regions using 1K resolution (SN: 93) SDO/HMI images.
AR 14436 [N19W38] produced a few C flares. The
proximity to the leading polarity area of AR S12063 appears to be the cause
of the instability observed the last days. C1 flares: C1.1 @ 11:32 UT
AR 14439 [N06E54] was mostly quiet and stable. C1 flares: C1.0 @
04:44, C1.0 @ 12:07 UT
AR 14440 [N17E56] was quiet and stable.
AR 14441 [N08E13] developed slowly and quietly.
New AR 14442 [S16E42] emerged with a few spots.
New AR 14443 [S14E60] emerged on May 16 and was numbered the next day
by SWPC.
Spotted regions not observed (or interpreted
differently) by SWPC/USAF:
AR S12063 [N15W27] was quiet and stable.
New AR S12073 [S17W37] emerged with tiny spots.
AR 14435 behind the northwest limb was the source of a C1.1 flare at 12:38 UT
C2+ flares
| Magnitude | Peak time (UT) | Location | Source | Recorded by | Comment |
| M1.4 | 03:39 | behind northwest limb | 14435 | GOES18 | |
| C2.0 | 05:32 | behind northwest limb | 14435 | GOES18 | |
| C9.7 | 20:53 | 14436 | GOES18 |
May 15, 17: No obviously Earth directed CMEs were observed in
available coronagraph imagery.
May 16: An assymetric CME was observed after the M1 flares in AR
14436 after 16h UT. The CME could reach Earth late on May 18 or on May 19.
[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 negative polarity trans equatorial coronal hole (CH1366) was Earth facing on May 12-15. A northern hemisphere negtive polarity coronal hole (CH1367) rotated across the central meridian on May 16.
The geomagnetic field is expected to be at mostly quiet levels on May 18, very weakly under the influence of a high speed stream associated with CH1366. Quiet to active is possible on May 19 due to influence from CH1367. There's a chance the May 16 CME could reah Earth on May 18/19 and cause unsettled to minor storm levels.
| 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 |
STAR | SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 14436 | 2026.05.08 2026.05.09 |
4 | 12 | 4 | N19W39 | 0100 | DSO | CSO |
 |
 |
was AR S12051 area: 0180 location: N19W38 |
| 14438 | 2026.05.12 2026.05.13 |
5 | N20W84 | 0060 | DAO |
 |
was AR S12058 spotless SWPC spot data unchanged from the previous day |
||||
| S12060 | 2026.05.12 | S06W43 | |||||||||
| S12063 | 2026.05.13 | 6 | 1 | N15W27 | 0010 | BXO |
 |
 |
|||
| S12065 | 2026.05.13 | S14W04 | |||||||||
| S12066 | 2026.05.14 | S17W18 | |||||||||
| 14440 | 2026.05.15 2026.05.16 |
1 | 5 | 2 | N17E57 | 0030 | HAX | CAO |
 |
 |
was AR S12067 area: 0040 location: N17E56 |
| 14439 | 2026.05.15 2026.05.16 |
2 | 4 | 3 | N06E55 | 0040 | CSO | DAO |
 |
 |
was AR S12068 area: 0120 |
| 14441 | 2026.05.16 2026.05.16 |
4 | 17 | 7 | N18E14 | 0050 | DAO | DAO |
 |
 |
was AR S12069 area: 0200 location: N08E13 |
| 14443 | 2026.05.16 2026.05.17 |
2 | 4 | 3 | S15E60 | 0010 | BXO | CRO |
 |
 |
was AR S12070 area: 0020 location: S14E60 |
| S12071 | 2026.05.16 | N17E40 |
 |
||||||||
| 14442 | 2026.05.17 2026.05.17 |
2 | 6 | 3 | S16E44 | 0020 | CRO | CRO |
 |
was AR S12072 location: S16E42 |
|
| S12073 | 2026.05.17 | 2 | S17W37 | 0003 | BXO |
 |
|||||
| Total spot count: | 20 | 56 | 23 | ||||||||
| Sunspot number: | 90 | 136 | 93 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 48 | 82 | 49 | (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): | 99 | 75 | 74 | ||||||||
| Month | Average solar flux | International sunspot number (WDC-SILSO) |
Smoothed sunspot number (4) | Average
ap (3) |
|
|---|---|---|---|---|---|
| Measured | 1 AU | ||||
| 2024.05 | 187.7 | 191.9 | 172.1 | 149.1 (+4.6) | 23.56 (SC25 peak) |
| 2024.08 | 246.1 (SC25 peak) |
252.2 | 216.0 (SC25 peak) | 156.8 (+1.8) | 15.96 |
| 2024.10 | 221.0 | 219.6 | 165.8 | 160.9 (+1.5) (SC25 solar max) | 18.99 |
| 2025.02 | 184.2 | 179.7 | 155.7 | 139.8 (-6.4) | 14.42 |
| 2025.03 | 163.7 | 162.1 | 134.2 | 135.9 (-3.9) | 15.96 |
| 2025.04 | 162.5 | 163.6 | 141.4 | 133.3 (-2.6) | 17.62 |
| 2025.05 | 135.3 | 138.3 | 78.5 | 128.6 (-4.7) | 17.26 |
| 2025.06 | 131.3 | 135.4 | 114.6 | 124.7 (-3.9) | 21.43 |
| 2025.07 | 137.8 | 142.3 | 125.9 | 122.4 (-2.3) | 11.80 |
| 2025.08 | 154.9 | 158.7 | 133.7 | 118.2 (-4.2) | 9.97 |
| 2025.09 | 154.4 | 156.0 | 129.7 | 112.9 (-5.3) | 14.02 |
| 2025.10 | 139.5 | 138.6 | 114.6 | 108.3 (-4.6) | 15.64 |
| 2025.11 | 140.3 | 137.3 | 91.7 | (105.8 projected, -2.5) | 21.01 |
| 2025.12 | 160.8 | 155.8 | 124.0 | (104.3 projected, -1.5) | 13.35 |
| 2026.01 | 148.7 | 144.0 | 112.6 | (100.4 projected, -3.9) | 22.47 |
| 2026.02 | 136.4 | 133.1 | 78.2 | (96.1 projected, -4.3) | 12.88 |
| 2026.03 | 131.0 | 129.7 | 85.9 | (91.5 projected, -4.6) | 15.44 |
| 2026.04 | 120.0 | 120.9 | 79.3 | (87.6 projected, -3.9) | 12.10 |
| 2026.05 | 121.5 (1) | 50.7 (2A) / 92.5 (2B) / 97.7 (2C) | (86.4 projected, -1.2) | (10.6) | |
| 2026.06 | (84.3 projected, -2.1) | ||||
| 2026.07 | (79.9 projected, -4.4) | ||||
| 2026.08 | (77.7 projected, -2.2) | ||||
| 2026.09 | (76.8 projected, -0.9) | ||||
| 2026.10 | (74.8 projected, -2.0) | ||||
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 27 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 appears to have exited the solar max phase as of February
2026 with a strong decrease in the number of sunspots observed. The northern
polar field has weakened considerably over the last months, and although
there is a chance the the field could recover over the next 1-2 years, there
is an increasing chance that solar cycle 26 will be very weak. The southern
polar field is not impressive either, however, a southern polar coronal hole
has formed early in 2026 and appears to be growing.
All 365 day smoothed sunspot numbers reached a maximum on October 11-12, 2024.
This became the peak of SC25 (365 day smoothed peaks: STAR 1K: 236.1, STAR 2K: 364.3, NOAA SN: 156.0, ISN: 163.9),
while the 365d
smoothed solar flux peaked on October 13, 2024, just 1.7% below the SC23
peak, and 62.6% above the SC24 peak.
--------------------------------------------------------------------------------------
This report has been prepared by Jan Alvestad. It is based on the analysis of data from whichever 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.
