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Solar activity forecast for the period May 23 - May 29, 2025

Activity level: low to moderate
X-ray background flux (1.0-8.0 A): in the range B3.5-C4.0
Radio flux (10.7 cm): a fluctuation in the range 100-160
Events: class C (2-10/day), class M (0-5/period), class X (0-1/period), proton (0-1/period)
Relative sunspot number (Ri): in the range 40-150

Karolina Knesplova
RWC Prague, Astronomical Institute, Solar Dept., Ondrejov, Czech Republic

Geomagnetic activity forecast for the period May 23 - May 29, 2025

Quiet: May 24 - 27
Unsettled: May 23  - 24, 26 - 27
Active: May 27 - 29
Minor storm: May 28 - 29
Major storm:  0
Severe storm: 0

Next week, we expect geomagnetic activity decrease till Tuesday, May 27.
At the end of currently forecasted period, we expect a new active episode with probable storming event. Till this event, we expect geomagnetic activity at the range of quiet and unsettled level, generally.

Tomas Bayer
RWC Prague
Institute of Geophysics of the ASCR, Prague
Department of Geomagnetism
Budkov observatory (BDV)

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere May 23 - May 29, 2025

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere – May 22, 2025

Compared to previous months, there was a significant decrease in solar activity in May. For example, on May 2, there were only two groups of spots on the entire solar disk observed. After that, spot activity in the northern half of the solar disk increased slightly, but solar flux dropped significantly during the second third of the month. Additionally, a large coronal hole appeared in the southern hemisphere of the sun. Although this coronal hole was observed during previous rotations in March and April, it is much larger this time.

Consistent with this observation, after geomagnetic activity quieted down at the end of April, we experienced several days of strong geomagnetic disturbances in the first third of May. Starting in the second third of May, the solar flux dropped significantly, reaching values not seen since October 2024.

The combination of low solar activity and high geomagnetic activity resulted in a significant deterioration of ionospheric shortwave propagation conditions, manifested by a drop in the critical frequencies of the F2 layer and an increase in attenuation and scattering. This occurred especially on May 7-12 and May 14-18, and is likely to continue in the coming days.

The latest attempts to forecast further developments suggest that conditions should improve by the end of May. The summer ionosphere of the northern hemisphere of Earth is characterized by lower maximal frequencies and higher lows, not counting the sporadic layer E surprises.

F. K. Janda, A.R.S. OK1HH
http://ok1hh.nagano.cz/
Emails: ok1hh(at)crk.cz, ok1hh(at)rsys.cz
Pmail: OK1HH(at)OK0NAG.#BOH.CZE.EU

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