Solar activity forecast for the period May 16 - May 22, 2025

Activity level: low to moderate
X-ray background flux (1.0-8.0 A): in the range B8.0-C5.0
Radio flux (10.7 cm): a fluctuation in the range 111-162
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 31-102

Vlastislav Feik
RWC Prague, Astronomical Institute, Solar Dept., Ondrejov, Czech Republic

Geomagnetic activity forecast for the period May 16 - May 22, 2025

Quiet: May 17, 22
Unsettled: May 16 - 18, 20 - 21
Active: May 18 - 19
Minor storm: possible about May 19
Major storm:  0
Severe storm: 0

Because of current coronal hole, we expect the main active episode with possible minor storm event about Monday, May 19.
Before and after this event, we expect the geomagnetic activity at most at unsettled level.
Between the unsettled episode, we expect a few quiet days only.

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 16 - May 22, 2025

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere – May 15, 2025

The level of solar activity in the first half of May mostly did not resemble the current peak of the 25th 11-year cycle. The total number of sunspot groups across the disk ranged from two (May 2) to six (May 11), with no more than one larger group - first the relatively quiet AR4079 and then the eruptively very active AR4086 (whose growth could already be tracked prior to disk rise on the http://jsoc.stanford.edu/ - "Helioseismic Far-Side Imaging" website).

Ionospheric shortwave propagation conditions were mostly poor to below average. The main culprit was not the slightly lower level of solar radiation, but was mainly the solar wind. The Earth's ionosphere was under the influence of elevated free electron concentrations on most days, while was later bombarded by protons following the increase in flare activity in AR4086 with subsequent CMEs. The consequence was not so much lower MUF values as increased attenuation and scattering in the ionosphere. This was all the more advantageous for stations with higher powers and, in particular, with antenna systems with low radiation angles.

Further increases in solar activity in the northern half of the solar disk are still expected in the coming months, but cannot be predicted more accurately. In modern times, however, we can monitor it closely - and prepare for it all the better and in good time.

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