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Solar activity forecast for the period July 17 - July 23, 2026

Activity level: low to moderate 
X-ray background flux (1.0-8.0 A): in the range B5.5-C1.5
Radio flux (10.7 cm): a fluctuation in the range: 105-125
Events: class C (2-5/day), class M (0-1/day), class X (0/period), proton (0/period)
Relative sunspot number (Ri): in the range 50-120

Martina Pavelkova
RWC Prague, Astronomical Institute, Solar Dept., Ondrejov, Czech Republic

Geomagnetic activity forecast for the period July 17 - July 23, 2026

Quiet:   Jul 17 - 21
Unsettled: Jul 17 - 18, 21 - 22
Active:  Jul 22 - 23
Minor storm:  about  Jul 23
Major storm:  0
Severe storm: 0

Next days, we expect geomagnetic activity decrease generally. At most, we expect the
geomagnetic activity at quiet to unsettled level. At the end of currently forecasted period, 
another active to minor storm event is possible.

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 July 17 - July 23, 2026

The significant decline in solar activity throughout the first half of July is clearly illustrated by the solar flux values, which fell from 203 s.f.u. (July 2) to 100 s.f.u. (July 14–15), as well as by the number of sunspot groups, which dropped from five to two. A significant drop in the critical frequencies of the F2 layer began as early as July 4 during the geomagnetic disturbance of July 4–5, and due to the sharp decline in solar activity, these values returned to average levels only very slowly in the following days. Consequently, the sporadic E layer had an even greater impact on shortwave propagation (particularly in the mid-latitudes of Europe on July 14–16).

The increase in solar activity, which is expected to begin as early as the end of this week, while should last nearly until the end of the month, will result in significantly better shortwave propagation conditions than those experienced in the first half of the month. More significant changes (possibly an initial rise, but then very likely a temporary drop in MUF) will likely be caused by a geomagnetic disturbance, which is tentatively expected on July 21–22

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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