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

Activity level: low
X-ray background flux (1.0-8.0 A): in the range B2.5-B6.5
Radio flux (10.7 cm): a fluctuation in the range: 90-115
Events: class C (1-6/day), class M (0-2/period), class X (0/period), proton (0/period)
Relative sunspot number (Ri): in the range 44-110

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

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

Quiet:  Apr 21 - 23
Unsettled: Apr 19 - 21
Active: Apr 17 - 18
Minor storm:   Apr 17 - 18
Major storm:  possible about Apr 18
Severe storm: 0

Because of the large coronal hole (42/-4), we expect geomagnetic activity enhance during the coming two days. It can be accompanieed by minor to major storm event, this warning is actual till Sunday, April 19.
Then, since Monday, April 20, we expect a partial activity decrease and, at the end of currently forecasted period, quiet to unsettled conditions return.

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 April 17 - April 23, 2026

It is as if we were not just past the 11-year solar activity maximum; the solar flux fell and remained below 100 s,f,u for five days (April 9–13), while the number of sunspot groups dropped to just three. Flare activity declined similarly. However, more significant for the future development of solar activity—and especially for its impact on Earth—is the large coronal hole No. 42, which is approaching the central meridian from the northeast. Its western border  can be considered a potential source of solar wind that will reach Earth in the coming days.

Initially, it seemed that this would not happen until April 19, but closer observation of its development shows that the Earth will be hit by a fast solar wind as early as April 18 during the day. Or perhaps as early as the late afternoon of April 17, in which case the disturbance could begin with a positive phase (with an increase in MUF) while should  continue through the negative phase for much of the weekend.

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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