Weekly forecast

Forecast issued date:

Solar activity forecast for the period September 11 - September 17, 2026

Activity level: low
X-ray background flux (1.0-8.0 A): in the range B1.0-B5.5
Radio flux (10.7 cm): a fluctuation in the range: 85-130
Events: class C (1-4/day), class M (0-1/period), class X (0/period), proton (0/period)
Relative sunspot number (Ri): in the range 55-125

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

Geomagnetic activity forecast for the period September 11 - September 17, 2026

Quiet:   Sep 11 - 12, 16 - 17
Unsettled: Sep 12 - 14
Active:  Sep 13 - 15
Minor storm: possible about Sep 14
Major storm:  0
Severe storm: 0
Coming weekend, we expect geomagnetic activity decrease til Sunday, September 13.
Since this day, we expect at most active conditions since September 15. This active episode can be accompanied by a minor storm event.
The last days, we expect 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 September 11 - September 17, 2026

The observed number od sunspot groups ranged from six to seven starting on September 4, while there were occasional Class C and M solar flares. Sun emitted two coronal mass ejections (CMEs) toward Earth, but they missed the planet. Nevertheless, the intensified solar wind following a geomagnetically quiet period from September 1 to 6 contributed to a noticeable increase in geomagnetic activity, particularly on September 7–8. The positive phase of the disturbance during the afternoon and especially the evening hours UT on the first day was interesting and impressive. This was, however, inexorably followed by a negative phase, which significantly affected shortwave ionospheric propagation as late as September 10.

No increase in solar activity is expected in the coming days either. However, after the erratic and disrupted conditions expected in the second third of September, a calmer period—with significantly more favorable shortwave propagation conditions—should follow for the remainder of the month, particularly around the equinox.

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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