Weekly forecast

Solar activity forecast for the period September 15 - September 22, 2023

Activity level: mostly low too moderate
X-ray background flux (1.0-8.0 A): in the range B8.5 - C1.1
Radio flux (10.7 cm): a fluctuation in the range 130-161
Events: class C (4-10/day), class M (1-7/period), class X (0-1/period), proton (0/period)
Relative sunspot number (Ri): in the range 80 - 195

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

Geomagnetic activity forecast for the period September 15 - September 22, 2023

Quiet: Sep 15 - 20
Unsettled: Sep 15 - 16, 21
Active: unlikely Sep 21
Minor storm: 0
Major storm: 0
Severe storm: 0

After the last active episode at Sepember 12 and 13, we expect geomagnetic activity decrease to quiet to unsettled level. Since Saturday, September 16, we expect at most quiet conditons return.
Unsettled to active conditions are possible at the end of currently forecasted period, about September 21.

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 15 - September 22, 2023

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere – September 14, 2023
 
A week ago, the active sunspot group AR3414 dominated the solar disk. It is now on the far side of the Sun. This role has been taken over by AR3423, now approaching the western limb of the solar disk. It will be followed the next day by the slightly smaller AR3425. The important information is that we observe a coronal hole near both of them (closer to AR3425). This configuration was the likely cause of the surprise: Few people expected the Earth to be hit by a CME on September 12 at 1237 UT.

Then a massive disturbance of the Earth's magnetic field developed. Its initial positive phase increased the MUF values on September 12. This was followed by a negative phase, which in turn caused a significant decrease in MUF, while worsened shortwave propagation conditions on 13 September. This was followed by a gradual improvement on 14 September, however, when the magnetic filament connecting sunspots AR3423 and AR3425 erupted. The consequence could be a G1 to G2 class geomagnetic storm in the Earth's vicinity on 17 September.

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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