Weekly forecast

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Forecast issued date:

Solar activity forecast for the period September 22 - September 28, 2023

Activity level: mostly moderate
X-ray background flux (1.0-8.0 A): in the range B9.5 - C1.8
Radio flux (10.7 cm): a fluctuation in the range 145-65
Events: class C (4-10/day), class M (0-3/day), class X (0-1/period), proton (0/period)
Relative sunspot number (Ri): in the range 130 - 280

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

Geomagnetic activity forecast for the period September 22 - September 28, 2023

Quiet: Sep 24 - 27
Unsettled: Sep 22 - 24, 27 - 28
Active: Sep 23, 28
Minor storm: Sep 28
Major storm: 0
Severe storm: 0

After the last active episode with minor storm event (at Budkov 
observatory, the highest local K-index peaked at level 5), we expect 
geomagnetic activity decrese to unsettled level wduring coming two days.
At the start of the new week, since Monday, September 25, we expect at 
most quiet conditions till the end of currently forecasted interval. At 
the end of this weekly forecast, another active event with posible 
storming event is expectable.

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 22 - September 28, 2023

Although the site SolarHam.net (https://solarham.net/, launched on March
15, 2006, created and still maintained solely by Kevin VE3EN) is primarily
intended for amateur radio users, it is also very well regarded by
professional astronomers. In addition to information about the Sun, it
contains everything needed to understand the causes of changes in the
ionosphere, and also provides an overview and forecast of the Earth's
magnetic field activity. On Thursday, September 21, we read: 'Solar
activity is predicted to remain at low (C-Flares) to moderate (M-Flares)
levels during the next 24 hours. AR 3435 is considered the most likely
region to produce a moderate to strong solar flare."

The information can be supplemented by saying that the level of solar
activity has been rising in recent days, and this rise was accompanied by
an increase in solar wind speed from 400 km/s to over 600 km/s between
18-20 September. In particular, the solar wind proton influx increased
significantly on 18 September; moreover, a geomagnetic disturbance with
intensity G2 (Moderate) to G3 (Strong) took place on 18-19 September.

The Earth's ionosphere responded to these events with a significant
decrease in MUF, especially since 18 September. Shortwave propagation
conditions were above average for the last time on 10-12 September,
including a positive phase of the disturbance on the latter day. Around the
equinox we usually expect improvement, but now it was the opposite as a
result of disturbances.

As another very good source of information, I can particularly recommend
the Space Weather Monitor (https://www.ionosonde.iap-kborn.de/actuellz.htm),
as it also contains the most important data on the Earth's ionosphere.

F. K. Janda, A.R.S. OK1HH
Emails: ok1hh(at)crk.cz, ok1hh(at)rsys.cz

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