Predikce sluneční a geomagnetické aktivity

Michael Vavra
RWC Prague, Astronomical Institute, Solar Dept., Ondrejov, Czech Republic
e-mail: sunwatch(at)asu.cas.cz
 

Tomas Bayer, RWC Prague 
Institute of Geophysics of the ASCR, Prague
Department of Geomagnetism
Budkov observatory (BDV)
 

Remarks:

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere February 28 – March 06, 2025
Weekly Commentary on the Sun, the Magnetosphere, and the Earth's Ionosphere – February 27, 2025

Solar activity is now increasing, but the increase is irregular, which causes, among other things, a decrease in the reliability of forecasts. Geomagnetically quiet periods, especially when associated with an increase in total solar activity (such as 20-23 February), are accompanied by improved conditions for ionospheric radio wave propagation. A subsequent disturbance can cause even further improvement (which happened on 24 February).

Following the increase in solar flare activity (from 23 February), two proton flares were observed on 24 February. In the following days, the Earth's ionosphere was under the influence of a solar-derived proton rain, after which the density of free electrons in it decreased due to recombination. However, the worsening of conditions was only noticeable on 25 February. The very next day, 26 February, there was an improvement, in particular an increase in the MUF on a global scale. The jump in the solar wind speed also contributed. However, the changes were so rapid, even within a single day, that our assessment of the level of conditions could have been reversed, depending on the time of day and the frequency bands used.

The developments described can be considered as a harbinger of a March increase in solar activity. Since the spring equinox is approaching, it will contribute to an improvement in ionospheric shortwave propagation, more accurately called decameter waves. The possible shorter worse spells on March 1-2 and March 5-6 will make no difference, with the seasonal improvement not fully manifesting itself until the second half of the month.

Poznámka:

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