Update on Solar Cycle No. 25
(by the Director of the Ionising Radiation Monitoring Department - Ing. C. Grad. Marco Citterio)
2024 was a very interesting year from the point of view of space meteorology. This was also due to the fact that solar cycle No. 25 had reached its period of maximum activity and generated very powerful events. Let us recall the solar storms of very strong intensity due to which it was possible to see the northern lights as far as latitudes in central Italy. Beyond the romantic aspect of the phenomenon, it must be remembered that these phenomena entail a considerable increase in the dose of ionising radiation absorbed by the crews in flight (and also by passengers who are not covered by any protection regulations, even if they are flying for businnes...).

Our company has issued its customers with a large number of flight altitude limitation recommendations in order to keep exposure to high dose values as low as possible. This is in accordance with the ALARA principle ('As Low As Reasonably Achievable'). Class G5 (Extreme), S3 (Strong) and R4 (Severe) phenomena were recorded. Class 'G' phenomena represent geomagnetic storms and are characterised by electron fluxes, Class 'S' phenomena are solar storms and are characterised by powerful fluxes of protons, neutrons and Helium nuclei (all particles with mass and therefore very destructive). Finally, 'R' class phenomena represent Radio Blackouts and are characterised by powerful flows of X-rays that disrupt - to the point of totally preventing - radio communications on certain frequencies.

What do we expect by 2025? Although activity has decreased slightly at the moment, the peak value of solar activity has not yet been reached, so we must not let our guard down under any circumstances. It is still possible that a combined S5-G5-R4 event could occur that would set us back a couple of centuries. Power lines and computers are in fact the first to be damaged by such an event. Continuous currents of several hundred Amps would develop on the very high voltage power lines running north-south, leading to the melting of transformers, with catastrophic damage to the electricity supply. In such a scenario, the functioning of the electronic systems installed on board the aircraft is not even guaranteed, with a clear and certain impact on the flight profile.
Flyrad's task is to monitor the events and recommend to its customers the altitude limitations to be observed in order to protect the crews (and thus indirectly the passengers) from exposure to dangerous doses of ionising radiation.
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