The interaction of solar activity with the Earth’s atmosphere occurs through a complex series of events called Space Weather (SW). The main quest of solar activity research is to clearly understand the causes and dynamics of Space Weather phenomena in order to protect mankind and our sophisticated technological systems that might be at considerable risk from high-speed charged particles often blowing abruptly off the Sun. The continuous flux of solar particles suddenly increases in the upper atmosphere when a high-intensity (e.g. above M5-class) solar flare, causing massive plasma ejection labeled as CME, reaches the Earth. These most energetic eruptions of the entire Solar System follow the 11-year solar cycle hinting towards their magnetic solar origin. At the peak of the cycle, several dangerously high-intensity class flares and CMEs may occur. Most solar flares and CMEs originate from magnetically active regions (ARs) around sunspot groups. During flaring magnetic reconnection takes place, causing the breaking and reconnecting of magnetic field lines. In this process, magnetic energy is converted into radiative, kinetic and thermal energy causing particle acceleration with energy bursts of up to 1021-1026 joules. A part of the energetic particles are confined within closed magnetic structures, and are forced to follow the magnetic fields back down to the solar Interface Region. However, another part of the high-speed particles break free of their magnetic cage, moving outward into interplanetary space along open magnetic field lines (see Figure above). Flares are frequently accompanied by CMEs. High-energy flares can cause long-lasting radiation storms in Earth’s upper atmosphere, and trigger serious radio blackouts. However, if an associated CME hits Earth's upper atmosphere, this interaction can result in dramatic consequences on a number of ground-based (pipelines, power lines) and space-based infrastructures (telecommunication, GPS). These societal assets and services are vital to the economic welfare and security of every citizen but may be subject to failure due to solar activity.