What is the effect on Earth's atmosphere of a strong solar flare?

The Earth has a magnetic field which prevents the energetic charged particles (high-energy protons) and electromagnetic radiation (x-rays) to penetrate the Earth's atmosphere. However, despite the presence of magnetic field, there are still some noted effects of solar flare towards Earth. Solar flares cause the Earth's atmosphere to obtain high level of ions. There are also some disruptions in wireless communications when solar flares occurs. Another effect of solar flares which is considered of high beauty is the auroras. The magnetic field cannot prevent all charged particles produced from solar flares from penetrating the Earth's atmosphere. Some of this charged particles, specially the electrons, find their way at the poles, either the North or the South. These particles collide with the present particles in the atmosphere which causes friction among particles and glow.