Auroras are very bright displays of light in the sky which typically occur in the southern and northern regions of the Earth, also known as Arctic and Antarctic regions. Auroras are usually caused by the interaction between energetic charged particles coming from the Sun and the atoms present in the thermosphere. Auroras are commonly known as the northern lights in the northern latitudes and the southern lights in the southern latitudes.
The solar wind
Auroras are closely related to a flow of charged particles, known as the solar wind, continuously flowing outward from the sun. When these particles reach the Earth´s magnetic field, they are directed toward the poles, where they are accelerated toward the Earth. The collisions produced by the accelerated particles and the molecules and atoms present in the atmosphere cause a release of energy, which is what produces auroras at the Earth´s poles. Auroras may appear brighter during the solar maximum, which is when the Sun´s activity intensifies.
Solar flares during a solar maximum
Solar activity follows a cycle of eleven years, during which the Sun´s activity varies from a solar minimum to a solar maximum. During a solar maximum, which is when the solar activity intensifies, darker regions known as hotspots can be seen on the Sun. Sunspots are active regions of intense magnetic activity. Magnetic activity causes a huge release of energy known as a solar flare. This release of energy is usually followed by a coronal mass ejection.
The solar flare emits clouds of electrons, ions and atoms into space. The clouds of energy form the solar wind and usually travel through space, taking a day or two to reach the Earth. When the solar wind carrying these energetic particles reaches the magnetosphere, it is redirected to the Earth´s magnetic field at the poles, where the particles interact with the atoms and molecules in one of the Earth´s atmospheric layers, known as the thermosphere. In this part of the atmosphere, the charged particles and the atmospheric atoms and molecules interact, producing luminous displays of light known as auroras.
In the northern latitudes, the interaction between the sun´s charged particles and the atoms and molecules present in the atmosphere is what produces the northern lights, also known as aurora borealis. Auroras display various colors due to the emission of photons by atoms collisioning, or returning to their ground state, after being excited. The same mechanism produces the southern lights, also known as aurora australis.
The more intense light displays of auroras usually occur when the sun reaches its solar maximum every eleven years. During this period, the solar activity intensifies at the region of the sunspots where magnetic field lines reconnect, producing solar flares. The more energetic the solar flares are, the further away from the poles the aurora displays will be seen. According to nasa.gov, auroras rely on the Sun´s energy to produce the currents that make them glow.