What are Solar flares
Brilliant flashes of light in the solar atmosphere, lasting less than an hour, or even perhaps only a few seconds, are called Solar Flares. The brightest are visible in white light, but they are easier to see in the light of hydrogen or calcium lines. A flare is a highly concentrated, explosive release of energy, usually in the vicinity of an active region. Flares spring up in active regions where the magnetic field has been stressed into a strong, unstable & configuration. A major puzzle in solar physics is the reason for the sudden release of energy through the flare mechanism. Once they have started to release energy at a particular place they may flash on & off several times. Simultaneously X-ray & ultraviolet detectors register intense blasts. In the hard X-ray region, the total emission from the Sun may rise by 100 times during a flare. For this reason it is considered hazardous to send astronauts into space at times when strong flares are likely to erupt on the Sun. Flares also eject copious bursts of energetic charged particles, such as protons & electrons, from the sun. After a major outburst it is not uncommon to see material crashing back to the Sun in the form of a loop prominence.
Flare studies expanded considerably once engineers had developed instruments that could be launched in rockets & satellites. The copious X-rays (wavelength shorter than 0.1 nm) is detected, followed by a gradual rise & fall of soft X-rays (wavelength between 0.1 & 2nm). In the soft spectrum are emission lines from highly ionized species. Flares have observable consequences for Earth. The energetic particles streaming into our atmosphere about two days after a flare excite atoms & electrons, causing them to emit light when they do-excite; the results is the auroral displays, which are strongest at high latitudes where the magnetic field emerges vertically from the Earth’s surface & at solar maximum. The
X-rays bursts indirectly cause the fadeout of shortwave radio communications on the sunlit side of Earth & cause geomagnetic disturbances. Powerful surges in the Sun’s radio emission also occur.