History of Solar flare in Timeline

Solar flares are intense bursts of electromagnetic radiation emanating from active regions in the Sun's atmosphere. These localized emissions are frequently associated with other solar events, such as coronal mass ejections and solar particle events. The frequency of solar flares fluctuates according to the Sun's 11-year solar cycle.

1942: British Radar Operators Observe Solar Emission

On February 25 and 26, 1942, British radar operators observed radiation interpreted as solar emission by Stanley Hey. This discovery remained unpublicized until the end of World War II. In the same year, Southworth also observed the Sun in radio, but these observations were only known after 1945.

1943: First Radioastronomical Observations of the Sun

In 1943, Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz, revealing new peculiarities of solar activity like storms and bursts related to the flares.

1945: Observations Known After WWII

The observations of the Sun in radio made by Southworth in 1942, as well as the discovery of solar emission by British radar operators in 1942, were only known after 1945, following the conclusion of World War II.

1970: Original Solar Flare Classification System Devised

In 1970, a classification system for solar flares was originally devised, including only the letters C, M, and X to avoid confusion with optical classification systems.

1984: Discovery of Rieger Period

In 1984, Erich Rieger and his coworkers discovered an approximately 154-day period in the occurrence of gamma-ray emitting solar flares, dating back to at least solar cycle 19. This period, now commonly known as the Rieger period, has been confirmed in most heliophysics data and the interplanetary magnetic field.

November 2003: Largest Solar Flare Measured with Instruments

In November 2003, the largest solar flare ever measured with instruments occurred. The event saturated the GOES detectors, leading to an approximate classification, initially estimated at X28 and later revised to X45 based on ionospheric effects. This flare produced the first clear evidence of a new spectral component above 100 GHz.