History of Solar flare in Timeline

By Popular Timelines Editorial Team · Updated: April 25, 2026

Solar flares are intense bursts of electromagnetic radiation emanating from the Sun's atmosphere, typically occurring in active regions. These events are frequently associated with coronal mass ejections and solar particle events, contributing to eruptive solar activity. The frequency of solar flares fluctuates in accordance with the Sun's 11-year solar cycle, highlighting a periodic pattern in their occurrence. These flares can impact space weather, affecting satellite communications and potentially causing disruptions to Earth-based technologies.

1942: Observation of Solar Emission by British Radar Operators

On February 25 and 26, 1942, British radar operators, including Stanley Hey, observed radiation interpreted as solar emission during World War II.

1943: First Radioastronomical Observations of the Sun

In 1943, Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz.

1945: Knowledge of Southworth's and Hey's observations made public.

After 1945, Southworth's and Hey's observations became public.

1970: Development of Solar Flare Classification System

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

1984: Discovery of 154-day Period in Gamma-Ray Emitting Solar Flares

In 1984, Erich Rieger and 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 is now known as the Rieger period.

November 2003: Largest Solar Flare Measured with Instruments

In November 2003, the largest solar flare measured with instruments occurred, saturating the GOES detectors. Initial estimates placed it at X28, later revised to X45 based on ionospheric effects. This flare produced the first clear evidence of a new spectral component above 100 GHz.