Solar Flares: How they occur and how are they classified?

Johnson Francis | October 12, 2026 | Amateur Radio (Ham Radio) | No Comments

Solar flares are sudden, intense bursts of electromagnetic radiation triggered by a process called magnetic reconnection near sunspots. They are classified based on their peak X-ray brightness into five categories: A, B, C, M, and X.

How They Occur

Magnetic Tangling: The Sun’s plasma generates powerful, complex magnetic fields. In active regions (sunspots), these field lines become highly twisted and tangled by the Sun’s rotation and churning outer layers.
Magnetic Reconnection: As tension builds, the tangled magnetic lines reach a breaking point. They violently snap apart and instantly realign into simpler, more stable configurations.
Energy Release: This sudden snapping releases massive amounts of stored magnetic energy. It accelerates charged particles to near light-speed and emits intense radiation across the entire electromagnetic spectrum, from radio waves to gamma rays.

The Classification System

Flares are classified by their peak X-ray flux (measured in watts per square meter) as detected by Earth-orbiting Geostationary Operational Environmental Satellites (GOES). The system is logarithmic—each letter class represents a 10-fold increase in energy output over the previous one. Each letter is further divided by a linear scale from 1 to 9 to designate finer strength (e.g., M1, M5, M9).

Class	Intensity Level	Earth Impact
A & B	Background	None. These are common and barely register above the Sun’s background radiation.
C	Minor	Few noticeable consequences, though they may slightly elevate background X-ray levels.
M	Medium	Can cause brief high-frequency (HF) radio blackouts on the sunlit side of Earth and minor solar radiation storms.
X	Major	The most powerful flares (the only class that can exceed level 9, e.g., the historic X28 flare). Capable of planet-wide HF radio blackouts, severe radiation storms, and satellite disruptions.