A solar flare is a sudden burst of electromagnetic radiation from the Sun's atmosphere, released when magnetic energy stored in active regions lets go. Flares are classed A, B, C, M and X by X-ray intensity — X being the strongest — and can disrupt radio communications, degrade GPS accuracy and endanger astronauts.
Understanding Solar Flare
Flare Classification
| Class | Peak X-ray Flux (W/m²) | Effect | Frequency (at solar max) |
|---|---|---|---|
| A | < 10⁻⁷ | No significant effect | Very common |
| B | 10⁻⁷ – 10⁻⁶ | Negligible | Common |
| C | 10⁻⁶ – 10⁻⁵ | Minor HF radio degradation | Frequent |
| M | 10⁻⁵ – 10⁻⁴ | Moderate radio blackouts, GPS errors | Several per month |
| X | > 10⁻⁴ | Severe radio blackouts, radiation storms | Several per year |
Solar Flares vs Coronal Mass Ejections
Flares and CMEs often occur together but are fundamentally different. A flare is a flash of radiation — its effects are immediate but generally short-lived (minutes to hours). A CME is a massive ejection of magnetised plasma — billions of tonnes of solar material hurled into space. If a CME is directed toward Earth, it arrives 1–3 days later and can trigger geomagnetic storms lasting days, causing auroras, satellite anomalies, and power grid disruptions. Not all flares produce CMEs, and not all CMEs are preceded by flares.
Impact on Space Systems
Solar flares affect space infrastructure in several ways: increased ionospheric density disrupts HF radio communication and GPS accuracy (space weather and GPS); enhanced atmospheric drag at LEO altitudes accelerates orbital decay; and energetic particles can damage satellite electronics and increase radiation dose for astronauts. During the October 2003 "Halloween storms," several satellites experienced anomalies, and one (ADEOS-II) was permanently disabled.