Space Weather
X-ray Flux — live and explained
The raw GOES satellite measurement behind every solar flare classification — the number that turns into letters like C, M, and X.
Current X-ray Flux
Updated every minute from live GOES data.
Data Layer: GOES Satellites
Why it matters
X-rays from a flare reach Earth in about 8 minutes (at the speed of light) and can ionize the upper atmosphere on the sunlit side, disrupting high-frequency radio communication — this is why strong flares cause immediate radio blackouts, unlike CMEs or geomagnetic storms which take hours to days to arrive.
Normal range
Background (quiet-sun) flux sits below 10⁻⁷ W/m² (A-class). C-class flares (10⁻⁶-10⁻⁵ W/m²) are common and mostly unnoticed on Earth. M-class (10⁻⁵-10⁻⁴) can cause brief blackouts near the poles. X-class (≥10⁻⁴) are the rare, major events capable of wide-area radio blackouts.
What today's value means
Waiting for live data to interpret…
What is X-ray flux?
GOES weather satellites carry X-ray sensors (XRS) that continuously measure how much X-ray radiation is reaching Earth from the Sun. This page shows the "long" channel (0.1-0.8 nanometers), the standard measurement used to classify solar flares. Flux rises sharply — sometimes a hundredfold within minutes — during a flare, then decays back toward background levels over the following hour or so.
Flare classification scale
| Class | X-ray flux threshold | Typical effect |
|---|---|---|
| A | < 10⁻⁷ W/m² | Background level, no flare. |
| B | 10⁻⁷ – 10⁻⁶ W/m² | Minor, no noticeable effects on Earth. |
| C | 10⁻⁶ – 10⁻⁵ W/m² | Small flares, minimal Earth effects. |
| M | 10⁻⁵ – 10⁻⁴ W/m² | Moderate — can cause brief radio blackouts near the poles. |
| X | ≥ 10⁻⁴ W/m² | Major — can cause wide-area radio blackouts and radiation storms. |
FAQ
How is flare class calculated from X-ray flux?
Each letter represents a tenfold jump in flux. The number after the letter is a linear multiplier — an M5.0 flare has 5 times the flux of M1.0, and an X2.0 flare has twice the flux of X1.0.
Why do X-ray flares affect radio communication?
X-rays from a flare reach Earth in about 8 minutes and ionize the upper atmosphere on the sunlit side, which can absorb or disrupt high-frequency radio signals — this is why strong flares cause radio blackouts.