Solar Flare Tracker
Explore a 30-day snapshot of GOES X-ray flux data. Classify flares from A to X class on a logarithmic chart. See how the 11-year solar cycle and rare large flares drive space weather risks on Earth.
Guided Experiment: Count flares by class
How many flares of each class do you expect to find in a 30-day window during a moderately active sun? Predict the ratio of C to M to X events.
Write your hypothesis in the Lab Report panel, then click Next.
GOES X-ray flux
Logarithmic Y axis from 10⁻⁹ to 10⁻³ W/m². Bands mark A, B, C, M, X flare classes. Detected flares are highlighted at their peak.
Controls
Detection summary
Solar cycle, monthly sunspot number
Data Table
(0 rows)| # | Peak Time | Class | Peak Flux(W/m^2) | Duration(min) |
|---|
Reference Guide
Flare classification
The GOES Space Environment In-Situ Suite measures soft X-ray flux from the sun in two bands. The long channel covers 1.0 to 8.0 Å and defines the flare class.
- A below 10⁻⁷ W/m². Background level.
- B 10⁻⁷ to 10⁻⁶ W/m². Minor.
- C 10⁻⁶ to 10⁻⁵ W/m². Small flare.
- M 10⁻⁵ to 10⁻⁴ W/m². Medium. Can cause brief radio blackouts.
- X above 10⁻⁴ W/m². Major. Severe space weather impact.
Each letter step is 10 times the previous. Subclass numbers add detail. M1.5 means 1.5 times 10⁻⁵ W/m². X28 means 28 times 10⁻⁴ W/m².
The 11-year solar cycle
Sunspot number rises and falls on an average period of about 11 years. The rise phase is shorter than the decline phase. Each cycle is numbered in sequence from cycle 1 in 1755.
Flare frequency tracks the sunspot number. Near solar maximum the sun can produce several X-class flares per month. Near solar minimum many months pass without one.
Cycle 25 began in December 2019 and reached maximum in 2024 to 2025. It has produced multiple X-class events including the May 2024 superstorm sequence.
Space weather effects
Large solar flares emit X-rays that reach Earth in about 8 minutes. They ionise the dayside upper atmosphere and cause high-frequency radio blackouts.
- Aviation HF radio drops out on polar routes.
- GPS accuracy degrades during the strongest events.
- Coronal mass ejections that follow can drive geomagnetic storms.
- Satellites in low Earth orbit can experience drag and single-event upsets.
- Aurora can reach mid latitudes during severe events.
NOAA grades radio blackouts on an R1 to R5 scale. An M1 flare is R1. An X10 flare is R3 and above.
GOES X-ray sensor
The Geostationary Operational Environmental Satellite (GOES) program has carried X-ray sensors since the 1970s. The current GOES-16 and GOES-18 spacecraft use the X-Ray Sensor (XRS) on the EXIS instrument.
XRS-A measures the short channel from 0.5 to 4.0 Å. It responds to the hottest plasma and peaks earlier in a flare.
XRS-B measures the long channel from 1.0 to 8.0 Å. It defines the flare class and tracks the bulk thermal emission.
Data is sampled at 1-second cadence and downlinked continuously to the NOAA Space Weather Prediction Center.
Data note
The flux timeseries in this lab is a static snapshot synthesized to match the statistics of a moderately active 30-day window during solar cycle 25. Historical flare entries reflect real published events. The solar cycle data is modeled to match observed sunspot number trends.
For live GOES X-ray flux, visit the NOAA Space Weather Prediction Center at swpc.noaa.gov/products/goes-x-ray-flux.
