IonoFlux field guide
TEC (total electron content)
How to understand the TEC ionosphere map and its limits.
In simple terms
TEC counts free electrons between the ground and the top of the ionosphere. More electrons can change how signals bend and delay, but TEC alone does not say whether your contact will succeed.
How to read it
Use the map to spot broad day/night and regional patterns. Combine it with MUF, geomagnetic data and live reception reports.
A practical example
A bright TEC region does not automatically mean every band is open. A path crossing it may still fail because of absorption, geometry or a disturbed ionosphere.