XMM, because it is sensitive to X-ray light, can see the emission coming from the hot electrons themselves.

In an incandescent light bulb, very hot electrons vibrate very fast.

Such replacement of "hot" electrons by "cold" ones is in complete accord with the 2nd law of thermodynamics.

The term "hot electron" was originally introduced to describe non-equilibrium electrons (or holes) in semiconductors.

Because of the high effective temperatures, hot electrons are very mobile, and likely to leave the semiconductor and travel into other surrounding materials.

The hot electrons may jump from the channel region or from the drain, for instance, and into the gate or the substrate.

These hot electrons do not contribute to the amount of current flowing through the channel as intended and instead are a leakage current.

Many failures result in generation of hot electrons.

Power coupled to the electron system drives it out of thermal equilibrium with the phonon system, creating hot electrons.

However, due to the laser's strong coupling with hot electrons, premature heating of the dense plasma (ions) was problematic and fusion yields were low.