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How does the Sun create charged particles in Earth’s ionosphere?

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Diagram of Earth's atmosphere layers-troposphere, stratosphere, mesosphere, and thermosphere-showing how temperature and air pressure change with increasing altitude, with key features like the ozone layer and pressure percentages at various heights. — Ionosphere and magnetosphere The layers of Earth's atmosphere, with a yellow line showing the air temperature at various heights.

The Sun creates charged particles in Earth’s ionosphere primarily through a process called photoionization.12

When high-energy photons from the Sun—specifically those in the ultraviolet and X-ray portions of the spectrum—strike neutral atoms and molecules in the upper atmosphere, they are absorbed. This absorption provides enough energy to eject an electron from the neutral species, converting it into a pair of charged particles: a negatively charged electron and a positively charged ion.341

The specific layers of the ionosphere are produced by different wavelengths of solar radiation:
* F regions: Produced by photons with wavelengths between 10 and 80 nm.3
* E layer: Produced by photons between 90 and 100 nm, as well as "soft" X-rays.3
* D region: Produced by "hard" X-rays (below 5 nm) and solar emissions at the Lyman α wavelength (121.7 nm), which ionizes nitric oxide.3

While photoionization is the primary mechanism, auroras can also create charged particles when beams of electrons are accelerated into the atmosphere.4