[2] The definition of a GLE is as follows: "A GLE event is registered when there are near-time coincident and statistically significant enhancements of the count rates of at least two differently located neutron monitors including at least one neutron monitor near sea level and a corresponding enhancement in the proton flux measured by a space-borne instrument(s).
"[3] Charged particles from the Sun generally do not possess the energy required to penetrate the Earth's magnetic field or Upper atmosphere.
However, a small number of solar events produce charged particles which are able to penetrate these layers, causing an air shower.
[4] GLEs are distinct from individual cosmic rays because multiple charged particles enter the Earth's atmosphere simultaneously, leading to a synchronized event over a wide area.
[2] The method by which solar flares and coronal mass ejections (CMEs) produce such high-energy particles is still uncertain, with some studies suggesting that they are produced mostly by a CME shock wave, by strong flare events or some combination, or related to the connection between the active solar region and the magnetic field of the Earth.