On 06/04/2021 08:29, Tim Streater wrote:
On 05 Apr 2021 at 23:31:30 BST, Andrew
wrote:

On 05/04/2021 17:14, Tim Streater wrote:
On 05 Apr 2021 at 16:34:17 BST, "Brian Gaff \ Sofa\)"
wrote:

I heard on the radio the other day that scientists are still not sure what
it is that triggers the sudden breakdown and a discharge. Fingers are
pointing at high energy cosmic rays from deep space apparently, which ionise
the air just enough to allow the discharge.

That's entirely possible. There's no shortage of cosmic rays.


At the poles. The earths magnetic fields keep (?most of) them away from
the rest of us.

You're thinking of solar wind particles. High energy cosmic rays are millions
of times more energetic than those, and are not deflected significantly by the
Earthe's magnetic field. Most biff into an atmosphere molecule at some
altitude and produce showers of secondaries, many of which reach Earth.


Different definitions? "Cosmic rays" covers an enormous range of
energies and sources, from solar eruptions through supernovae to more
exotic sources (of which I know nought). The ultra-high energy laugh at
the Earth's magnetic field but the overall flux does vary with latitude.

--
Robin
reply-to address is (intended to be) valid