Cheers Doc.
I know I said last week that the pics of Wicklow would be the last I would post,
but I found these at the weekend and just had to share them.
This photo was captured by Ole Christian Salomonsen in Norway, using a Canon 5D Mark II
with Canon EF 16-35 Mark II lens and settings at f/2.8, ISO2500, 7sec. It is a long exposure
photo, that’s why you can see some satellites streaks and one made by a plane. The aurora
lets you see the background full of stars, because it is colorful but a little bit transparent.
Auroras emit light because of the emission of photons by oxygen and nitrogen atoms in the
upper atmosphere. Those atoms get excited—or ionized—by the collision with solar wind particles,
which are accelerated by the Earth’s magnetic field. As the atoms get excited or return to their
normal state, they emit visible energy. When it is an oxygen atom, the light emitted is either
green or brownish-red, depending on the energy level absorbed by the molecule. Blue happens
when nitrogen gets ionized, and red when it returns to ground state.