A photograph of the diffuse aurora by Jan Curtis in Fairbanks, Alaska. The dark regions covering the aurora are clouds.

Diffuse Aurora: pitch-angle scattering

Unlike the discrete aurora, which is due to the parallel acceleration of electrons down along the earth's magnetic field lines into the atmosphere, diffuse aurora "dribbles" in from the plasma sheet. This dribbling comes from wave-particle interactions that scatter electrons and give them velocities that are more parallel to the magnetic field line. This change of velocity will put the electrons in the loss cone in phase space and they will precipitate into the atmosphere, exciting atoms and molecules to produce the diffuse aurora. The quantitative study of the wave-particle interaction with different types of waves and with electrons having different energies is a complicated matter. It is what we will study here using homework sets.

Homework 1:

We'll start by studying how electron cyclotron harmonic (ECH) waves that are measured at the magnetic equator can scatter electrons into the loss cone. First, find the following papers in the Journal of Geophysical Research: Lyons [1974], JGR, pg. 575 and T.S.T. Young et al. [1973], JGR, pg. 1082. Read the introduction in Lyons [1974] and read through Young et al. [1973]. Next, answer the questions posed in the first homework set.

Start homework 1

We'll continue with our study of ECH waves by looking more closely at the paper by Young et al.[1973]. Read carefully through this paper and then answer the questions in the next homework set.

Start homework 2

Come back next time for more diffuse aurora homework.