Editing Aurora (section)

=== Auroral particles ===
The immediate cause of the ionization and excitation of atmospheric constituents leading to auroral emissions was discovered in 1960, when a pioneering rocket flight from Fort Churchill in Canada revealed a flux of electrons entering the atmosphere from above.<ref>{{cite journal|last1=McIlwain|first1=C E|title=Direct Measurement of Particles Producing Visible Auroras|journal=Journal of Geophysical Research|year=1960|volume=65|issue=9|page=2727|doi=10.1029/JZ065i009p02727|bibcode=1960JGR....65.2727M}}</ref> Since then an extensive collection of measurements has been acquired painstakingly and with steadily improving resolution since the 1960s by many research teams using rockets and satellites to traverse the auroral zone. The main findings have been that auroral arcs and other bright forms are due to electrons that have been accelerated during the final few 10,000&nbsp;km or so of their plunge into the atmosphere.<ref>{{Cite journal|doi=10.1029/JA093iA07p07441|title=Determination of auroral electrostatic potentials using high- and low-altitude particle distributions|journal=Journal of Geophysical Research|volume=93|issue=A7|page=7441|year=1988|last1=Reiff|first1=P. H.|last2=Collin|first2=H. L.|last3=Craven|first3=J. D.|last4=Burch|first4=J. L.|last5=Winningham|first5=J. D.|last6=Shelley|first6=E. G.|last7=Frank|first7=L. A.|last8=Friedman|first8=M. A.|bibcode=1988JGR....93.7441R }}</ref> These electrons often, but not always, exhibit a peak in their energy distribution, and are preferentially aligned along the local direction of the magnetic field.

Electrons are mainly responsible for diffuse and pulsating auroras have, in contrast, a smoothly falling energy distribution, and an angular (pitch-angle) distribution favouring directions perpendicular to the local magnetic field. Pulsations were discovered to originate at or close to the equatorial crossing point of auroral zone magnetic field lines.<ref>{{Cite journal|doi=10.1038/215045a0|title=Evidence for Velocity Dispersion in Auroral Electrons|journal=Nature|volume=215|issue=5096|page=45|year=1967|last1=Bryant|first1=D. A.|last2=Collin|first2=H. L.|last3=Courtier|first3=G. M.|last4=Johnstone|first4=A. D.|bibcode=1967Natur.215...45B|s2cid=4173665 }}</ref> Protons are also associated with auroras, both discrete and diffuse.