Abstract
Abstract. There is mounting evidence which suggests that pulsating auroral patches often move with convection. This study is an initial step at identifying the differences between patches that move with convection and those that do not. While many properties of pulsating patches vary, here we outline criteria for separating pulsating auroral patches into three categories based on two properties: their structural stability and the spatial extent of their pulsations. Patchy aurora is characterized by stable structures whose pulsations are limited to small regions. Patchy pulsating aurora consists of stable patches whose pulsations are far less subtle and occur throughout much of their area. Amorphous pulsating auroral structures are unstable – very rapidly evolving – and can pulsate over their entire area. The speed with which amorphous pulsating aurora evolves makes their motion difficult to ascertain and seems unrelated to the E×B drifting of cold, equatorial plasma.
Highlights
The immediate cause of aurora is the precipitation of electrons and protons into the atmosphere
This work confirmed the long-held belief that electrons with energies on the order of 100 eV–10 keV are able to resonate with electron cyclotron harmonic (ECH) and whistler mode chorus waves
Regions of each figure have been classified based on the type of pulsating auroral patch that appears most prevalent within the all-sky imager (ASI) field-ofview during a given period
Summary
The immediate cause of aurora is the precipitation of electrons and protons into the atmosphere. Pulsating aurora is a type of diffuse aurora which is characterized by quasi-periodic transitions between bright and dim states typically recurring on the order of 10 s whose precipitating electrons have energies ranging from a few keV to hundreds of keV (Johnstone, 1978). This type of aurora is widely believed to arise from cyclotron resonance between plasma waves and equatorial electrons This study will describe the distinction between these structures and outline a scheme for separating pulsating auroral patches into at least three categories based on the spatial extent of their pulsations as well as the stability of their shape
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