Abstract
Diffuse aurora is generated by the precipitation of hot electrons from the central plasma sheet due to wave-particle interaction. Near magnetic local noon (MLN), the diffuse aurora was often observed in structured forms, such as in stripy or patchy. In the magnetosphere, when the hot electrons meet with a cold plasma structure, the threshold of resonance energy for the electrons in the cold plasma region can be lowered, leading to more electrons being involved in the wave-particle interaction and being scattered into the loss cone. As a result, stronger diffuse aurora can be produced in the correspondent region. Based on this mechanism, the structured dayside diffuse auroras have been suggested to correspond to the cold plasma structures in the dayside outer magnetosphere. This brief review focuses on showing that 1) the stripy diffuse auroras observed near MLN are specifically informative, 2) there are two types of diffuse aurora near MLN, which may correspond to cold plasmas originating from inside and outside the magnetosphere, respectively, and 3) we can study the inside-outside coupling by using the interaction between diffuse and discrete auroras observed near MLN.
Highlights
The auroras observed on the ground can be classified into two broad categories, i.e., discrete and diffuse auroras, which are different in appearance and generation mechanisms
Diffuse aurora studies mainly focused on where the source particles are from, whether these particles have been accelerated, or how these particles are scattered into the loss cone
In the 1970s, thanks to the rapid development of satellites, it was revealed that the electrons for producing the diffuse aurora originated from the central plasma sheet (CPS) (Meng et al, 1979), and their energy did not significantly change from the source region to the topside ionosphere
Summary
Background About Diffuse AuroraThe auroras observed on the ground can be classified into two broad categories, i.e., discrete and diffuse auroras, which are different in appearance and generation mechanisms. This paper will not discuss the electron scattering mechanism for producing the diffuse aurora but will focus on the implications of structured dayside diffuse aurora on the cold plasma structuring in the dayside outer magnetosphere. The observational results were explained as follows by considering the source particle properties of diffuse aurora and the cold plasma structuring in the dayside magnetosphere (Han et al, 2015; Han et al, 2017).
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