Dawn-dusk Asymmetries in the Auroral Particle Precipitation and Their Modulations by Substorms
Document Type
Contribution to Book
Publication Date
10-20-2017
Keywords
Auroral particle precipitation, Broadband electron aurora, Diffuse electron aurora, Earth's magnetic field lines, Electron auroral dawn‐dusk asymmetry, Modulations, Ion aurora monoenergetic electron, Aurora nightside electron auroral power, Planetary plasma environments, Substorm cycle
Abstract
Auroral particle precipitation exhibits dawn‐dusk asymmetries that reflect the asymmetries in the particle populations, waves, and processes in the magnetosphere. The diffuse auroral electrons can be observed mainly in 22:00–09:00 MLT, which coincides with much of the spatial distribution of the whistler‐mode chorus waves that have been shown to be the predominant mechanism for pitch‐angle scattering magnetospheric electrons into the loss cone. On the other hand, the monoenergetic auroral electrons can be observed in the dusk‐midnight sector. The monoenergetic electrons are magnetospheric electrons that have gone through a quasistatic parallel electric field in the upward field‐aligned current regions. The broadband auroral electrons can be found mostly at 22:00–02:00 MLT where a peak in the Poynting flux of Alfvén waves is observed. Alfvén waves are known to cause broadband acceleration of electrons. There may be a connection between monoenergetic and broadband electrons in that the low‐frequency Alfvén wave–electron interaction can result in monoenergetic electron signature. Substorms increase the power of the diffuse, monoenergetic, and broadband electron aurora by 310%, 71%, and 170%, respectively. The duration of the substorm cycle for monenergetic and broadband auroral is ~5 h, but it is larger than 5 h for diffuse auroral electrons.
First Page
255
Last Page
272
Book Title
Dawn‐Dusk Asymmetries in Planetary Plasma Environments
Editor
Haaland, Stein, Andrei Runov, Colin Forsyth
Publisher
John Wiley and Sons
City
Hoboken, NJ
Series
Geophysical Monograph Series
ISBN
9781119216322
DOI
10.1002/9781119216346
First Department
Engineering
Recommended Citation
Johnson, Jay R.; Wing, Simon; and Camporeale, Enrico, "Dawn-dusk Asymmetries in the Auroral Particle Precipitation and Their Modulations by Substorms" (2017). Faculty Publications. 700.
https://digitalcommons.andrews.edu/pubs/700