Global Driving of Auroral Precipitation: 1. Balance of Sources
Abstract
The accurate determination of auroral precipitation in global models has
remained a daunting and rather inexplicable obstacle. Understanding the
calculation and balance of multiple sources that constitute the aurora,
and their eventual conversion into ionospheric electrical conductance,
is critical for improved prediction of space weather events. In this
study, we present a semi-physical global modeling approach that
characterizes contributions by four types of precipitation -
monoenergetic, broadband, electron and ion diffuse - to ionospheric
electrodynamics. The model uses a combination of adiabatic kinetic
theory and loss parameters derived from historical energy flux patterns
to estimate auroral precipitation from magnetohydrodynamic (MHD)
quantities. It then converts them into ionospheric conductance that is
used to compute the ionospheric feedback to the magnetosphere. The model
has been employed to simulate the April 5 - 7, 2010 “Galaxy15” space
weather event. Comparison of auroral fluxes show good agreement with
observational datasets like NOAA-DMSP and OVATION Prime. The study shows
a dominant contribution by electron diffuse precipitation, accounting
for ~74% of the auroral energy flux. However,
contributions by monoenergetic and broadband sources dominate during
times of active upstream conditions, providing for up to 61% of the
total hemispheric power. The study also indicates a dominant role played
by broadband precipitation in ionospheric electrodynamics which accounts
for ~31% of the Pedersen conductance.