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Alfvén waves in the auroral region, their Poynting flux, and reflection coefficient as estimated from Swarm observations
Author(s) -
Park Jaeheung,
Lühr Hermann,
Knudsen David J.,
Burchill Jonathan K.,
Kwak YoungSil
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023527
Subject(s) - poynting vector , physics , geophysics , flux (metallurgy) , magnetosphere , northern hemisphere , reflection (computer programming) , asymmetry , energy flux , latitude , cusp (singularity) , computational physics , atmospheric sciences , ionosphere , plasma , magnetic field , astronomy , geometry , quantum mechanics , metallurgy , programming language , materials science , mathematics , computer science
The European Space Agency's Swarm constellation can measure electric field, magnetic field, and plasma density on board multiple satellites at altitudes of about 500 km. Based on the data set at high latitudes, we estimate Poynting flux and ionospheric reflection coefficients of Alfvén waves with scale sizes of about 10–100 km. The reflection coefficients are generally higher surrounding the cusp and auroral regions than in the polar cap and higher in the summer than in the winter hemisphere. In the summer (winter) hemisphere the reflection coefficients generally peak on the dayside (nightside). Distributions of the reflection coefficients are not controlled by those of in situ plasma density. Poynting flux of the Alfvén waves maximizes surrounding the cusp and near‐midnight auroral region with magnitudes approaching 1 mW/m 2 , which are consistent with previous magnetospheric observations. The observed Poynting flux is downward on average for both hemispheres, and the magnitudes do not exhibit clear hemispheric asymmetry.