Alfvén waves in the auroral region, their Poynting flux, and reflection coefficient as estimated from Swarm observations. Issue 2 (15th February 2017)

• Record Type: Journal Article
• Authors: Park, Jaeheung; Lühr, Hermann; Knudsen, David J.; Burchill, Jonathan K.; Kwak, Young‐Sil
• Is Part Of: Journal of geophysical research. Volume 122:Issue 2(2017)
• Page Start: 2345
• Page End: 2360
• Publication Date: 2017-02-15
• Subjects: Alfvén wave reflection -- Alfvén wave Poynting flux -- Swarm constellation; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA023527
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: 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. Key Points: Ionospheric reflection coefficients of Alfvén waves are estimated from Swarm measurements The ionospheric reflection coefficients are higher in summer than in winter, mostly peaking at the cusp and nightside auroral latitudes Poynting flux of the Alfvén waves is generally downward without notable hemispheric asymmetry in magnitudes