Alfvén wave‐driven ionospheric mass outflow and electron precipitation during storms. Issue 8 (27th August 2016)

• Record Type: Journal Article
• Authors: Hatch, S. M.; Chaston, C. C.; LaBelle, J.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 8(2016:Aug.)
• Page Start: 7828
• Page End: 7846
• Publication Date: 2016-08-27
• Subjects: geomagnetic storms -- Alfvén waves -- transition region -- magnetosphere‐ionosphere coupling -- field‐aligned currents; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022805
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We explore the global Alfvénic response of the transition region between the topside ionosphere and magnetosphere to geomagnetic storms. From superposed epoch and storm phase‐dependent analyses, it is found that subsequent to storm commencement the occurrence rate of Alfvénic field variations on electron inertial scales through this region increases by as much as a factor of 5 relative to prestorm levels. This increase is accompanied by order‐of‐magnitude enhancements in coincident energy deposition rates into the ionosphere and ion outflow rates into the magnetosphere, particularly near noon, premidnight, and on the dawn flank. During main phase on the dayside these waves shift to lower invariant latitudes (ILATs), expanding over a large range of ILATs and magnetic local times, where they are associated with significant enhancements in upward ion flux. Nightside storm‐enhanced occurrence probability of Alfvén waves and upward ion flux is lower than on the dayside, but the average precipitating electron energy flux is larger. There is also a localized region of intense ion outflow premidnight at low latitudes during storm main phase. Wave occurrence rates subside to prestorm levels about 20 h after storm commencement. Key Points: Occurrence rates of inertial Alfvén waves at 60–80° ILAT increase by factors of 4–5 during geomagnetic storms Rates of Alfvénic electron and wave energy deposition, as well as ion outflow, increase by an order of magnitude at stormtime Storm‐enhanced ion outflow and Alfvén wave occurrence rates are higher on the dayside; electron energy fluxes are higher on the nightside