Dayside flow bursts in the Earth's outer magnetosphere

Abstract

Observations from the Polar/Thermal Ion Dynamics Experiment indicate the presence of cold magnetospheric/ionospheric H+, He+, and a trace of O+ in the vicinity of the subsolar magnetopause during intervals of moderate geomagnetic activity (Kp ∼ 4). These cold ions were accelerated to a perpendicular speed (ΔV⊥B) of the order of 100 km s-1 or 0.3 MA outward, relative to the magnetopause boundary oscillations. The accelerated flows produced ∼4 mV m-1 in convection electric field and carried ∼1-100 ions cm -3 in number density or ∼0.1-5 × 108 ions cm-2 s-1 in particle flux or 4 × 1025-2 × 1027 ions s-1 in transfer rate (assuming sunward convecting flux tube with latitudinal cross-section of 1 RE in width and 10 RE in length along magnetopause). This rate of plasma transfer from inside the magnetopause is comparable with that entering the LLBL with the same incident cross section on the magnetopause from the solar wind influx. The occurrence of these flow burst events is accompanied by changes in the local magnetic field orientation, departing from nominal magnetospheric magnetic field, and is sensitive to the variation in the IMF clock angle. We suggest that the magnetospheric/ionospheric ions contribute plasma of dynamical significance to physical processes such as magnetic reconnection, for the cases presented in this study at the subsolar magnetopause. Copyright 2004 by the American Geophysical Union.