The GEM Focus Group on Diffuse Aurora

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PIXIE X-ray observations of the global distribution of diffuse aurora under different levels of geomagnetic activity.


A new Focus Group on the Diffuse Aurora (co-chaired by Richard M. Thorne and Joseph Borovsky) was initiated at the NSF-sponsored Geophysical Environmental Modeling meeting in 2007. For the next four years (till 2011) the focus group will explore the basic physical process that cause the diffuse aurora and its effect on the Earth’s upper atmosphere.


Diffuse precipitation of energetic electrons from the magnetosphere is a consequence of pitch-angle scattering by a variety of plasma waves. The precipitation of energetic electrons and (to a lesser extent ions) constitutes an important source of ionizing energy input to the middle atmosphere. Diffuse auroral precipitation occurs over a broad range of geomagnetic latitudes, which map along field lines from the outer radiation belts and the plasmasheet. Although the diffuse aurora is sub-visual, the net global energy input into the atmosphere is substantially larger than that associated with the localized discrete auroral arcs. The global pattern of precipitation can dramatically change the conductivity of the ionosphere, which can in turn influence the global pattern of magnetospheric convection. Diffuse auroral precipitation therefore provides a strong coupling mechanism between the magnetosphere and the ionosphere, which needs to be included in the development of global models for the Earth’s magnetosphere.