Estimating energy spectra of electron precipitation above auroral arcs from ground-based observations with radar and optics

摘要: [1] In 2008, coordinated radar-optical auroral observations were organized in Northern Scandinavia using the European Incoherent Scatter Radar (EISCAT) and Auroral Large Imaging System (ALIS). A bright arc was imaged on 5 March 2008 from four ground-based stations, remaining stable between 18:41 18:44 UT coinciding with increased electron densities. This work presents a unified inversion framework deriving energy spectrum either optical (N2+ 1NG(0,1) emission at 4278 A) or radar (electron density) observations. An updated forward model of ionosphere based 1-D kinetic Monte Carlo is described, characterizing linear system to invert. The 3-D blue volume rate first estimated an iterative reconstruction technique. Also presented novel way calculate accurate initial guess for tomography taking into account horizontal/vertical nonuniformity region. technique supersedes often-used Chapman profile as when high spatial resolution needed. second step, performed time ALIS observations, uses retrieve rates 2-D latitude/longitude map spectrum. same methods are finally applied EISCAT density profiles derive temporal precipitating electrons along magnetic zenith. Energy spectra optics good agreement. Results suggest that generated by complex reminiscent dispersive Alfven waves two main peaks (2.5, 6 keV) typical latitudinal width 7.5 km.