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Large field-of-view maps of the characteristic energy of the precipitating particles at high latitudes are being generated using absorption images from IRIS and all-sky images from DASI for the brightest auroral optical emission at 557.7 nm. The method was calibrated using the EISCAT radar at one point and then applied to the entire common field of view of DASI and IRIS. Currently, a good temporal (10 s) and spatial (10 km) resolution over a large area (240x240 km) is achieved. The technique is important because it offers a new and quantitative way of viewing particle precipitation, which includes energy information. Energy maps are a much more relevant way to describe auroral precipitation than the long-used white-light all- sky images, which relate to total particle flux without any energy information. Currently, the technique is limited to high and medium energies > 1 keV, which are measured in the D- and E-regions respectively, because DASI only has a single wavelength capability. However, there is significant particle precipitation for energies < 1 keV with the corresponding energy deposition in the F-region. Such particles excite the second brightest auroral emission at 630 nm. The initial study found that a Maxwellian distribution described the energy spectrum best. This means that the data now available only covers the exponentially dominated part of the Maxwellian spectrum. Adding optical measurements at 630 nm would considerably extend the useful energy range to lower energies. In addition, the energy calibration would dramatically improve because data would be available for the linearly dominated part of the Maxwellian spectrum. In addition, having 3 measurements at different energies gives the opportunity to check which spectral shape is the most relevant (e.g. Maxwellian, exponential or power law). Knowledge of the energy spectrum of the precipitating particles into the atmosphere is important for understanding the acceleration processes that are occurring in the magnetosphere. The energy maps enable studies of auroral phenomena during geomagnetic storms in terms of the spatial and temporal morphology of the energy of the precipitating particles in calibrated units over a significant fraction of the auroral oval. In addition, projecting the energy maps up along the magnetic field lines reveals the spatial and temporal morphology of the particle acceleration region with unprecedented resolution.
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