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<p>Precipitations of auroral electrons characterize the relationship of the magnetosphere and the upper atmosphere, therefore state of near-Earth space depending on their localization and their intensity. One of the main gaps in both data and modelling is the monitoring of the precipitation of low-energy (0.02 – 35 keV) particles in the ionosphere. These particles are responsible of the surface charging on satellites, which lead to trigger electrostatic discharge (ESD) on components. This impact is the most recurrent in space and need to better understand. The method present here, allows an alternative to particle detectors that do not have access to this area.</p><p>From optical data, it can be very interesting to reconstruct low energy electron flux in the aurora region. Therefore, the interpretation of the auroral intensities is made using the Transsolo code, a kinetic code which use as input the electron flux and the solar EUV flux on the dayside. It calculates the transport of the suprathermal electrons along a line of sight or a vertical and the subsequent auroral emissions. A optimization method is worked to trying to retrieve electron flux from optical measurements.</p><p>The study present here is based on ALIS network data which provides very useful data (Brandstorm, 2003). Tomographic data of the volume emission rate are built from ALIS measurements (Gustavsson, 2000). From tomographic data and transsolo simulations, we adapt the optimization method to reconstruct energetic particles flux. We focus on measurements of the event of 05 March 2008 at 18:41:30 UT and 18:42:40 UT acquired by 5 stations and centred above Skibotn city. Results are presented in the form of maps of mean energy and total energy (corresponding to the energy flux) depending on geographic coordinates. </p>

In the context of the creation of a Distributed Space Weather Sensor System (D3S), the European Space Agency (ESA) is planning to fly a miniaturized payload for the monitoring of the auroral emissions with the project Wide Field Auroral Imager (WFAI). In order to meet ESA's requirements for an Auroral Optical Spectral Imager (AOSI), CSUG will build a breadboard as a proof of concept based on Imager Spectrometer on Chip (ImSPOC) technology.Imaging Spectrometer on Chip (ImSPOC) technology consists of a matrix composed by multiple, low finesse, Fabry-Perot modules mounted in one unique structure. Each Fabry-Perot cavity has a fixed optical path difference distributed from optical contact up to maximum elevation in order to have the desired spectral resolution and the spectral coverage. So, in one snapshot it is possible to "scan" several optical path differences and reconstruct the spectrum for each point of the field of view. The advantage of this technology is to reduce the mass and dimensions but also that it collects sufficient number of photons allowing the observation of the faintest aurora (Not visible with naked eye) with short integration time. This makes it a particularly well-suited technology for small satellite payload design in the framework of polar lights monitoring.We present here the optimization of the ImSPOC technology in the context of WFAI mission. This optimization allows us to recorded polar lights spectra in the wavelength range of 350 to 950 nm within an exposure between 10 and 60 s. The field of view of the instruments is 57° × 57°, obtained by combination of 9 individual modules with small dimension (one module fits in a 60 × 45 × 55 mm 3 box). The simulated performances of the instrument are really encouraging. The spectrometer must have a spectral resolution of 1 nm at 350 nm.

<p>Studying the auroral emission is of strong importance since they are created in an atmospheric layer (80-300 km) where in situ measurements are complicated. They represent a good proxy of the particle precipitations into atmosphere.</p> <p>The spectrum of the aurora is complex made of both atomic and molecular lines. The intensities of these emissions vary with the activity, especially the particle precipitations.</p> <p>Transsolo is the kinetic code which solve the transport equation of the electrons along a vertical or a magnetic field line. It allows to obtain the particles fluxes at different energies, angles and altitudes. From this, the code is able to calculate the related emissions.</p> <p>The emission modules have recently been updated by including the vibrational structures of the molecular bands. Several atomic lines have also been added. We can consider that we include more than 95% of the full emission spectra. From this, it is now possible to obtain some almost complete synthetic spectra of the aurora parametrized by the mean energy of the particle fluxes at the top of the atmosphere and the total precipitated energy.</p> <p>Recently Robert et al. show that it is possible to reconstruct the energetic precipitation from the N<sub>2</sub><sup>+</sup> 427 nm line. However, it remains clear that multiplying the number of considered lines, will allow to get more accurate measurements of these particle fluxes. Moreover, a large number of auroral monitoring instruments are done with filters with variable widths. Such synthetic spectra can help to identify the possible perturbation of the measurements due to wavelength coincidences. For example, the green line at 557 nm is in coincidence with several O<sub>2</sub><sup>+</sup> and N<sub>2</sub> bands in a +/- 5 nm range. Calculating the relative ratio of these lines in different conditions is then crucial.</p> <p>In parallel, we are developing a series of calibrated high sensitivity spectrometers to validate the data and enhance the quality of particle precipitation reconstructions.</p> <p>In this presentation, we will detail the links between these instruments and these synthetic spectra.</p>

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