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Observations of hydrogen emissions along the magnetic zenith at\udLongyearbyen (78.2 N, 15.8 E geographic) are used to investigate\udthe energy and source of protons precipitating into the high\udlatitude region. During the hours around local solar noon (11:00 UT),\udmeasurements of the hydrogen Balmer β line are severely\udaffected by sunlight, such that most data until now have been\uddisregarded during these times. Here we use a simple technique to\udsubtract sunlight contamination from such spectral data. An\udexample is shown in which the removal of twilight contamination\udreveals a brightening of Hβ aurora over Svalbard on 27\udNovember 2000 between 08:00 UT and 10:00 UT, which is centred on\udmagnetic noon (08:48 UT). These data were measured by the High\udThroughput Imaging Echelle Spectrograph (HiTIES), one instrument\udon the Southampton-UCL Spectrographic Imaging Facility (SIF). Data\udfrom the IMAGE satellite confirms the location of a cusp "spot"\udover Svalbard at the time of the ground-based measurements, which\udmoved in response to changes in the IMF conditions. A coincident\udpass of the DMSP F12 satellite provided input spectra for\udmodelling studies of the Hβ profiles, which confirm that\udthe method for removing the twilight contamination is robust. The\udresults described here are the first ground-based optical\udmeasurements of Hβ Doppler profiles from the cusp region\udclose to local solar noon, when scattered sunlight swamps the raw\uddata

First ground-based optical analysis of H&lt;sub&gt;β&lt;/sub&gt; Doppler profiles close to local noon in the cusp

First ground-based optical analysis of H<sub>β</sub> Doppler profiles close to local noon in the cusp