Abstract
Abstract. Measurements in the visible wavelength range at high spectral resolution (1.3 Å) have been made at Longyearbyen, Svalbard (15.8 E,78.2 N) during an interval of intense proton precipitation. The shape and Doppler shift of hydrogen Balmer beta line profiles have been compared with model line profiles, using as input ion energy spectra from almost coincident passes of the FAST and DMSP spacecraft. The comparison shows that the simulation contains the important physical processes that produce the profiles, and confirms that measured changes in the shape and peak wave-length of the hydrogen profiles are the result of changing energy input. This combination of high resolution measurements with modeling provides a method of estimating the incoming energy and changes in flux of precipitating protons over Svalbard, for given energy and pitch-angle distributions. Whereas for electron precipitation, information on the incident particles is derived from brightness and brightness ratios which require at least two spectral windows, for proton precipitation the Doppler profile of resulting hydrogen emission is directly related to the energy and energy flux of the incident energetic protons and can be used to gather information about the source region. As well as the expected Doppler shift to shorter wavelengths, the measured profiles have a significant red-shifted component, the result of upward flowing emitting hydrogen atoms.Key words. Ionosphere (auroral ionosphere; particle precipitation) – Magnetospheric physics (auroral phenomena)
Highlights
Renewed interest has recently developed in auroral hydrogen emissions, the spectroscopic signature of energetic proton precipitation into the atmosphere
The DMSP F12 satellite passed through the region of proton precipitation between 14:36 UT and 14:40 UT, with maximum energy flux measured between 14:37–38 UT when the satellite was to the east of Longyearbyen
Measured Hβ profiles give an excellent estimate of the variations of incoming proton mean energy and energy flux
Summary
Renewed interest has recently developed in auroral hydrogen emissions, the spectroscopic signature of energetic proton precipitation into the atmosphere. We report the first results of measurements of the Hβ line of hydrogen acquired at Svalbard (15.8 E, 78.2 N) with a new spectrograph, operating at a resolution (FWHM) of 1.3 Aand with integration times as short as 10 s We show that these instrumental parameters are sufficient to identify clearly a redshifted wing of the profile and variations in the shape and peak of the emission profile. These measurements are well explained by a recently developed proton/hydrogen transport model (Galand et al, 1998). The implications and future direction of this work are discussed in Sect. 5 and Sect. 6
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