Lanchester, B.S., Galand, M., Robertson, S.C., Rees, M.H., Lummerzheim, D., Furniss, I., Peticolas, L.M., Frey, H.U., Mendillo, M. and Baumgardner, J.
High resolution measurements and modeling of auroral hydrogen emission line profiles.
Annales Geophysicae, 21, (7), .
Measurements in the visible wavelength range at
high spectral resolution (1.3 A° ) 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 wavelength
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.
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