  Context. Young supernova remnants (SNRs) exhibit narrow filaments of
non-thermal X-ray emission whose widths can be limited either by electron
energy losses or damping of the magnetic field. Aims. We want to investigate
whether or not different models of these filaments can be observationally
tested. Methods. Using observational parameters of four historical remnants, we
calculate the filament profiles and compare the spectra of the filaments with
those of the total non-thermal emission. For that purpose, we solve an
one-dimensional stationary transport equation for the isotropic differential
number density of the electrons. Results. We find that the difference between
the spectra of filament and total non-thermal emission above 1 keV is more
pronounced in the damping model than in the energy-loss model. Conclusions. A
considerable damping of the magnetic field can result in an observable
difference between the spectra of filament and total non-thermal emission, thus
potentially permitting an observational discrimination between the energy-loss
model and the damping model of the X-ray filaments.
