Tuesday, February 12, 2013

1302.2424 (M. S. Potgieter et al.)

A local interstellar spectrum for galactic electrons    [PDF]

M. S. Potgieter, R. R. Nndanganeni
We present a heliopause spectrum at 120 AU from the Sun for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The primary focus of this work is on the spectral shape of the LIS below ~1.0 GeV. This is done by using a comprehensive numerical model for solar modulation in comparison with Voyager 1 observations at 110 AU from the Sun and PAMELA data at Earth. Below ~1.0 GeV this LIS exhibits a power law with E^-1.5, where E is the kinetic energy of these electrons. However, reproducing the PAMELA electron spectrum for 2009, requires a LIS with a different power law of the form E^-3.15 above ~5 GeV. Combining the two power laws with a smooth transition from low to high energies yields a LIS over the full energy range that is relevant and applicable to the modulation of cosmic ray electrons in the heliosphere. The power-law form of this LIS below ~1.0 GeV produces a challenge to the origin of these low energy galactic electrons.
View original: http://arxiv.org/abs/1302.2424

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