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The l = 2 spherical harmonic expansion coefficients of the sky brightness distribution between 0.5 and 7 MHz
Author | Page, B.; Bassett, N.; Lecacheux, A.; Pulupa, M.; Rapetti, D.; Bale, S.~D.; |
Keywords | Parker Data Used; radio continuum: ISM; Galaxy: disk; opacity; methods: data analysis |
Abstract | Context. The opacity of the ionosphere prevents comprehensive Earth- based surveys of low frequency \ensuremath\nu \ensuremath\lesssim 10 MHz astrophysical radio emissions. The limited available data in this frequency regime show a downturn in the mean sky brightness at \ensuremath\nu \ensuremath\lesssim 3 MHz in a divergence from the synchrotron emission power-law that is observed at higher frequencies. The turning over of the spectrum coincides with a shift in the region of maximum brightness from the Galactic plane to the poles. This implicates free-free absorption by interstellar ionized gas, whose concentration in the plane causes radiation that propagates in this region to suffer stronger absorption than radiation from the poles. \ Aims: Using observations from Parker Solar Probe |
Year of Publication | 2022 |
Journal | \aap |
Volume | 668 |
Number of Pages | A127 |
Section | |
Date Published | dec |
ISBN | |
URL | |
DOI | 10.1051/0004-6361/202244621 |