Abstract
Ganguly and Rao recently presented evidence for the possibility of the penetration of high energy solar particles to ionospheric heights at the equator1. Their letter, based on ionospheric absorption data obtained at Calcutta (geomagnetic latitude 12° 15′ N), together with optical observations of solar flares and tabulated proton flux data, is very interesting in the light of extensive work recently on the penetration of solar particles to low magnetospheric L-values (L∼4–7 RE) at the equator2–7. Because the observations of Ganguly and Rao would have a profound and far-reaching impact on current ideas of the mechanisms for the access of such solar particles to the geomagnetic equator2–4,6, the ionospheric and solar evidence presented by the Calcutta group has been examined carefully. We conclude that there is little basis for their contention that solar particles can penetrate directly to low altitudes and thus influence ionospheric absorption at the equator.
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LANZEROTTI, L., GRAEDEL, T. Penetration of Solar Particles to Ionospheric Heights at Low Latitudes. Nature 228, 45 (1970). https://doi.org/10.1038/228045a0
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DOI: https://doi.org/10.1038/228045a0
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