Geofísica Internacional (Jan 2000)
Indirect determination of the energy spectra of particles precipitated in the lower ionosphere associated with solar proton events
Abstract
Electron density profiles previously measured using the phase and amplitude of VLF radio signals during outstanding solar proton events (SPE), together with the associated energy spectra of protons and electrons simultaneously measured by satellite, allowed the calculation of the electron-ion pair production rate q(h), for the sub-Antarctic and South Atlantic Geomagnetic Anomaly (SAGA) regions. Plots of q(h) together with the predetermined electron density vertical profiles were used to calculate the effective recombination coefficient ψ(h) for the SAGA region. Assuming that the chemical processes in the lower ionosphere due to the impact of neutral atmospheric constituents are basically the same, the spectra of the energetic particles responsible for the delayed ionization detected in the SAGA were estimated indirectly. The parameters obtained are in good agreement with results for the northern hemisphere and the spectra deduced are within the limits imposed by the cutoff rigidity and the penetration depth of the incident particles. The experimental data correspond to VLF signals transmitted from Australia (NWC - 22.3 kHz ) and from Ω-Trinidad (13.6 kHz) and received respectively in Atibaia and Curitiba, Brasil, during the SPE of August 4-7, 1972.
