Proton impact ionization and a fast calculation method

Abstract

[1] We present a coupled Monte Carlo and multistream model simulating primary ionization and secondary electron ionization, respectively, from energetic proton precipitation in the Earth's upper atmosphere. Good agreement is obtained with previous model results. It is found that while secondary electrons make a negligible contribution to ionization from low-energy (Ä10 keV) auroral proton precipitation, their importance increases with increasing incident proton energy, confirming earlier findings. It becomes significant or even comparable to primary ionization from protons and generated hydrogen atoms in charge-changing collisions. Our calculations of the mean energy loss per ion pair production show a nearly monotonic increase with incident proton energy, ranging from about 22 eV to 33 eV when incident energy increases from 100 eV to 1 MeV. To facilitate a fast calculation in large-scale computations, we develop a parameterization for total (primary plus secondary) ionization from monoenergetic proton precipitation. This is obtained by fitting to a large set of numerical results from the coupled model. The quick method applies to a wide energy range of 100 eV to 1 MeV for incident monoenergetic protons, and its validity has been extensively tested under a variety of background atmospheric conditions. Our new parameterization can be used to rapidly calculate the ionization altitude profile from precipitating protons with any spectral distributions without any significant compromise in accuracy. By considering branching ratios of ionized atmospheric species, the fast calculation method is thus useful for self-consistently including proton impact effects in large community models.Citation: Fang, X., D. Lummerzheim, and C. H. Jackman (2013), Proton impact ionization and a fast calculation method,

Simultaneous Measurements of Substorm‐Related Electron Energization in the Ionosphere and the Plasma Sheet

“…Precipitating charged particles cause ionization at different altitudes depending on their incident energy. Although both electrons and protons precipitate in high‐latitude regions, we assume negligible contribution toward ionization from proton precipitation for altitudes <110 km because of the extreme energies required for protons to penetrate to these altitudes (Fang et al, ). Hence, we estimate the ion production rates due to electron precipitation from altitude profiles of electron density measured by PFISR.…”

Ionization due to electron and proton precipitation during the August 2011 storm

“…Fang et al [2013] calculates the primary ionization and secondary electron ionization from precipitating protons through coupling a Monte Carlo proton transport model and a multistream electron transport model. The Fang2013 parameterization is derived to provide a fast and accurate method to calculate the total ionization rate from individual monoenergetic proton precipitation with energy ranges from 100 eV to 1 MeV.…”

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Abstract The parameterizations of monoenergetic particle impact ionization in Fang et al (2010) (Fang2010) and Fang et al (2013 are applied to the complex energy spectra measured by DMSP F16 satellite to calculate the ionization rates from electron and ion precipitations for a Northern Hemisphere pass from 0030 UT to 0106 UT on 6 August 2011. Clear enhancement of electron flux is found in the polar cap.

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The Propitious Role of Solar Energetic Particles in the Origin of Life

“…To calculate the penetration of SEPs through the atmosphere, we apply a continuously slowing down approximation (CSDA) energy loss model that was developed by Jackman et al (1980) and recently improved by Fang et al (2013b). The model has been extensively validated for energetic particle transport, showing excellent agreement with results from more sophisticated collision-by-collision calculations of the combined primary ion effects (Fang et al 2004;Jolitz et al 2017) and secondary electron effects (Lummerzheim et al 1989).…”