A Generalized Method for Calculating Atmospheric Ionization by Energetic Electron Precipitation

Abstract

Accurate specification of ionization production by energetic electron precipitation is critical for atmospheric chemistry models to assess the resultant atmospheric effects. Recent model-observation comparison studies have increasingly highlighted the importance of considering precipitation fluxes in the full range of electron energy and pitch angle. However, previous parameterization methods were mostly proposed for isotropically precipitation electrons with energies up to 1 MeV, and the pitch angle dependence has not yet been parameterized. In this paper, we first characterize and tabulate the atmospheric ionization response to monoenergetic electrons with different pitch angles and energies between ∼3 keV and ∼33 MeV. A generalized method that fully accounts for the dependence of ionization production on background atmospheric conditions, electron energy, and pitch angle has been developed based on the parameterization method of Fang et al. (2010, https://doi.org/10.1029/2010GL045406). Moreover, we validate this method using 100 random atmospheric profiles and precipitation fluxes with monoenergetic and exponential energy distributions, and isotropic and sine pitch angle distributions. In a suite of 6,100 validation tests, the error in peak ionization altitude is found to be within 1 km in 91% of all the tests with a mean error of 2.7% in peak ionization rate and 1.9% in total ionization. This method therefore provides a reliable means to convert space-measured precipitation energy and pitch angle distributions into ionization inputs for atmospheric chemistry models.

Chemical Response of the Upper Atmosphere Due to Lightning‐Induced Electron Precipitation

“…Different from VLF measurements, X-ray measurements at balloon altitudes are directly linked to the precipitation fluxes and energy spectra of LEP bursts; WIPP results can fully explain the X-ray fluxes, temporal signature, and energy spectra measured by BARREL (Marshall, Xu, Sousa, et al, 2019). As for the BERI model (Xu et al, 2020), it shows good agreements with the parameterization method of Fang et al (2010) in terms of the peak ionization rate and altitude, with a maximum difference of 20% among tests using different precipitation energy and pitch angle distributions. The SIC model has been employed for the estimation of atmospheric chemical effects due to a wide variety of external sources, including radiation belt electron precipitation (e.g., Turunen et al, 2016;Xu et al, 2018), solar eclipse (e.g., , and solar proton events (e.g., Clilverd et al, 2005).…”

“…In this study, we combine the WIPP-LEP simulations of LEP (Bortnik, 2004;Lauben et al, 1999;Sousa, 2018), the Boulder Electron Radiation to Ionization (BERI) model (Xu et al, 2020), and the Sodankylä Ion and Neutral Chemistry (SIC) model (Turunen et al, 1996;Verronen et al, 2005), specifically in three steps. First, following the framework formulated by Lauben et al (1999); Bortnik (2004), the WIPP model is employed to simulate LEP events produced by source lightning discharges at different magnetic latitudes and calculate the resultant precipitation fluxes at different observation locations (L values).…”

“…In this study, we combine the WIPP‐LEP simulations of LEP (Bortnik, 2004; Lauben et al., 1999; Sousa, 2018), the Boulder Electron Radiation to Ionization (BERI) model (Xu et al., 2020), and the Sodankylä Ion and Neutral Chemistry (SIC) model (Turunen et al., 1996; Verronen et al., 2005), specifically in three steps. First, following the framework formulated by Lauben et al.…”

“…Knowing the precipitation fluxes, we calculate the ionization production at altitudes below 150 km altitude (the upper boundary of the SIC model) using the BERI model (Xu et al., 2020). This model is largely based on a lookup table of atmospheric ionization production by monoenergetic electrons with energies between 3 keV and 33 MeV, and pitch angles between and .…”

The Kinetics of O2 Singlet Electronic States in the Upper and Middle Atmosphere During Energetic Electron Precipitation

“…(2009). Now numerous modern models (Fang et al., 2010; Xu et al., 2018, 2020) have been developed to study the interaction between energetic electrons and the Earth's atmosphere. Nevertheless, we apply the simplified method in our study of electronic kinetics of and , since the main aim of the study is the investigation of the role of intramolecular and intermolecular processes in the redistribution of the energy between electronically excited molecules.…”