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- Title
Time‐Dependent Inversion of Energetic Electron Precipitation Spectra From Ground‐Based Incoherent Scatter Radar Measurements.
- Authors
Juarez Madera, Diana; Marshall, Robert A.; Elschot, Sigrid; Kaeppler, Stephen; Reyes, Pablo; Varney, Roger H.; Crew, Alexander B.
- Abstract
In the D‐region, the ionization rate cannot be detected directly with any known measurement technique, therefore it must be estimated. Starting from space‐based measurements of precipitating particle flux, we estimate the ionization rate in the atmosphere using the Electron Precipitation Monte Carlo transport method. This ionization rate is used to calculate the expected electron density in the D‐region with the Glukhov‐Pasko‐Inan five species (GPI5) atmospheric chemistry model. We then compare the simulated electron density with that measured by the Poker Flat Incoherent Scatter Radar (PFISR). From ground‐based radar measurements of electron density enhancements due to sub‐relativistic and relativistic electron precipitation, we present a method to extract the ionization rate altitude profiles using inverse theory. We use this estimation of ionization rate to find the energy distribution of the precipitating particles. With this inverse method, we are able to link ground measurements of electron density to the precipitating flux in a time dependent manner and with uncertainty in the inverted parameters. The method was tested on synthetic data and applied to specific PFISR data sets. The method is able to retrieve the ionization rate altitude profiles that, when forward modeled, return the expected electron densities within ∼7% error as compared to the PFISR data. For the case presented here, the arbitrary energy distribution inversion results are comparable in magnitude and shape to those presented in Turunen et al. (2016, https://doi.org/10.1002/2016jd025015) for the inversion of a single event of pulsating aurora observed by EISCAT. Plain Language Summary: Electrons expelled from the Earth's radiation belts by electromagnetic waves enter the upper atmosphere and travel through it. Interactions of these electrons with atmospheric constituents lead to the ionization of the atmospheric species. This ionization produces enhancements of electron density in certain altitude ranges that depend on the incoming particles' energy. Satellites orbiting Earth at an altitude of a few hundred km can measure the flux of the entering particles. We use a modeling technique to simulate their behavior in the atmosphere, including the electron density modification, starting from the satellite measurements. Radars at ground stations on Earth can detect the electron density enhancements in the atmosphere. We use inverse theory to estimate the ionization rate and flux of precipitating particles starting from the radar electron density measurements. Key Points: We compare D‐region radar measurements of electron density to a forward‐modeled electron precipitation flux and spectrumA method is presented to infer ionization rates from D‐region electron density measurements made by radar, accounting for time dependence and to infer precipitating flux from D‐region ionization rates with exponential or arbitrary energy distributionsWe establish a time‐dependent inversion from radar‐observed electron density to an estimate of the precipitating energetic electron source
- Subjects
INCOHERENT scattering; ELECTRON density; ATMOSPHERIC chemistry; ELECTRON impact ionization; RADAR; ATMOSPHERIC ionization; ELECTRON scattering
- Publication
Journal of Geophysical Research. Space Physics, 2023, Vol 128, Issue 5, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2022JA031000