Abstract
AbstractThe injection, and subsequent precipitation, of 20 to 300 keV electrons during substorms is modeled using parameters of a typical substorm found in the literature. When combined with onset timing from, for example, the SuperMAG substorm database, or the Minimal Substorm Model, it may be used to calculate substorm contributions to energetic electron precipitation in atmospheric chemistry and climate models. Here the results are compared to ground‐based data from the Imaging Riometer for Ionospheric Studies riometer in Kilpisjärvi, Finland, and the narrowband subionospheric VLF receiver at Sodankylä, Finland. Qualitatively, the model reproduces the observations well when only onset timing from the SuperMAG network of magnetometers is used as an input and is capable of reproducing all four categories of substorm associated riometer spike events. The results suggest that the different types of spike event are the same phenomena observed at different locations, with each type emerging from the model results at a different local time, relative to the center of the injection region. The model's ability to reproduce the morphology of spike events more accurately than previous models is attributed to the injection of energetic electrons being concentrated specifically in the regions undergoing dipolarization, instead of uniformly across a single‐injection region.
Highlights
The accurate modeling of medium-energy particle precipitation (20 keV to 1 MeV), and the corresponding absorption measured by a riometer, has long been considered a very difficult problem [see, e.g., Hargreaves, 2007]
The results suggest that the different types of spike event are the same phenomena observed at different locations, with each type emerging from the model results at a different local time, relative to the center of the injection region
The substorm model is capable of representing medium-energy electron precipitation well, only requiring the number of electrons injected in each substorm to be adjusted for an overall good fit between the model and IRIS riometer data
Summary
The accurate modeling of medium-energy particle precipitation (20 keV to 1 MeV), and the corresponding absorption measured by a riometer, has long been considered a very difficult problem [see, e.g., Hargreaves, 2007]. The mesospheric effects of medium-energy electron precipitation have been modeled by Codrescu et al [1997] and found to produce significant increases in ne, HOX , NO2, and NO, along with significant decreases in O3 between 70 and 80 km in the polar regions. The aim of this work is to provide a model of the medium-energy electron precipitation produced by substorms, which may be used as a driver in climate models, or for predicting D region ionospheric conditions in the short term (minutes to hours) following a detected substorm onset. In the growth phase energy gradually accumulates in the magnetosphere. This energy is rapidly released during the expansion phase, so named because a brightening of the aurora, which typically begins at 23.5 ± 2 h magnetic local time [Nagai, 1991], expands in latitude and local time
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