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Atmospheric Ionization during Substorm Activity (AISStorm)

Applicant Dr. Jan Maik Wissing, since 1/2021
Subject Area Atmospheric Science
Term from 2015 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 274901643
 
Final Report Year 2023

Final Report Abstract

Atmospheric ionization by precipitating particles is a major source of nitric oxydes and hydroxyls that impact ozone chemistry and thus change atmospheric chemistry and dynamics. While early ionization models concentrated solar particles that ionize the lower atmosphere, the altitude range of climate models and atmospheric ionization models steadily rised and now include the thermosphere. This also reduced the lower particle energy threshold of ionization models in order to include auroral particles. Ionization models suffered from significant limitations. Especially magnetospheric particle precipitation does not take place uniformly in the auroral oval but depends on very localized substorm activity. Even though substorms have been investigated in detail by the THEMIS mission, the resulting atmospheric ionization has not been investigated on a global level. Consequently this project should investigate the impact of substorm activity on atmospheric ionization. The project should also provide an atmospheric ionization model that includes substorm activity. While the proposed setup relies solely on magnetometer measurements in order to determine substorm activity and following precipitation, the final setup includes particle measurements and the SML index as indicator for substorm activity. While the main substorm impact is connected with night-time particle precipitation in agreement with expectations, the low energetic impact is almost entirely concentrated on the dayside and shifts by a few degrees towards the equator. The strongest substorm impact for precipitation modeling however, is linked with high energetic electron precipitation. Here the precipitation pattern of no-substorm and substorm activity is completely different. High energy electrons mostly precipitate in the dayside atmosphere, while substorm activity boosts the night-side precipitation in a relatively narrow magnetic local time region. In consequence ionization models without expliced substorm handling cannot represent the strong dynamics that are connected to single substorms and thus typically fail in estimating relatively quiet time atmospheric ionization while this model represents the substorm dynamics. Since the preface of a magnetic storms is also connected to substorm activity, significant ionization is added to more active periods as well, which is in agreement to the needs shown in comparisons with multiple satellite observations. The designed model AISstorm is public accessable and ionization rates can be used for arbitrary setups in order to provide long-term forcing with high spatial and temporal resolution.

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