Role of internal atmospheric variability in the estimation of ionospheric response to solar and magnetospheric proton precipitation in January 2005

The purpose of this study is to investigate the role of internal atmospheric variability in the detection of ionospheric response to precipitating protons of solar and magnetospheric origin during 17-23 January 2005. For this purpose, we analyzed the results of ensemble runs of the whole atmosphere model EAGLE. We confirmed that the proton precipitation produces (directly and indirectly) significant TEC (Total Electron Content) enhancements at different latitudes. However, we also showed that internal atmospheric variability can strongly mask the forced signal, especially its after-effects, which can lead to false interpretation if only one model realization is considered. The ensemble standard deviation, or an atmospheric noise level, in TEC has a clear UT variation and spatial distribution, which defines the derivability of the signal depending on the time and the region of the forced effects. The noise itself is also affected by the increased ionization from protons, but its behavior is nonlinear and depends on the latitude, spectrum of the event and its time of occurrence. We conclude that studies of the ionospheric response to various space weather phenomena require the application of whole atmosphere models in ensemble mode to ensure statistical significance of the obtained results and a reliable interpretation of the observational data. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.