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We present an analysis of the ionosphere and thermosphere response to Solar Proton Events (SPE) and magnetospheric proton precipitation in January 2005, which was carried out using the model of the entire atmosphere EAGLE. The ionization rates for the considered period were acquired from the AIMOS (Atmospheric Ionization Module Osnabrück) dataset. For numerical experiments, we applied only the proton-induced ionization rates of that period, while all the other model input parameters, including the electron precipitations, corresponded to the quiet conditions. In January 2005, two major solar proton events with different energy spectra and proton fluxes occurred on January 17 and January 20. Since two geomagnetic storms and several sub-storms took place during the considered period, not only solar protons but also less energetic magnetospheric protons contributed to the calculated ionization rates. Despite the relative transparency of the thermosphere for high-energy protons, an ionospheric response to the SPE and proton precipitation from the magnetotail was obtained in numerical experiments. In the ionospheric E layer, the maximum increase in the electron concentration is localized at high latitudes, and at heights of the ionospheric F2 layer, the positive perturbations were formed in the near-equatorial region. An analysis of the model-derived results showed that changes in the ionospheric F2 layer were caused by a change in the neutral composition of the thermosphere. We found that in the recovery phase after both solar proton events and the enhancement of magnetospheric proton precipitations associated with geomagnetic disturbances, the TEC and electron density in the F region and in topside ionosphere/plasmasphere increase at low- and mid-latitudes due to an enhancement of atomic oxygen concentration. Our results demonstrate an important role of magnetospheric protons in the formation of negative F-region ionospheric storms. According to our results, the topsid

We apply the Entire Atmosphere GLobal (EAGLE) model to investigate the upper atmosphere response to the January 2009 sudden stratospheric warming (SSW) event. The model successfully reproduces neutral temperature and total electron content (TEC) observations. Using both model and observational data, we identify a cooling in the tropical lower thermosphere caused by the SSW. This cooling affects the zonal electric field close to the equator, leading to an enhanced vertical plasma drift. We demonstrate that along with a SSW-related wind disturbance, which is the main source to form a dynamo electric field in the ionosphere, perturbations of the ionospheric conductivity also make a significant contribution to the formation of the electric field response to SSW. The post-sunset TEC enhancement and pre-sunrise electron content reduction are revealed as a response to the 2009 SSW. We show that at post-sunset hours the SSW affects low-latitude TEC via a disturbance of the meridional electric field. We also show that the phase change of the semidiurnal migrating solar tide (SW2) in the neutral wind caused by the 2009 SSW at the altitude of the dynamo electric field generation has a crucial importance for the SW2 phase change in the zonal electric field. Such changes lead to the appearance of anomalous diurnal variability of the equatorial electromagnetic plasma drift and subsequent low-latitudinal TEC disturbances in agreement with available observations. Plain Language Summary - Entire Atmosphere GLobal model (EAGLE) interactively calculates the troposphere, stratosphere, mesosphere, thermosphere, and plasmasphere-ionosphere system states and their response to various natural and anthropogenic forcing. In this paper, we study the upper atmosphere response to the major sudden stratospheric warming that occurred in January 2009. Our results agree well with the observed evolution of the neutral temperature in the upper atmosphere and with low-latitude ionospheric disturbances

In this paper, we discuss perturbations in neutral temperature, total electron content (TEC), and critical frequency of the maximum of the F2 layer (foF2) during the sudden stratospheric warming in January 2009. The calculations were performed using the first version of the EAGLE (Entire Atmosphere Global Model), which is a combination of the models of the low–middle atmosphere (HAMMONIA) and the upper atmosphere (GSM TIP). The EAGLE reproduces observed stratospheric warming and related mesospheric cooling in the northern polar cap in January 2009. At thermospheric altitudes, the neutral temperature perturbations have a quasi-wave character with a wavelength of ∼40 km in the vertical direction. Our results indicate that the HAMMONIA model should be used in the EAGLE instead of the GSM TIP model for the neutral temperature calculations in the altitude region from 80 to 120 km. It is shown that the obtained model foF2 and TEC perturbations are mainly related to seasonal variations. The most-pronounced perturbations in the ionospheric electron density due to stratospheric warming are formed near the equator and are basically negative. Our analysis of the neutral temperature and electron density perturbations made it possible to conclude that the dependence of ionospheric parameters on seasonal changes in solar zenith angle is stronger than for the thermosphere parameters. © 2018, Pleiades Publishing, Ltd.

Propagation of the Russian Academy of Sciences (WD IZMIRAN), Kaliningrad, Russia There are two approaches for radio wave ray tracing when the endpoints of the ray are fixed. The standard approach is the shooting method where a ray is sent out in some direction and its landing point is used to modify the shooting direction and obtain the desired endpoint. However, there is no systematic, universal algorithm for refining the shooting direction. Another approach is based on direct utilization of the variational principle for the optical path (Fermat’s principle). The idea is to transform an arbitrary trajectory to an optimal one, while the endpoints of the trajectory are kept fixed according to the boundary conditions., QC 20160516