Coronal mass ejections and high-speed solar wind streams effect on HF ionospheric communication channel

This article analyzes the degree of solar coronal mass ejections and high-speed solar wind streams influence on the ionospheric communication channel in the short-wavelength range. Regularities in the coronal mass ejections influence on the parameters of the ionosphere are revealed. It is shown that there is a decrease in the values of the used differential parameter of critical frequency of the ionosphere F2 layer after the onset of coronal mass ejections of the loop type, while no significant changes are observed from other types of coronal mass ejections. The contribution of the high-speed solar wind flux to the features of the behavior of ionospheric parameters is demonstrated. Deviations of critical frequency and maximum observed frequency of the ionosphere F2 layer indicate a change in conditions in the ionosphere, leading to disruption of radio communication in the short-wavelength range. The results of ground-based measurements of the ionospheric plasma parameters were obtained by the methods of oblique and vertical sounding of the ionosphere. The use of the method of oblique sounding made it possible to obtain data on the state of the ionosphere where there are no vertical sounding stations.

Solar wind structures and their effects on energetic electron precipitation

<p>Energetic electron precipitation (EEP) into the Earth's atmosphere can collide with gases and deposit their energy there. The collisions between electrons and atmospheric gasses initiate several chemical reactions which can reduce the ozone concentration. Ozone is critically important in the middle atmosphere energy budget as changes in the ozone concentration impact temperature and winds. EEP is not fully understood in terms of how much energy is being deposited and what the associated drivers are. An accurate quantification of EEP has limitations due to instrumental challenges and therefore imposes limitations of the associated EEP parameterization into climate models. A solution to this problem is a better understanding of the driver processes of energetic electron acceleration and precipitation, alongside optimized data handling. In this study the bounce loss cone fluxes are inferred from EEP measurements by the Medium Energy Proton and Electron Detector (MEPED) on board the Polar Orbiting Environmental Satellite (POES) and the Meteorological Operational Satellite Program of Europe (METOP) at tens of keV to relativistic energies. It investigates EEP in contexts of different solar wind structures: high-speed solar wind streams (HSSs) and coronal mass ejections (CMEs), during an eleven-year period from 2004 – 2014. While today's chemistry climate models only provide snapshots of EEP, independent of context, this study aims to understand the context EEP is created in, which will allow a more accurate estimate of the EEP to be applied in atmospheric climate models.</p>

Selective acceleration of O+ by drift-bounce resonance in the Earth’s magnetosphere: MMS observations

<p>We studied O<sup>+</sup>drift-bounce resonance using Magnetospheric Multiscale (MMS) data. A case study of an event on 17 February 2016 shows that O<sup>+</sup> flux oscillations at ~10–30 keV occurred at MLT ~ 5 hr and <em>L</em>~ 8–9 during a storm recovery phase. These flux oscillations were accompanied by a toroidal Pc5 wave and a high-speed solar wind (~550 km/s). The azimuthal wave number (<em>m</em>-number) of this Pc5 wave was found to be approximately –2. The O<sup>+</sup>/H<sup>+</sup> flux ratio was enhanced at ~10–30 keV corresponding to the O<sup>+</sup> flux oscillations without any clear variations of H<sup>+</sup> fluxes, indicating the selective acceleration of O<sup>+</sup> ions by the drift-bounce resonance. A search for the similar events in the time period from September 2015 to March 2017 yielded 12 events. These events were mainly observed in the dawn to the afternoon region at <em>L</em>~ 7–12 when the solar wind speed is high, and all of them were simultaneously identified on the ground, indicating low <em>m</em>-number. Correlation analysis revealed that the O<sup>+</sup>/H<sup>+</sup> energy density ratio has the highest correlation coefficient with peak power of the electric field in the azimuthal component (<em>E<sub>a</sub></em>). This statistical result supports the selective acceleration of O<sup>+</sup> due to the <em>N </em>= 2 drift-bounce resonance.</p>