Nonstationarity of the quasi-perpendicular terrestrial bow shock is analyzed from magnetic field measurements, comparison with 2D particle-in-cell (PIC) simulations, and a careful and accurate methodology in the data processing. The results show evidence of a strong variability of the microstructures of the shock front (foot and ramp), confirming the importance of dissipative effects. These results indicate that these features can be signatures of the shock front self-reformation.

In collisionless systems like space plasma, particle velocity distributions contain fingerprints of ongoing physical processes. However, it is challenging to decode this information from observations. We used hybrid-Vlasov simulations to obtain ion velocity distribution functions at different locations and at different stages of the Earth's magnetosphere dynamics. The obtained distributions provide valuable examples that may be directly compared with observations by satellites in space.

We investigate the reflection of magnetosonic (MS) waves at the local two-ion cutoff frequency in the outer plasmasphere, which is rarely reported. The observed wave signals demonstrate the reflection at the local two-ion cutoff frequency. From simulations, the waves with small incident angles are more likely to penetrate the thin layer where the group velocity reduces significantly before reflection. These results may help to predict the global distribution of MS waves.

Based on on-site measurements and numerical modelling, we eliminated the electrostatic shielding effect of nearby trees from the atmospheric electric potential gradient (PG) time series recorded at Nagycenk, Hungary, Central Europe, revealing their actual variation between 1962 and 2009. The comparison with PG data from another station in the same region implies that there may have been coherent regional changes in Earth’s atmospheric electric field during the investigated time period.

We investigate the role of eddy diffusion in the delayed ionospheric response against solar flux changes in the solar rotation period using the CTIPe model. The study confirms that eddy diffusion is an important factor affecting the delay of the total electron content. An increase in eddy diffusion leads to faster transport processes and an increased loss rate, resulting in a decrease in the ionospheric delay.

The 30 August–2 September 2019 geospace storm and its influence on the characteristics of high frequency radio waves over the People's Republic of China have been analyzed. The geospace storm was weak, the magnetic storm was moderate, and the ionospheric storm was moderate to strongly negative, which manifested itself by the reduction in the ionospheric F-region electron density. Appreciable disturbances were also observed to occur in the ionospheric E-region and possibly in the E_s layer.

The high-latitude ionosphere has a very dynamic structure and causes a negative influence via radio wave propagation on, for example, global positioning system (GPS) signals and satellite communication. In this study, we have determined which type of high-latitude ionosphere disturbance has a stronger influence on GPS signals using a GPS receiver on Svalbard. It is shown that a substorm ionosphere disturbance leads to stronger GPS signal fluctuations than other types of ionosphere disturbances.

In this paper, we propose a new explanation for shoulder-like formations based on the test particle model. The simulation reproduced three shoulders in a substorm case. The physical explanation of shoulder formation is not yet understood. The paper suggests that the physical mechanism of shoulder formation is the result of plasma extrusion in the predawn sector, caused by the outer plasmasphere drifting radially outward and rotating faster.

Micro-size particles entering the Earth’s atmosphere do not emit enough light to be observed as meteors, but they can be probed with radars. The echo from these meteors depends on particle size and the atmosphere in which the particle travels. In this paper, we study the importance of neutral winds in forming meteor returns sensed by radars. We show that meteor trails can exhibit unique radar signatures due to neutral winds, explaining unique signatures in radar maps.

Plasma waves are an integral part of cometary physics, as they facilitate the transfer of energy and momentum. From intermediate to strong activity, nonlinear asymmetric plasma and magnetic field enhancements dominate the inner coma of 67P/CG. We present a statistical survey of these structures from December 2014 to June 2016, facilitated by Rosetta's unprecedented long mission duration. Using a 1D MHD model, we show they can be described as a combination of nonlinear and dissipative effects.

We analyse the climatology of the ionosphere over Nepal based on GPS-derived vertical total electron content (VTEC) during 2008–2018. The study illustrates the diurnal, monthly, annual, seasonal and solar cycle variations in VTEC. The results show equinoctial asymmetry in TEC in maximum phases in 2014, followed by descending, ascending and minimum phases. The winter anomalies are seen during increasing and maximum phases of the solar cycle (2011–2014) from almost all stations considered.

The concept of electromotive force appears in various electromagnetic applications in geophysical and astrophysical fluid studies. The electromotive force is being recognized as a useful tool to construct a more complete picture of turbulent space plasma and has the potential to test for the fundamental processes of dynamo mechanism in space.

Climate change is affecting the stability of the atmosphere and increasing the occurrence of extreme rainfall and floods, which pose natural hazards with major socio-economic and health impacts. We show that such events tend to follow arrivals of high-speed solar wind. The role of atmospheric waves generated in the auroral region as the mechanism mediating the influence of solar wind coupling to the magnetosphere–ionosphere–atmosphere system on the troposphere is highlighted.