Boundaries in the plasma around comet 67P separate regions with different properties. Many have been identified, including a new boundary called an infant bow shock. Here, we investigate how the plasma and fields behave at this boundary and where it can be found. The main result is that the infant bow shock occurs at intermediate activity and intermediate distances to the comet. Most plasma parameters behave as expected; however, some inconsistencies indicate that the boundary is non-stationary.

In this work, we simulated the effect of atmospheric drag on satellites in low Earth orbit (LEO) during 1-month intervals of disturbed and quiet solar geomagnetic activity. Our results show that geomagnetic storms (e.g. the Bastille Day event) can cause a significant drop in LEO satellite altitudes and increase their background orbit decay rate by 50–70 %. This work can contribute to improved situational awareness and mitigation of potential threats solar energetic events pose to satellites.

The nature of the semi-annual variation in the relativistic electron fluxes in the Earth's outer radiation belt has been a debate for over 30 years. Our work shows that it is primarily driven by the Russell–McPherron effect, which indicates that reconnection is responsible not only for the short-scale but also the seasonal variability of the electron belt as well. Moreover, it is more pronounced during the descending phase of the solar cycles and coexists with periods of fast solar wind speed.

This work explores the role of EISCAT 3D as a tool for planetary mapping. Due to the challenges inherent in detecting the signals reflected from faraway bodies, we have concluded that only the Moon is a viable mapping target. We estimate the impact of the ionosphere on lunar mapping, concluding that its distorting effects should be easily manageable. EISCAT 3D will be useful for mapping the lunar nearside due to its previously unused frequency (233 MHz) and its interferometric capabilities.

Prague's Clementinum belongs to a few magnetic observatories that have been operational from the 1840s to the late 19th century. However, up to now these unique data from 1839 to 1871 have been available exclusively in printed yearbooks and only in raw instrumental units. In this paper, the data were analysed, transformed to physical units, and made available to the scientific community. Application of the data to the analysis of the geomagnetic disturbances in September 1839 is also shown.

The ionosphere is a partly ionized medium above the atmosphere. Because of its anisotropic properties, the imposed electric fields from the magnetosphere produce space charge. Polarization electric fields induced in the ionosphere by this process generate ion drifts (Pedersen currents) and plasma evaporation along the field lines, thus achieving a quasi-neutral equilibrium of the ionosphere. The evaporation grows as a large-scale parallel potential structure in the magnetosphere.

We report an event where hiss wave intensity decreased, associated with the enhanced convection and a substorm. We suggest that the enhanced magnetospheric electric field causes the outward and sunward motion of energetic electrons. This leads to the decrease of energetic electron fluxes on the duskside, which provide free energy for hiss amplification. The study reveals the important role of magnetospheric electric field in the variation of the energetic electron flux and hiss wave intensity.

We report observations of sporadic-E (Es) layers and visual meteor count data simultaneously observed during night-time over the Arabian Peninsula. A constant and well-established presence of Es has been reported with a consistent count of meteors also present throughout the 1-year observation period. Data show that the Es observations are not dependent on the presence of meteor flux; i.e., the presence of meteors is not the main cause of the presence of Es over the Arabian Peninsula.

The paper discusses the excitation of monochromatic ELF/VLF electromagnetic waves produced by HF heating facility currents in the nighttime ionosphere. The ground-based magnetic field is predominantly located under the source, and the wave has right-hand polarization typical for a whistler but left-hand polarization at large distances from the source. About half of the source energy propagates upward, and approximately 20 % propagates to the Earth–ionosphere waveguide.

There is great scientific interest in extending atmospheric models upwards to include the upper atmosphere. The Met Office’s Unified Model has recently been successfully extended to include this region. Atmospheric tides are an important driver of atmospheric motion at these greater heights. This paper provides a first comparison of winds and tides produced by the new extended model with meteor radar observations, comparing key tidal properties and discussing their similarities and differences.

Our approach compares infrasound data and simulated microbarom soundscapes in multiple directions. Data recorded during 2014–2019 at Infrasound Station 37 in Norway were processed and compared to model results in different aspects (directional distribution, signal amplitude, and ability to track atmospheric changes during extreme events). The results reveal good agreement between the model and data. The approach has potential for near-real-time atmospheric and microbarom diagnostics.

This paper discusses the charge generation for impacts of nano- to micro-scale dust on metal surfaces at speeds below a few kilometres per second. By introducing a model of capacitive coupling between the dust and the impact surface, we find that at such low speeds, the charge can be dominated by contact charging as opposed to plasma generation.

We present a study of ultralow-frequency waves in the ionosphere and on the ground. These waves are very slow (their periods are about several minutes). They are registered on the ground as geomagnetic pulsations. No simple dependence exists between geomagnetic and ionospheric pulsations. Here we study not only selected pulsations with very high amplitudes but also usual pulsations and try to answer the question, which pulsation parameters are favorable for modulation of the ionosphere?

In this work we present the first analytical magnetosheath plasma flow model for the space environment around Mercury. The proposed model is relatively simple to implement and provides the possibility to trace the flow lines inside the Hermean magnetosheath. It can help to determine the the local plasma conditions of a spacecraft in the magnetosheath exclusively on the basis of the upstream solar wind parameters.