A VLF chorus is a very intense electromagnetic plasma wave that is naturally excited as a succession of discrete emissions near the magnetic equatorial plane outside the plasmasphere. We introduce a mechanism of chorus excitation under conditions when known mechanisms become ineffective. This kind of excitation is related to the amplification of short electromagnetic pulses from the noise level even in a stable plasma. Obtained results can explain some important features of the chorus emissions.

The solar wind interacts with the Earth’s magnetic field, forming a magnetosphere. On the night side solar wind stretches the magnetosphere into a long tail. A process called magnetic reconnection opens the magnetic field lines and reconnects them, accelerating particles to high energies. We study this in the magnetotail using a numerical simulation model of the Earth’s magnetosphere. We study the motion of the points where field lines reconnect and the fast flows driven by this process.

Magnetosheath jets are high-velocity plasma structures that are commonly observed within the Earth's magnetosheath. Previously, they have mainly been investigated with spacecraft observations, which do not allow us to infer their spatial sizes, temporal evolution, or origin. This paper shows for the first time their dimensions, evolution, and origins within a simulation whose dimensions are directly comparable to the Earth's magnetosphere. The results are compared to previous observations.

Many studies carried out for model validation are realised under geomagnetically quiet conditions. For climatological models this is not an issue. But for models like NeQuick, which plays a crucial role in daily human activities, it has to be evaluated under different conditions. Our study, which is probably a preliminary study, shows the advantage of the ingestion of ionospheric data. Thus, through this technique, a model could be assessed regardless of the geomagnetic activity.

A record has been found of an "aurora" observed on 27 October 1856 in the Philippines, practically at the magnetic equator. An analysis of this report indicates that it could belong to a "sporadic aurora" because of low magnetic activity at that time. We provide a possible physical mechanism that could explain the appearance of this sporadic, low-latitude aurora, according to the analyses on the observational report and magnetic observations at that time.

The position of the external boundary of the outer electron radiation belt (ORB), relative to the auroral oval's position, is hard to determine. It was done using simultaneous measurements of energetic and auroral electrons onboard METEOR-M1. Our analysis shows that the ORB boundary is often located inside the auroral oval and that the number of such events increases with growing geomagnetic activity. These results are relevant to our understanding of the topology of the geomagnetic field.

This paper describes an algorithm that automatically detects vortices around the Earth's magnetosphere using the velocity field from simulated data. It also describes how the tool can be used to analyze further properties of the vortices including the velocity changes within their motion across the magnetosheath. Vortices developed at the magnetopause boundary contribute to the process of mass, momentum and energy transfer from the solar wind into the Earth's magnetosphere.

We used sounding rockets to obtain four high-resolution temperature profiles in the mesosphere over a limited area. We found consistent deep isothermal and adiabatic layers, but variable and finely structured turbulence preferentially in the lower stable mesosphere. Accompanying tracer releases showed horizontal winds in the lower thermosphere with extreme shears and 200 m  s⁻¹ winds under moderately disturbed geomagnetic conditions, and convection-like structures just below the mesopause.

At the bow shock the solar wind is slowed down in front of Earth's magnetosphere. This is accompanied by a gain in strength of the magnetic field, which implies that the bow shock carries electric currents. We present the a comprehensive statistical study of bow shock currents making use of multi-point data collected by Cluster spacecraft. We find that the currents depend on the shock geometry and the interplanetary magnetic field and are in good accordance with theory and simulation results.

We use the Vlasiator code to study the characteristics of transient structures that exist in the Earth's foreshock, i.e. upstream of the bow shock. The structures are cavitons and spontaneous hot flow anomalies (SHFAs). These transients can interact with the bow shock. We study the changes the shock suffers via this interaction. We also investigate ion distributions associated with the cavitons and SHFAs. A very important result is that the arrival of multiple SHFAs results in shock erosion.

Does the reformation of perpendicular shocks really exist in the real space plasma? The reformation was first reported in numerical simulations in one spatial dimension, and then was indicated by in situ observation by the Cluster spacecraft. The present study aimed to answer this question by performing advanced numerical simulations in two spatial dimensions. The present study suggests that the reformation exists under a limited plasma condition.

This paper proposes an optimal tropospheric tomography approach with the support of an auxiliary area, which has the ability to use the signals crossing out from the top boundary of the tomographic area. Additionally, the top height of the tomography body is determined based on the average water vapour distribution derived from the COSMIC data. The compared result reveals the superiority of the proposed method when compared to the conventional method.

The Earth's magnetic field is shaped by the solar wind. On the dayside the field is compressed and on the nightside it is stretched as a long tail. The tail has been observed to occasionally undergo flapping motions, but the origin of these motions is not understood. We study the flapping using a numerical simulation of the near-Earth space. We present a possible explanation for how the flapping could be initiated by a passing disturbance and then maintained as a standing wave.

The physics of the magnetic mirror mode in its final state of saturation, the thermodynamic equilibrium, is re-examined to demonstrate that the mirror mode is the classical analogue of a superconducting effect in an anisotropic-pressure space plasma. Three different spatial correlation scales are identified which control the behaviour of its evolution into large-amplitude chains of mirror bubbles.