The spatial and temporal evolution of the aurora provides information about plasma dynamics throughout the magnetosphere. The THEMIS all-sky imager network has been operating for over 10 years and has accumulated millions of auroral images. To speed the extraction of information from this dataset, it is desirable to implement automated algorithms to track and classify the aurora. This paper demonstrates an automatic method of extracting the motion of the aurora from sequences of images.

Gravity waves (GWs) are one of the most important dynamical features of the middle atmosphere that extends from the tropopause to the lower thermosphere. They originate from the troposphere and propagate upward. Here, we show the impact of the horizontal GW distribution in the lower atmosphere on the dynamics of the middle atmosphere using a global circulation model. As a result, we find that non-zonal GW structures can force additional stationary planetary waves.

In this paper, we summarize the difficulties that Sfe detection presents and explain a line of work we initiated to overcome these difficulties with the goal of achieving a system capable of performing automatic detection. Some properties of Sfe, including spherical symmetry around the vortex and different time durations between Sfe and other natural variations, were used to construct an index allowing us to detect Sfe.

A review is given of major progress towards addressing unsolved fundamental puzzles about the Sun. The solar magnetic field is generated by dynamo action in the solar interior. Several mechanisms may heat the corona to 106 K and drive the solar wind. Occasionally, giant flux ropes (prominences) erupt and produce huge CMEs and solar flares. A new theory is presented for the origin of the twist observed in erupting prominences and the nature of reconnection in the rise phase of a flare or CME.

Galactic cosmic rays are high-energy particles from outside of the solar system. The products of their interaction with the atmosphere are counted by a network of neutron monitors. The number of cosmic rays reaching Earth is affected by the magnetic field embedded in the solar wind. The result is a number of regular variations in the neutron monitor data, including a diurnal variation. We have found that this variation is influenced by 1–2 h by the polarity of the Sun's magnetic field.

Through the selection of 172 urban–rural station pairs, this study noted that urbanization significantly influenced the dimming trend in sunshine duration in China from 1960 until it leveled off after 1990. During 1960–1989, rural dimming was around two-thirds the rate of urban dimming; this ratio generally shows a positive correlation with urbanization level. There may be an overestimation of dimming in China when a dataset with more urban-scale sites than rural-scale sites is applied.

The ion total transports in the near-Earth plasma sheet have been investigated and quantified. Specifically, the net O⁺ transport is about 10²⁴ s⁻¹ in the earthward direction, which is 1 order of magnitude smaller than the typical O⁺ ionospheric outflows, strongly indicating that most outflow will eventually escape, leading to significant atmospheric loss. The study also shows that low-velocity flows (< 100 km s⁻¹) dominate the mass transport in the near-Earth plasma sheet.

MESSENGER magnetic field data from the magnetosphere of Mercury have been investigated to identify ultra-low-frequency (ULF) waves. ULF waves in the Kelvin–Helmholtz (KH) wave frequency range are frequently observed in the magnetosphere. These ULF waves often have similar characteristics to previously identified, likely KH-driven ULF waves, indicating that ULF waves in a specific frequency band can be used as a detection tool for KH waves on Mercury.

A large energy release can occur in association with magnetic field line reconnection. In order to understand the detailed process of the energy release, accurate satellite observations are invaluable. However, it is usually difficult to identify where a single satellite is located with respect to the reconnection process. The present study proposes using a whistler burst to identify the plasmoid collisions and associated electron acceleration in the reconnection process.

A comparison between winds and tides in the mesosphere and lower thermosphere based on measurements from a meteor radar (MR) and a medium-frequency radar in northern Norway was done to estimate potential biases between the two systems. Our results indicate reasonable agreement for the zonal and meridional wind components between 78 and 92 km. Based on these findings, we have taken the MR data as a reference and thus construct a consistent and homogenous wind from approximately 60 to 110 km.

We studied the impact on global MHD simulations from different simulation initialisation methods. While the global MHD code used is GUMICS-4 we conclude that the results might be generalisable to other codes as well. It is found that different initialisation methods affect the dynamics of the Earth's space environment by creating differences in momentum transport several hours afterwards. These differences may even grow as a response to rapid solar wind condition changes.

Using model–data analysis we emphasize a new result – formation of the positive daytime disturbances in foF2 and TEC at middle and low latitudes due to n(O)/n(N₂) enhancement during the recovery storm phase. The spatial extent of this phenomenon depends on the longitudinal sector. The positive disturbances in the electron content at heights of 800–20 000 km at high latitudes can appear simultaneously with the negative disturbances in TEC and foF2 due to electron and neutral temperature heating.

Chambon-la-Forêt magnetic observatory distributes definitive second data that are contaminated by noise with a standard variation below 400 pT. This noise is low compared to the international standard set by INTERMAGNET. It is mainly due to local signals of unknown origins that have short wavelengths in space (less than 200 m) and in time (less than a day).

The sequence of phenomena consisting of solar flares, coronal mass ejections (CMEs), auroral substorm, and geomagnetic storms is mostly a manifestation of electromagnetic energy dissipation. Thus, first of all, it is natural to consider each of them in terms of a sequence of power supply (dynamo), power transmission (electric currents/circuits), and dissipation (mostly observed phenomena), i.e., as an input–output process and the electric current line approach.

This work sheds new light on the size distribution of dust grains of meteoric origin in the mesosphere and lower thermosphere region using rocket-borne instrumentation. We found that a large number of very small (~ 0.5 nm) particles are charged and therefore have a significant influence on the charge balance of the lower ionosphere.

It is suggested that collisionless reconnection under conditions of very strong current-parallel guide fields in dilute plasmas should become a rather efficient source of electromagnetic radiation in the free space modes X and O and their harmonics. The mechanism is based on the electron cyclotron maser instability (ECMI), which can be excited by the anisotropic weakly relativistic electron distribution in the many inertial lengths long electron exhausts caused in reconnection.