Highlight articles

New insights for mesospheric OH: multi-quantum vibrational relaxation as a driver for non-local thermodynamic equilibrium

The question of whether mesospheric rotational population distributions of vibrationally excited OH are in equilibrium with the local kinetic temperature has been debated over several decades. We examine the relationship of multi-quantum relaxation pathways with the behavior exhibited by OH(v) rotational population distributions and find that the effective rotational temperatures of mesospheric OH(v) deviate from local thermodynamic equilibrium for all observed vibrational levels.

The electric current approach in the solar–terrestrial relationship

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.

A high-altitude balloon experiment to probe stratospheric electric fields from low latitudes

Results from a high-altitude balloon experiment conducted from a low-latitude station in India are presented in this work. The objectives of this experiment were to probe and understand the processes driving the various electric field sources at low latitudes. During this experiment, electric fields in the range of 5–6 mV m⁻¹ were observed at the balloon float altitude of 35 km. Atmospheric waves of few 100 km horizontal wavelength are suggested to be a potential source of these electric fields.

Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko

A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to comet P67/Churyumov-Gerasimenko. We provide the analytical model of this wave excitation from linear perturbation theory. A modified ion-Weibel instability is identified as source of this wave excited by a cometary current. The waves predominantly grow perpendicular to this current. A fan-like phase structure results from superposing the strongest growing waves in a cometary rest frame.

Statistical analysis of magnetotail fast flows and related magnetic disturbances

This study presents an investigation on the occurrence of fast flows in the magnetotail using the complete available data set of the THEMIS spacecraft for the years 2007 to 2015. First, basic statistical findings concerning velocity distributions, occurrence rates, group structures and key features of 16 000 events are presented using Superposed Epoch and Minimum Variance Analysis techniques.

Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 2: The IGRF

The method of electric field mapping along geomagnetic field lines, derived in an accompanying paper, is applied to the International Geomagnetic Reference Field. Formulae for the geomagnetic field gradient tensor are derived and these are used in a software package developed to map the electric field. A number of examples are presented illustrating the method. The method will be of importance in conjugate studies of ionospheric convection when the external magnetic field can be neglected.

Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field.

Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries

Adaptive magnetospheric models based on THEMIS magnetic observations made at 6-9Re in the nightside magnetosphere are used to map the magnetically conjugate 30 and 80keV proton isotropy boundaries (IBs) to investigate the value of Kib=Rc/rc (magnetic curvature radius to particle gyroradius) in the neutral sheet at the IB generation place. For the most accurate mapping, the group Kib spread spans from 4 to 32; its median value is ~13, slightly larger than Kib8 expected for current sheet scatter.

Recent highlights from Cluster, the first 3-D magnetospheric mission

This paper presents recent highlights from the Cluster mission on solar wind turbulence, magnetopause asymmetries and magnetosheath density enhancements, dipolarisation currents, reconnection variability, FTE in greatest detail, plasmaspheric wind and re-filling of the plasmasphere, radiation belts, updates of magnetospheric electric and magnetic field models, and magnetosheath and magnetopause properties under low Mach number. Public access to all high-resolution data (CSA) is also presented.

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40 mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism.

PS Planetary and Solar System Sciences Highlight articles

Highlight articles

New insights for mesospheric OH: multi-quantum vibrational relaxation as a driver for non-local thermodynamic equilibrium

The electric current approach in the solar–terrestrial relationship

A high-altitude balloon experiment to probe stratospheric electric fields from low latitudes

Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko

Statistical analysis of magnetotail fast flows and related magnetic disturbances

Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 2: The IGRF

Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries

Recent highlights from Cluster, the first 3-D magnetospheric mission

Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko

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