Algorithm for numerical simulation of electron density and stochastically convecting high latitude ionosphere

The problem of modeling the inhomogeneities of the electron density in the polar ionosphere at the level of the F - layer is considered. It is known that the distribution of ionospheric plasma changes under the action of the electric field of large-scale magnetospheric convection. Since the electric field undergoes significant fluctuations in the auroral zone, it is proposed to use the Monte Carlo method to solve this problem, simulating the process of plasma motion, like the Wiener one with deterministic drift.

Are drivers of northern lights in the ionosphere?

Known as northern lights, auroral spirals are distinct features of substorm auroras composed of large-scale spirals (100s km Surges) mixed with smaller scale ones (10s km Folds, and 1 km Rays). Spiral patterns are generally interpreted in terms of the field line mapping of the upward field-aligned currents produced in the magnetosphere during the field line dipolarization. The field line mapping results in opposing spiral rotations of small- and large-scale auroras. Because of a rotational symmetry deformation and similarity in deformation speeds (6~8 km/s) of small- and large-scale spirals, it has been suggested that common physical processes may underlie the deforming processes. Internal processes in the polar ionosphere (ionospheric driver) will be proposed as the general dynamic for spiral auroras. The ionospheric driver rotated in the ionosphere to produce spirals that characteristically differ from the field line mapping scenario.

Electric Field Multifractal Features in the High-Latitude Ionosphere: CSES-01 Observations

In the polar ionosphere, the electric field is characterized by broadband and power law spectral densities at small/short spatio-temporal scales, which support a possible turbulent nature of the electric field fluctuations. Here, we investigate the multifractal character of the full three-dimensional electric field in the polar ionosphere as recorded on board the first Chinese Seismo-Electromagnetic Satellite (CSES-01). The results of our analysis prove a clear different degree of multifractality of the electric field fluctuations approaching either the polar cap trailing edge or the auroral region. The observed differences in the multifractal character are interpreted in terms of the different natures of the particle precipitation in the polar cap and in the auroral region. A possible link between the multifractal nature of electric field fluctuations, parallel to the geomagnetic field, and filamentation of field aligned currents (FACs) is established.

Ionospheric control of space weather

As proposed by Saka (2019), plasma injections arising out of the auroral ionosphere (ionospheric injection) are a characteristic process of the polar ionosphere at substorm onset. The ionospheric injection is triggered by westward electric fields transmitted from the convection surge in the magnetosphere at field line dipolarization. Localized westward electric fields result in local accumulation of ionospheric electrons and ions, which produce local electrostatic potentials in the auroral ionosphere. Field-aligned electric fields are developed to extract excess charges from the ionosphere. This process is essential to the equipotential equilibrium of the auroral ionosphere. Cold electrons and ions that evaporate from the auroral ionosphere by ionospheric injection tend to generate electrostatic parallel potential below an altitude of 10 000 km. This is a result of charge separation along the mirror fields introduced by the evaporated electrons and ions moving earthward in phase space.

On Magnetic Helicity and Field-Aligned Currents in the Polar Ionosphere

<p>Magnetic helicity, which is a measure of twist and linkage of magnetic field lines, is a useful quantity to investigate some processes occurring in space plasmas. In particular, there is a strong link between magnetic helicity, magnetic flux structures, turbulence and dissipation. We investigate the connection between the reduced magnetic helicity and the structure of field-aligned currents in the high-latitude ionosphere using high resolution (50 Hz) magnetic data collected on board the ESA Swarm constellation. We show the existence of a clear link between the multiscale coarse-grained structure of reduced magnetic helicity and the field-aligned currents. This finding strongly supports the idea that turbulence processes might be at the origin of the observed small-scale current structures. A discussion of the relevance of our results in the framework of the filamentary nature of the field-aligned current is also presented.</p><p><span>This work is supported by Italian PNRA under contract </span>PNRA18_00289-A “Space weather in Polar Ionosphere: the Role of Turbulence ".</p>

Plasma injections arising out of dynamic ionosphere

<p>We propose ionospheric plasma injections to the magnetosphere (ionospheric injection) as a new plasma process in the polar ionosphere. The ionospheric injection is first triggered by westward electric fields transmitted from the convection surge in the magnetosphere in association with dipolarization onset. Localized westward electric fields yield electrostatic potential in the ionosphere as a result of differing electron and ion mobility in the E-layer. To ensure quasi-neutrality of ionospheric plasmas, excess charges are released as injections out of the ionosphere, specifically electrons from positive potential region in higher latitudes and ions from negative potentials in lower latitudes. Potential difference on the order of 10 kV in north-south directions produces southward electric fields (100mv/m) at the footprint of the convection surge in both northern and southern hemispheres. Resultant geomagnetic field lines are not in equipotential equilibrium during ionospheric injections but instead develop downward electric fields in positive potential regions in higher latitudes to extract electrons and upward electric fields in negative potential regions in lower latitudes to extract ions. Parallel electric fields can exist in the magnetic mirror geometry of auroral field lines if the magnetospheric plasma follows quasi-neutral equilibrium. Because ionospheric injection has inherent dynamo processes as well as load, we term the polar ionosphere “dynamic ionosphere”.</p><p>Cold plasmas injected out of the dynamic ionosphere are transported along the dynamical trajectories to the magnetosphere conserving the total energy (including electrostatic potentials) and first adiabatic invariant. Electrons/ions traveling in downward/upward electric fields lose perpendicular and lower velocities in parallel component, leaving only the energetic part of ionospheric plasmas collimated along the field lines. Steady-state and one-dimensional dynamical trajectory shows that ion and electron temperatures at the ionosphere initially at 1 eV increased parallel temperatures to 202 eV and decreased perpendicular temperatures to 0.001 eV at geosynchronous altitudes where the electrostatic potential difference between ionosphere and magnetosphere was assumed to be 200 V. When potential difference increased to 600 V, the parallel temperatures increased to 602 eV, while perpendicular temperatures remain unchanged. Parallel potentials preferentially heated the ionospheric cold plasmas in parallel directions and transported tailward to feed the magnetosphere.</p>