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.

Impact of Storm-Enhanced Density (SED) on Ion Upflow Fluxes During Geomagnetic Storm

The impact of the dynamic evolution of the Storm-Enhanced Density (SED) on the upward ion fluxes during the March 06, 2016 geomagnetic storm is studied using comprehensive multi-scale datasets. This storm was powered by a Corotating Interaction Region (CIR), and the minimum Sym-H reached ∼−110 nT. During the ionospheric positive storm phase, the SED formed and the associated plume and polar cap patches occasionally drifted anti-sunward across the polar cap. When these high-density structures encountered positive vertical flows, large ion upward fluxes were produced, with the largest upward flux reaching 3 × 1014 m−2s−1. These upflows were either the type-1 ion upflow associated with fast flow channels, such as the subauroral polarization stream (SAPS) channel, or the type-2 ion upflow due to soft particle precipitations in the cusp region. The total SED-associated upflow flux in the dayside cusp can be comparable to the total upflow flux in the nightside auroral zone despite the much smaller cusp area compared with the auroral zone. During the ionospheric negative storm phase, the ionospheric densities within the SED and plume decreased significantly and thus led to largely reduced upward fluxes. This event analysis demonstrates the critical role of the ionospheric high-density structures in creating large ion upward fluxes. It also suggests that the dynamic processes in the coupled ionosphere-thermosphere system and the resulting state of the ionospheric storm are crucial for understanding the temporal and spatial variations of ion upflow fluxes and thus should be incorporated into coupled geospace models for improving our holistic understanding of the role of ionospheric plasma in the geospace system.

Observed Auroral Ovals Secular Variation Inferred from Auroral Boundary Data

We analyze the auroral boundary corrected geomagnetic latitude provided by the Auroral Boundary Index (ABI) database to estimate long-term changes of core origin in the area enclosed by this boundary during 1983–2016. We design a four-step filtering process to minimize the solar contribution to the auroral boundary temporal variation for the northern and southern hemispheres. This process includes filtering geomagnetic and solar activity effects, removal of high-frequency signal, and additional removal of a ~20–30-year dominant solar periodicity. Comparison of our results with the secular change of auroral plus polar cap areas obtained using a simple model of the magnetosphere and a geomagnetic core field model reveals a decent agreement, with area increase/decrease in the southern/northern hemisphere respectively for both observations and model. This encouraging agreement provides observational evidence for the surprising recent decrease of the auroral zone area.

Auroral zone over the last 3000 years

We investigated the global shape of the auroral zone over the last 3000 years using paleomagnetism CALS models. A similar method of apex latitude as proposed by Oguti (1993a; 1993b) was adopted to draw the auroral zone. The Oguti method is examined using 50-year data from ground-based magnetometers located at high latitudes, using IGRF models. The equatorward auroral limit during magnetic storms was also examined using more than 20 years data from the DMSP satellites. The reconstructed auroral zone and the equatorward auroral limit were compared with the historical auroral witness records for 1200 AD and 1800 AD. We concluded that the 12th and 18th centuries were excellent periods for Japan and the United Kingdom, respectively, to observe auroras over the last 3000 years.

Spacecraft charging of JUICE in the auroral zone of Ganymede

<p>Ganymede is the only moon in our Solar System known to have its own global magnetic field, which generates a miniature moon magnetosphere inside the Jovian magnetosphere. Due to this unique characteristic of Ganymede, its auroral zone is also of particular scientific interest, as it is the only known example of this specific kind of interaction. The JUICE spacecraft will orbit Ganymede for almost a year, with a high inclination orbit with multiple auroral zone crossings. JUICE will study the auroral zone of Ganymede in more detail than ever before, providing both in-situ and remote sensing observations.</p> <p>In this work, we use Spacecraft Plasma Interaction Software (SPIS) simulations to study the spacecraft charging of JUICE in the auroral zone. Hubble Space Telescope observations of the aurora of Ganymede show localized regions of bright spots superimposed on a continuous background emission (e.g. Feldman et al. 2000, Eviatar et al. 2001). In order to produce bright auroras, the electron population needs to be accelerated up to hundreds of eV (Eviatar et al. 2001). Preliminary simulation results, using an auroral electron population with temperature T<sub>e</sub> = 200 eV and density n<sub>e</sub> = 300 cm<sup>-3</sup>, shows frame charging (i.e. spacecraft ground) of around 10 V and differential charging of around 30 V. High frame and differential potentials can cause disturbances in both particle and electric field measurements and prevent accurate characterization of the environment. Since the auroral zone of Ganymede is of particular scientific interest, it is important to study and prepare for this kind of disturbances.</p> <p> </p> <p>References</p> <p>D. Feldman et al., HST/STIS ultraviolet imaging of polar aurora on Ganymede, The Astrophysical Journal, 535(2), 2000</p> <p>A. Eviatar et al., Excitation of the Ganymede ultraviolet aurora, The Astrophysical Journal, 555(2), 2001</p>

Statistics of Large Impulsive Magnetic Events In The Auroral Zone

Impulsive geomagnetic variations, latitudinally localized to the auroral zone, have been observed over the period from 2015-2020. These impulsive events have been observed mostly in the pre-midnight sector as upward vertical perturbations. Diurnal variations in geomagnetically-triggered harmonic distortion events observed in Hydro-Québec's Système de Mesure de Décalage (SMDA) synchrophasor measurement system have been found to have a peak in the number of events around midnight. This was similar to diurnal rates of occurrence of negative B z geomagnetic impulsive events, observed at nearby auroral zone magnetometers. Superposed epoch analysis demonstrates the impulses are regularly associated with increases in harmonic distortion observed at a nearby substation transformer. These large impulsive vertical geomagnetic perturbations appear to be local vortical ionospheric disturbances.

Geomagnetic data recovery approach based on the concept of digital twins

There is no ground-based magnetic station or observatory that guarantees the quality of information received and transmitted to it. Data gaps, outliers, and anomalies are a common problem affecting virtually any ground-based magnetometer network, creating additional obstacles to efficient processing and analysis of experimental data. It is possible to monitor the reliability and improve the quality of the hardware and soft- ware modules included in magnetic stations by develop- ing their virtual models or so-called digital twins. In this paper, using a network of high-latitude IMAGE magnetometers as an example, we consider one of the possible approaches to creating such models. It has been substantiated that the use of digital twins of magnetic stations can minimize a number of problems and limitations associated with the presence of emissions and missing values in time series of geomagnetic data, and also provides the possibility of retrospective forecasting of geomagnetic field parameters with a mean square error (MSE) in the auroral zone up to 11.5 nT. Integration of digital twins into the processes of collecting and registering geomagnetic data makes the automatic identification and replacement of missing and abnormal values possible, thus increasing, due to the redundancy effect, the fault tolerance of the magnetic station as a data source object. By the example of the digital twin of the station “Kilpisjärvi” (Finland), it is shown that the proposed approach implements recovery of 99.55 % of annual information, while 86.73 % with M not exceeding 12 nT.

Geomagnetic data recovery approach based on the concept of digital twins

There is no ground-based magnetic station or observatory that guarantees the quality of information received and transmitted to it. Data gaps, outliers, and anomalies are a common problem affecting virtually any ground-based magnetometer network, creating additional obstacles to efficient processing and analysis of experimental data. It is possible to monitor the reliability and improve the quality of the hardware and soft- ware modules included in magnetic stations by develop- ing their virtual models or so-called digital twins. In this paper, using a network of high-latitude IMAGE magnetometers as an example, we consider one of the possible approaches to creating such models. It has been substantiated that the use of digital twins of magnetic stations can minimize a number of problems and limitations associated with the presence of emissions and missing values in time series of geomagnetic data, and also provides the possibility of retrospective forecasting of geomagnetic field parameters with a mean square error (MSE) in the auroral zone up to 11.5 nT. Integration of digital twins into the processes of collecting and registering geomagnetic data makes the automatic identification and replacement of missing and abnormal values possible, thus increasing, due to the redundancy effect, the fault tolerance of the magnetic station as a data source object. By the example of the digital twin of the station “Kilpisjärvi” (Finland), it is shown that the proposed approach implements recovery of 99.55 % of annual information, while 86.73 % with M not exceeding 12 nT.