How the IMF By\mathit{B}_{y} Induces a Local By\mathit{B}_{y} Component During Northward IMF Bz\mathit{B}_{z} and Characteristic Timescales

We use the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study the effects of the interplanetary magnetic field (IMF) $\mathit{B}_{y}$ component on the coupling between the solar wind and magnetosphere-ionosphere system when IMF $\mathit{B}_{z}$ $>$0. We describe the evolution of how a magnetospheric $\mathit{B}_{y}$ component is induced on closed field lines during these conditions. Starting from dayside lobe reconnection, the magnetic tension on newly reconnected field lines redistribute the open flux asymmetrically between the two hemispheres. This results in asymmetric magnetic energy density in the lobes. Shear flows are induced to restore equilibrium, and these flows are what effectively induces a local $\mathit{B}_{y}$ component. We show the radial dependence of the induced $\mathit{B}_{y}$ and compare the results to the induced $\mathit{B}_{y}$ during southward IMF conditions. We also show the response and reconfiguration time of the inner magnetosphere to IMF $\mathit{B}_{y}$ reversals during northward IMF $\mathit{B}_{z}$. A superposed epoch analysis of magnetic field measurements from seven Geostationary Operational Environmental Satellite spacecraft at different local times both for negative-to-positive and positive-to-negative IMF $\mathit{B}_{y}$ reversals is presented. We find that the induced $\mathit{B}_{y}$ responds within 16 min of the arrival of IMF $\mathit{B}_{y}$ at the bow shock, and it completely reconfigures within 47 min

Spatial Resolution in Inverse Problems: The EZIE Satellite Mission

Under embargo until: 2023-11-16Inverse modeling has become one of the primary methods for studying ionospheric electrodynamics, especially when using magnetic field measurements from below the ionosphere. We present a method for quantifying the spatial resolution in an inverse model for non-uniformly sampled spatial data. This method provides a tool for assessing if a model can resolve the physical phenomena of interest. We quantify the spatial resolution for the Spherical Elementary Current System basis functions to model the ionospheric dynamics. Our results apply to models with spatially confined model parameters, unlike spherical harmonics where the model parameters describe the amplitude of global surface functions. The method is demonstrated for the upcoming Electrojet Zeeman Imaging Explorer cubesat mission which will provide spatially distributed remote sensing measurements of the magnetic field in the mesosphere. We show that, including measurements from a single ground magnetometer can significantly improve the spatial resolution. However, the impact of including a ground magnetometer depends on the relative position of the station with respect to the mesospheric measurements. In addition, a method for reducing two regularization parameters to one is presented. Reducing the amount of regularization parameters simplifies the optimization problem and facilitates a fair comparison between the models with and without a ground magnetometer.publishedVersio

The Lompe code: A Python toolbox for ionospheric data analysis

A recent paper by Laundal et al. (2022c) presented a new technique to combine all available measurements of polar ionospheric electrodynamics; magnetic field measurements from ground and space, ionospheric convection data from radars and satellites, and conductance measurements; to a full 2D map within analysis regions of arbitrary resolution and extent. The technique, called Local Mapping of Polar Ionospheric Electrodynamics (Lompe), is implemented in Python (Laundal et al., 2022a). The Lompe technique combines spherical elementary current system analysis, finite element analysis on a cubed-sphere projection, the use of empirical models like the International Geomagnetic Reference Field, and visualization tools. In this paper, we go through these different components of the Lompe code and show how they are useful on their own, for example in the analysis of ground magnetometer data or data from the upcoming Electrojet Zeeman Imaging Explorer mission. We also demonstrate how to use the Lompe code to produce a coherent picture of ionospheric electrodynamics

Background removal from global auroral images: Data-driven dayglow modeling

Global images of auroras obtained by cameras on spacecraft are a key tool for studying the near-Earth environment. However, the cameras are sensitive not only to auroral emissions produced by precipitating particles, but also to dayglow emissions produced by photoelectrons induced by sunlight. Nightglow emissions and scattered sunlight can contribute to the background signal. To fully utilize such images in space science, background contamination must be removed to isolate the auroral signal. Here we outline a data-driven approach to modeling the background intensity in multiple images by formulating linear inverse problems based on B-splines and spherical harmonics. The approach is robust, flexible, and iteratively deselects outliers, such as auroral emissions. The final model is smooth across the terminator and accounts for slow temporal variations and large-scale asymmetries in the dayglow. We demonstrate the model by using the three far ultraviolet cameras on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission. The method can be applied to historical missions and is relevant for upcoming missions, such as the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission

Liquid electrolytes for lithium-ion accumulators

Cieľom tejto diplomovej práce bolo meranie elektrickej vodivosti a dynamickej viskozity elektrolytov. Na základe týchto meraní bolo možné overiť Waldenov vzťah medzi meranými veličinami. Boli použité elektrolyty na bázy sulfolanu v kombinácií s propylenkarbonátom a so soľou. Diplomová práca sa tiež zaoberá meraním dielektrických vlastností elektrickou metódou a optickou metódou pomocou refraktometrie. Taktiež boli stanovené body tuhnutia zmesi sulfolanu a propylenkarbonátu pomocou kryoskopie.The aim of this master´s thesis was the measurement of electrical conductivity and dynamic viscosity of the electrolytes. Based on these measurements to verify Walden theorem between measured variables. Electrolytes were used on sulfolane base in combination with propylene carbonate and salt. The thesis also deals with the measuring method of dielectric properties of electrical and optical method with a refractometer. The freezing point of combination of sulfolan and propylene carbonate were determined by cryoscopy.

Evolution of Asymmetrically Displaced Footpoints During Substorms

It is well established that a transverse (y) component in the interplanetary magnetic field (IMF) induces a By component in the closed magnetosphere through asymmetric loading and/or redistribution of magnetic flux. Simultaneous images of the aurora in the two hemispheres have revealed that conjugate auroral features are displaced longitudinally during such conditions. Although the direction and magnitude of this displacement show correlations with IMF clock angle and dipole tilt, single events show large temporal and spatial variability of this displacement. For instance, we know little about how the displacement changes during a substorm. A previous case study demonstrated that displaced auroral forms, associated with the prevailing IMF orientation, returned to a more symmetric configuration during the expansion phase of two substorms. Using the far ultraviolet cameras on board the Imager for Magnetopause‐to‐Aurora Global Exploration and Polar satellites, we have identified multiple events where conjugate auroral images are available during periods with substorm activity and IMF By≠0. We identify conjugate auroral features and investigate how the asymmetry evolves during the expansion phase. We find that the system returns to a more symmetric state in the events with a clear increase in the nightside reconnection rate and that the displacement remains unchanged in the events with little or no net closure of open magnetic flux. The return to a more symmetric state can therefore be interpreted as the result of increased reconnection rate in the magnetotail during the expansion phase, which reduces the asymmetric lobe pressure

Observations of Asymmetric Lobe Convection for Weak and Strong Tail Activity

In this study we use high‐quality convection data from the Electron Drift Instrument on board Cluster to investigate how near‐Earth tail activity affects the average convection pattern in the magnetotail lobes when the interplanetary magnetic field has a dominating east‐west (By) component. Two different proxies have been used to represent different levels of reconnection in the near‐Earth tail: The value of the AL index and the substorm phases identified by the Substorm Onsets and Phases from Indices of the Electrojet algorithm. We find that the convection changes from a dominantly YGSM direction, but opposite in the two hemispheres, to a flow oriented more toward the plasma sheet, as the north‐south component of the convection increases when reconnection enhances in the near Earth tail. This result is consistent with recent observations of the convection in the ionosphere, which suggest that the nightside convection pattern becomes more north‐south symmetric when tail reconnection increases. This is also supported by simultaneous auroral observations from the two hemispheres, which shows that conjugate auroral features become more symmetric during substorm expansion phase. The reduced asymmetry implies that the asymmetric pressure balance in the lobes is altered during periods with strong reconnection in the near‐Earth tail