Estimating the Rate of Cessation of Magnetospheric Activity in AMPERE Field-Aligned Currents

The decay of magnetospheric activity when driving is turned off (to a minimum) was measured in total field‐aligned current estimates from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) project. Events of distinct northward turnings of the interplanetary magnetic field were identified, with prolonged periods of stable southward driving conditions followed by northward interplanetary magnetic field conditions. All but 4 of 43 identified events exhibit a well‐defined exponential decay in the total hemispheric field‐aligned current following the northward turning. A superposed epoch analysis yields a generic decay constant of 0.9, corresponding to an e‐folding time of 1.1 hr. A statistical analysis of the ensemble of events also reveals a seasonal variation in the decay parameter with faster decay observed in the winter than in the summer hemisphere. This result can be understood in terms of stronger/weaker line tying of the ionospheric foot points of magnetospheric field lines for higher/lower conductivity.publishedVersio

Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from conjugate auroral imaging. This is interpreted as evidence of closed field lines having very asymmetric footpoints associated with the persistent positive y component of the interplanetary magnetic field before and during the event. At the same time, the Super Dual Auroral Radar Network observes the ionospheric nightside convection throat region in both hemispheres. The radar data indicate faster convection toward the dayside in the dusk cell in the Southern Hemisphere compared to its conjugate region. We interpret this as a signature of a process acting to restore symmetry of the displaced closed magnetic field lines resulting in flux tubes moving faster along the banana cell than the conjugate orange cell. The event is analyzed with emphasis on Birkeland currents (BC) associated with this restoring process, as recently described by Tenfjord et al. (2015). Using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during the same conditions as the presented event, the large-scale BC pattern associated with the event is presented. It shows the expected influence of the process of restoring symmetry on BCs. We therefore suggest that these observations should be recognized as being a result of the dynamic effects of restoring footpoint symmetry on closed field lines in the nightside

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

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.