We review the morphology and dynamics of electrical current systems terrestrial magnetosphere ionosphere. Observations from Active Magnetosphere Planetary Electrodynamics Response Experiment (AMPERE) over three years 2010 to 2012 are employed illustrate variability field-aligned currents that couple ionosphere, on timescales minutes years, in response impact solar wind disturbances changes level illumination polar ionospheres. The is discussed within context occurrence magnetic reconnection...

We used the Lyon-Fedder-Mobarry global magnetohydrodynamics model to study effects of interplanetary magnetic field (IMF) IMF $\mathit{B}_{y}$ component on coupling between solar wind and magnetosphere-ionosphere system. When reconnects with terrestrial $\neq$ 0, flux transport is asymmetrically distributed two hemispheres. describe how induced in closed magnetosphere both dayside nightside present governing equations. The imposes asymmetric forces ionosphere, ionospheric flow are...

[1] Magnetic reconnection in the Earth's magnetotail converts open magnetic flux to closed, producing fast flows plasma sheet. Earthward can thus be used as a proxy for energy and momentum transfer into closed magnetosphere during course of substorm. Characteristics observed before substorm onset provide information on role triggering well sequence substorm-related processes. We use 15 years data obtained by Geotail, Cluster, THEMIS study statistically distribution earthward sheet substorms....

Abstract The interaction between the interplanetary magnetic field (IMF) and geomagnetic at dayside magnetopause leads to transfer of momentum energy which changes magnetospheric configuration, but only after a certain time. In this study we quantify time, advance our understanding causes for delayed response magnetosphere. We reconfiguration time inner magnetosphere IMF B y reversals. A superposed epoch analysis measurements from four Geostationary Operational Environmental Satellite...

In the exploration of global-scale features Earth's aurora, little attention has been given to radial component Interplanetary Magnetic Field (IMF). This study investigates global auroral response in both hemispheres when IMF is southward and lies $\textit{xz}$ plane. We present a statistical average 12-24 magnetic local time (MLT) sector an $\textit{x}$ IMF. Maps intensity for two $\mathit{B}_{x}$ dominated conditions($ \pm $ $\mathit{B}_{x}$) are shown during periods negative...

Abstract. This article describes observations of a bursty bulk flow (BBF) in the outer central plasma sheet. The are made with Cluster satellites, located approximately 19 RE downtail, close to midnight sector Southern Hemisphere. 40–60 s after first detected BBF, there was large bipolar perturbation magnetic field. A Grad-Shafranov reconstruction has revealed that this is created by field-aligned current at flank BBF. Further analysis moments shown BBF properties depleted flux tube....

Magnetic perturbations on ground at high latitudes are directly associated only with the divergence-free component of height-integrated horizontal ionospheric current, $\textbf{J}_{\perp,df}$. Here we show how $\textbf{J}_{\perp,df}$ can be expressed as total current $\textbf{J}_\perp$ minus its curl-free component, latter being completely determined by global Birkeland pattern. Thus in regions where $\textbf{J}_\perp = 0$, distribution alone determines local magnetic perturbation. We...

Abstract We use the Lyon‐Fedder‐Mobarry global magnetohydrodynamics model to study effects of interplanetary magnetic field (IMF) B y component on coupling between solar wind and magnetosphere‐ionosphere system when IMF z >0. describe evolution how a magnetospheric is induced closed lines during these conditions. Starting from dayside lobe reconnection, tension newly reconnected redistribute open flux asymmetrically two hemispheres. This results in asymmetric energy density lobes. Shear...

Abstract Ground magnetic field measurements can be mathematically related to an overhead ionospheric equivalent current. In this study we look in detail at how the global current, calculated using more than 30 years of SuperMAG magnetometer data, changes with sunlight conditions. The calculations are done spherical harmonic analysis quasi‐dipole coordinates, a technique which leads improved accuracy compared previous studies. Sorting data according location terminator and orientation...

During southward interplanetary magnetic field, dayside reconnection will drive the Dungey cycle in magnetosphere, which is manifested as a two-cell convection pattern ionosphere. We address response of ionospheric to changes rate by examining field perturbations at 780 km altitude. The Active Magnetosphere and Planetary Electrodynamics Response Experiment data products derived from Iridium constellation provide global maps perturbations. Cluster just upstream Earth's bow shock have been...

Abstract. Previous studies have shown that conjugate auroral features are displaced in the two hemispheres when interplanetary magnetic field (IMF) has a transverse (Y) component. It also been BY component is induced closed magnetosphere due to asymmetric loading of flux lobes following dayside reconnection IMF Y The lines with azimuthally footpoints map into “banana”-shaped convection cell one hemisphere and an “orange”-shaped other. Due Parker spiral our system most often exposed...

Abstract It is well established that a transverse ( y ) component in the interplanetary magnetic field (IMF) induces B closed magnetosphere through asymmetric loading and/or redistribution of flux. Simultaneous images aurora two hemispheres have revealed conjugate auroral features are displaced longitudinally during such conditions. Although direction and magnitude this displacement show correlations with IMF clock angle dipole tilt, single events large temporal spatial variability...

In this paper we use simultaneous global UV images of the aurora in two hemispheres to study differences polar cap boundary location. We show that northern and southern auroral ovals circumvent same amount magnetic flux, providing additional evidence poleward coincides with open/closed field line boundary. During a period significant flux closure, large asymmetries boundaries developed between hemispheres. The asymmetry was strongest regions where caps contracted most, suggesting emerging...

Abstract Principal component analysis is performed on Birkeland or field‐aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, to determine response of dayside nightside FACs reversals in orientation interplanetary magnetic field (IMF) occurrence substorms. Dayside respond promptly changes IMF B Y , but delayed by up an hour can take 4 hr develop fully, especially during northward IMF. Nightside FAC asymmetries grow substorm...

We have examined three typical substorm growth phase signatures in the magnetotail two hours before near Earth reconnection; namely current sheet thinning, field line stretching and increase lobe magnetic pressure. The reconnection events were identified from situ measurements plasma by Cluster spacecraft. signified high speed flows, often lasting more than one hour. list of contains time intervals with solar wind driving strong intensification auroral westward electrojet, other weak no...

Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift nightside about 3 h, being largest relative reported on conjugate auroral imaging. This is interpreted as evidence closed field lines having very asymmetric footpoints associated with persistent positive $\textit{y}$ component interplanetary magnetic before and during event. At same time, Super Dual Auroral Radar Network observes ionospheric convection throat...

In this paper, we present observations of cold (0-70 eV) plasma density in the magnetotail lobes. The and results are based on 16 years Cluster observation spacecraft potential measurements converted into local densities. Measurements from all four have been used, survey indicates a persistent asymmetry lobe density, with consistently higher densities northern lobe. External influences, such as daily seasonal variations Earth's tilt angle, can introduce temporary north-south asymmetries...

Previous statistical studies have found a close relationship between high‐speed streams and high‐latitude geomagnetic activity. The speed by itself would increase the geoeffectivity of solar wind. But it is also believed that pure Alfvénic fluctuations, often in trailing part streams, play role wind driving activity amplifying north‐south component magnetic field ( B Z ), thereby dayside reconnection electric field. By automatically identifying slow fast analyzing them for more than one...

Abstract Statistical analyses have shown that the sunward component of interplanetary magnetic field, B x (Geocentric Solar Magnetospheric), moderately but significantly affects auroral intensity. These observations been interpreted as signatures a similar field control on Birkeland currents yet to be observed directly. Such control, attributed differences in tension newly opened lines, would lead stronger region 1 (R1) for negative (positive) conditions Northern (Southern) Hemispheres than...

In a recent case study, Borg et al. (2007) reported that an inverted V structure, caused by field‐aligned potential drop of 30 kV producing very strong X‐ray aurora, was found in connection with tail reconnection. However, the situ particle measurements indicated clearly particles responsible for aurora were not accelerated reconnection process. this article, we report predicted auroral intensities thirteen events where Cluster passed through region. For six events, global imaging data...

Abstract It is known that the magnetic field of Earth's closed magnetosphere can be highly displaced from quiet‐day configuration when interacting with interplanetary (IMF), an asymmetry largely controlled by dawn‐dusk component IMF. The corresponding ionospheric convection has revealed footprints in one hemisphere tend to move faster reduce displacement, a process we refer as restoring symmetry. Although influence on return flow symmetry been shown strongly IMF, internal magnetospheric...

During a fortuitous conjunction event observed by Cluster, Double Star TC1, and Magnetometers–Ionospheric Radars–All‐Sky Cameras Large Experiment (MIRACLE) magnetometer stations at almost the same local time, crossings of plasma sheet boundary layer (PSBL) are with 45–50 s delay between two spacecraft located approximately 6 R E apart in X . Taking into account different polarity B Y , Cluster curlometer current density, curl equivalent on ground, associated system resembles that bubble...

Magnetic reconnection in Earth's magnetotail produces fast earthward flows the plasma sheet. Tailward are often observed associated with flows. Both return flow vortices at flanks of an channel and rebound from intense dipolar magnetic field inner magnetosphere have been shown to explain tailward near Earth. We combine sheet measurements Cluster conjugate ground‐based auroral data examine development signatures during a substorm onset. show for first time observations ionospheric that appear...