Comparison of different techniques to estimate the direction of the Poynting vector of EMIC emissions

2021 ◽  
Author(s):  
Benjamin Grison ◽  
Ondrej Santolik
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Poynting Vector ◽  
Source Region ◽  
Transverse Component ◽  
Equatorial Region ◽  
Magnetic Equator ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Single Plane

<p>Electromagnetic Ion Cyclotron (EMIC) waves usually grow in the inner magnetosphere from hot ion temperature anisotropy. The main source region is located close to the magnetic equator and there is a secondary EMIC source region off the magnetic equator in the dayside magnetosphere. The source region can be identified using measurements of the Poynting vector direction.</p><p>The Poynting vector is ideally derived from the measurement of 3 components of the wave electric field and 3 components of components of the wave magnetic field. However, spinning spacecraft often have only two long mutually perpendicular electric antennas in the spin plane, deployed by the centrifugal force. The third antenna, when present, is usually shorter owing to difficulties of deploying a antenna along the spin axis.</p><p>Estimations of the Poynting vector from measurements of three magnetic field components and two electric field components can be obtained assuming the presence of a single plane wave (and thus perpendicularity of the electric field and the magnetic field vectors, according to the Faraday’s law), following the method developed by Loto'aniu et al. (2005). Applying this method to Cluster data, Allen et al. (2013) found the presence of bidirectional EMIC emissions off the magnetic equatorial region.</p><p>Another technique proposed earlier by Santolík et al. (2001) considers the phase shift estimation between the electric signals from each antenna and synthetic perpendicular magnetic field components obtained from the three-dimensional measurements. The method is based on cross-spectral estimates in the frequency domain and can be used to estimate sign of each component of the Poynting vector. Using this technique Grison et al. (2016) showed the importance of the transverse component of the EMIC emissions far from the source region.</p><p>We compare these methods for different events to check how the results of these two techniques differ. We also discuss what we can learn about the EMIC source region from these measurements.</p>

scholarly journals Search for magnetically quiet CHAMP polar passes and the characteristics of ionospheric currents during the dark season

2006 ◽  
Vol 24 (11) ◽  
pp. 2997-3009 ◽  
Author(s):  
P. Ritter ◽  
H. Lühr
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Transverse Field ◽  
Transverse Component ◽  
Local Times ◽  
Time Interval ◽  
Polar Regions ◽  
Ionospheric Currents ◽  
Ionospheric Conductivity ◽  
Field Modelling

Abstract. The magnetic activity at auroral latitudes is strongly dependent on season. During the dark season, when the solar zenith angle in the polar region is larger than 100° at all local times, the ionospheric conductivity is much reduced, and generally low activity is encountered. These time intervals are of special interest for the main field modelling, because then the geomagnetic field readings, in particular the field magnitude, are only slightly affected by ionospheric currents. Based on CHAMP data, this study examines how these quiet periods are reflected in the different magnetic field components. The peak FAC density is used as a possible proxy for the deviation of the total field. As a second option, the transverse field component, which is aligned with the auroral oval, is investigated, because it presents a measure for the FAC total current. Correlation analyses with the scalar residuals are performed and both proxies are tested for their suitability of predicting the intensity of the auroral electrojet during the dark polar seasons. The indicators based on the local FAC strength or on the amplitude of the transverse component show a reasonable correlation with the electrojet intensity for these periods, but fail when limited to small amplitudes. The predictability improves considerably if the time sector is limited to dayside hours (08:00–16:00 MLT). As the activity at high latitudes is strongly controlled by the solar wind input, we also consider IMF quantities which may support very quiet conditions. Correlations of the magnetic field scalar residuals with the merging electric field are strongest if only passes in the dayside sector are considered. Best selection results for quiet passes are obtained by combining four conditions: dark season, small average merging electric field, Em<0.8 mV/m, absence of peak values of Em>1.2 mV/m during a time interval of 40 min centred at the polar crossing, and limitation to the dayside sector (08:00–16:00 MLT). The set of quiet polar passes identified by these criteria may be used beneficially in crustal field modelling of the polar regions.

The inhomogeneous ion temperature anisotropy instabilities of magnetic-field-aligned plasma sheared flow

2016 ◽  
Vol 23 (11) ◽  
pp. 112122 ◽  
Author(s):  
V. V. Mikhailenko ◽  
V. S. Mikhailenko ◽  
Hae June Lee
Keyword(s):  
Magnetic Field ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Sheared Flow

scholarly journals Effect of electron temperature in a magnetized plasma sheath using kinetic trajectory simulation

BIBECHANA ◽  
2021 ◽  
Vol 18 (1) ◽  
pp. 58-66
Author(s):  
R Chalise ◽  
S K Pandit ◽  
G Thakur ◽  
R Khanal
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electron Temperature ◽  
Electron Emission ◽  
Plasma Sheath ◽  
Magnetized Plasma ◽  
Total Charge ◽  
Ion Temperature ◽  
Trajectory Simulation ◽  
Total Charge Density

The understanding of the properties of magnetized plasma sheath has been various beneficial applications in surface treatment, electron emission gun, ion implantation, and nuclear fusion, etc. The effect of electron temperature on the magnetized plasma sheath has been studied for a fixed magnetic field and ion temperature. It has been observed that various plasma sheath parameters can be prominently altered by the varying temperature of the electron. The density of ion is influenced more by the change in electron temperature rather than the electron density. The temperature of the electron has a great effect at the wall, when electron temperature increases, the ion and electron densities at the wall decreases. This shows the potential at the wall also decreases follows the Poisson’s equation. Similarly, the electric field also decreases but total charge density increases when the electron temperature is increased. BIBECHANA 18 (2021) 58-66

scholarly journals Results of an intercomparison for electric field strength measurements within the German calibration service

2017 ◽  
Vol 15 ◽  
pp. 243-248
Author(s):  
Reiner Pape ◽  
Uwe Karsten ◽  
Frank-Michael Lindner ◽  
Frank Rittmann ◽  
Joachim von Freeden ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Poynting Vector ◽  
Primary Standard ◽  
National Metrology Institute ◽  
Small Field ◽  
The Magnetic Field ◽  
Commercial Field

Abstract. In this paper we discuss the results of an intercomparison for electric field strength measurements within the German Calibration Service (Deutscher Kalibrierdienst – DKD). The comparison has been carried out on the field strength value required to reach a display reading of 20 V m−1 of the field probes for frequencies between 100 MHz and 18 GHz. Five laboratories joined the intercomparison including the Physikalisch-Technische Bundesanstalt (PTB), the German National Metrology Institute that keeps the primary standard for electric field strength. As measurement artefacts both a small 1-axis probe usually used as transfer sensor at PTB and a larger 3-axis commercial field probe have been used. While the results agree well for the small field probe and when the larger commercial 3-axis field probe is oriented in the direction of the magnetic field, larger deviations occur, when the larger 3-axis field probe is oriented into the direction of the Poynting vector of the calibration field.

scholarly journals Nonlinear low-frequency wave aspect of foreshock density holes

2008 ◽  
Vol 26 (12) ◽  
pp. 3707-3718 ◽  
Author(s):  
N. Lin ◽  
E. Lee ◽  
F. Mozer ◽  
G. K. Parks ◽  
M. Wilber ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Plane Electromagnetic Wave ◽  
Timing Analysis ◽  
Low Frequency ◽  
Resonant Interaction ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Frequency Wave ◽  
Wave Nature ◽  
The Waves

Abstract. Recent observations have uncovered short-duration density holes in the Earth's foreshock region. There is evidence that the formation of density holes involves non-linear growth of fluctuations in the magnetic field and plasma density, which results in shock-like boundaries followed by a decrease in both density and magnetic field. In this study we examine in detail a few such events focusing on their low frequency wave characteristics. The propagation properties of the waves are studied using Cluster's four point observations. We found that while these density hole-structures were convected with the solar wind, in the plasma rest frame they propagated obliquely and mostly sunward. The wave amplitude grows non-linearly in the process, and the waves are circularly or elliptically polarized in the left hand sense. The phase velocities calculated from four spacecraft timing analysis are compared with the velocity estimated from δE/δB. Their agreement justifies the plane electromagnetic wave nature of the structures. Plasma conditions are found to favor firehose instabilities. Oblique Alfvén firehose instability is suggested as a possible energy source for the wave growth. Resonant interaction between ions at certain energy and the waves could reduce the ion temperature anisotropy and thus the free energy, thereby playing a stabilizing role.

scholarly journals Latitudinal profile of the ionospheric disturbance dynamo magnetic signature: comparison with the DP2 magnetic disturbance

2009 ◽  
Vol 27 (9) ◽  
pp. 3523-3536 ◽  
Author(s):  
K. Z. Zaka ◽  
A. T. Kobea ◽  
P. Assamoi ◽  
O. K. Obrou ◽  
V. Doumbia ◽  
...  
Keyword(s):  
Electric Field ◽  
Magnetic Storm ◽  
Current Flow ◽  
Ionospheric Disturbance ◽  
Equatorial Region ◽  
Magnetic Equator ◽  
Magnetic Disturbance ◽  
Magnetic Signature ◽  
Low Latitudes ◽  
Latitudinal Profile

Abstract. During magnetic storms, the auroral electrojets intensification affects the thermospheric circulation on a global scale. This process which leads to electric field and current disturbance at middle and low latitudes, on the quiet day after the end of a storm, has been attributed to the ionospheric disturbance dynamo (Ddyn). The magnetic field disturbance observed as a result of this process is the reduction of the H component amplitude in the equatorial region which constitutes the main characteristic of the ionospheric disturbance dynamo process, associated with a westward electric current flow. The latitudinal profile of the Ddyn disturbance dynamo magnetic signature exhibits an eastward current at mid latitudes and a westward one at low latitudes with a substantial amplification at the magnetic equator. Such current flow reveals an "anti-Sq" system established between the mid latitudes and the equatorial region and opposes the normal Sq current vortex. However, the localization of the eastward current and consequently the position and the extent of the "anti-Sq" current vortex changes from one storm to another. Indeed, for a strong magnetic storm, the eastward current is well established at mid latitudes about 45° N and for a weak magnetic storm, the eastward current is established toward the high latitudes (about 60° N), near the Joule heating region, resulting in a large "anti-Sq" current cell. The latitudinal profile of the Ddyn disturbance as well as the magnetic disturbance DP2 generated by the mechanism of prompt penetration of the magnetospheric convection electric field in general, show a weak disturbance at the low latitudes with a substantial amplification at the magnetic equator. Due to the intensity of the storm, the magnitude of the DP2 appears higher than the Ddyn over the American and Asian sector contrary to the African sector.

Ion temperature anisotropy due to perpendicular heating by Alfvén wave propagating along magnetic field lines

2016 ◽  
Vol 23 (9) ◽  
pp. 092903 ◽  
Author(s):  
C.-R. Choi ◽  
M.-H. Woo ◽  
K. Dokgo ◽  
K.-W. Min ◽  
D.-Y. Lee ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Alfven Wave ◽  
Ion Temperature ◽  
Temperature Anisotropy ◽  
Field Lines

GRACE-FO and Swarm integrated data analysis reveals ionospheric disturbances on the accelerometer measurements

2020 ◽  
Author(s):  
Myrto Tzamali ◽  
Athina Peidou ◽  
Spiros Pagiatakis
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Poynting Vector ◽  
Field Measurements ◽  
Temporal Variations ◽  
Space Environment ◽  
The Earth ◽  
Leo Satellites ◽  
The Magnetic Field

&lt;p&gt;Low Earth Orbit (LEO) satellites are subject to numerous disturbances related to the Earth&amp;#8217;s upper ionosphere. Perturbations induced by the activity of the electromagnetic field (EM) at the upper ionospheric layers have not been fully understood yet. This study focuses on the disturbances shown on GRACE-FO accelerometer measurements when the EM field was disturbed by an intense geomagnetic storm occurred on August 2018. A thorough analysis of the accelerometer measurements of GRACE-C as well as the magnetic and electric field measurements from Swarm constellation is conducted, to enlighten their impulse-response relationship. We derive the temporal variations of the magnetic field by removing the main static field and we calculate the Poynting vector employing the Swarm magnetic field measurements and electric field data, by implementing rigorous data analyses to analyze the spatiotemporal characteristics of the energy flow of the electromagnetic field. Results show that GRACE-C accelerometer measurements are highly disturbed in the higher latitudes especially near the auroral regions. The signature of the spatial temporal variations of the magnetic field and the Poynting vector demonstrates very similar behaviour with GRACE-C disturbances. Cross wavelet analysis between Poynting vector and GRACE-C accelerometer disturbances shows a very strong coherence. With the two LEO missions, i.e. GRACE-FO and Swarm, orbiting the Earth in very similar orbits, further analysis towards integrating their measurements will enhance our understanding of the interaction of LEO satellites with the space environment and how this interaction is depicted in their measurements.&lt;/p&gt;

Magnetic structure of ionizing shock waves Part 1. Skew shocks

1972 ◽  
Vol 7 (1) ◽  
pp. 133-155 ◽  
Author(s):  
B. P. Leonard
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Shock Waves ◽  
Magnetic Energy ◽  
Diffusion Mechanism ◽  
Field Vector ◽  
Transverse Component ◽  
Ohmic Dissipation ◽  
Single Plane ◽  
Wave Normal

Initially non-conducting gas is ionized by a thin viscous shock wave. Upstream there can be no magnetohydrodynamic interaction because of the zero conductivity, but the conducting downstream region may have a magneticStructure which interacts with the flow variables. A theoretical analysis is made in the zeromagnetic-Prandtl-number (‘non-viscous ’) limit, i.e. ohmic dissipation is the dominant diffusion mechanism. Unlike magnetohydrodynamic shocks in a pre-ionized gas, ionizing shock waves are not necessarily plane-polarized. Thus ‘skew ’ shock structures can exist, in which the upstream and downstream magnetic field vectors and the shock wave normal do not all lie in a single plane. Explicit solutions are given for typical values of the governing parameters, showing how the magnetic field vector rotates about the shock wave normal as its transverse component changes in magnitude through the shock layer. Skew shocks are necessarily sub-Alfvénic downstream. Unlike the pre-ionized case, the range of trans-Alfvénic shock waves is not excluded, since these shocks can absorb Alfvén waves within their structure. With strong magnetic fields it is possible to achieve very high downstream temperatures by Joule heating. Alternatively, in some cases, magnetic energy can be fed into directed kinetic energy, producing an overall expansion shock.

scholarly journals On the characterization of magnetic reconnection in global MHD simulations

2006 ◽  
Vol 24 (11) ◽  
pp. 3059-3069 ◽  
Author(s):  
T. V. Laitinen ◽  
P. Janhunen ◽  
T. I. Pulkkinen ◽  
M. Palmroth ◽  
H. E. J. Koskinen
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Poynting Vector ◽  
Diffusion Region ◽  
Characterization Methods ◽  
Mhd Simulations ◽  
Open Field Line ◽  
Field Lines ◽  
Definition Of

Abstract. The conventional definition of reconnection rate as the electric field parallel to an x-line is problematic in global MHD simulations for several reasons: the x-line itself may be hard to find in a non-trivial geometry such as at the magnetopause, and the lack of realistic resistivity modelling leaves us without reliable non-convective electric field. In this article we describe reconnection characterization methods that avoid those problems and are practical to apply in global MHD simulations. We propose that the reconnection separator line can be identified as the region where magnetic field lines of different topological properties meet, rather than by local considerations. The global convection associated with reconnection is then quantified by calculating the transfer of mass, energy or magnetic field across the boundary of closed and open field line regions. The extent of the diffusion region is determined from the destruction of electromagnetic energy, given by the divergence of the Poynting vector. Integrals of this energy conversion provide a way to estimate the total reconnection efficiency.

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