Two-Spacecraft Charged Particle Observations Interpreted in Terms of Electrostatic Potential Drops Along Polar Cap Field Lines

2013 ◽  
pp. 111-118 ◽  
Author(s):  
C.J. Pollock ◽  
C. R. Chappell ◽  
J. L. Horwitz ◽  
J. D. Winningham
Keyword(s):  
Charged Particle ◽  
Electrostatic Potential ◽  
Polar Cap ◽  
Field Lines

Preliminaries

1996 ◽  
Author(s):  
Wolfgang Schmickler
Keyword(s):  
Charged Particle ◽  
Surface Science ◽  
Electrostatic Potential ◽  
Point Charge ◽  
Chemical Interaction ◽  
Dipole Moments ◽  
Great Success ◽  
Definition Of ◽  
Electrified Interfaces ◽  
Electrochemical Interfaces

In this chapter we introduce and discuss a number of concepts that are commonly used in the electrochemical literature and in the remainder of this book. In particular we will illuminate the relation of electrochemical concepts to those used in related disciplines. Electrochemistry has much in common with surface science, which is the study of solid surfaces in contact with a gas phase or, more commonly, with ultrahigh vacuum (uhv). A number of surface science techniques has been applied to electrochemical interfaces with great success. Conversely, surface scientists have become attracted to electrochemistry because the electrode charge (or equivalently the potential) is a useful variable which cannot be well controlled for surfaces in uhv. This has led to a laudable attempt to use similar terminologies for these two related sciences, and to introduce the concepts of the absolute scale of electrochemical potentials and the Fermi level of a redox reaction into electrochemistry. Unfortunately, there is some confusion of these terms in the literature, even though they are quite simple. Electrochemical interfaces are sometimes referred to as electrified interfaces, meaning that potential differences, charge densities, dipole moments, and electric currents occur. It is obviously important to have a precise definition of the electrostatic potential of a phase. There are two different concepts. The outer or Volta potential ψα of the phase a is the work required to bring a unit point charge from infinity to a point just outside the surface of the phase. By "just outside" we mean a position very close to the surface, but so far away that the image interaction with the phase can be ignored; in practice, that means a distance of about 10-5 — 10-3 cm from the surface. Obviously, the outer potential ψα is a measurable quantity. In contrast, the inner or Galvani potential ϕα is defined as the work required to bring a unit point charge from infinity to a point inside the phase α; so this is the electrostatic potential which is actually experienced by a charged particle inside the phase. Unfortunately, the inner potential cannot be measured: If one brings a real charged particle - as opposed to a point charge - into the phase, additional work is required due to the chemical interaction of this particle with other particles in the phase. For example, if one brings an electron into a metal, one has to do not only electrostatic work, but also work against the exchange and correlation energies.

scholarly journals A Geometrical origin of the Pulsar Core and Conal Emissions

1996 ◽  
Vol 160 ◽  
pp. 229-230 ◽  
Author(s):  
R.C. Kapoor ◽  
C.S. Shukre
Keyword(s):  
Polar Angle ◽  
Quadratic Equation ◽  
Magnetic Axis ◽  
Polar Cap ◽  
The Core ◽  
The North ◽  
Polar Caps ◽  
Inclination Angles ◽  
Field Geometry ◽  
Field Lines

We have analysed the dipole magnetic field geometry for the general case of an oblique rotator and have found that open field lines which define the polar cap divide into two branches (Kapoor and Shukre 1996) which appear naturally relevant for distinguishing the core and conal emissions. The polar cap shape is actually determined by a quadratic equation having two roots leading to two values of the polar angle,θ+andθ−with respect to the magnetic axis for a given azimuth φ. For the north pole bothθ+andθ−branches are shown as polar plots in Fig. 1 for various inclination angles α and a typical pulsar period. The discussion of pulsar polar caps hitherto (e.g. Biggs 1990) had not distinguished between theθ+and theθ−solutions. The region defined by theθ+solution is completely contained inside the polar cap. It has a peculiar triangular shape whose lowest vertex is always on the magnetic axis. This naturally suggests an identification of theθ+and theθ−regions with the core and conal emission zones.

scholarly journals Polar cap convection/precipitation states during Earth passage of two ICMEs at solar minimum

2010 ◽  
Vol 28 (4) ◽  
pp. 1023-1042 ◽  
Author(s):  
P. E. Sandholt ◽  
Y. Andalsvik ◽  
C. J. Farrugia
Keyword(s):  
Solar Minimum ◽  
Flow Direction ◽  
Magnetic Clouds ◽  
Polar Cap ◽  
Polar Rain ◽  
Summer Hemisphere ◽  
Northern Winter ◽  
Field Lines ◽  
Ground Magnetic ◽  
Rain Precipitation

Abstract. We report important new aspects of polar cap convection and precipitation (dawn-dusk and inter-hemisphere asymmetries) associated with the different levels of forcing of the magnetosphere by two interplanetary (IP) magnetic clouds on 20 November 2007 and 17 December 2008 during solar minimum. Focus is placed on two intervals of southward magnetic cloud field with large negative By components (Bx=−5 versus 0 nT) and with high and low plasma densities, respectively, as detected by spacecraft Wind. The convection/precipitation states are documented by DMSP spacecraft (Southern Hemisphere) and SuperDARN radars (Northern Hemisphere). The (negative) By component of the cloud field is accompanied by a newly-discovered flow channel (called here FC 2) threaded by old open field lines (in polar rain precipitation) at the dusk and dawn sides of the polar cap in the Northern and Southern Hemispheres, respectively, and a corresponding Svalgaard-Mansurov (S-M) effect in ground magnetic deflections. On 20 November 2007 the latter S-M effect in the Northern winter Hemisphere appears in the form of a sequence of six 5–10 min long magnetic deflection events in the 71–74° MLAT/14:30–16:00 MLT sector. The X-deflections are consistent with the flow direction in FC 2 (i.e. caused by Hall currents) in both IP cloud cases. The presence of a lobe cell and associated polar arcs in the Southern (summer) Hemisphere in the low density (1–2 cm−3) and Bx=0 ICME case is accompanied by the dropout of polar rain precipitation in the dusk-side regime of sunward polar cap convection and inward-directed Birkeland current. The low-altitude observations are discussed in terms of momentum transfer via dynamo processes in the high- and low-latitude boundary layers and Birkeland currents located poleward of the traditional R1-R2 system.

scholarly journals Determination of the zeta potential for highly charged colloidal suspensions

2011 ◽  
Vol 369 (1945) ◽  
pp. 2546-2554 ◽  
Author(s):  
Giovanni Giupponi ◽  
Ignacio Pagonabarraga
Keyword(s):  
Steady State ◽  
Charged Particle ◽  
Zeta Potential ◽  
Electric Fields ◽  
Electrostatic Potential ◽  
Colloidal Suspension ◽  
Colloidal Suspensions ◽  
Ion Concentration ◽  
Lattice Resolution

We compute the electrostatic potential at the surface, or zeta potential ζ , of a charged particle embedded in a colloidal suspension using a hybrid mesoscopic model. We show that, for weakly perturbing electric fields, the value of ζ obtained at steady state during electrophoresis is statistically indistinguishable from ζ in thermodynamic equilibrium. We quantify the effect of counter-ion concentration on ζ . We also evaluate the relevance of the lattice resolution for the calculation of ζ and discuss how to identify the effective electrostatic radius.

scholarly journals Plasma flows, Birkeland currents and auroral forms in relation to the Svalgaard-Mansurov effect

2012 ◽  
Vol 30 (5) ◽  
pp. 817-830 ◽  
Author(s):  
P. E. Sandholt ◽  
C. J. Farrugia
Keyword(s):  
Magnetic Field ◽  
Open Field ◽  
Central Element ◽  
Flow Channel ◽  
Plasma Convection ◽  
Polar Cap ◽  
Flow Channels ◽  
Field Lines ◽  
Current Systems ◽  
Birkeland Currents

Abstract. The traditional explanation of the polar cap magnetic deflections, referred to as the Svalgaard-Mansurov effect, is in terms of currents associated with ionospheric flow resulting from the release of magnetic tension on newly open magnetic field lines. In this study, we aim at an updated description of the sources of the Svalgaard-Mansurov effect based on recent observations of configurations of plasma flow channels, Birkeland current systems and aurorae in the magnetosphere-ionosphere system. Central to our description is the distinction between two different flow channels (FC 1 and FC 2) corresponding to two consecutive stages in the evolution of open field lines in Dungey cell convection, with FC 1 on newly open, and FC 2 on old open, field lines. Flow channel FC 1 is the result of ionospheric Pedersen current closure of Birkeland currents flowing along newly open field lines. During intervals of nonzero interplanetary magnetic field By component FC 1 is observed on either side of noon and it is accompanied by poleward moving auroral forms (PMAFs/prenoon and PMAFs/postnoon). In such cases the next convection stage, in the form of flow channel FC 2 on the periphery of the polar cap, is particularly important for establishing an IMF By-related convection asymmetry along the dawn-dusk meridian, which is a central element causing the Svalgaard-Mansurov effect. FC 2 flows are excited by the ionospheric Pedersen current closure of the northernmost pair of Birkeland currents in the four-sheet current system, which is coupled to the tail magnetopause and flank low-latitude boundary layer. This study is based on a review of recent statistical and event studies of central parameters relating to the magnetosphere-ionosphere current systems mentioned above. Temporal-spatial structure in the current systems is obtained by ground-satellite conjunction studies. On this point we emphasize the important information derived from the continuous ground monitoring of the dynamical behaviour of aurora and plasma convection during intervals of well-organised solar wind plasma and magnetic field conditions in interplanetary coronal mass ejections (ICMEs) during their Earth passage.

scholarly journals Multi-instrument observation of simultaneous polar cap auroras on open and closed magnetic field lines

2017 ◽  
Vol 122 (4) ◽  
pp. 4367-4386 ◽  
Author(s):  
J. A. Reidy ◽  
R. C. Fear ◽  
D. K. Whiter ◽  
B. S. Lanchester ◽  
A. J. Kavanagh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Polar Cap ◽  
Field Lines ◽  
Instrument Observation

scholarly journals Global MHD Simulation of the Weak Southward IMF Condition for Different Time Resolutions

2021 ◽  
Vol 8 ◽  
Author(s):  
Kyung Sun Park
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Three Dimensional ◽  
Slow Solar Wind ◽  
Polar Cap ◽  
Plasma Properties ◽  
Simulation Results ◽  
Field Lines ◽  
The Impact

We performed high-resolution three-dimensional global MHD simulations to determine the impact of weak southward interplanetary magnetic field (IMF) (Bz = −2 nT) and slow solar wind to the Earth’s magnetosphere and ionosphere. We considered two cases of differing, uniform time resolution with the same grid spacing simulation to find any possible differences in the simulation results. The simulation results show that dayside magnetic reconnection and tail reconnection continuously occur even during the weak and steady southward IMF conditions. A plasmoid is generated on closed plasma sheet field lines. Vortices are formed in the inner side of the magnetopause due to the viscous-like interaction, which is strengthened by dayside magnetic reconnection. We estimated the dayside magnetic reconnection which occurred in relation to the electric field at the magnetopause and confirmed that the enhanced electric field is caused by the reconnection and the twisted structure of the electric field is due to the vortex. The simulation results of the magnetic field and the plasma properties show quasi-periodic variations with a period of 9–11 min between the appearances of vortices. Also the peak values of the cross-polar cap potential are both approximately 50 kV, the occurrence time of dayside reconnections are the same, and the polar cap potential patterns are the same in both cases. Thus, there are no significant differences in outcome between the two cases.

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