When Size Matters: Large Electrodes Induce Greater Stimulation-related Cutaneous Discomfort Than Smaller Electrodes at Equivalent Current Density

2014 ◽  
Vol 7 (3) ◽  
pp. 460-467 ◽  
Author(s):  
Zsolt Turi ◽  
Géza Gergely Ambrus ◽  
Kerrie-Anne Ho ◽  
Titas Sengupta ◽  
Walter Paulus ◽  
...  
Keyword(s):  
Current Density ◽  
Equivalent Current

scholarly journals A model for estimating the relation between the Hall to Pedersen conductance ratio and ground magnetic data derived from CHAMP satellite statistics

2007 ◽  
Vol 25 (3) ◽  
pp. 721-736 ◽  
Author(s):  
L. Juusola ◽  
O. Amm ◽  
K. Kauristie ◽  
A. Viljanen
Keyword(s):  
Current Density ◽  
Geomagnetic Latitude ◽  
Magnetic Data ◽  
Equivalent Current ◽  
Champ Satellite ◽  
Long Time ◽  
Conductance Ratio ◽  
Ground Magnetic ◽  
Eiscat Radar ◽  
Magnetic Satellite

Abstract. The goal of this study is to find a way to statistically estimate the Hall to Pedersen conductance ratio α from ground magnetic data. We use vector magnetic data from the CHAMP satellite to derive this relation. α is attained from magnetic satellite data using the 1-D Spherical Elementary Current Systems (SECS). The ionospheric equivalent current density can either be computed from ground or satellite magnetic data. Under the required 1-D assumption, these two approaches are shown to be equal, which leads to the advantage that the statistics are not restricted to areas covered by ground data. Unlike other methods, using magnetic satellite measurements to determine α ensures reliable data over long time sequences. The statistical study, comprising over 6000 passes between 55° and 76.5° northern geomagnetic latitude during 2001 and 2002, is carried out employing data from the CHAMP satellite. The data are binned according to activity and season. In agreement with earlier studies, values between 1 and 3 are typically found for α. Good compatibility is found, when α attained from CHAMP data is compared with EISCAT radar measurements. The results make it possible to estimate α from the east-west equivalent current density Jφ; [A/km]: α=2.07/(36.54/|Jφ|+1) for Jφ<0 (westward) and α=1.73/(14.79/|Jφ+1) for Jφ0 (eastward). Using the same data, statistics of ionospheric and field-aligned current densities as a function of geomagnetic latitude and MLT are included. These are binned with respect to activity, season and IMF BZ and BY. For the first time, all three current density components are simultaneously studied this way on a comparable spatial scale. With increasing activity, the enhancement and the equatorward expansion of the electrojets and the R1 and R2 currents is observed, and in the nightside, possible indications of a Cowling channel appear. During southward IMF BZ, the electrojets and the R1 and R2 currents are stronger and clearer than during northward BZ. IMF BY affects the orientation of the pattern.

On the Passivity of Iron★

CORROSION ◽  
1955 ◽  
Vol 11 (7) ◽  
pp. 32-36 ◽  
Author(s):  
KARL FRIEDRICH BONHOEFFER
Keyword(s):  
Nitric Acid ◽  
Current Density ◽  
Nitrous Acid ◽  
Redox System ◽  
Equivalent Current ◽  
Passivation Current Density ◽  
Passivation Potential

Abstract Descriptions are given of the various phenomena associated with the passivation and reactivation of iron in concentrated nitric acid. Covered are apparent and true passivation potential, apparent and true passivation current density, passivity producing and passivity maintaining current density. Information is given also on equivalent current density in a redox system, the role of nitrous acid in passivation by concentrated nitric acid, the corrosion of passive iron, refractoriness toward activation, rhythms and activity waves.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

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