307 research outputs found
Earth Potential Electrodes in Permafrost and Tundra
Introduction : During the past two years, the authors installed a number of electrodes
in the permafrost and tundra area of Point Barrow to obtain earth potential
data. As ground temperatures decreased during the winter, the resistances of
the first set of electrodes increased by several orders of magnitude and thus
became useless. A second set of electrodes, with sodium chloride incorporated
in the fill, proved entirely adequate for recording earth potentials. The installations
and procedure for determining electrode resistances are described
herein. Electrode resistance data versus time and ground temperatures are also
presented.Ye
Rapid Fluctuations in Earth-Currents at College
An unusual type of earth-current variation is regularly observed in the
College records. The phenomena consist of more or less regular fluctuations
with range from a few mv/km to more than 1000 mv/km, and periods ranging upwards
from 6 seconds. The fluctuations may continue from a few minutes to
several hours. They have a strong diurnal variation at College with a broad
maximum at 0600 local time. The fluctuations also occur at a site about 100 km
southeast of College, but are not observed at Barrow« Thus these rapid fluctuations
display characteristics quite different from the previously classified
magnetic and earth-current continuous pulsations, pc's, and train pulsations,
pt's. Special equipment was devised to count and record the period of the
fluctuations on a continuous basis. Typical rapid, fluctuation, traces.and charts
showing their activity patterns are presented.This research is sponsored by the Geophysics Research Directorate,
Air Force Cambridge Research Center, Air Research and Development Command
under Contract No. AF 19(604)-3075 and by a grant from the National Science
Foundation.Abstract -- Introduction -- Equipment : Geographic location of electrode field ; Stray electric fields ; Electrodes ; Lines ; Recorders ; Cycle counting equipment -- Records and Scaling : Rapid fluctuation records ; Rapid fluctuation at College - selected days ; Rapid fluctuation activity - February 1958 -- Diurnal variation in rapid fluctuation -- Diurnal variation in amplitude and frequency activity ; Rapid fluctuation frequency and period ; Rapid fluctuations at College and at Barrow -- Discussion : Comparison of earth-current rapid fluctuations with geomagnetic pulsations ; Comparison with other earth-current pulsation studies ; Diurnal Variation in amplitude and fluctuation
frequency activity at College ; Generation of earth-current rapid fluctuation -- Summary -- Bibliography -- FiguresYe
Earth Current Activity at College, Alaska, July 1959
This report presents College N-S earth current records
for the month of July 1959. The scale of 1 inch per hour
permits detailed scaling directly from the reproductions
in the report. Scalings of hourly range in amplitude and
rapid fluctuation activity are given. The amplitude scalings
are also presented as curves together with average curves for
a period of several years to show the relative magnitudes of
the July 1959 activity. The earth current always displays
much more pronounced fine structure than the corresponding
geomagnetic activity.Scientific Report No. 4 --
Contract No. AF 19(604)-3075 -- June 15, 1960 -- Geophysics Research Directorate
Air Force Cambridge Research Center
Air Research and Development Command
United States Air Force
Bedford, MassachusettsYe
High latitude geophysical data, October-December 1966
Geophysical data related to polar ionospheric activit
High latitude geophysical data
High latitude geophysical data on cosmic noise, and north-south telluric current activities over Alask
High latitude geophysical data, July-September 1966
High latitude graphical and tabular geophysical data of ionospheric activit
High latitude geophysical data, october - december, 1964
High altitude data on polar ionospheric activity, and cosmic noise leve
Initial-state dependence in time-dependent density functional theory
Time-dependent density functionals in principle depend on the initial state
of the system, but this is ignored in functional approximations presently in
use. For one electron it is shown there is no initial-state dependence: for any
density, only one initial state produces a well-behaved potential. For two
non-interacting electrons with the same spin in one-dimension, an initial
potential that makes an alternative initial wavefunction evolve with the same
density and current as a ground state is calculated. This potential is
well-behaved and can be made arbitrarily different from the original potential
Spin currents and spin dynamics in time-dependent density-functional theory
We derive and analyse the equation of motion for the spin degrees of freedom
within time-dependent spin-density-functional theory (TD-SDFT). Results are (i)
a prescription for obtaining many-body corrections to the single-particle spin
currents from the Kohn-Sham equation of TD-SDFT, (ii) the existence of an
exchange-correlation (xc) torque within TD-SDFT, (iii) a prescription for
calculating, from TD-SDFT, the torque exerted by spin currents on the spin
magnetization, (iv) a novel exact constraint on approximate xc functionals, and
(v) the discovery of serious deficiencies of popular approximations to TD-SDFT
when applied to spin dynamics.Comment: now includes discussion of OEP and GGA; to appear in Phys. Rev. Let
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