Total Energy Dissipation Rate Research Articles

Solar wind variations and geomagnetic storms: A study of individual storms based on high time resolution ISEE 3 data

We employ two independent methods to determine the relationship between the ε parameter and the total energy dissipation rate of the magnetosphere by selecting disturbed periods from the same data set used by Baker et al. (1983). Specifically, four storms are examined in detail, since the accuracy of estimating UT is significantly improved during disturbed periods. The first method assumes UT = MA2α ε, where MA is the Alfvén Mach number and α varies with time. The second method considers a linear, time‐invariant dynamic system with ε as input and UT as output. This means UT = W*ε, where * is convolution and W is a transfer function characteristic of the system. It is found that α values fluctuate mainly between 0 and −0.25. The transfer function analysis indicates that W often resembles a δ‐function or a narrow rectangular impulse. Both results give the same implication (namely, UT ∼ ε) and thus are consistent with the view that the magnetosphere is primarily a directly driven system during disturbed periods.

A study of the polar current systems using the IMS meridian chains of magnetometers

Magnetic field data from a meridian chain of observatories and the recently developed computer codes constitute a powerful tool in studying substorm current systems in the polar region. In this paper, we summarize some of the results obtained from the IMS Alaska meridian chain of observatories. The basic data are the average daily magnetic field variations for 50 successive days (March 9–April 27, 28) which represent a moderately disturbed period. With the aid of the two computer codes, we obtained the distribution of the following quantities in the polar ionosphere in invariant-MLT coordinates: (1) the total ionospheric current; (2) the Pedersen current; (3) the Hall current; (4) the field-aligned currents; (5) the Pedersen-associated field-aligned currents; (6) the Hall-associated field-aligned currents; (7) the electric potential; (8) the Joule heat production rate; (9) the auroral particle energy injection rate; (10) the total energy dissipation rate.

Synchronization of magnetic stars in binary systems

Asynchronous rotation of magnetic stars in close binary systems drives substantial field-aligned electrical currents between the magnetic star and its companion. The resulting magnetohydrodynamic torque is able to account for the heretofore unexplained synchronous rotation of the strongly magnetic degenerate dwarf component in systems like AM Her, VV Pup, AN UMa, and EF Eri as well as the magnetic A type component in systems like HD 98088 and 41 Tauri. The electric fields produced by even a small asynchronism are large and may accelerate some electrons to high energies, producing radio emission. The total energy dissipation rate in systems with degenerate dwarf spin periods as short as 1 minute may reach 10 to the 33rd ergs/s. Total luminosities of this order may be a characteristic feature of such systems.

A high time resolution study of the solar wind-magnetosphere energy coupling function

A high time resolution study of the relationship between the solar wind-magnetosphere energy coupling function ϵ and the total energy dissipation rate U T of the magnetosphere is made using 5-min average values of solar wind data and of the geomagnetic indices AE and Dst. All the results are essentially the same as those obtained by the earlier studies which were based on the hourly average data set. Therefore, we confirm that the magnetosphere is primarily a driven system.

On viscous dissipation rates of velocity component kinetic energies

It is shown by an example that in the balance equation for the kinetic energy of a velocity component in a Newtonian viscous fluid, the term usually interpreted as viscous dissipation rate can have negative regions, although the second law of thermodynamics requires that total kinetic energy dissipation rate be positive at each point in space-time. After exploration of an alternate form, it is concluded that the conventional form is correct, and that the thermodynamic requirement is simply not relevant for kinetic energies of individual velocity components.

Dynamo process governing solar wind-magnetosphere energy coupling

Based on the method of dimensional analysis, the energy transfer rate from the solar wind into the magnetosphere can be characterized by a magnetic coupling parameter α on open field lines and by a viscous coupling parameter β on closed field lines. By assuming that the energy transfer rate can be monitored by the total energy dissipation rate of the magnetosphere, the histogram of α is constructed and is found to peak around −0.1 < α < 0.1. This result implies that the energy transfer is governed primarily by the MHD dynamo process on open field lines and indicates that the ϵ function obtained by Perreault and Akasofu is verified as the first approximation of the solar wind-magnetosphere energy coupling function.

Horizontal Random Temperature Structure of the Ocean

Abstract A theoretical model of the spatial spectrum of horizontally distributed thermal microstructure is developed for anisotropic turbulence. A two-term power law representation is obtained for the horizontal temperature spectrum which includes the influence of buoyancy and convective forces and which applies in a wavenumber range between internal waves and dissipation. The form of the spectrum is TBC(k) = A1k−5/3+A2k−3 where BC refers to bouyancy-convective and k is wavenumber. The coefficients A1 and A2 are functions of depth through their dependence on the total rate of energy dissipation, the total rate of dissipation of temperature variance and the Brunt-Vaisala frequency. Companion experimental data from 54 long horizontal tows at depths between 97.5 and 1454 m at two widely separated stations near Bermuda support the theoretical predictions.

Ocean turbulence with application to acoustic coherence

The coherence of long range underwater acoustic signals is strongly influenced by the complex transmission medium, in particular, by the power in the fluctuating temperature field. A statistical description of horizontal thermal microstructure in anisotropic turbulence is developed for application with an existing acoustic propagation theory. A two-term power law representation for buoyancy and convective forces is applicable for wavenumbers greater than those of the internal-wavefield, but less than those in the dissipation range. The model predicts a temperature power density spectrum which decays as −53 and −3 with wavenumber in the convective and buoyancy ranges, respectively. The power in the two ranges (i.e., the strength of the turbulence) is a function of depth and depends on the total rate of energy dissipation, the total rate of dissipation of temperature variance, and the Brunt-Väisälä frequency. Companion experimental data from 54 long horizontal tows at depths between 97.5 and 1454 m at two widely separated stations in the Bermuda area of the North Atlantic verify the theoretical predictions. The environmental effects on the theoretical acoustic correlation length are examined for limiting values of measured strengths of turbulence.

EXTREMUM PRINCIPLES FOR SLOW VISCOUS FLOW AND THE APPROXIMATE CALCULATION OF DRAG

A complementary pair of extremum principles are proved for a Newtonian viscous fluid in quasi-static flow. It is shown how these can be used to obtain arbitrarily close approximations from above and below to the total rate of energy dissipation and hence to the drag on a translated or rotated body in the fluid.