ENERGY TRANSFER BETWEEN A MOVING BODY AND A MAGNETIC FIELD

1962 ◽  
Vol 40 (3) ◽  
pp. 301-316 ◽  
Author(s):  
P. R. Smy
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Scaling Laws ◽  
Maximum Energy ◽  
The Body ◽  
Initial Kinetic Energy ◽  
Plasma Propulsion ◽  
Moving Body ◽  
Direct Energy ◽  
Oscillating Magnetic Field

The inductive transfer of energy between a moving body and a magnetic field is discussed together with its significance in the fields of direct energy conversion and plasma propulsion. The investigation is centered upon the interaction between a moving body and a sinusoidally oscillating magnetic field of idealized distribution. Scaling laws governing the various physical variables of the interaction are derived, and the values of the resultant parameters necessary to obtain maximum energy transfer are calculated. It is found that under these conditions the initial kinetic energy of the body can be increased by ~14× or decreased to ~1/14 during the interaction. The relation between these parameters (and hence the energy transfer) and the all important energy transfer/recirculating energy ratio is obtained and it is shown that, in fact, a working energy factor ~6 (or 1/6) is a more feasible proposition.

scholarly journals On energetics and inertial-range scaling laws of two-dimensional magnetohydrodynamic turbulence

2012 ◽  
Vol 703 ◽  
pp. 238-254 ◽  
Author(s):  
Luke A. K. Blackbourn ◽  
Chuong V. Tran
Keyword(s):  
Energy Transfer ◽  
Kinetic Energy ◽  
Energy Flux ◽  
Scaling Laws ◽  
Magnetic Energy ◽  
Inertial Range ◽  
Two Dimensional ◽  
Magnetohydrodynamic Turbulence ◽  
Direct Energy ◽  
Energy Equipartition

AbstractWe study two-dimensional magnetohydrodynamic turbulence, with an emphasis on its energetics and inertial-range scaling laws. A detailed spectral analysis shows that dynamo triads (those converting kinetic into magnetic energy) are associated with a direct magnetic energy flux while anti-dynamo triads (those converting magnetic into kinetic energy) are associated with an inverse magnetic energy flux. As both dynamo and anti-dynamo interacting triads are integral parts of the direct energy transfer, the anti-dynamo inverse flux partially neutralizes the dynamo direct flux, arguably resulting in relatively weak direct energy transfer and giving rise to dynamo saturation. This result is consistent with a qualitative prediction of energy transfer reduction due to Alfvén wave effects by the Iroshnikov–Kraichnan theory (which was originally formulated for magnetohydrodynamic turbulence in three dimensions). We numerically confirm the correlation between dynamo action and direct magnetic energy flux and investigate the applicability of quantitative aspects of the Iroshnikov–Kraichnan theory to the present case, particularly its predictions of energy equipartition and ${k}^{\ensuremath{-} 3/ 2} $ spectra in the energy inertial range. It is found that for turbulence satisfying the Kraichnan condition of magnetic energy at large scales exceeding total energy in the inertial range, the kinetic energy spectrum, which is significantly shallower than ${k}^{\ensuremath{-} 3/ 2} $, is shallower than its magnetic counterpart. This result suggests no energy equipartition. The total energy spectrum appears to depend on the energy composition of the turbulence but is clearly shallower than ${k}^{\ensuremath{-} 3/ 2} $ for $r\approx 2$, even at moderate resolutions. Here $r\approx 2$ is the magnetic-to-kinetic energy ratio during the stage when the turbulence can be considered fully developed. The implication of the present findings is discussed in conjunction with further numerical results on the dependence of the energy dissipation rate on resolution.

scholarly journals Planetary Magnetic Fields and Habitability in Super Earths

2018 ◽  
Vol 27 (1) ◽  
pp. 183-231 ◽  
Author(s):  
Pablo Cuartas-Restrepo
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Scaling Laws ◽  
Thermal Evolution ◽  
Solid Core ◽  
Direct Influence ◽  
Physical Processes ◽  
Planetary Magnetic Fields ◽  
Planetary Magnetic Field ◽  
Planetary Dynamos

Abstract This work seeks to summarize some special aspects of a type of exoplanets known as super-Earths (SE), and the direct influence of these aspects in their habitability. Physical processes like the internal thermal evolution and the generation of a protective Planetary Magnetic Field (PMF) are directly related with habitability. Other aspects such as rotation and the formation of a solid core are fundamental when analyzing the possibilities that a SE would have to be habitable. This work analyzes the fundamental theoretical aspects on which the models of thermal evolution and the scaling laws of the planetary dynamos are based. These theoretical aspects allow to develop models of the magnetic evolution of the planets and the role played by the PMF in the protection of the atmosphere and the habitability of the planet.

scholarly journals Flux expulsion with dynamics

2016 ◽  
Vol 791 ◽  
pp. 568-588 ◽  
Author(s):  
Andrew D. Gilbert ◽  
Joanne Mason ◽  
Steven M. Tobias
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Lorentz Force ◽  
Differential Rotation ◽  
Time Scale ◽  
Scaling Laws ◽  
Dynamical Regime ◽  
Kinematic Evolution ◽  
Flux Expulsion ◽  
The Magnetic Field

In the process of flux expulsion, a magnetic field is expelled from a region of closed streamlines on a $TR_{m}^{1/3}$ time scale, for magnetic Reynolds number $R_{m}\gg 1$ ($T$ being the turnover time of the flow). This classic result applies in the kinematic regime where the flow field is specified independently of the magnetic field. A weak magnetic ‘core’ is left at the centre of a closed region of streamlines, and this decays exponentially on the $TR_{m}^{1/2}$ time scale. The present paper extends these results to the dynamical regime, where there is competition between the process of flux expulsion and the Lorentz force, which suppresses the differential rotation. This competition is studied using a quasi-linear model in which the flow is constrained to be axisymmetric. The magnetic Prandtl number $R_{m}/R_{e}$ is taken to be small, with $R_{m}$ large, and a range of initial field strengths $b_{0}$ is considered. Two scaling laws are proposed and confirmed numerically. For initial magnetic fields below the threshold $b_{core}=O(UR_{m}^{-1/3})$, flux expulsion operates despite the Lorentz force, cutting through field lines to result in the formation of a central core of magnetic field. Here $U$ is a velocity scale of the flow and magnetic fields are measured in Alfvén units. For larger initial fields the Lorentz force is dominant and the flow creates Alfvén waves that propagate away. The second threshold is $b_{dynam}=O(UR_{m}^{-3/4})$, below which the field follows the kinematic evolution and decays rapidly. Between these two thresholds the magnetic field is strong enough to suppress differential rotation, leaving a magnetically controlled core spinning in solid body motion, which then decays slowly on a time scale of order $TR_{m}$.

Magnetic field modulated upconversion luminescence in NaYF4:Yb,Er nanoparticles

2015 ◽  
Vol 3 (34) ◽  
pp. 8794-8798 ◽  
Author(s):  
P. Chen ◽  
H. Jia ◽  
Z. Zhong ◽  
J. Han ◽  
Q. Guo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Upconversion Luminescence

Magnetic field enhanced the upconversion luminescence for the enhanced energy transfer from Yb3+ to Er3+ in NaYF4 nanoparticles.

scholarly journals Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

2012 ◽  
Vol 30 (3) ◽  
pp. 515-526 ◽  
Author(s):  
M. Palmroth ◽  
R. C. Fear ◽  
I. Honkonen
Keyword(s):  
Magnetic Field ◽  
Energy Transfer ◽  
Interplanetary Magnetic Field ◽  
Large Data ◽  
Seasonal Effect ◽  
Dipole Orientation ◽  
Data Set ◽  
Axis Orientation ◽  
Simulation Results ◽  
The Imf

Abstract. We examine the spatial variation of magnetospheric energy transfer using a global magnetohydrodynamic (MHD) simulation (GUMICS-4) and a large data set of flux transfer events (FTEs) observed by the Cluster spacecraft. Our main purpose is to investigate whether it is possible to validate previous results on the spatial energy transfer variation from the GUMICS-4 simulation using the statistical occurrence of FTEs, which are manifestations of magnetospheric energy transfer. Previous simulation results have suggested that the energy transfer pattern at the magnetopause rotates according to the interplanetary magnetic field (IMF) orientation, and here we investigate whether a similar rotation is seen in the locations at which FTE signatures are observed. We find that there is qualitative agreement between the simulation and observed statistics, as the peaks in both distributions rotate as a function of the IMF clock angle. However, it is necessary to take into account the modulation of the statistical distribution that is caused by a bias towards in situ FTE signatures being observed in the winter hemisphere (an effect that has previously been predicted and observed in this data set). Taking this seasonal effect into account, the FTE locations support the previous simulation results and confirm the earlier prediction that the energy transfers in the plane of the IMF. In addition, we investigate the effect of the dipole orientation (both the dipole tilt angle and its orientation in the plane perpendicular to the solar wind flow) on the energy transfer spatial distribution. We find that the energy transfer occurs mainly in the summer hemisphere, and that the dayside reconnection region is located asymmetrically about the subsolar position. Finally, we find that the energy transfer is 10% larger at equinox conditions than at solstice, contributing to the discussion concerning the semiannual variation of magnetospheric dynamics (known as "the Russell-McPherron effect").

Energy Transfer and Molecule-Radiation Interaction in Optical Microcavities

2006 ◽  
Author(s):  
Haiyong Quan ◽  
Zhixiong (James) Guo
Keyword(s):  
Energy Transfer ◽  
Molecular Detection ◽  
Laser Energy ◽  
Maximum Energy ◽  
Whispering Gallery Modes ◽  
Optical Microcavities ◽  
Optical Wavelength ◽  
Whispering Gallery ◽  
Microcavity Devices ◽  
And Storage

Laser energy transfer and molecule-radiation interaction in optical microcavity devices are characterized. The device is operated at whispering-gallery modes, and consists of a microcavity and a micro-waveguide coupled by a sub-micrometer air-gap. Emphases are placed on the influences of microcavity size and waveguide compatibility on the energy transfer and storage capability, on the interactions of foreign molecules with the evanescent radiation field surrounding a resonant microcavity. An optimal gap is found for the considered device configuration where maximum energy storage is achieved. This optimal gap is dependent on the resonance mode as well as the morphology. The Q factor increases exponentially with increasing gap and saturates as the gap approaches the optical wavelength. The influence of molecules attachment is demonstrated and the potential in molecular detection is discussed.

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