نتایج جستجو برای: magnetic sources
تعداد نتایج: 621492 فیلتر نتایج به سال:
Using two new well defined 4-dimensional potential vectors, we formulate the classical Maxwell’s field theory in a form which has manifest Lorentz covariance and SO(2) duality symmetry in the presence of magnetic sources. We set up a consistent Lagrangian for the theory. Then from the action principle we get both Maxwell’s equation and the equation of motion of a dyon moving in the electromagne...
We extend the formulation of spin 2 fields on Minkowski space which makes the action manifestly invariant under duality rotations to the case of interactions with external electric and magnetic sources by adding suitable potentials for the longitudinal and trace parts. In this framework, the string singularity of the linearized Taub-NUT solution is resolved into a Coulomb-like solution. Suitabl...
Due to their extremely weak intensity, biomagnetic fields are usually detected by means of superconducting interference devices (SQUID) which are currently the most sensitive magnetic sensors available. To reduce construction and running costs, extensive efforts have been dedicated to the development of High-Tc SQUIDs working at liquid nitrogen temperature and suitable for biomagnetic applicati...
Magnetic fields likely play a fundamental intermediary role between gravity and radiation in many astrophysical rotators. They can, among other things, 1) induce and be amplified by turbulence, 2) energize coronae, 3) launch and collimate outflows in “spring” or “fling” mechanisms The first is widely recognized to be important for angular momentum transport, but can also produce intrinsic varia...
Stochastic noise, susceptibility artifacts, magnetic field and radiofrequency inhomogeneities, and other noise components in magnetic resonance images (MRIs) can introduce serious bias into any measurements made with those images. We formally introduce three regression models including a Rician regression model and two associated normal models to characterize stochastic noise in various magneti...
Magnetic fields play a dual role in gamma-ray bursts (GRBs). First, GRB and afterglow spectra (the latter interpreted as emission from external shocks) imply synchrotron radiation in a magnetic field that is a significant fraction of equipartition with the particle energy density. Second, magnetized rotators with ∼ 10 Gauss field may power GRB by transporting Poynting flux to large distances wh...
In an attempt to test current initiation models of coronal mass ejections (CMEs), with an emphasis on the magnetic breakout model, we inspect the magnetic topology of the sources of 26 CME events in the context of their chromospheric and coronal response in an interval of approximately nine hours around the eruption onset. First, we perform current-free (potential) extrapolations of photospheri...
Two main results are included in this paper. The first one deals with the leading asymptotic term of the magnetic field outside any conductive medium. In accord with physical reality, it is proved mathematically that the leading approximation is a quadrupole term which means that the conductive brain tissue weakens the intensity of the magnetic field outside the head. The second one concerns th...
We study the effect of random extra-galactic magnetic fields on the propagation of protons of energy larger than 10 eV. We show that for reasonable field values (in the 100 nG range) the transition between diffusive and ballistic regimes occurs in the same energy range as the GZK cutoff (a few 10 eV). The usual interpretation of the flux reduction above the GZK energy in terms of a sudden reduc...
The 1612 and 1667 MHz OH maser lines have been measured in all four Stokes parameters in 47 proto-planetary nebula (PPN) candidates. Out of 42 objects detected, 40 and 34 are 1612 and 1667 MHz emitters, respectively. The spectral extent of the 1667 MHz line overshoots that of the 1612 MHz line in about 80% of the targets. 52% and 26% of the 1612 and 1667 MHz sources, respectively, show linear p...
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