5 research outputs found
Electro-Mechanical Resonant Magnetic Field Sensor
We describe a new type of magnetic field sensor which is termed an
Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a
small conductive elastic element with low damping rate and therefore a high Q
fundamental mode of frequency . An AC current is driven through the
elastic element which, in the presence of a magnetic field, causes an AC force
on the element. When the frequency of the AC current matches the resonant
frequency of the element, maximum vibration of the element occurs and this can
be measured precisely by optical means. We have built and tested a model sensor
of this type using for the elastic element a length of copper wire of diameter
0.030 mm formed into a loop shape. The wire motion was measured using a light
emitting diode photo-transistor assembly. This sensor demonstrated a
sensitivity better than 0.001G for an applied magnetic field of G and
a good selectivity for the magnetic field direction. The sensitivity can be
easily improved by a factor of by more sensitive measurement of
the elastic element motion and by having the element in vacuum to reduce the
drag force.Comment: 8 pages, 9 figure
ACCRETION DISKS WITH A LARGE SCALE MAGNETIC FIELD AROUND BLACK HOLES
We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated
ACCRETION DISKS WITH A LARGE SCALE MAGNETIC FIELD AROUND BLACK HOLES
We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated
ACCRETION DISKS WITH A LARGE SCALE MAGNETIC FIELD AROUND BLACK HOLES
We consider accretion disks around black holes at high luminosity, and the problem of the formation of a large-scale magnetic field in such disks, taking into account the non-uniform vertical structure of the disk. The structure of advective accretion disks is investigated, and conditions for the formation of optically thin regions in central parts of the accretion disk are found. The high electrical conductivity of the outer layers of the disk prevents outward diffusion of the magnetic field. This implies a stationary state with a strong magnetic field in the inner parts of the accretion disk close to the black hole, and zero radial velocity at the surface of the disk. The problem of jet collimation by magneto-torsion oscillations is investigated