Investigations of magnetic field disturbances at an air force base compass calibration hardstand

Geophysics ◽  
1993 ◽  
Vol 58 (3) ◽  
pp. 434-440 ◽  
Author(s):  
Dwain K. Butler ◽  
Thomas B. Kean
Keyword(s):  
Magnetic Field ◽  
Air Force ◽  
Concrete Aggregate ◽  
Large Bulk ◽  
The Status ◽  
Bulk Magnetic Susceptibility ◽  
Compass Calibration ◽  
Air Force Base ◽  
The Magnetic Field

Investigations were conducted to determine the nature and cause of magnetic field disturbances at the calibration hardstand (compass rose) at an air force base. The disturbances have prevented the normal and routine use of the hardstand since its construction in the mid-1950s, with heightened concern over the problem every 10–12 years. The investigations included the characterization of the horizontal, vertical, and temporal variation of the total magnetic field strength both on and off the hardstand. On the hardstand, the field varies by as much as 1,000 nT over 10 m horizontally and by as much as 600 nT over 2.5 m vertically. Also, on the hardstand, the magnetic field varies extremely erratically with time by 50–60 nT over periods of a few seconds. Off the hardstand, the magnetic field is extremely stable, and varies by less than 10 nT over 10 m horizontally, 2.5 m vertically, and over periods of 10–15 min. The magnetic field “stabilizes” at distances less than 10 m horizontally from the edge of the hardstand. Both on and off the hardstand, the magnetic field variations are independent of the status (on or off) of a nearby instrument landing system (ILS) (approach radar). The results of the magnetic field characterization indicate that the cause of the problem is the hardstand itself. The hardstand concrete was found to have a large bulk magnetic susceptibility, and the concrete aggregate has a permanent magnetization sufficiently large to visibly deflect a compass needle; these factors, coupled with a correlation with the 11-year solar cycle, suffice to explain the magnetic “disturbances” at the hardstand.

Characterization of Shock Wave–Endwall Boundary Layer Interactions in a Transonic Compressor Rotor

1988 ◽  
Vol 110 (3) ◽  
pp. 386-392 ◽  
Author(s):  
D. C. Rabe ◽  
A. J. Wennerstrom ◽  
W. F. O’Brien
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Air Force ◽  
Leading Edge ◽  
Transonic Compressor ◽  
Laser Measurements ◽  
Compressor Rotor ◽  
Boundary Layer Interaction ◽  
Air Force Base

The passage shock wave–endwall boundary layer interaction in a transonic compressor was investigated with a laser transit anemometer. The transonic compressor used in this investigation was developed by the General Electric Company under contract to the Air Force. The compressor testing was conducted in the Compressor Research Facility at Wright-Patterson Air Force Base, OH. Laser measurements were made in two blade passages at seven axial locations from 10 percent of the axial blade chord in front of the leading edge to 30 percent of the axial blade chord into the blade passage. At three of these axial locations, laser traverses were taken at different radial immersions. A total of 27 different locations were traversed circumferentially. The measurements reveal that the endwall boundary layer in this region is separated from the core flow by what appears to be a shear layer where the passage shock wave and all ordered flow seem to end abruptly.

scholarly journals Magnetic properties of cobalt microwires measured by piezoresistive cantilever magnetometry

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
G. Tosolini ◽  
J. M. Michalik ◽  
R. Córdoba ◽  
J. M. de Teresa ◽  
F. Pérez-Murano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Room Temperature ◽  
Signal To Noise Ratio ◽  
Static Deflection ◽  
Magnetic Structures ◽  
Dual Beam ◽  
Piezoresistive Cantilevers ◽  
Good Signal ◽  
The Magnetic Field

AbstractWe present the magnetic characterization of cobalt wires grown by focused electron beam-induced deposition (FEBID) and studied using static piezoresistive cantilever magnetometry. We have used previously developed high force sensitive submicron-thick silicon piezoresistive cantilevers. High quality polycrystalline cobalt microwires have been grown by FEBID onto the free end of the cantilevers using dual beam equipment. In the presence of an external magnetic field, the magnetic cobalt wires become magnetized, which leads to the magnetic field dependent static deflection of the cantilevers. We show that the piezoresistive signal from the cantilevers, corresponding to a maximum force of about 1 nN, can be measured as a function of the applied magnetic field with a good signal to noise ratio at room temperature. The results highlight the flexibility of the FEBID technique for the growth of magnetic structures on specific substrates, in this case piezoresistive cantilevers.

scholarly journals Stochastic Dosimetry for the Assessment of Children Exposure to Uniform 50 Hz Magnetic Field with Uncertain Orientation

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
E. Chiaramello ◽  
S. Fiocchi ◽  
P. Ravazzani ◽  
M. Parazzini
Keyword(s):  
Magnetic Field ◽  
Central Nervous System ◽  
Nervous System ◽  
Electric Field ◽  
Stochastic Model ◽  
Significant Difference ◽  
The Central Nervous System ◽  
Children Exposure ◽  
The Magnetic Field

This study focused on the evaluation of the exposure of children aging from five to fourteen years to 50 Hz homogenous magnetic field uncertain orientation using stochastic dosimetry. Surrogate models allowed assessing how the variation of the orientation of the magnetic field influenced the induced electric field in each tissue of the central nervous system (CNS) and in the peripheral nervous system (PNS) of children. Results showed that the electric field induced in CNS and PNS tissues of children were within the ICNIRP basic restrictions for general public and that no significant difference was found in the level of exposure of children of different ages when considering 10000 possible orientations of the magnetic field. A “mean stochastic model,” useful to estimate the level of exposure in each tissue of a representative child in the range of age from five to fourteen years, was developed. In conclusion, this study was useful to deepen knowledge about the ELF-MF exposure, including the evaluation of variable and uncertain conditions, thus representing a step towards a more realistic characterization of the exposure to EMF.

scholarly journals Characterization of the magnetic field of the Herbig Be star HD 200775★

2008 ◽  
Vol 385 (1) ◽  
pp. 391-403 ◽  
Author(s):  
E. Alecian ◽  
C. Catala ◽  
G. A. Wade ◽  
J.-F. Donati ◽  
P. Petit ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Be Star ◽  
The Magnetic Field

Characterization of an Analytical Theta-Pinch Plasma Generated with a Unidirectional Capacitive Discharge

1988 ◽  
Vol 42 (1) ◽  
pp. 77-83 ◽  
Author(s):  
E. T. Johnson ◽  
R. D. Sacks
Keyword(s):  
Magnetic Field ◽  
Discharge Current ◽  
Discharge Circuit ◽  
Radiative Properties ◽  
Plasma Properties ◽  
Capacitive Discharge ◽  
Zero Crossings ◽  
Theta Pinch ◽  
The Magnetic Field

The plasma produced by a high-current capacitive discharge through a graphite fiber bundle is compressed by a magnetic field coaxial with the plasma. The magnetic field is generated by the plasma current in a large coil surrounding the plasma. The field induces an azimuthal (theta) current in the plasma. This current couples with the external magnetic field and produces a radial Lorentz force which reduces the rate of plasma expansion. A diode shunt in the capacitive discharge circuit is used for the generation of a unidirectional discharge current. This arrangement eliminates zero-crossings of the discharge current and thus increases the effectiveness of the magnetic field in controlling the radiative properties of the plasma. Design features of the discharge circuit are presented, as well as a comparison of the plasma properties with oscillatory and unidirectional discharge current waveforms.

scholarly journals Harmonic generation in the interaction of laser with a magnetized overdense plasma

2021 ◽  
Vol 87 (5) ◽  
Author(s):  
Srimanta Maity ◽  
Devshree Mandal ◽  
Ayushi Vashistha ◽  
Laxman Prasad Goswami ◽  
Amita Das
Keyword(s):  
Magnetic Field ◽  
Harmonic Generation ◽  
Laser Energy ◽  
Magnetized Plasma ◽  
Plasma Region ◽  
Particle In Cell ◽  
Incident Laser Intensity ◽  
Overdense Plasma ◽  
The Magnetic Field

The mechanism of harmonic generation in both O- and X-mode configurations for a magnetized plasma has been explored here in detail with the help of particle-in-cell simulations. A detailed characterization of both the reflected and transmitted electromagnetic radiation propagating in the bulk of the plasma has been carried out for this purpose. The efficiency of harmonic generation is shown to increase with the incident laser intensity. A dependency of harmonic efficiency has also been found on magnetic field strength. This work demonstrates that there is an optimum value of the magnetic field at which the efficiency of harmonic generation maximizes. The observations are in agreement with theoretical analysis. For the O-mode configuration, this is compelling as the harmonic generation provides for a mechanism by which laser energy can propagate inside an overdense plasma region.

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