Low-Frequency Search Coil Magnetometers

2017 ◽  
pp. 289-303
Author(s):  
Asaf Grosz ◽  
Eugene Paperno
Keyword(s):  
Low Frequency ◽  
Search Coil ◽  
Frequency Search

Analytical Optimization of Low-Frequency Search Coil Magnetometers

2012 ◽  
Vol 12 (8) ◽  
pp. 2719-2723 ◽  
Author(s):  
A. Grosz ◽  
E. Paperno
Keyword(s):  
Low Frequency ◽  
Search Coil ◽  
Frequency Search

Simplified Design of a Low Frequency Search Coil Magnetometer

2019 ◽  
Author(s):  
Madalina BUCUR ◽  
Georgiana ROSU ◽  
Adelina BORDIANU ◽  
Lucian PETRESCU ◽  
Valentin IONITA ◽  
...  
Keyword(s):  
Low Frequency ◽  
Search Coil ◽  
Frequency Search

Low‐frequency search unit for ultrasonic testing of concrete

1988 ◽  
Vol 84 (S1) ◽  
pp. S72-S72
Author(s):  
Kanji Imoto ◽  
Koji Ohta ◽  
Takeharu Watanabe
Keyword(s):  
Ultrasonic Testing ◽  
Low Frequency ◽  
Frequency Search

Search Coil Magnetometer Based on Multi-parameter Joint Optimization Design in Ultra Low-Frequency Communication

2018 ◽  
Vol 23 (2) ◽  
pp. 312-317 ◽  
Author(s):  
Chunteng Li ◽  
Yuzhong Jiang ◽  
Guanghui Yang ◽  
Fangjun Liu
Keyword(s):  
Optimization Design ◽  
Low Frequency ◽  
Joint Optimization ◽  
Search Coil

scholarly journals KIC 8975515: A fast-rotating (γ Dor – δ Sct) hybrid star with Rossby modes and a slower δ Sct companion in a long-period orbit

2020 ◽  
Vol 638 ◽  
pp. A57
Author(s):  
A. Samadi-Ghadim ◽  
P. Lampens ◽  
D. M. Jassur ◽  
P. Jofré
Keyword(s):  
Fourier Spectrum ◽  
Low Frequency ◽  
Careful Analysis ◽  
Rotational Frequency ◽  
Echelle Spectrograph ◽  
Mean Values ◽  
Frequency Regime ◽  
Rotating Star ◽  
Frequency Search ◽  
Fast Rotating

Aims. KIC 8975515 is a double-lined spectroscopic binary system with hybrid nature. Regular monitoring with the échelle spectrograph HERMES show that both components have matching atmospheric properties (Teff ∼ 7400 K), and that one of them is a fast rotator (v sin i = 162 versus 32 km s−1). Our aim is to study the Kepler light curve in order to determine the frequencies of the pulsations, to search for regular spacing patterns in the Fourier spectrum, if any, and to discuss their origin in the context of binarity and fast rotation. Methods. In this paper, we study the properties of the stellar pulsations based on a careful analysis of the Fourier spectrum. This was done by performing repeated frequency-search analyses with successive prewhitenings of all the significant frequencies detected in the spectrum. Moreover, we searched for regular period spacing among the g modes as well as frequency splitting among the g and p modes in frequency. Results. In the low-frequency regime, one series of prograde g modes and four series of retrograde r modes, were detected. The r modes are well-distributed with respect to the harmonics of the rotational frequency of the fast-rotating star frot = 1.647 d−1. The dominant g mode is f2 = 2.37 d−1. The strongest p mode is f1 = 13.97 d−1. We identified two multiplets of regularly split p modes with the mean values of 0.42 d−1 and 1.65 d−1. In addition, we also identified a few incidences of mode coupling (between f1 and a g or r mode). Conclusions. We detected five series of retrograde r and prograde g modes as well as two multiplets of p modes with rotational frequency splitttings related to both components of KIC 8975515. We identified the fast-rotating component as a hybrid pulsator with r modes, and the slowly-rotating component as a δ Sct pulsator.

scholarly journals CalMagNet – an array of search coil magnetometers monitoring ultra low frequency activity in California

2008 ◽  
Vol 8 (2) ◽  
pp. 359-368 ◽  
Author(s):  
J. Cutler ◽  
J. Bortnik ◽  
C. Dunson ◽  
J. Doering ◽  
T. Bleier
Keyword(s):  
Low Frequency ◽  
Magnetic Fluctuations ◽  
Resonant Structures ◽  
Search Coil ◽  
Long Term Study ◽  
Local Site ◽  
Timing System ◽  
Field Fluctuations ◽  
Alfven Resonator

Abstract. The California Magnetometer Network (CalMagNet) consists of sixty-eight triaxial search-coil magnetometer systems measuring Ultra Low Frequency (ULF), 0.001–16 Hz, magnetic field fluctuations in California. CalMagNet provides data for comprehensive multi-point measurements of specific events in the Pc 1–Pc 5 range at mid-latitudes as well as a systematic, long-term study of ULF signals in active fault regions in California. Typical events include geomagnetic micropulsations and spectral resonant structures associated with the ionospheric Alfvén resonator. This paper provides a technical overview of the CalMagNet sensors and data processing systems. The network is composed of ten reference stations and fifty-eight local monitoring stations. The primary instruments at each site are three orthogonal induction coil magnetometers. A geophone monitors local site vibration. The systems are designed for future sensor expansion and include resources for monitoring four additional channels. Data is currently sampled at 32 samples per second with a 24-bit converter and time tagged with a GPS-based timing system. Several examples of representative magnetic fluctuations and signals as measured by the array are given.

Observations of seismo-electromagnetic earthquake precursor radiation signatures along Southern Californian fault zones: Evidence of long-distance precursor ultra-low frequency signals observed before a moderate Southern California earthquake episode

1991 ◽  
Vol 69 (8-9) ◽  
pp. 1138-1145 ◽  
Author(s):  
Jack Y. Dea ◽  
Charles I. Richman ◽  
Wolfgang-M. Boerner
Keyword(s):  
San Diego ◽  
Southern California ◽  
Measurement Data ◽  
Low Frequency ◽  
Earthquake Precursor ◽  
Fault Zones ◽  
Frequency Noise ◽  
Long Distance ◽  
Unique Region ◽  
Search Coil

Although questioned for a long time, there is accumulating growing evidence for the existence of detectable seismo-electromagnetic phenomena worldwide. California is geologically as well as seismically a unique region for studying these phenomena in depth; and, in particular, the southern California geologic province with a multitude of offshore and inland fault zones with San Diego in its center. At the Naval Ocean Systems Center Low Frequency Noise Laboratory, San Diego CA., we monitor 0.1–10 Hz ultra-low frequency (ULF) and 10–40 Hz extremely low-frequency (ELF) signals using mu-metal loaded multitum search coil sensors, as well as 10–100 kHz very low-frequency signals using large 1 m diameter loop antennas. We have observed precursor seismo-electromagnetic emissions of several earthquake events. In this paper, we report on observations of broadband ULF signals before and during the Upland quake of April 17, 1990 (Ms = 4.6), centered 200 km N of San Diego. The signals were detected with the vertically oriented search coil sensor and not with the horizontally oriented sensors, which suggests a disturbed ionosphere as the most likely source of these signals. The large prequake ULF activity, the rapid decay of ULF activity after the quake, and the absence of any geomagnetic storms indicate a good correlation of the ULF activity with the Upland quake. Although the exact mechanisms for coupling geologic activity to the ionosphere is not known, we cite a number of hypotheses concerning these mechanisms. Based on this succinct overview, an interpretation of our radio observations of seismic activity is presented and extended to earthquake precursor or predictor studies. We are in the process of expanding this research with the building of more monitoring stations and the improvement of our measurement, data collection, formatting, and data processing capabilities.

Sign in / Sign up

Export Citation Format

Share Document