Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： With a homogeneous model of the Moon, the induced magnetic field caused by step-transient disturbation of interplanetary magnetic field is simulated by the electromagnetic induction theory. As the range of conductivity assigned, the variation from step to calm of both the vectors and magnitudes can be obtained with a fixed permeability mu_o. Then the magnetic characteristic transient response function, the field components and total field at 3 different points selected in a longitude line can all be given in different conductivities by numerical inverse Laplace transformation. The calculation provides a reasonable result that components perpendicular to the external step-transient field will disappear in a long-enough time, whereas the parallel component will become unity with it. When the external field step varies, the maximum field value which can be detected in the vicinity of the equator and the polar region are 13.65 nT and 2.71 nT, respectively. The processes of parallel component change are remarkably different in low latitude and polar region. This phenomenon reflects that magnetometers in different sites of lunar surface may lead to different field curves.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-05-13
Abstract： A kind of front-end signal processing circuit of the electric field instrument, which would be used in the Earth's magnetosphere measurement, is investigated and presented in this work. The double-probe electric field instrument outputs drive current to the ambient plasma environment, and measures the potential difference between the two probes to detect the electric field. Plasma impedance of the magnetosphere is high, so the probe of the electric field instrument will operate in a high voltage to match the electric current requirement. When the operating voltage is close to or surpasses the circuit threshold voltage, the measuring results would be affected, and the instrument will be possibly damaged. This paper adopts voltage scheme with low bias current and feedback floating power supply control scheme, to solve the weak current sampling problem and high dynamic potential handling problem in measuring the electric field of a thin plasma. Test results show that the circuit can make the probe adapt to the floating ground in the dynamic voltage range of 100 V, and measure the electric field from DC to 150kHz, with a low noise level below 14nV?mHz~(-1/2), which meets the needs of electric field measurements in magnetosphere.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract： The magnetometer based on Giant Magneto-Impedance (GMI) effect becomes one of the hottest points on magnetometer research in recent years. Compared with other magnetometers, GMI magnetometer has the advantages of miniaturization, high sensitivity, quick response, high temperature stability and low power consumption. Based on the sensitive material of Fe-based nano-crystalline ribbon, a GMI probe and subsequent signal processing circuit have been designed and realized to compose a GMI magnetometer. Experimental results suggest that in the magnetic field ranging from-25000nT to 25000nT, the sensitivity is 0.176mV穘T-1, which attains the measurement requirement of a weak magnetic field. The magnetometer has advantages of small size and low power consumption so that could be used in space magnetic field measurement.
Peer Review Status:Awaiting Review
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