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The Earth’s Magnetosphere

The Earth’s Magnetosphere. The Earth’s magnetic field The Magnetosphere Magnetic variation and index. 北地理磁極位置變化. 南地理磁極位置變化. http://ourworld.compuserve.com/homepages/dp5/magnet.htm. 地理北. D ：磁偏角 . I . ：磁傾角. 地磁北. X = H cosD Y = H sin D Z = F sin I. H D Z = F sin I.

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The Earth’s Magnetosphere

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  1. The Earth’s Magnetosphere The Earth’s magnetic field The Magnetosphere Magnetic variation and index

  2. 北地理磁極位置變化 南地理磁極位置變化

  3. http://ourworld.compuserve.com/homepages/dp5/magnet.htm

  4. 地理北 D：磁偏角 .I.：磁傾角 地磁北 X = H cosD Y = H sin D Z = F sin I H D Z = F sin I

  5. The South Atlantic Anomaly (SAA) is located within the region between 10-40°S and between 280-360°E. USGS figure

  6. 台灣的磁場特徵(25.0 °N,121.5°E) Total Intensity (F): 45008.8 nT 磁偏角 (D): -3.879o 磁傾角 (I): 36.218o

  7. Dipole magnetic field θ: co-latitude

  8. USGS figure

  9. Field line equation (I) In spherical coordinate, At tangent point, Combine Earth’s magnetic field,

  10. Field line equation (II) Integral (5.06), At magnetic equator, Let req=L x RE and for r = RE RE RE

  11. 運動方程式 (Equation of motion)

  12. 重新整理可得 當等號右式為零時

  13. 對於磁層邊界： 其中

  14. Closed model

  15. Open model

  16. Magnetospheric Current System Dayside magnetopause current R1 and R2 filed-aligned currents Partial ring current Nightside magnetopause current Cross tail current Ring current

  17. Dayside magnetopause current R1 and R2 filed-aligned currents Partial ring current Nightside magnetopause current Cross tail current Ring current

  18. Dayside magnetopause current R1 and R2 filed-aligned currents Partial ring current Nightside magnetopause current Cross tail current Ring current

  19. 帶電粒子在地球磁場中的運動方式

  20. Magnetometer • A magnetometer is a scientific instrument used to measure the strength and/or direction of the magnetic field. Magnetism varies from place to place and differences in Earth's magnetic field can be caused by the differing nature of rocks and the interaction between charged particles from the Sun and the magnetosphere. Magnetometers are a frequent component instrument on spacecraft that explore planets.

  21. Types • Scalar magnetometers measure the total strength of the magnetic field to which they are subjected, and • Vector magnetometers have the capability to measure the component of the magnetic field in a particular direction, relative to the spatial orientation of the device.

  22. Early magnetometers • In 1833, Carl Friedrich Gauss, head of the Geomagnetic Observatory in Göttingen, published a paper on measurement of the Earth's magnetic field. It described a new instrument that Gauss called a "magnometer" (a term which is still occasionally used instead of magnetometer).It consisted of a permanent bar magnet suspended horizontally from a gold fibre.A magnetometer may also be called a gaussmeter.

  23. Modern magnetometers • Rotating coil magnetometer • Hall effect magnetometer • Proton precession magnetometer • Gradiometer • Fluxgate magnetometer • Induction magnetometer • Caesium vapor magnetometer • Spin-exchange relaxation-free (SERF) atomic magnetometers

  24. Rotating coil magnetometer • The magnetic field induces a sine wave in a rotating coil. The amplitude of the signal is proportional to the strength of the field, provided it is uniform, and to the sine of the angle between the rotation axis of the coil and the field lines.

  25. Hall effect magnetometer • The most common magnetic sensing devices are solid-state Hall effect sensors. These sensors produce a voltage proportional to the applied magnetic field and also sense polarity.

  26. Proton precession magnetometer • Proton precession magnetometers, also known as proton magnetometers, measure the resonance frequency of protons (hydrogen nuclei) in the magnetic field to be measured, due to nuclear magnetic resonance (NMR). Because the precession frequency depends only on atomic constants and the strength of the ambient magnetic field, the accuracy of this type of magnetometer is very good.

  27. Gradiometer • Magnetic gradiometers are pairs of magnetometers with their sensors horizontallyseparated by a fixed distance. The readings are subtracted in order to measure the difference between the sensed magnetic fields, which measures the field gradients caused by magnetic anomalies. This is one way of compensating both the variability in time of the Earth's magnetic field and for other sources of electromagnetic interference, allowing more sensitive detection of anomalies.

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