“geomagnetism”的概念、定义、翻译、参考文献-科学参考

geomagnetism

Physics

The science concerned with the earth’s magnetic field. If a bar magnet is suspended at any point on the earth’s surface so that it can move freely in all planes, the north-seeking end of the magnet (N-pole) will point in a broadly northerly direction. The angle (D) between the horizontal direction in which it points and the geographic meridian at that point is called the magnetic declination. This is taken to be positive to the east of geographic north and negative to the west. The needle will not, however, be horizontal except on the magnetic equator. In all other positions it will make an angle (I) with the horizontal, called the inclination (or magnetic dip). At the magnetic poles I=90° (+90° at the N-pole, −90° at the S-pole) and the needle will be vertical. The positions of the poles, which vary with time, were in the 1970s approximately 76.1°N, 100°W (N) and 65.8°S, 139°E (S). The vector intensity F of the geomagnetic field is specified by I, D, and F, where F is the local magnetic intensity of the field measured in gauss or tesla (1 gauss=10⁻⁴ tesla). F, I, and D, together with the horizontal and vertical components of F, and its north and east components, are called the magnetic elements. The value of F varies from about 0.2 gauss to 0.6 gauss, in general being higher in the region of the poles than at the equator, but values vary irregularly over the earth’s surface with no correlation with surface features. There is also a slow unpredictable change in the local values of the magnetic elements called the secular magnetic variation. For example, in London between 1576 and 1800 D changed from +11° to −24° and I varied between 74° and 67°. The study of palaeomagnetism has extended knowledge of the secular magnetic variation into the geological past and it is clear that the direction of the geomagnetic field has reversed many times. The source of the field and the cause of the variations are not known with any certainty but the source is believed to be associated with dynamo action in the earth’s liquid core.

https://geomag.usgs.gov/ The website of the USGS National Geomagnetism Program

http://www.kayelaby.npl.co.uk/general_physics/2_7/2_7_6.html Geomagnetic data at the NPL website

Astronomy

A broad term used to describe phenomena of the Earth’s magnetic field, which originates from dynamo effects associated with convection in the fluid outer parts of the planet’s metallic core. The Earth’s magnetic field is a comparatively strong (3–6 × 10⁻⁵ tesla) dipole field. For reasons as yet poorly understood, the geomagnetic poles wander over time, and have reversed polarity quite frequently over the course of geological history, as demonstrated by the remanent magnetization preserved in rocks of various ages. The north geomagnetic pole currently lies between Ellesmere Island in northern Canada and Greenland. Interactions between the geomagnetic field and the solar wind give rise to the magnetosphere.

Geography

The magnetic field of the Earth. The axis runs through the magnetic poles, whose position varies over time; sometimes the north and south magnetic poles switch places (Maus et al. (2005) Geophys. J. Int. 161, 3). The pattern of the magnetic field at any one time will be preserved in contemporary extrusions of volcanic rock. The study of past magnetic fields, palaeomagnetism, can yield information about the creation of new material at the oceanic ridges, and continental drift; see Chauvin et al. (1991) J. Geophys. Res. 96, B2.

单词	geomagnetism
释义	geomagnetism Physics The science concerned with the earth’s magnetic field. If a bar magnet is suspended at any point on the earth’s surface so that it can move freely in all planes, the north-seeking end of the magnet (N-pole) will point in a broadly northerly direction. The angle (D) between the horizontal direction in which it points and the geographic meridian at that point is called the magnetic declination. This is taken to be positive to the east of geographic north and negative to the west. The needle will not, however, be horizontal except on the magnetic equator. In all other positions it will make an angle (I) with the horizontal, called the inclination (or magnetic dip). At the magnetic poles I=90° (+90° at the N-pole, −90° at the S-pole) and the needle will be vertical. The positions of the poles, which vary with time, were in the 1970s approximately 76.1°N, 100°W (N) and 65.8°S, 139°E (S). The vector intensity F of the geomagnetic field is specified by I, D, and F, where F is the local magnetic intensity of the field measured in gauss or tesla (1 gauss=10⁻⁴ tesla). F, I, and D, together with the horizontal and vertical components of F, and its north and east components, are called the magnetic elements. The value of F varies from about 0.2 gauss to 0.6 gauss, in general being higher in the region of the poles than at the equator, but values vary irregularly over the earth’s surface with no correlation with surface features. There is also a slow unpredictable change in the local values of the magnetic elements called the secular magnetic variation. For example, in London between 1576 and 1800 D changed from +11° to −24° and I varied between 74° and 67°. The study of palaeomagnetism has extended knowledge of the secular magnetic variation into the geological past and it is clear that the direction of the geomagnetic field has reversed many times. The source of the field and the cause of the variations are not known with any certainty but the source is believed to be associated with dynamo action in the earth’s liquid core. https://geomag.usgs.gov/ The website of the USGS National Geomagnetism Program http://www.kayelaby.npl.co.uk/general_physics/2_7/2_7_6.html Geomagnetic data at the NPL website Astronomy A broad term used to describe phenomena of the Earth’s magnetic field, which originates from dynamo effects associated with convection in the fluid outer parts of the planet’s metallic core. The Earth’s magnetic field is a comparatively strong (3–6 × 10⁻⁵ tesla) dipole field. For reasons as yet poorly understood, the geomagnetic poles wander over time, and have reversed polarity quite frequently over the course of geological history, as demonstrated by the remanent magnetization preserved in rocks of various ages. The north geomagnetic pole currently lies between Ellesmere Island in northern Canada and Greenland. Interactions between the geomagnetic field and the solar wind give rise to the magnetosphere. Geography The magnetic field of the Earth. The axis runs through the magnetic poles, whose position varies over time; sometimes the north and south magnetic poles switch places (Maus et al. (2005) Geophys. J. Int. 161, 3). The pattern of the magnetic field at any one time will be preserved in contemporary extrusions of volcanic rock. The study of past magnetic fields, palaeomagnetism, can yield information about the creation of new material at the oceanic ridges, and continental drift; see Chauvin et al. (1991) J. Geophys. Res. 96, B2.
随便看	labour theory of value labour turnover Labrador current labradorite Labriola, Antonio (1843–1904) labrum La Bruyère, Jean de (1645–96) lab-scale labyrinth labyrinth karst labyrinth loudspeaker Labyrinthodontia labyrinthus Lacaille, Nicolas Louis de (1713–62) Lacan, Jacques (1901–81) laccolith lacemaking Lacerta Lacertid lacewing Lack, David Lambert lack of memory lac operon lacrimal gland lactams