{"thcode":2,"term":{"code":677,"name":"magnetic field (earth)","parent":287,"scope":"The magnetic region surrounding earth.  It is generated by the dipolar characteristic of earth's core whereby earth itself acts as a great spherical magnet with poles near, but not exactly at, the North and South poles."},"uf":[{"name":"geomagnetic field","usewith":false},{"name":"geomagnetics","usewith":false},{"name":"geomagnetism","usewith":false},{"name":"magnetic anomaly maps","usewith":{"code":700,"name":"maps and atlases","parent":808,"scope":"Representation, usually on a flat surface, of a part or whole of the Earth or other parts of the universe.  Collections of maps linked digitally or bound together in a book are called atlases."}},{"name":"magnetic field","usewith":false},{"name":"magnetosphere","usewith":false}],"bt":[{"code":287,"name":"earth characteristics","parent":1174,"scope":"The measurable, definable properties and features of the earth."},{"code":1174,"name":"topics","parent":1,"scope":"Themes, subjects, and concerns for which USGS information resources are relevant."},{"code":1,"name":"Categories","parent":null,"scope":"Thematic terms for categorizing information resources.  This thesaurus is intended to support finding and understanding scientific information."}],"nt":[],"rt":[{"code":470,"name":"geophysics","parent":291,"scope":"Branch of geology studying the physical characteristics and phenomena of the earth and its atmosphere."},{"code":2298,"name":"inverse modeling","parent":713,"scope":"An iterative approach to estimate the form and characteristics of a physical system explained by observations or measurements. Frequently used to determine a subsurface geological structure from measurements of physical properties obtained at or near the earth's surface."},{"code":1721,"name":"magnetic storms","parent":451,"scope":"A period of time during which the earth's magnetic field varies rapidly.  During magnetic storms, satellite electronics can be damaged through the build up and subsequent discharge of static electric charges and astronauts and high-altitude pilots can be subjected to increased levels of radiation."}]}