Open AccessA comprehensive model of the quiet‐time, near‐Earth magnetic field: phase 3
Author(s) -
Sabaka Terence J.,
Olsen Nils,
Langel Robert A.
Publication year - 2002
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1046/j.1365-246x.2002.01774.x
Subject(s) - magnetosphere , earth's magnetic field , geophysics , ionosphere , spurious relationship , ionospheric dynamo region , physics , parametrization (atmospheric modeling) , field (mathematics) , geomagnetic secular variation , computational physics , dipole model of the earth's magnetic field , dynamo , geology , magnetic field , geodesy , geomagnetic storm , solar wind , interplanetary magnetic field , mathematics , quantum mechanics , machine learning , computer science , radiative transfer , pure mathematics
Summary The near‐Earth magnetic field is caused by sources in the Earth's core, ionosphere, magnetosphere, lithosphere and from coupling currents between the ionosphere and the magnetosphere, and between hemispheres. Traditionally, the main field (low degree internal field) and magnetospheric field have been modelled simultaneously, with fields from other sources being modelled separately. Such a scheme, however, can introduce spurious features, especially when the spatial and temporal scales of the fields overlap. A new model, designated CM3 (Comprehensive Model: phase 3), is the third in a series of efforts to coestimate fields from all of these sources. This model has been derived from quiet‐time Magsat and POGO satellite and observatory hourly means measurements for the period 1960–1985. It represents a significant advance in the treatment of the aforementioned field sources over previous attempts, and includes an accounting for main field influences on the magnetosphere, main field and solar activity influences on the ionosphere, seasonal influences on the coupling currents, a priori characterization of the influence of the ionosphere and the magnetosphere on Earth‐induced fields, and an explicit parametrization and estimation of the lithospheric field. The result is a model that describes well the 591 432 data with 16 594 parameters, implying a data‐to‐parameter ratio of 36, which is larger than several popular field models.