Global quantitative models of the geomagnetic field in the cislunar magnetosphere for different disturbance levels

Abstract

A previously proposed model (Tsyganenko and Usmanov, 1982, Planet. Space Sci. 30, 985) is further developed, using IMP-A, C, D, E, F, G, H, I, J and HEOS-1, -2 spacecraft measurements made during 1966–1980. The main improvement consists of a considerable extension of the modeling region by adding to the original data set a large number of magnetotail field measurements. Data points used in the present study cover a vast range of distances 4≲R≲70R_E and comprise an unprecedentedly large number of measurements (a total of 36682 vector averages, almost twice as many as in our earlier data set). The data have been divided into groups corresponding to a sequence of K_p-index intervals, as well as different conditions in the solar wind. Mathematical representation of the magnetic field follows in its general features the approach developed in our earlier work, with some modifications. Two versions of the model are proposed, namely, (i) a “long” one with 26 parameters, valid up to distances ∼70R_E, and (ii) a “truncated” one with 20 parameters and an applicability limit of ∼30R_E.