Heliomagnetic latitude dependence of the heliospheric magnetic field

ICE and IMP-8 magnetic field data from 1984–1988 have been analyzed in a magnetic coordinate system defined by the orientation of the solar magnetic dipole. The heliomagnetic latitude dependence of the radial component of the magnetic field (Br) has then been investigated in a wide range of magnetic latitudes above and below the heliospheric current sheet (HCS). Br reverses sign abruptly across the current sheet, consistent with the solar magnetic field models of Pneuman and Kopp [1971] and Wolfson [1985] but inconsistent with the source surface models [Hoeksema, 1986]. No evidence is found for an asymmetry in the magnetic field suggested by earlier studies of interplanetary magnetic field data [Luhmann, 1987, Burton, 1990]. A slight ($\text{∼.03\hspace{0.17em}}\mathrm{nT}$ per degree) latitude gradient has been found which is consistent with the MHD model of Pneuman and Kopp and the recent model of Zhao and Hoeksema [1995].