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The magnetotail neutral sheet is best represented by an arched surface which separates field lines of opposite polarity. The deviations of this surface from the solar magnetospheric XY plane can be represented by the equation δz = (H o +D) (1 ‐ Y²/Y o 2 ) 1/2 −Dsin χ when Y <Y o and δz = − Dsin χ when Y ≥Y o , where Y is an east‐west location relative to the center of an aberrated tail, χ is the tilt of the dipole, and H o , Y o , and D are constants. Optimum values of H o = 10.5 R E , Y o = 22.5 R E , and D = 14 R E have been determined by minimizing the number of erroneous predictions of tail magnetic field polarity in a large set of Imp 6, 7, and 8 magnetometer data. The model with D ≠ 0 is found to be superior to the D=0 model used in all previous studies of the neutral sheet. This nonzero D value implies that during northern hemisphere summer the neutral sheet is raised above the solar magnetospheric equatorial plane near the center of the tail but is depressed below this plane on the flanks. The neutral sheet tends to be slightly nearer the equatorial plane during intense magnetic activity, but there is little tendency for the neutral sheet to approach this plane at large distances down the tail.
D. H. Fairfield (Fri,) studied this question.