This study presents cross-sectional vector maps of the magnetic field
derived from IMP 8 magnetometer in the magnetosheath at 30 R-c behind
the Earth. In addition the vector patterns of the magnetosheath field
for northward, southward, and east-west interplanetary magnetic field
(IMF) directions are qualitatively compared with those obtained from t
he Spreiter-Stahara gas dynamic (GD) and Fedder-Lyon magnetohydrodynam
ic models (MHD). The main purpose is to display the cross-sectional di
fferences in relation to the dayside merging with different IMF direct
ions, allowing the reader to make direct visual comparisons of the vec
tor patterns. It is seen that for east-west IMF direction, the data-ba
sed and MHD-based patterns differ noticeably in a similar way from the
GD model, presumably reflecting the influence of dayside magnetic mer
ging of the Earth's magnetic field with the y-component of the interpl
anetary magnetic field. All three northward IMF cross sections show co
mparable field draping patterns as expected for a closed magnetosphere
. For southward IMF case, on the other hand, differences between the t
hree cross-sectional patterns are greater as seen in the field vector
sizes and directions, especially closer to the magnetopause where more
disturbed magnetospheric conditions are known to be exist. The data c
omparisons with the MHD and GD models show that the differences result
from the magnetic field-flow coupling and that the effects of dayside
reconnection are present in IMP 8 magnetic field measurements.