Intercomparison of NEAR and Wind interplanetary coronal mass ejection observations

Nearly 4 months of continuous interplanetary magnetic field measurements Se ptember 1997 through December 1997 have allowed us to compare four interpla netary coronal mass ejection (ICME) events seen by the NEAR and Wind spacec raft. When the spacecraft are in close proximity (separated by 1 degrees in azimuth relative to the sun) the ICMEs seen by Wind and NEAR have similar signatures as expected for structures with dimensions along the solar wind flow of similar to 0.2 AU. When the NEAR spacecraft is separated by similar to 5.4 degrees in azimuth from the Earth the vector signature of ICMEs see n at NEAR begins to differ from those seen at Wind even though the magnitud e of the field in the events and the background solar wind show similaritie s at the two spacecraft. When the spacecraft are separated by 11.3 degrees the magnetic signatures are quite different and sometimes ICMEs are seen on ly at one of the two locations. Nevertheless, in all cases the magnetic hel icity of the cloud structures seen at NEAR is the same as at Wind. The radi al speeds of the shock and ICME leading edge as they cross Wind and the tim e delays of those events, for which we have some assurance that they also a rrived at NEAR, indicate that the ICMEs decelerate measurably as they trave l near 1 AU.