Multiple spacecraft flux rope modeling of the Bastille Day magnetic cloud

The Bastille Day magnetic cloud in July 2000 occurred with NEAR in conjunct ion with the Earth at a radial distance of 1.76 AU and 1.9 degrees from the Earth-Sun line. Propagation time from ACE at 0.99 AU to NEAR indicates the cloud did not decelerate significantly between the Earth and 1.76 AU. Usin g a non-force-free, kinematic flux rope model we find the rope contained 13 0 TWb of magnetic flux, was oriented with clock and cone angles of 50 degre es and 83 degrees, and had a radius of 0.25 AU at ACE. At NEAR its radius h ad expanded to 0.43 AU. Simultaneous modeling, of ACE and NEAR data indicat e the axial and poloidal magnetic fields vary as R-1.4 and R-1.2 where R is heliocentric distance. Magnetosheath thicknesses of 0.14 AU and 0.23 AU in dicate the rope cross section is elongated normal to the cloud axis and the radial direction.