Radial variation of solar wind electrons inside a magnetic cloud observed at 1 and 5 AU

The fortuitous observations of a magnetic cloud during the ACE/Ulysses radi al alignment in March 1998 provide one of the first opportunities to study the same magnetic cloud at two different radial distances. In this paper, w e use data from both ACE and Ulysses to examine the expansion of the cloud as well as of the adjacent noncloud solar wind. In particular, we study the evolution of the electrons as the cloud expanded from 1 to 5.4 AU, includi ng the core, halo, and total electron populations. We find that the core an d total electron temperatures at either spacecraft are moderately anticorre lated with electron density. However, combined observations from the two sp acecraft show that both temperature and density decreased as the cloud expa nded and thus that single point measurements cannot be used to determine a polytropic index describing the expansion of solar wind electrons within th e cloud.