Ion cyclotron waves in the high altitude cusp:: CLUSTER observations at varying spacecraft separations -: art. no. 2263 - Nykyri,K; Cargill,PJ; Lucek,EA; Horbury,TS; Balogh,A; Lavraud,B; Dandouras,I; Rème,H (GEOPHYSICAL RESEARCH LETTERS, 2003)