Ion temperature anisotropy limitation in high beta plasmas

Measurements of parallel and perpendicular ion temperatures in the Large Ex periment on Instabilities and Anisotropies (LEIA) space simulation chamber display an inverse correlation between the upper bound on the ion temperatu re anisotropy and the parallel ion beta (beta = 8 pi nkT/B-2). Fluctuation measurements indicate the presence of low frequency, transverse, electromag netic waves with wave numbers and frequencies that are consistent with pred ictions for Alfven Ion Cyclotron instabilities. These observations are also consistent with in situ spacecraft measurements in the Earth's magnetoshea th and with a theoretical/computational model that predicts that such an up per bound on the ion temperature anisotropy is imposed by scattering from e nhanced fluctuations due to growth of the Alfven ion cyclotron instability. (C) 2000 American Institute of Physics. [S1070-664X(00)91405-8].