  The first observed connection between kinetic instabilities driven by proton
temperature anisotropy and estimated energy cascade rates in the turbulent
solar wind is reported using measurements from the Wind spacecraft at 1 AU. We
find enhanced cascade rates are concentrated along the boundaries of the
($\beta_{\parallel}$, $T_{\perp}/T_{\parallel}$)-plane, which includes regions
theoretically unstable to the mirror and firehose instabilities. A strong
correlation is observed between the estimated cascade rate and kinetic effects
such as temperature anisotropy and plasma heating, resulting in protons 5-6
times hotter and 70-90% more anisotropic than under typical isotropic plasma
conditions. These results offer new insights into kinetic processes in a
turbulent regime.
