Heavy ions impinging on thin silicon dioxide layers generate a dense plasma of electrons and holes. Under particular conditions, such as in thin oxide layer surrounding isolated conductive lines, this plasma can act as a conductive medium, able to carry current for very short times (10-14 s). We studied this phenomenon by using large data set obtained on state-of-the art floating gate memory arrays. Floating gates hit by ions experience a charge loss linearly dependent on ion linear energy transfer and on the electric field across the tunnel oxide. Despite its absolute low value, reaching at most thousands of electrons, charge lost from floating gate exceeds by orders of magnitude that expected from relatively simple models, such as generation and recombination. The model we are proposing is fully consistent with a broad range of theoretical and experimental results, and has excellent fitting capabilities.