The full electric and magnetic field data set from the subpayload of the CRIT II sounding rocket experiment is presented for the first time. CRIT II was an ionospheric injection experiment aimed at studying the critical ionization velocity (CIV) effect. It consisted of two payloads located on nearly the same magnetic field line. By using the data from both payloads, we are able to reach a good understanding of the momentum transfer between the injected ions and the ambient ionosphere. The data also make it possible to resolve the conflict between the two competing models for the energy transfer from the newly created ions to hot electrons in the CIV process. The results give a natural coupling between the energy and momentum transfer processes in CIV experiments. ¿ 1996 American Geophysical Union