Time- and latitude-dependence of the compression ratio and the injection rate at the heliospheric termination shock

Abstract

In recent years, a lot of effort was put in modeling of the heliospheric structures and their effects on cosmic ray transport. The interest has risen as Voyager 1 recently passed the solar wind termination shock (Dec. 2004). While a lot of emphasis was put on the global modeling of the shock structure and plasma conditions, questions regarding the injection rate and acceleration of anomalous cosmic rays still remain. The answers to those will depend on the details of the shock structure, which have not been studied extensively with global models, so far. Especially for the dynamic heliosphere the latitudinal variation of the compression ratio during the solar activity cycle has never been shown. The same holds true for the time dependence of the injection rate of pickup ions into the process of diffusive shock acceleration as well as its variation with the heliospheric latitude. Because these two quantities are important for transport models and for the interpretation of the recent Voyager data, they are computed using a hydrodynamic model and discussed in detail.