Determination of interstellar pickup ion distributions in the solar wind with SOHO and Cluster

摘要

Over the last 10 years, the experimentalbasis for the study of the local interstellar medium has been substantiallyenhanced by the direct detection of interstellar pickup ions and of interstellarneutral helium within the heliosphere. Pickup ions can be studied for a widerange of interstellar species. However, currently the accuracy of the method todetermine the parameters of the interstellar medium, namely neutral density,temperature and relative velocity, is hampered by two problems: (1) In mostcases the crucial ionization rates are not available from simultaneousmeasurements and (2) the transport of the pickup ions in the interplanetarymedium substantially modifies the measured spatial distribution of the ions. Inthis study we will discuss how the enhanced capabilities of the instrumentationon SOHO and Cluster in combination with ongoing efforts to model the pickup iondistributions will lead to a significant improvement over the coming years.