The Interstellar H Flow: Updated Analysis of SOHO/SWAN Data

摘要

We update two kinds of results obtained with the SWAN instrument on board SOHO. First, we use H cell data recorded in 2001 and derive the H flow direction in the same way the study was done at solar minimum. We again compare with the Helium flow direction and doing so correct for the coordinate system change between the Ulysses and SOHO missions. The deflection plane we obtain is compatible with our previous result within error bars, confirming the potential predominant role of the interstellar magnetic field. In a second part, we extend the computation of the interstellar H ionization as a function of heliographic latitude and time, a quantity which reflects closely the SW flux latitudinal structure. The pattern for the present solar minimum is strikingly different from the previous minimum, with a much wider slow solar wind equatorial belt which persists until at least 2008. Comparing with synoptic LASCO/C2 electron densities we infer from a preliminary study that the acceleration of the high speed solar wind occurs at a higher altitude during this minimum compared to the previous one, a difference expansion models must be able to reproduce.