Multi-spacecraft Observations to Study the Shock Propagation in the Inner Heliosphere

Aline de Lucas¹, Rainer Schwenn², Eckart Marsch¹, Alisson dal Lago¹, Alicia Clara de Gonzalez¹, Ezequiel Echer¹, Walter Demetrio Gonzalez¹

¹Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Sao Paulo, Brazil
²Max-Planck-Institut fur Sonnensystemforschung, Katlenburg-Lindau, Germany

The two Helios probes traveled at variable longitudinal and radial separations through the inner heliosphere. They collected most valuable high-resolution plasma data for more than 11 years (1974-1985). A set with 397 shock waves driven by Interplanetary Coronal Mass Ejections (ICMEs) was identified. From this set, some shocks were observed subsequently by Helios 1 and Helios 2 or vice-versa giving information about two different points of observation. Including plasma and magnetic field data from the ISEE-3 and IMP-8 spacecrafts gives another point for comparison of the evolution of the shocks in the inner heliosphere. With a third referential the set of shocks observed by the three spacecrafts totalizes 29 events from where three different Mach numbers are evaluated and used to analyze the shock propagation in the interplanetary medium.