Interplanetary shock waves and large‐scale structures: Ulysses' observations in and out of the ecliptic plane

We present a study of 153 fast shock waves and their relation to other large‐scale features in the solar wind: corotating interaction regions (CIRs), interplanetary counterparts of coronal mass ejections (ICMEs), and the magnetic sector structure, observed by Ulysses from October 1990 to the south solar polar pass in the summer of 1994. This is a comprehensive statistical study of interplanetary shock waves and their possible causes between 1 and 5.4 AU, in particular, out of the ecliptic. We identify six different heliographic intervals with distinct dynamic characteristics and shock wave populations (transient and corotating shocks). We present maps of large‐scale features, which provide a general context to studies of particular events observed by Ulysses and a comparison of Ulysses observations with results from other missions. From our analysis of the associations between interplanetary shocks and their possible causes we find that the strongest in‐ecliptic shock waves were leading CIRs about 4–5 AU. The strongest out‐of‐ecliptic shock waves were attributed to diverse causes at about 20° south. We observed many quasi‐parallel (θBn < 45°) corotating shocks; in fact, most of the corotating reverse shocks detected during the in‐ecliptic trajectory were quasi‐parallel. The correlation between transient forward shocks and ICMEs (ejecta signatures) is similar to previous results within 1 AU: during the in‐ecliptic trajectory Ulysses detected 25 ICMEs and 31 transient forward shocks, 13 of which were associated with ICMEs. The out‐of‐ecliptic results show an analogous correlation. After the Jupiter flyby we observed a significant number of nonrecurrent reverse shocks that do not show any association with ICMEs. This type of shock, instead of being driven by supermagnetosonic plasma clouds, might be produced by a different mechanism.