Temporal variation of the time percentage during 3 months of isotropic periods (blue) and bidirectional periods (green). From top to bottom: percentages of time appearance calculated for a running window of three months of isotropy for STEREO-A, isotropy for STEREO-B, and with the heliocentric distance of both s/c overplotted; BDE for STEREO-A, BDE for STEREO-B, accompanied by the time transit of ICMEs catalogued in ICME list; finally, SSN and latitudinal angle of the HCS (see text for details).