Abstract. In the publication Troshichev et al. (2006) on the Polar Cap (PC) indices, PCN (North) and PCS (South), an error was made by using components of the Interplanetary Magnetic Field (IMF) in their Geocentric Solar Ecliptic (GSE) representation instead of the prescribed Geocentric Solar Magnetosphere (GSM) representation for calculations of index scaling parameters in the version AARI_1998-2001 (named AARI#3) issued from the Arctic and Antarctic Research Institute (AARI) in St Petersburg, Russia. The mistake has caused a trail of incorrect relations and wrong conclusions extending since 2006 up to now (2020). The authors of the publication commented here, Troshichev, Podorozhkina, Janzhura (2011): Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field, Ann. Geophys., 29, 1479-1489, state that they have used scaling parameters of the (invalid) AARI#3 PC index version in their work but have substituted parameters from the more recent AARI_1995-2005 (AARI#4) version instead. The mingling of PC index versions have resulted in erroneous illustrations in their Figs. 1, 2, 3, 6, 7, and 8 and the issuing of non-substantiated statements.
Comment on Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field by Troshichev et al. (2011)