2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/1187We derive easy-to-handle approximations for the polar gap electric field due to inertial frame dragging as derived by Harding & Muslimov 1998. A simple formula valid for polar gap height comparable to the polar cap radius is presented.4 pages, 3 figs, latex2e, Astronomy and Astrophysics, accepted for publicationAstrophysicstext