The interplanetary shock and substorm impact on geomagnetic fields and electrical power lines on 23 December 2014: SC (left panel) and substorm onset (right panel). The panels from top to the bottom are the solar wind density N and velocity V (1-min data from the OMNI database), X-components of geomagnetic field at BJN, NOR, IVA (10-s data), and AAE (1-s data), time derivative of magnetic field dX/dt [nT s⁻¹] at IVA, and GIC [Amperes (A)] at VKH (10-s data).