Abstract
New magnetotelluric (MT) data, combined with older MT data are used to simulate geomagnetically induced currents (GIC) in the power network of the North Island of Aotearoa New Zealand for two geomagnetic storms. For the May 2024 G5 Gannon Storm, simulations use magnetic field data from two separate locations—the Intermagnet geomagnetic observatory at Eyrewell (EYR) in the South Island of New Zealand, and a magnetometer (OAKS) in the north‐west of the North Island which is part of the MANA (Magnetometer Array for New Zealand Aotearoa) network. All simulations indicate that the largest GIC occur in transformers around Auckland, at Stratford in the west and Redcliff on the east coast. Simulations for the Gannon Storm using the OAKS magnetic field data match measured GIC at a single transformer at Henderson in Auckland with a peak GIC of approximately 30 A. In contrast, simulations using the more distant EYR data (>200 km south) produce peak GIC exceeding 100 A in two transformers at Henderson, and over 50 A at Stratford and Redcliff. Although the EYR simulation yields similar patterns of GIC impact on substations, transmission lines and individual transformers, these values are inconsistent with both the OAKS‐driven simulations and the available GIC observations in the North Island. A significant conductivity contrast between the western and eastern parts of the Northland peninsula identified by the new MT data may be partly responsible for the large GIC in transformers around Auckland.