The Penetration Electric Fields During the 10 May 2024 Superstorm Observed by ISRs Over Sanya and Jicamarca

We used the incoherent scatter radar observations at Sanya (18.3 degrees N, 109.6 degrees E) and Jicamarca (11.9 degrees S, 76.9 degrees W) to analyze the day-night difference of penetration electric fields during the 10 May 2024 superstorm. The dawn-dusk electric field penetrated into the night ionosphere more efficiency, and the night-to-day penetration ratio was similar to 2. Specially, the zonal electric field became westward in the post-midnight, while it did not change significantly in the afternoon in response to the IMF-Bz southward turning at 17:45-18:25 UT and 19:30-22:30 UT. These indicated that the penetration electric field was rapidly and long-lastingly canceled by shielding electric field, which had rarely been reported. In this period, the enhanced Region-2 field-aligned current shifted to mid-latitudes and the enhanced sunward convection penetrated to low-latitudes, indicating the shielding layer might closely move to Earth. Under this condition, the shielding layer would promptly reconfigure to cancel the penetration electric field and lead to the perfect shielding.