Ionosphere small-scale magnetic perturbations associated with GPS scintillations in the auroral and cusp regions

Magnetosphere and ionosphere coupling is largely driven by electromagnetic waves (e.g., Alfven waves) and particle precipitation in the polar cusp and auroral region. Magnetic perturbations (dB) in the ionosphere span scales from >1,000 km across the auroral zone—associated with Region-1 and Region-2 field-aligned currents (FACs)—down to <1 km, approaching the electron inertial length, corresponding to fine-scale auroral arcs (~100 m). These smaller scale dB are often linked to inertial Alfven waves that carry parallel electric fields, accelerate electrons, and produce dynamic auroral structures. During geomagnetic storms, transient currents associated with these small-scale dB can exceed several hundred μA/m2, leading to significant ionosphere total electron content (TEC) perturbations and plasma irregularities that cause GPS scintillations and disrupt communication. However, it remains a challenge to fully understand how these small-scale FACs and associated particle precipitation drive ionosphere irregularities and GPS scintillations. NASA's TRACERS mission, launched on 23 July 2025, offers new opportunities to address this problem. We present initial observations from TRACERS showing coincident small-scale dB, particle precipitation, and strong GPS scintillation events in the nightside auroral and dayside cusp regions.