Subauroral Flow Channel Structures and Auroral Undulations Triggered by Kelvin-Helmholtz Waves

We investigate Kelvin-Helmholtz (K-H) waves on/near the magnetopause and surface waves near the plasmapause—in the outer region of the plasmasphere: in the hot zone—by utilizing multi-instrument/satellite observations. Our main aim is to study how the K-H waves and the K-H instability mechanisms impacted the subauroral and auroral regions during the geomagnetic storms of May 27–29 and July 16, 2017. For the subauroral region, we specify the structured flows as Sub-Auroral Polarization Streams Wave Structures (SAPS-WS) and the combined flows—created by Abnormal Sub-Auroral Ion Drifts (ASAID) and SAID or SAPS—as a complex equatorward-poleward ASAID-SAID or SAPS-ASAID. For the auroral zone, we identify the large auroral undulations appearing inside the auroral zone. The correlated observations of the K-H waves, the structured or complex subauroral flows and large auroral undulations, and the local geomagnetic field oscillations confirm the connections of both the subauroral flows and the auroral undulations with the K-H waves via the eigenfrequency of the Near-Earth Plasma Sheet (NEPS) resonator activated by the K-H waves. For the first time, we demonstrate the simultaneous detections of K-H waves near the magnetopause and surface waves near the plasmapause in the hot zone on July 16, 2017, and conclude their coupling via the NEPS resonator s eigenfrequency. Thus, the surface waves near the plasmapause were the manifestation of the undulating (or rippled) earthward inner boundary of the NEPS that led to the development of ASAID-SAID/SAPS-ASAID or SAPS-WS in the subauroral region and to the large auroral undulation inside the auroral zone.