Cluster spacecraft observations of a ULF wave enhanced by Space Plasma Exploration by Active Radar (SPEAR)

Abstract

Abstract. Space Plasma Exploration by Active Radar (SPEAR) is a high-latitude ionospheric heating facility capable of exciting ULF waves on local magnetic field lines. We examine an interval from 1 February 2006 when SPEAR was transmitting a 1 Hz modulation signal with a 10 min onoff cycle. Ground magnetometer data indicated that SPEAR modulated currents in the local ionosphere at 1 Hz, and enhanced a natural field line resonance with a 10 min period. During this interval the Cluster spacecraft passed over the heater site. Signatures of the SPEAR-enhanced field line resonance were present in the magnetic field data measured by the magnetometer on-board Cluster-2. These are the first joint ground-and space-based detections of field line tagging by SPEAR.

Joint Cluster/Ground‐Based Studies in the First 20 Years of the Cluster Mission

“…Finally, ULF waves can also be stimulated artificially by ionospheric heating. Badman et al (2009) reported the results of an experiment where the SPEAR ionospheric heater transmitted a 1 Hz modulation signal with a 10 min (1.67 mHz) on-off cycle during a conjunction with the Cluster spacecraft. The 10 min period was intended to enhance an existing field-line eigenmode at that frequency.…”