Abstract
We herein describe a harmonic Pi2 wave that started at 09:12 UT on August 19, 2010, with data that were obtained simultaneously at 19:00–20:00 MLT by three mid-latitude Asian-Oceanian Super Dual Auroral Radar Network (SuperDARN) radars (Unwin, Tiger, and Hokkaido radars), three Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites (THEMIS A, THEMIS D, and THEMIS E), and ground-based magnetometers at low and high latitudes. All THEMIS satellites, which were located in the plasmasphere, observed Pi2 pulsations dominantly in the magnetic compressional (B //) and electric azimuthal (E A) components, i.e., the fast-mode component. The spectrum of Pi2 pulsations in the B // and E A components contained two spectral peaks at approximately 12 to 14 mHz (f 1, fundamental) and 23 to 25 mHz (f 2, second harmonic). The Poynting flux derived from the electric and magnetic fields indicated that these pulsations were waves propagating earthward and duskward. Doppler variations (V) from the 6-s or 8-s resolution camping beams of the Tiger and Unwin SuperDARN radars, which are associated with Pi2 pulsations in the eastward electric field component in the ionosphere, observed Pi2 pulsations within and near the footprint of the plasmapause, whose location was estimated by the THEMIS satellites. The latitudinal profile of f 2 power normalized by f 1 power for Doppler velocities indicated that the enhancement of the normalized f 2 power was the largest near the plasmapause at an altitude-adjusted corrected geomagnetic (AACGM) latitude of 60° to 65°. Based on these features, we suggest that compressional waves propagate duskward away from the midnight sector, where the harmonic cavity mode is generated.
Highlights
Pi2 pulsations with a period of 40 to 150 s and damping waveforms usually occur at the onset of a substorm (Keiling and Takahashi 2011)
By using the magnetic field data from the equatorial orbiting Active Magnetospheric Particle Tracer Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite and data from the Kakioka (KAK), Japan, ground station located at L = 1.23, Takahashi et al (1995) statistically investigated the spatial characteristics of Pi2 pulsations in the inner magnetosphere and found that Pi2 pulsations in the compressional (B//) and radial (BR) components, which have high coherence with those observed in the northward (H) component on the ground on the nightside, are primarily observed on the nightside at L < 4
We investigated the spatial characteristics of Pi2 pulsations from data obtained simultaneously by the mid-latitude SuperDARN radars, THEMIS satellites, and ground stations, which were located along the 210° magnetic meridian on the nightside
Summary
Pi2 pulsations with a period of 40 to 150 s and damping waveforms usually occur at the onset of a substorm (Keiling and Takahashi 2011). To clarify the relationships between Pi2 pulsations and the plasmapause in more detail, Takahashi et al (2003a) studied the radial structure of the amplitude and cross-phase between Pi2 pulsations in the inner magnetosphere and on the ground as well as their dependence on the plasmapause position by using electron density and electric and magnetic field data obtained from the Combined Release and Radiation Effects Satellite (CRRES) They showed that the EA-H cross-phase is approximately 90° at all distances in the plasmasphere even near the plasmapause, whereas the B//-H cross-phase clusters at either 0° or 180° near the plasmapause. These radial properties of amplitude and cross-phase imply that the fundamental cavity mode resonance is excited in the plasmasphere
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
