Investigation of PC5 pulsations during a TRINNI event

Abstract

UKZN and SANSA operate a HF (High Frequency. radar at SANAE, Antarctica. It, and 35 similar HF radars, form an international network called SuperDARN which routinely measures ionospheric convection. A “map potential” technique is used to produce a global convection map every 2 minutes for each hemisphere which utilizes all existing radars ionospheric measurements of velocity with a spherical harmonic representation of the ionospheric electrostatic potential. High speed ionospheric plasma flows in the night sidesector, map to the magnetospheric tail, during periods which are magnetically quiet. They may be interpreted to be associated with the release of energy from a rapid reconfiguration of tail magnetic field lines due to reconnection. Such events are now known as ‘TRINNIs’ or ‘tail reconnection during IMF northward, non-substorm intervals’. Changes in the cross-polar cap potential, determined during the production of these maps, will be used as proxy for TRINNI events in this analysis. During a TRINNI event, we propose here that a portion of released energy may manifest as Pc5 (1-5 mHz. pulsations. Their presence will be sought by Fourier analysis of the radar’s Doppler velocity data. SuperDARN has the unique ability (due to its insituionospheric measurements over a very large area. to determine spectral information, azimuthal wave number, phase and group velocity and polarization properties of the Pc5 resonance. These parameters are essential clues to determine the generation mechanism. In particular, a sunward phase velocity would effectively rule out a number of popular candidates for the generation mechanism such as Kelvin-Helmholtz, solar wind coherent pulsations and solar wind pressure perturbations. Identifying the energy sources of Pc5 pulsations is an important and open question in space physics. The nature of the magnetosphere makes it a complex problem. For the first time, a different perturbation source may be proposed of magnetic reconnection in the magnetotail, such as during a TRINNI event. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.