New, highly sensitive proton magnetometers

Abstract

Considerable attention has recently been focused on the interaction between downgoing hydromagnetic waves, manifested as ULF pulsations on ground magnetometer records, and the ionospheric plasma. Models of the interaction involve parameters which require experimental evaluation. We consider two aspects. First, new measurements of standing oscillations of low latitude geomagnetic field lines permit the calculation of the ionospheric scale size of the pulsation signal and the damping factor. The role and diurnal variation of ionospheric O+ may also be monitored. Second, we discuss observations of correlated ULF oscillations measured in the F region using HF Doppler sounders, and on the ground with magnetometers, during a six month campaign. Statistical data and case studies illustrate that a simple phase relationship exists between certain classes of magnetic and ionospheric oscillations. These results raise new questions on the modelling of hydromagnetic waves in the ionosphere.