Broadband electrostatic noise in the magnetotail - Its relation to plasma sheet dynamics,

Intense broadband electrostatic noise is often observed in the magnetotail when the fast tailward flow and the southward polarity of the magnetic field indicate the progress of reconnection. We compare features of the noise with simultaneous observations of the magnetic field, plasma and energetic electrons. The noise intensity seems to maximize when the plasma density minimizes and the energetic electron flux rises in a spikelike fasion, appreciably later than the onset of the fast tailward flow associated with the southward magnetic polarity. Spectral characteristics of the noise suggest that in its high frequency math formula part at least the noise does not belong to normal modes of plasma waves. Several possibilities are considered for what this noise might be, including quasi-thermal noise in the non-Maxwellian plasma, artificial noise generated by spacecraft interaction with the medium, or electrostatic noise with wavelengths less than a Debye length.