- Conference date: 17-31 June 2002
- Location: Pisa (Italy)
In the solar wind at 1 AU, coherent electrostatic waveforms in the ion acoustic frequency range (between the ion and electron plasma frequencies) have been recently observed by the WAVES/TDS instrument on WIND. Many of these structures have been interpreted in terms of Weak Double Layers (WDL), since they sustain a net potential drop of roughly 1 mV directed towards the Earth. The TDS data are compared to the continuous measurements of thermal and non thermal electric spectra above 4 kHz obtained by the WAVES/TNR instrument : this allows us to determine the frequency of occurrence of the WDL at the L1 Lagrange point. Extrapolating this result provides a total potential drop of about 300 to 1000 Volts on the Sun‐Earth distance, compatible with the potential needed to maintain the global charge neutrality in the solar wind. This suggests that the interplanetary electrostatic potential is not continuous but results from a succession of WDL, distributed intermittently between the Sun and the Earth. We also find that the energy of the non thermal fluctuations on TNR between 4 and 6 kHz is correlated to the interplanetary electrostatic field, parallel to the spiral magnetic field, calculated with a two‐fluid model, thus providing further evidence of a relation between the interplanetary electrostatic field and the electrostatic fluctuations in the ion acoustic range.
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