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.
|Original language||English (US)|
|Title of host publication||Solar Wind Ten|
|Subtitle of host publication||Proceedings of the 10th International Solar Wind Conference|
|Editors||Marco Velli, Roberto Bruno, Francesco Malara|
|Publisher||American Institute of Physics Inc.|
|Number of pages||5|
|State||Published - Sep 2 2003|
|Event||10th International Solar Wind Conference - Pisa, Italy|
Duration: Jun 17 2002 → Jun 21 2002
|Name||AIP Conference Proceedings|
|Other||10th International Solar Wind Conference|
|Period||6/17/02 → 6/21/02|
Bibliographical noteFunding Information:
Work at UC Berkeley is supported by NASA grant FDNAG5-11804 to the University of California. The french contribution is supported by the Centre National D'Etudes Spatiales and the Centre National de la Recherche Scientifique.