Solar wind structure at large heliocentric distances: An interpretation of Pioneer 10 observations
Abstract
Examination of hourly values of the solar wind speed observed by the Pioneer 10 spacecraft beyond a heliocentric distance of 4 AU reveals (1) a prevalent ‘sawtoothlike’ speed-time profile, most speed fluctuations displaying a rapid rise and a much slower decline, and (2) the nearly universal appearance of abrupt (on the 1-hour time resolution of these data) changes in the speed on the rising portions of the speed fluctuations. These previously unreported characteristics, as well as the rate of decay of stream amplitudes derived earlier by Collard and Wolfe, are in general agreement with the predictions of stream propagation models that neglect any conversion of kinetic energy to thermal energy outside of shock fronts. Thus the Pioneer 10 observations give the first confirmation of the general concept of solar wind stream evolution employed in these models, i.e., that solar wind speed inhomogeneities appear to steepen to form shock waves and that the ‘wave amplitudes’ decay slowly as the shock waves propagate outward from the sun.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- March 1976
- DOI:
- 10.1029/JA081i007p01436
- Bibcode:
- 1976JGR....81.1436H
- Keywords:
-
- Interplanetary Medium;
- Pioneer 10 Space Probe;
- Solar Wind Velocity;
- Amplitudes;
- Astronomical Models;
- Decay Rates;
- Propagation Modes;
- Shock Wave Propagation;
- Time Response;
- Velocity Distribution;
- Particles and Fields-Interplanetary Space: Solar wind plasma