Fast magnetic fluctuations in the solar wind: Helios 1
Abstract
The Helios search coil experiment provides accurate low background noise measurements of interplanetary magnetic fluctuation spectra from about 4 Hz to 2.2 kHz adjacent to the frequency band from 0 to 4 Hz of the Technical University of Braunschweig flux-gate magnetometer. Apart from a slowly varying fluctuation component ranging up to 100 Hz near 1 AU and beyond 500 Hz near 0.3 AU the following superposed ‘events’ can be discerned in the fluctuation spectra which also have a distinct signature in the slowly varying magnetic field: (1) directional discontinuities acting as wave guide boundaries, (2) directional discontinuities producing whistler wave fields because of instability, (3) reversible magnetic field variations, mostly dips of about 1 min duration associated with whistler wave fields, (4) interplanetary shocks, where, for example, the oblique shock of January 8, 1975, has a thickness of about 1 proton gyroradius and produces an increase in whistler wave fields by more than 2 orders o‧ magnitude in power spectral density leading to a power spectrum of 1 γ²/Hz f-3.64 in the wake region.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- August 1977
- DOI:
- 10.1029/JA082i022p03201
- Bibcode:
- 1977JGR....82.3201N
- Keywords:
-
- Helios 1;
- Interplanetary Medium;
- Magnetic Variations;
- Solar Wind;
- Low Noise;
- Magnetic Signatures;
- Oblique Shock Waves;
- Power Spectra;
- Satellite-Borne Instruments;
- Waveguides;
- Whistlers;
- Particles and Fields-Interplanetary Space: Electromagnetic radiation;
- Particles and Fields-Interplanetary Space: Shock waves;
- Particles and Fields-Interplanetary Space: Solar wind magnetic fields;
- Particles and Fields-Interplanetary Space: Instruments and techniques