Statistical properties of the interplanetary microscale fluctuations
Abstract
We present a statistical study of shortperiod fluctuations in the interplanetary plasma velocity and magnetic field, using spacecraft observations with a time resolution of 72 s (Pioneer 6) and 5 min (Mariner 5). The goal of our analysis is a characterization of the parent population from which all individual microscale events on these time scales are drawn. As a rough measure of the energy density of a given fluctuation we consider the quantity ½ρV_{2}  V_{1}² + B_{2}  B_{1}²/8π, where ρ = (ρ_{1} + ρ_{2})/2 and the subscripts denote any two consecutive observations. If we group microscale changes according to their energy densities as compared to the energy density of the background magnetic field, we find that each grouping exhibits the following statistical properties, within the limits of observational uncertainty. (1) The vectors (V_{2}  V_{1}) and B_{2} × B_{1} tend to be perpendicular. (2) The vector (V_{2}  V_{1}) has a strong tendency to be parallel or antiparallel to the vector (B_{2}/ρ_{2}  B_{1}/ρ_{1}). (3) The magnitude of V_{2}  V_{1} tends to be of the order of (ρ/4π)^{1/2} B_{2}/ρ_{2}  B_{1}/ρ_{1} however, there are a significant number of events with V_{2}  V_{1} much less than (ρ/4π)^{1/2} B_{2}/ρ_{2}  B_{1}/ρ_{1}.
 Publication:

Journal of Geophysical Research
 Pub Date:
 December 1975
 DOI:
 10.1029/JA080i034p04713
 Bibcode:
 1975JGR....80.4713B
 Keywords:

 Cosmic Plasma;
 Interplanetary Magnetic Fields;
 Magnetic Variations;
 Plasma Dynamics;
 Statistical Analysis;
 Flow Velocity;
 Interplanetary Gas;
 Magnetohydrodynamic Waves;
 Mariner 5 Space Probe;
 Periodic Variations;
 Pioneer 6 Space Probe;
 Plasma Diagnostics;
 Radial Velocity;
 Tables (Data);
 Astrophysics;
 Particles and FieldsInterplanetary Space: Solar wind electric fields;
 Particles and FieldsInterplanetary Space: Solar wind magnetic fields