Publication Date:
2018-03-15
Description:
It has long been a goal of the heliophysics community to understand solar wind variability at heliocentric distances other than 1 AU, especially at ∼1.5 AU not only due to the steepening of solar wind stream interactions outside 1 AU but also the number of missions available there to measure it. In this study, we use 35 months of solar wind and IMF data taken at Mars by the MAVEN spacecraft to conduct an autocorrelation analysis of the solar wind speed, density, and dynamic pressure, which is derived from the speed and density, as well as the IMF strength and orientation. We found that the solar wind speed is coherent, i.e. has an autocorrelation coefficient above 1/e, over roughly 56 hours, while the density and pressure are coherent over smaller intervals of roughly 25 and 20 hours, respectively, and that the IMF strength is coherent over time intervals of approximately 20 hours, while the cone and clock angles are considerably less steady but still somewhat coherent up to time lags of roughly 16 hours. We also found that when the speed, density, pressure, or IMF strength is higher than average, the solar wind or IMF becomes uncorrelated more quickly, while when they are below average, it tends to be steadier. This analysis allows us to make estimates of the values of solar wind plasma and IMF parameters when they are not directly measured, as well as provide an approximation of the error associated with that estimate.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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