Solar wind spatial scales in and comparisons of hourly Wind and ACE plasma and magnetic field data

TLDR

The study analyzed hourly averaged, Earth‑time‑shifted IMF and plasma data from ACE and Wind, normalizing ACE densities and temperatures to Wind values as part of the OMNI 2 dataset, to assess systematic and random differences. ACE proton densities are up to 18% higher and temperatures up to 25% lower than Wind/SWE values, with random differences between normalized ACE and Wind data growing with transverse separation—more rapidly for IMF than plasma parameters—and autocorrelation analysis shows progressively shorter spatial scales for flow speed, IMF magnitude, plasma density/temperature, and IMF components, with IMF scales shorter during solar quiet times but plasma scales independent of solar cycle.

Abstract

Hourly averaged interplanetary magnetic field (IMF) and plasma data from the Advanced Composition Explorer (ACE) and Wind spacecraft, generated from 1 to 4 min resolution data time‐shifted to Earth have been analyzed for systematic and random differences. ACE moments‐based proton densities are larger than Wind/Solar Wind Experiment (SWE) fits‐based densities by up to 18%, depending on solar wind speed. ACE temperatures are less than Wind/SWE temperatures by up to ∼25%. ACE densities and temperatures were normalized to equivalent Wind values in National Space Science Data Center's creation of the OMNI 2 data set that contains 1963–2004 solar wind field and plasma data and other data. For times of ACE‐Wind transverse separations <60 R E , random differences between Wind values and normalized ACE values are ∼0.2 nT for ∣ B ∣, ∼0.45 nT for IMF Cartesian components, ∼5 km/s for flow speed, and ∼15 and ∼30% for proton densities and temperatures. These differences grow as a function of transverse separation more rapidly for IMF parameters than for plasma parameters. Autocorrelation analyses show that spatial scales become progressively shorter for the parameter sequence: flow speed, IMF magnitude, plasma density and temperature, IMF X and Y components, and IMF Z component. IMF variations have shorter scales at solar quiet times than at solar active times, while plasma variations show no equivalent solar cycle dependence.