The essential role of multi-point measurements in investigations of turbulence, three-dimensional structure, and dynamics: the solar wind beyond single scale and the Taylor Hypothesis

TL;DR

This paper emphasizes the importance of multi-point measurements in space plasmas to accurately understand turbulence, structure, and dynamics, highlighting limitations of single spacecraft data and proposing mission strategies for comprehensive analysis.

Contribution

It advocates for multispacecraft missions to resolve the space-time structure of heliospheric plasmas, addressing key gaps in turbulence and space weather research.

Findings

Single spacecraft measurements are insufficient for full space-time characterization.

Multispacecraft measurements can resolve ambiguities in plasma turbulence analysis.

Various mission types are proposed to study turbulence across the Heliosphere.

Abstract

Space plasmas are three-dimensional dynamic entities. Except under very special circumstances, their structure in space and their behavior in time are not related in any simple way. Therefore, single spacecraft in situ measurements cannot unambiguously unravel the full space-time structure of the heliospheric plasmas of interest in the inner heliosphere, in the Geospace environment, or the outer heliosphere. This shortcoming leaves numerous central questions incompletely answered. Deficiencies remain in at least two important subjects, Space Weather and fundamental plasma turbulence theory, due to a lack of a more complete understanding of the space-time structure of dynamic plasmas. Only with multispacecraft measurements over suitable spans of spatial separation and temporal duration can these ambiguities be resolved. We note that these characterizations apply to turbulence across a wide range of scales, and also equally well to shocks, flux ropes, magnetic clouds, current sheets, stream interactions, etc. In the following, we will describe the basic requirements for resolving space-time structure in general, using turbulence' as both an example and a principal target or study. Several types of missions are suggested to resolve space-time structure throughout the Heliosphere.