Using in-situ solar-wind observations to generate inner-boundary conditions to outer-heliosphere simulations, 1: Dynamic time warping applied to synthetic observations

TL;DR

This paper demonstrates that dynamic time warping significantly improves the accuracy of solar-wind boundary conditions derived from in-situ 1-AU observations for outer-heliosphere simulations.

Contribution

It introduces the application of dynamic time warping to enhance the interpolation of solar-wind data from 1 AU for outer-heliosphere modeling, outperforming traditional methods.

Findings

DTW reduces errors in solar-wind input data by an order of magnitude.

Corotation methods introduce discontinuities and large errors.

Dynamic time warping offers a promising approach for better boundary conditions.

Abstract

The structure and dynamics of the magnetospheres of the outer planets, particularly Saturn and Jupiter, have been explored both through remote and in-situ observations. Interpreting these observations often necessitates simultaneous knowledge of the solar-wind conditions impinging on the magnetosphere. Without an available upstream monitor, solar-wind context is typically provided using models initiated with either the output of magnetogram-constrained coronal models or, more commonly, in-situ observations from 1 AU. While 1-AU observations provide a direct measure of solar wind conditions, they are single-point observations and thus require interpolation to provide inputs to outer-heliosphere solar-wind models. In this study we test the different interpolation methods using synthetic 1-AU observations of time-evolving solar-wind structure. The simplest method is "corotation", which assumes solar-wind structure is steady state and rotates with the Sun. This method of reconstruction produces discontinuities in the solar-wind inputs as new observations become available. This can be reduced by corotating both back and forward in time, but this still introduces large errors in the magnitude and timing of solar wind streams. We show how the dynamic time warping (DTW) algorithm can provide around an order-of-magnitude improvement in solar-wind inputs to outer-heliosphere model from in-situ observations near 1 AU. This is intended to build the foundation for further work demonstrating and validating methods to improve inner-boundary conditions to outer-heliosphere solar-wind models, including dealing with solar wind transients and quantifying the improvements at Saturn and Jupiter.