Spatial Variation in the Responses of the Surface External and Induced Magnetic Field to the Solar Wind

TL;DR

This study maps how the Earth's surface magnetic field responds spatially to solar wind variations, revealing systematic differences based on region, season, and magnetic local time, using a novel regression approach.

Contribution

Introduces a spatially resolved regression model of the geomagnetic response to solar wind, highlighting regional and temporal variations in lag and sensitivity.

Findings

SEIMF response varies systematically with ionospheric region and season.

Lag times between solar wind and geomagnetic response range from 15 to 65 minutes.

The model explains up to 75% of variance in the polar cap region.

Abstract

We analyze the spatial variation in the response of the surface geomagnetic field (or the equivalent ionospheric current) to variations in the solar wind. Specifically, we regress a reanalysis of surface external and induced magnetic field (SEIMF) variations onto measurements of the solar wind. The regression is performed in monthly sets, independently for 559 regularly spaced locations covering the entire northern polar region above 50 magnetic latitude. At each location, we find the lag applied to the solar wind data that maximizes the correlation with the SEIMF. The resulting spatial maps of these independent lags and regression coefficients provide a model of the localized SEIMF response to variations in the solar wind, which we call {\guillemotleft}Spatial Information from Distributed Exogenous Regression.{\guillemotright} We find that the lag and regression coefficients vary systematically with ionospheric region, season, and solar wind driver. In the polar cap region the SEIMF is best described by the (B$_{y}$) component of the interplanetary magnetic field (50-75% of total variance explained) at a lag the SEIMF is best described by the solar wind that varies with season and magnetic local time (MLT), from $\sim$15-20 min for dayside and afternoon MLT (except in Oct-Dec) to typically 30-40 min for nightside and morning MLT and even longer (60-65 min) around midnight MLT.