Preconditioning of the interplanetary medium due to isolated ICMEs

TL;DR

This study investigates how isolated ICMEs modify the interplanetary medium, affecting subsequent CME propagation and space weather modeling by analyzing pre- and post-event solar wind and magnetic field data.

Contribution

It provides a systematic analysis of the preconditioning effects of isolated ICMEs on the interplanetary medium, quantifying changes in solar wind and magnetic field properties.

Findings

Reduced solar wind density and pressure behind ICMEs

Increased solar wind velocity after ICMEs

Enhanced magnetic field intensity and radial alignment

Abstract

We perform a systematic study of the preconditioning of the interplanetary (IP) medium due to isolated interplanetary coronal mass ejections (ICMEs). Preconditioning is highly relevant when ICMEs, ejected in close succession and direction, modify the IP medium to allow subsequent ICMEs to propagate more freely, decelerate less, and retain higher kinetic energy at larger distances. We base our study on a sample of carefully selected events. The IP medium is analyzed during time intervals of 48 hours before and after the ICMEs in order to statistically quantify their impact on the properties of the solar wind (SW) and interplanetary magnetic field (IMF). We find that the SW behind ICMEs on average exhibits reduced density (-41%) and dynamic pressure (-29%), and increased total velocity (+15%), while the trailing IMF is more intense (+14%) and more radially aligned (13 degrees). The results suggest that even relatively low speed ICMEs can significantly precondition the IP medium. The results are relevant for better understanding of CME propagation and SW interaction, and hold implications for heliospheric models and applied research of space weather.