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Preconditioning of the Interplanetary Medium Due To Isolated ICMEs.

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Title: Preconditioning of the Interplanetary Medium Due To Isolated ICMEs.
Authors: Kajdič, Primož1 (AUTHOR) primoz@igeofisica.unam.mx, Temmer, Manuela2 (AUTHOR), Blanco‐Cano, Xochitl1 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Jun2025, Vol. 130 Issue 6, p1-15. 15p.
Subject Terms: Interplanetary magnetic fields, Solar magnetic fields, Space environment, Coronal mass ejections, Interplanetary medium, Solar wind
Abstract: We perform a systematic study of the preconditioning of the interplanetary (IP) medium due to isolated IP 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 hr 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° ${}^{\circ}$). 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. Plain Language Summary: Interplanetary coronal mass ejections (ICME) have been recognized as the drivers of the most intense geomagnetic storms. This study looks at how isolated ICMEs change the space environment around them, making it easier for later ICMEs to travel. When ICMEs are ejected close together and in the same direction, they can reduce resistance in the solar wind (SW), allowing the following ICMEs to move faster and retain more energy. By analyzing selected events and studying the SW and magnetic field 48 hr before and after each ICME, we found that the plasma behind an ICME tends to have lower density and pressure but higher speed and magnetic field strength. This means that even smaller ICMEs can significantly alter their surroundings. These findings help improve our understanding of SW behavior and space weather predictions. Key Points: Statistical study quantifying the potential preconditioning of the interplanetary medium by isolated interplanetary coronal mass ejections (ICMEs)Behind ICMEs, on average the solar wind is less dense, faster, and the magnetic field is stronger and more radial than upstreamOur results suggest that slow ICMEs precondition the interplanetary magnetic field more than fast ones [ABSTRACT FROM AUTHOR]
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Abstract:We perform a systematic study of the preconditioning of the interplanetary (IP) medium due to isolated IP 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 hr 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° ${}^{\circ}$). 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. Plain Language Summary: Interplanetary coronal mass ejections (ICME) have been recognized as the drivers of the most intense geomagnetic storms. This study looks at how isolated ICMEs change the space environment around them, making it easier for later ICMEs to travel. When ICMEs are ejected close together and in the same direction, they can reduce resistance in the solar wind (SW), allowing the following ICMEs to move faster and retain more energy. By analyzing selected events and studying the SW and magnetic field 48 hr before and after each ICME, we found that the plasma behind an ICME tends to have lower density and pressure but higher speed and magnetic field strength. This means that even smaller ICMEs can significantly alter their surroundings. These findings help improve our understanding of SW behavior and space weather predictions. Key Points: Statistical study quantifying the potential preconditioning of the interplanetary medium by isolated interplanetary coronal mass ejections (ICMEs)Behind ICMEs, on average the solar wind is less dense, faster, and the magnetic field is stronger and more radial than upstreamOur results suggest that slow ICMEs precondition the interplanetary magnetic field more than fast ones [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2025JA033887