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Investigating Interplanetary Coronal Mass Ejections

Study reveals key properties of ICMEs and their impact on space weather.

― 4 min read


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Table of Contents

Interplanetary coronal mass ejections (ICMEs) are large bursts of solar wind and magnetic fields rising above the solar corona or being released into space. These events have unique properties that make them interesting to study. They differ from the regular solar wind in several important ways, which helps scientists investigate various space plasma phenomena.

Characteristics of ICMEs

ICMEs typically show a strong magnetic field and low temperatures for protons, which means that the magnetic pressure is greater than the pressure from the ions in the plasma. This situation creates a specific environment for understanding fluctuations in the solar wind. The strong magnetic fields often found in ICMEs are linked to large-scale magnetic structures called Flux Ropes.

A flux rope is essentially a twisting structure of magnetic fields, and when a coronal flux rope erupts, it can travel out into space as an ICME. These ICMEs carry magnetic fields that are often much stronger than those found in the ambient solar wind. The combination of low proton temperatures and the unique magnetic structures contributes to specific behaviors in the plasma dynamics of ICMEs.

The Role of Magnetic Fluctuations

Similar to other types of solar wind, ICMEs contain fluctuations across different scales. These fluctuations are essential for understanding how energy moves and how the plasma behaves in a magnetic field. The fluctuations in the magnetic field follow certain patterns, described by power-law relationships. These patterns help identify the energy contributions from various sources as the solar wind evolves.

Fluctuations can be categorized into different ranges based on their scale. At larger scales, fluctuations are believed to originate from the solar corona, while at smaller scales, they become more chaotic and are associated with turbulence. Understanding these fluctuations helps scientists to better grasp the dynamics occurring within ICMEs.

Data Collection and Analysis

Researchers study ICMEs using data from advanced spacecraft designed to observe the inner heliosphere. These spacecraft measure the magnetic field and plasma properties during various ICME events. By collecting data from multiple events, scientists can analyze trends and changes related to the properties of ICMEs.

In a detailed analysis of 28 ICMEs observed between specific distances from the Sun, researchers focus on key parameters like fluctuation power, compressibility, and the way magnetic fields behave across different distances. Identifying how these properties change helps understand how ICMEs interact with the solar wind and the surrounding space environment.

Key Findings from the Analysis

  1. Fluctuation Power and Distance: There is a noticeable trend showing that fluctuation power decreases as the spacecraft moves further from the Sun. This behavior implies that the processes governing ICMEs evolve with distance.

  2. Spectral Indices: The spectral index, which indicates the steepness of the fluctuations, typically stays constant in a certain range. This consistency suggests that turbulence properties in ICMEs do not vary significantly with distance.

  3. Correlation Lengths: Researchers calculate correlation lengths to understand how the magnetic fields relate to each other at different distances. When comparing these lengths between different types of fields, distinct behaviors emerge, indicating the influence of the magnetic structure.

  4. Magnetic Compressibility: The study reveals that the magnetic compressibility of ICMEs does not increase with distance as is typical for the general solar wind. This finding indicates that ICMEs have a different mechanism at play, perhaps owing to their unique structure.

  5. Inertial Range Properties: The inertial range of fluctuations appears independent of the specific characteristics of the ICMEs themselves. This suggests that certain properties of turbulence in the solar system may be universal.

Implications for Understanding Space Weather

The work done in analyzing ICMEs has significant implications for space weather prediction. By understanding the mechanisms within ICMEs and their interactions with solar wind, scientists can develop better models for predicting how these events may impact Earth and other planets.

ICMEs can lead to disturbances in Earth’s magnetic field, potentially causing geomagnetic storms that affect satellite operations, communications, and power grids. Knowledge gained from ICMEs can enhance forecasting, which is crucial for preparing and mitigating the impacts of solar events.

Conclusion

ICMEs serve as a complex yet fascinating aspect of space plasma physics. By studying their properties, researchers gain valuable insights into the behavior of solar wind, magnetic fields, and the dynamics of space weather. Continued investigation into ICMEs is essential for improving our understanding of the sun's influence on the solar system and enhancing our capability to predict space weather events. Understanding the characteristics and fluctuations of ICMEs ultimately contributes to a broader comprehension of the interactions between the sun and planetary environments, paving the way for advancements in space exploration and safety measures.

Original Source

Title: Turbulence Properties of Interplanetary Coronal Mass Ejections in the Inner Heliosphere: Dependence on Proton Beta and Flux Rope Structure

Abstract: Interplanetary coronal mass ejections (ICMEs) have low proton beta across a broad range of heliocentric distances and a magnetic flux rope structure at large scales, making them a unique environment for studying solar wind fluctuations. Power spectra of magnetic field fluctuations in 28 ICMEs observed between 0.25 and 0.95 au by Solar Orbiter and Parker Solar Probe have been examined. At large scales, the spectra were dominated by power contained in the flux ropes. Subtraction of the background flux rope fields reduced the mean spectral index from $-5/3$ to $-3/2$ at $kd_i \leq 10^{-3}$. Rope subtraction also revealed shorter correlation lengths in the magnetic field. The spectral index was typically near $-5/3$ in the inertial range at all radial distances regardless of rope subtraction, and steepened to values consistently below $-3$ with transition to kinetic scales. The high-frequency break point terminating the inertial range evolved approximately linearly with radial distance and was closer in scale to the proton inertial length than the proton gyroscale, as expected for plasma at low proton beta. Magnetic compressibility at inertial scales did not show any significant correlation with radial distance, in contrast to the solar wind generally. In ICMEs, the distinctive spectral properties at injection scales appear mostly determined by the global flux rope structure while transition-kinetic properties are more influenced by the low proton beta; the intervening inertial range appears independent of both ICME features, indicative of a system-independent scaling of the turbulence.

Authors: S. W. Good, O. K. Rantala, A. -S. M. Jylhä, C. H. K. Chen, C. Möstl, E. K. J. Kilpua

Last Update: 2023-09-26 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2307.09800

Source PDF: https://arxiv.org/pdf/2307.09800

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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