The most energetic phenomena in the heliosphere are known to be coronal mass ejections (CMEs), which acquire their energy from the Sun's strained magnetic fields. Coronal Mass Ejections disrupt the flow of the solar wind and produce disturbances that strike the Earth with sometimes catastrophic results. Coronal mass ejections are often associated with solar flares and prominence eruptions but they can also occur in the absence of either of these processes. The frequency of CMEs varies with the sunspot cycle. At solar minimum we observe about one CME a week. Near solar maximum we observe an average of 2 to 3 CMEs per day. We have studied different characteristics of coronal mass ejection based on the observation form Large Angel and Spectrometric Coronagraph (LASCO) on board of the Solar and Heliospheric Observatory (SOHO) space craft during the period 1996 –2006. It is noteworthy that the rate of occurrence of Class B CMEs is more than class A CME’s. The occurrence spectrum of both classes of CMEs follows the trend of the phase of solar cycle and maximum number both types CME’s seems to be occurred during maximum solar activity. It is also observed that the maximum number of class A, Class B CMEs have speed range 0-500 km/sec. We have observed that maximum number of Class A, Class B CME’s occurred in apparent angular width range 00-900. It is also found that the maximum number of class A and class B CME’s have occurred when the position angle ranges in 50-1000 and 2500-3000 respectively.
Table of Contents
1. Introduction
2. Data and Analysis
3. Results and Discussion
4. Summary
Research Objectives
The primary objective of this work is to analyze the characteristics and occurrence patterns of Coronal Mass Ejections (CMEs) based on observational data from the SOHO/LASCO spacecraft for the period between 1996 and 2006, classifying them by position angle and speed to better understand their relationship with the solar cycle and geomagnetic activity.
- Analysis of CME occurrence frequency relative to the solar cycle phase.
- Classification of CMEs into two distinct groups (Class A and Class B) based on their position angle.
- Investigation of speed distributions and their correlation with mass ejection events.
- Examination of the relationship between solar activity, CMEs, and geomagnetic disturbances (space weather).
Excerpt from the Book
Introduction
So far, no consensus has been reached on a clear definition of coronal mass ejections (CMEs), which were previously known as "transient" after their discovery in 1971. The first experiments date back to 1984. Hundhausen et al. (1984) proposed an observational definition, i.e., "an observable change in the structure of the corona that (1) occurs over a period of minutes to several hours and (2) contains a new, clear, bright white light feature, the corona graphic field of view". In the first review of CMEs, Wagner (1984a) proposed a more physical description as "sudden outflows of dense plasma clouds from the outer atmosphere of the Sun" and added that "CMEs are a type of coronal transients, a general name for a coronal structure disturbance" for link to the original name.
Schwenn (1996) recommended and Hundhausen et al. (1984) suggests simply adding "appearance and external motion" to make it more precise, "because it emphasizes observation, it emphasizes the nature of the passing event, and it does not imply an interpretation of the feature and its possible origin." Surprisingly, he ignored the proposal of Wagner (1984a) without even citing it and preferred the terminology "solar mass ejections" (SME) after the early proposal of Gosling et al. (1975). Schwenn (1996) also ignored another alternative definition of a CME as “a new discrete luminosity on a scale of tens of minutes that is always observed moving outward” (e.g., Webb and Hundhausen 1987; Webb and Howard 2012) is implicitly related to their visual appearance in the chorographic field of view, but has the advantage of being more compact and mentions external motion, but may be too restrictive since we now know that very slow CMEs exist.
Summary of Chapters
Introduction: Provides a historical overview of CME studies, the lack of a standardized terminology, and the importance of CMEs for understanding solar and interplanetary physics.
Data and Analysis: Details the classification methodology, where CMEs are categorized into Class A (50°-200°) and Class B (200°-360°) based on their measurement position angle using SOHO/LASCO data.
Results and Discussion: Analyzes the statistical trends of CME occurrences, their speed distributions, and their connection to solar activity levels and geomagnetic storms.
Summary: Concludes that CME occurrences follow the solar cycle phase and provides synthesis regarding the physical characteristics observed during the study window.
Keywords
Coronal mass ejections, solar cycle, position angle, geomagnetic storm, heliosphere, solar flare, solar activity, plasma, SOHO, LASCO, space weather, magnetic flux, solar wind, proton flux, coronagraph.
Frequently Asked Questions
What is the core subject of this research paper?
The paper focuses on the statistical characteristics of Coronal Mass Ejections (CMEs) observed by the SOHO/LASCO spacecraft between 1996 and 2006.
What are the primary areas of research interest?
Key topics include CME classification, the relationship between solar cycle activity and CME frequency, speed distributions, and the impact of CMEs on geomagnetic disturbances.
What is the main objective of the study?
The research aims to classify CMEs based on position angle to characterize their properties and correlate these findings with overall solar activity cycles.
Which scientific methodology is employed?
The authors performed a large-scale statistical analysis using observational data from the SOHO/LASCO instrument, grouping CME events into specific position angle ranges (Class A and B).
What topics are discussed in the main body of the paper?
The main sections cover the historical evolution of CME definitions, the physics of magnetic energy release, the statistical categorization of CME speeds and position angles, and the resulting space weather implications.
Which keywords define this document?
Prominent keywords include Coronal mass ejections, solar cycle, position angle, geomagnetic storm, and heliosphere.
How are Class A and Class B CMEs defined in the paper?
Class A CMEs are defined as having a measurement position angle in the range of 50° to 200°, while Class B CMEs fall within the 200° to 360° range.
What does the study conclude regarding CME activity and the solar cycle?
The study concludes that the occurrence rate of both CME classes follows the solar cycle phase, with the maximum number of events occurring during maximum solar activity.
What correlation exists between solar activity and surface temperature mentioned in the text?
The text discusses studies suggesting that solar variability influenced northern hemisphere temperature trends since 1881, identifying it as a recurring topic in the debate surrounding climatic influences.
- Quote paper
- Rajesh Kumar Mishra (Author), Rekha Agarwal (Author), 2024, Geometry of Coronal Mass Ejections. CMEs Geometry, Munich, GRIN Verlag, https://www.grin.com/document/1471517
