Prof. DENG Linhua from Yunnan Observatories, Chinese Academy of Sciences (CAS) with collaborators (Prof. WANG Feng, Prof. DENG Hui, and LI Xia from Guangzhou University) investigated the quasi-periodic variations of the coronal mass ejection (CMEs) with different angular widths. The CMEs from 1996 January 1 to 2021 August 31 were classified by angular width. Frequency and time–frequency analysis methods were used to systematically analyze the quasi-periodic variations corresponding to CMEs with different angular widths in the northern and southern hemispheres. This work was published in The Astrophysical Journal Supplement Series.

CMEs are large expulsions of magnetized plasma from the Sun, and attract considerable attention as they have far reaching consequences in solar, coronal and interplanetary physics. Determining the spatial and temporal evolution characteristics of CMEs, especially their possible periodic patterns, is valuable for establishing the unique correlations among CMEs, intense solar flares, and geomagnetic disturbances.

The quasi-periodicity of the CMEs with different angular widths can reveal whether CMEs with different geomagnetic effectiveness might have different periods. In this study, the researchers used the latest Coordinated Data Analysis Workshops (CDAW) catalog to study the quasi-periodicity of CMEs with different angular widths based on the CME occurrence rate. The CMEs were classified into four types: narrow CMEs, normal CMEs, partial-halo CMEs, and halo CMEs. The researchers found that, for CMEs of different angular widths, there are indeed various periods: the Rieger-type periodicity, the 10 rotations, and the quasi-biennial oscillations.

The researchers also found that the occurrence rate of CMEs exhibits statistically significant short- and medium-range oscillations characterized by various periodicity, intermittency, and asymmetric development in the northern and southern solar hemispheres. The quasi-periodicities of the CMEs obtained in their work were previously found in solar flare activity, in the solar wind, in the interplanetary magnetic field, and in the geomagnetic activity. Therefore, the quasi-periodic variations of the CMEs should be a connecting agent among the oscillations in the coronal magnetic activity, solar flare eruptions and interplanetary space.

This work can be helpful for understanding of how magnetic energy is built up, stored, and released in magnetic flux systems, the origin and the formation process of CMEs, which are essential for solar physicists to reveal magnetic activity cycle and predict catastrophic space weather.

Contact:
DENG Linhua
Yunnan Observatories, CAS
Email: lhdeng@ynao.ac.cn