Coronal Mass Ejections In Solar Cycle Research Articles

Type II radio bursts and their association with coronal mass ejections in solar cycles 23 and 24

Context. Meter-wavelength type II solar radio bursts are thought to be the signatures of shock-accelerated electrons in the corona. Studying these bursts can give information about the initial kinematics, dynamics, and energetics of coronal mass ejections (CMEs) in the absence of white-light observations. Aims. We investigate the occurrence of type II bursts in solar cycles 23 and 24 and their association with CMEs. We also explore whether type II bursts might occur in the absence of a CME. Methods. We performed a statistical analysis of type II bursts that occurred between 200 and 25 MHz in solar cycles 23 and 24 and determined the temporal association of these radio bursts with CMEs. We categorized the CMEs based on their linear speed and angular width and studied the distribution of type II bursts with fast (≥500 km s−1), slow (< 500 km s−1), wide (≥60°), and narrow (< 60°) CMEs. We explored the dependence of type II bursts occurrence on the phases of the solar cycle. Results. Our analysis shows that during solar cycles 23 and 24, 768 and 435 type II bursts occurred, respectively. Of these, 79% were associated with CMEs in solar cycle 23, and 95% were associated with CMEs in solar cycle 24. However, only 4% and 3% of the total number of CMEs were accompanied by type II bursts in solar cycle 23 and 24, respectively. Most of the type II bursts in both cycles were related to fast and wide CMEs (48%). We also determined the typical drift rate and duration for type II bursts, which is 0.06 MHz s−1 and 9 min. Our results suggest that type II bursts dominate at heights ≈1.7 − 2.3 ± 0.3 R⊙. A clear majority have an onset height around 1.7 ± 0.3 R⊙ assuming the four-fold Newkirk model. Conclusions. The results indicate that most of the type II bursts had a white-light CME counterpart, but a few type II bursts lacked a clear CME association. There were more CMEs in cycle 24 than in cycle 23. However, cycle 24 contained fewer type II radio bursts than cycle 23. The onset heights of type II bursts and their association with wide CMEs reported in this study indicate that the early lateral expansion of CMEs may play a key role in the generation of these radio bursts.

Occurrence Rate of Radio-Loud and Halo CMEs in Solar Cycle 25: Prediction Using their Correlation with the Sunspot Number

The coronal mass ejections (CMEs) from the Sun are known for their space weather and geomagnetic consequences. Among all CMEs, so-called radio-loud (RL) and halo CMEs are considered the most energetic in the sense that they are usually faster and wider than the general population of CMEs. Hence the study of RL and halo CMEs has become important and the prediction of their occurrence rate in a future cycle will give a warning in advance. In the present paper, the occurrence rates of RL and halo CMEs in solar cycle (SC) 25 are predicted. For this, we obtained good correlations between the numbers of RL and halo CMEs in each year and the yearly mean sunspot numbers in the previous two cycles. The predicted values of sunspot numbers in SC 25 by NOAA/NASA were considered as representative indices and the corresponding numbers of RL and halo CMEs have been determined using linear relations. Our results show that the maximum number of RL and halo CMEs will be around 39 $/pm$ 3 and 45 $/pm$ 4, respectively. Removing backside events, a set of front-side events was also considered separately and the front-side events alone in SC 25 are predicted again. The peak values of front-side RL and halo events have been estimated to be around 31 $/pm$ 3 and 29 $/pm$ 3 respectively. These results are discussed in comparison with the predicted values of sunspots by different authors.

Quantifying the Propagation of Fast Coronal Mass Ejections from the Sun to Interplanetary Space by Combining Remote Sensing and Multi-point In Situ Observations

Abstract In order to have a comprehensive view of the propagation and evolution of coronal mass ejections (CMEs) from the Sun to deep interplanetary space beyond 1 au, we carry out a kinematic analysis of seven CMEs in solar cycle 23. The events are required to have coordinated coronagraph observations, interplanetary type II radio bursts, and multi-point in situ measurements at the Earth and Ulysses. A graduated cylindrical shell model, an analytical model without free parameters, and a magnetohydrodynamic model are used to derive CME kinematics near the Sun, to quantify the CME/shock propagation in the Sun–Earth space, and to connect in situ signatures at the Earth and Ulysses, respectively. We find that each of the seven CME-driven shocks experienced a major deceleration before reaching 1 au and thereafter propagated with a gradual deceleration from the Earth to larger distances. The resulting CME/shock propagation profile for each case is roughly consistent with all the data, which verifies the usefulness of the simple analytical model for CME/shock propagation in the heliosphere. The statistical analysis of CME kinematics indicates a tendency that the faster the CME, the larger the deceleration, and the shorter the deceleration time period within 1 au. For several of these events, the associated geomagnetic storms were mainly caused by the southward magnetic fields in the sheath region. In particular, the interaction between a CME-driven shock and a preceding ejecta significantly enhanced the pre-existing southward magnetic fields and gave rise to a severe complex geomagnetic storm.

On some statistical characteristics of radio-rich CMEs in the solar cycles 23 and 24

In this paper we have presented the properties of radio-rich coronal mass ejections (CMEs), during the period 1997–2013. The CME event accompanied by the type II radio burst is referred to as radio-loud (RL), while the one lacking a type II burst is termed radio-quiet (RQ). These radio rich CMEs produce type II (1–14MHz), i.e. decametric–hectometric or DH radio burst. It is found that the average width of all DH CMEs during the study period is 235° and 75% of the DH CMEs are halo CMEs in solar cycle 24. The DH CMEs linear speeds distribution is in the range 112–3387km/s, with an average speed of 1043km/s; the acceleration varies between 434m/s2 and −179m/s2. About 62% of the DH CMEs are decelerated. A CME associated with a type II burst and originating close to the center of the solar disk typically results in a shock at Earth in 2–3days and hence can be used to predict shock arrival at Earth.

Association of CMEs with solar surface activity during the rise and maximum phases of solar cycles 23 and 24

The cyclical behaviors of sunspots, flares and coronal mass ejections (CMEs) for 54 months from 2008 November to 2013 April after the onset of Solar Cycle (SC) 24 are compared, for the first time, with those of SC 23 from 1996 November to 2001 April. The results are summarized below. (i) During the maximum phase, the number of sunspots in SC 24 is significantly smaller than that for SC 23 and the number of flares in SC 24 is comparable to that of SC 23. (ii) The number of CMEs in SC 24 is larger than that in SC 23 and the speed of CMEs in SC 24 is smaller than that of SC 23 during the maximum phase. We individually survey all the CMEs (1647 CMEs) from 2010 June to 2011 June. A total of 161 CMEs associated with solar surface activity events can be identified. About 45% of CMEs are associated with quiescent prominence eruptions, 27% of CMEs only with solar flares, 19% of CMEs with both active-region prominence eruptions and solar flares, and 9% of CMEs only with active-region prominence eruptions. Comparing the association of the CMEs and their source regions in SC 24 with that in SC 23, we notice that the characteristics of source regions for CMEs during SC 24 may be different from those of SC 23.

On some properties of prominence eruptions and the associated CMEs in solar cycle 23

This work includes a study of some properties such as speed, apparent width, acceleration and latitudes, etc. of all types of Prominence Eruptions (PEs) and the associated Coronal Mass Ejections (CMEs) observed during the period of 1997–2006 by Nobeyama Radioheliograph (NORH) and SOHO/LASCO covering the solar cycle 23. The average speed of prominences and associated CMEs are 51 km/sec and 559 km/sec, respectively. The average angular width is 32∘ and 74∘, respectively. As expected the associated CMEs are relatively faster and wider than the prominences.

On distribution of CMEs speed in solar cycle 23

We have analyzed the data for more than 12900 coronal mass ejections (CMEs) which were obtained by SOHO/LASCO during the period of 1996–2007. The online CME catalogue contains all major CMEs detected by LASCO C2 and C3 coronagraphs. Basically we determine the CME speeds from the linear and quadratic fits to the height–time measurements. It is found that linear (constant speed) fit is preferable for 90% of the CMEs. The distribution of speeds of CMEs in solar cycle 23 is presented along with those obtained by others. As expected, the speeds decrease in the decay phase of the cycle 23. There is an unusual drop in speed in the year 2001 and an abnormal increase in speed in the year 2003 due to the high concentration of CMEs, X-class soft X-ray flares, solar energetic particle (SEP) events and interplanetary shocks observed during October–November period called Halloween events.