It is generally believed that the magnetic free energy accumulated in the corona serves as a main energy source for solar explosions such as coronal mass ejections (CMEs). In the framework of the flux rope catastrophe model for CMEs, the energy may be abruptly released either by an ideal magnetohydrodynamic (MHD) catastrophe, which belongs to a global magnetic topological instability of the sys...

Coronal mass ejections (CMEs) originate from closed magnetic field regions on the Sun, which are active regions and quiescent filament regions. The energetic populations such as halo CMEs, CMEs associated with magnetic clouds, geoeffective CMEs, CMEs associated with solar energetic particles and interplanetary type II radio bursts, and shock-driving CMEs have been found to originate from sunspo...

Coronal mass ejections (CMEs) are spectacular ejections of material from the Sun as seen in the coronal field of view. Regular observations are possible with both ground-based and space-based coronagraphs. I present our current understanding of CMEs based on multi-wavelength observations from groundbased instruments as well as from space missions such as SoHO. Based on the continuous and multi-...

Coronal Mass Ejections (CMEs) are large, energetic expulsions of mass and magnetic fields from the Sun; they can significantly affect large volumes of the heliosphere and appear to be a key cause of geomagnetic storms. The present study deals with the influence of Asymmetric 'Full' Halo CMEs, Partial Halo CMEs, Asymmetric and Complex 'Full' Halo CMEs and 'Full' Halo CMEs on cosmic ray intensity...

1. Basic Concepts 2. Sun and Heliosphere at Times of Solar Activity Minimum 2.1. Typical Solar Wind and its Sources 2.2. The Ballerina Model 2.3. Solar Wind Stream Structure 2.4. The Two Basic States of the Solar Wind 2.4.1. Differences 2.4.2. Communities 2.5. Solar Wind Acceleration and Expansion 2.6. Solar Wind Streams and Their Interactions 2.6.1. Corotating Interaction Regions in the Inner ...

We present a multiwavelength study of the 2005 September 13 eruption from NOAA 10808 that produced total four flares and two fast coronal mass ejections (CMEs) within ∼1.5 hours. Our primary attention is paid to the fact that these eruptions occurred in close succession in time, and that all of them were located along an S-shaped magnetic polarity inversion line (PIL) of the active region. In o...

Coronal mass ejections (CMEs) are large-scale magnetic structures expelled from the Sun due to MHD processes involving interaction between plasma and magnetic field in closed flux regions. I provide a summary of the observational signatures and current models on CME initiation. CMEs are traditionally observed using white light coronagraphs. I also provide a summary of various signatures of CMEs...

The interaction of multiple Coronal Mass Ejections (CMEs) has been observed by LASCO coronagraphs and by nearEarth spacecraft, and it is thought to be an important cause of geo-effective storms, large Solar Energetic Particles events and intense Type II radio bursts. New and future missions such as STEREO, the LWS Sentinels, and the Solar Orbiter will provide additional observations of the inte...

We compare the ‘‘magnetic breakout’’ model for coronal mass ejections (CMEs) with observed general properties of CMEs by analyzing in detail recent high-resolution MHD simulations of a complete breakout CME. The model produces an eruption with a three-part plasma density structure that shows a bright circular rim outlining a dark central cavity in synthetic coronagraphic images of total brightn...

Observations of type II radio bursts and energetic electron events indicate that shocks can form at 1Y3 solar radii and are responsible for the GeV nucleon 1 energies observed in ground level solar energetic particle (SEP) events. Here we provide the first study of the lower corona produced from 10 state-of-the-art models. In particular, we look to the Alfvén speed profiles as the criterion for...