[1] Many broadside coronal mass ejections (CMEs) propagate almost radially beyond the first couple of solar radii, and their angular widths remain nearly constant while propagating through the corona. Assuming that these characteristics hold true for halo CMEs that originate far from solar limbs, some useful geometric and kinematic properties of halo CMEs may be reproduced using a simple geomet...

[1] One of the main sources of uncertainty in quantifying the kinematic properties of coronal mass ejections (CMEs) using coronagraphs is the fact that coronagraph images are projected into the sky plane, resulting in measurements which can differ significantly from their actual values. By identifying solar surface source regions of CMEs using X-ray and Ha flare and disappearing filament data, ...

A solar flare was observed on 1997 April 7 with the Soft X-ray Telescope (SXT) on Yohkoh. The flare was associated with a “halo” coronal mass ejection (CME). The flaring region showed areas of reduced soft X-ray (SXR) brightness—“dimmings”—that developed prior to the CME observed in white light and persisted for several hours following the CME. The most prominent dimming regions were located ne...

We now have extensive X-ray (Yohkoh) and EUV observations of the behavior of coronal mass ejections (CMEs) at high temperatures in the lower corona. We also now have coronagraph observations from space with which to make identiications of the related phenomena. This paper reviews theories and observations of CMEs in this new context.

Coronal shocks are an important structure but without direct observations in solar and space physics. The strength of shocks plays a key role in shockrelated phenomena, such as radio bursts, SEP generation and so on. This paper will present an improved method of calculating Alfvén speed and shock strength near the Sun. In the method, observations as many as possible rather than onedimensional g...

Context. Coronal mass ejections (CMEs) are a manifestation of the Sun’s eruptive nature. They can have great impact on Earth, but also human activity in space and ground. Therefore, modelling their evolution as they propagate through interplanetary is essential. Aims. EUropean Heliospheric FORecasting Information Asset (EUHFORIA) data-driven, physics-based model, tracing CMEs background solar w...

We present general considerations regarding the derivation of the radial distances of coronal mass ejections (CMEs) from elongation angle measurements such as those provided by SECCHI and SMEI, focusing on measurements in the Heliospheric Imager 2 (HI-2) field of view (i.e. past 0.3 AU). This study is based on a three-dimensional (3-D) magneto-hydrodynamics (MHD) simulation of two CMEs observed...

The closest perihelion pass of Parker Solar Probe (PSP), so far, occurred between 16 and 26 November 2021 reached ~13.29 Rsun from Sun center. This resulted in very unique observations the solar corona by Wide-field Instrument for PRobe (WISPR). WISPR observed at least ten CMEs, some which were close that structures appear distorted. All CMEs appeared to have a magnetic flux rope (MFR) structur...

For some coronal mass ejections (CMEs), their interaction with the ambient solar wind can produce a forward-reverse shock pair. The high-speed mass ejecta compresses the plasma near the top of the CME on both sides of the tangential discontinuity which separates the CME plasma from the ambient solar wind plasma. The front of the compressed CME plasma propagates in the reverse direction relative...

Magnetic energy is believed to play amajor role in powering coronal mass ejections (CMEs). Freemagnetic energy is associated with electric currents that give the magnetic field more energy than a purely potential (current-free) field. For magnetic energy alone to power a CME, the energy must be sufficient to open the magnetic field to interplanetary space, to lift the ejecta against solar gravi...