Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter

Abstract

The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift and line width simultaneously over a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of the initiation and propagation of coronal mass ejections (CMEs). Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space weather monitoring.

A Solar Coronal Jet Event Triggers a Coronal Mass Ejection

“…However, another situation that the angular momentum of the jet was passed into that of the CME is not prohibited. As lack of direct observations on the rotational motion of the CME [discussions on this particular issue could be found in Tian et al, 2013, as an example], we could try to figure out if this situation is possible from the poloidal motion of magnetic clouds (MCs) which are the counterpart of CMEs in the interplanetary space. As derived from a velocity-modified cylindrical force-free flux rope model base on Wind observations, Wang et al [2015] found that almost all the MCs more or less had shown poloidal motion with meridian linear speed around 10 km s −1 .…”

Coronal Cavities: Observations and Implications for the Magnetic Environment of Prominences

“…viewer with radius). The Doppler measurements shown in Figure 7 incorporate a subtraction of the background coronal rotation using a median filter (Tian et al, 2013), so there is some ambiguity about precisely where flows shift from towards to away in the rotating frame. Nevertheless, there are clearly strong gradients in the flow of coronal plasma within the cavity, with functional dependence on radial distance from cavity center.…”

Coronal plasma diagnostics from ground‐based observations

“…The full width at half maximum (FWHM) of an optically thin spectral line is given by where c is the speed of light, λ 0 is the rest wavelength, k B is the Boltzmann constant, T i is the ion temperature, M is the ion mass, and v nth is a nonthermal velocity parameter which describes the unresolved, nonthermal motions of the ion. Line width measurements can thus provide critical information on the location of shocks, of turbulence, of ion heating in both closed and open magnetic field structures, identify subresolution rotating structures, to name a few, as discussed by Tian et al [].…”

“…These measurements encompass the region where a large fraction of the total energy of the CME event has already been released into CME plasma heating and acceleration. Tian et al [] already showed that such studies are possible.…”