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It is known that during Solar/Stellar Flare, plasma from the corona of the star is released into the space, and travels comparatively slowly.

In an hypothetical situation, does the coronal mass also consist of electromagnetic radiation within the optical wavelengths? And if so, is it possible to observe the incoming coronal mass ejection from the ground/surface of the Earth way before it approaches?

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Coronal mass ejections consist of a very hot, but thin, plasma. Their very weak intrinsic emission would be dominated by ultraviolet and X-ray lines and bremsstrahlung continuum. There is very little optical radiation.

However, CMEs can and are monitored at optical wavelengths using the light that they scatter from the Sun. The process is Thomson scattering from the free electrons in the plasma. This is done by spacecraft because the Earth's atmosphere makes it very difficult to achieve the contrast necessary to observe the scattered light close to the Sun (except during total solar eclipses).

A CME takes a couple of days to travel from the Sun to the Earth and such monitoring can give "space weather forecasts" associated with magnetospheric phenomena triggered by the impact of CMEs.

An example picture taken by the LASCO white light imager on board the SOHO spacecraft is shown below. Everything here is viewed in scattered light. The Sun is obscured by an occulting disk.I have picked an example showing the eruption of a CME.

LASCO image

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  • $\begingroup$ Don't forget that looking at the polarised light on optical wavelengths one can also observe the CMEs from Earth. One example is the Mark-IV K-coronameter in Mauna Loa. $\endgroup$
    – dvdgc13
    Apr 7, 2019 at 11:10
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We can see coronas normally by blocking out the main body of sun (think during eclipses) so I would assume yes? Except the sun is so bright in optical wavelength it would be hard to see

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Yes.It is possible to see the ejection of mass into the corona not only during eclipses but also by means of an instrument named Coronograph which blinds the light of the photosphere.

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