Coronal Mass Ejections. The collateral beauty

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Did you hear a transit static noise on the radio for a well-prepared station? Guess what .. May be there was a coronal mass ejection hit the Earth.

A Coronal Mass Ejection (CME) is a huge cloud of high-energetic plasma ejected from the Sun with an
intrinsic magnetic field and hurled into space with speeds in the order of thousands kilometers per
second!. It is one of the most spectacular phenomena of space weather, which is the field concerned with
studying the near-Earth space environment.

The Sun is a mid-size, relative young star. It is believed that it is formed about 5 billion years ago, since it
was just a nebula cloud remnants of interstellar gases from an old exploded star. Under its own gravity,
the cloud begun to collapse on itself and hence the temperature, pressure, and density increased
dramatically at the cloud’s center and a nuclear fusion reaction is ignited .. That is when our Sun was born.

It is so big, a million Earth-size planet can fit easily inside the Sun, and it is mainly consists of Hydrogen (~
80%), Helium (~ 19%), and traces of other metallic elements (~ 1%). It is so dynamic object, according to
the fact that it is a giant ball of plasma (i.e. excited gas) each latitude layer rotates with a different speed
relative to its neighbor layers. And because of that, the solar magnetic field get tangled and become
complex at some regions. These regions are often called “active regions” or “sunspots” that can be seen
using a special telescope as dark spots on the sun’s photosphere. The magnetic field at these regions is
almost a thousand time stronger than the magnetic field of a neighbor quiet region, and it is where the
real action happens.


A CME at the right-side as observed by the LASCO coronagraph onboard SOHO satellite. The white circle represents the sun behind the occultation disk of the coronagraph. The bright feature on the top-left side is called “coronal streamer” that is a stream of high-energetic particles ejected from the solar corona at high-speeds.

At the sunspot group, when some opposite magnetic field lines reconnect with each other they release their potential energy as a sudden-bright flash of high intense X-rays emitted, known as a “solar flare”, and often it is associated with a large high-speed CME. If the intrinsic magnetic field of the CME was opposite to that of our Earth, that is a nightmare! .. Probably not.

Our Earth has a natural magnetic shield that protects us from being burned by the cosmic radiation coming from the sun or from the deep space, and it can deflects most of the incoming threatens away from us. But in some cases the main event is strong enough to cause horrible things, like destroying the satellites, frying the transformers and cutting the electricity from the power grid, disrupt the radio communications, cause corrosion in the gas pipelines, threaten the astronauts’’ life onboard the space stations, and it may alter our climate to worse. That is why space weather researchers and scientists worldwide study this kind of phenomena, trying to predict it to protect ourselves and our infrastructure from being harmed, using a set of instruments onboard satellites and at the ground stations.

CMEs are truly magnificent phenomenon, but devastating.

References: Moldwin, M. (2008). An introduction to space weather. Cambridge University Press.

Hundhausen, A. (1999). Coronal mass ejections. In The Many Faces of the Sun (pp. 143-200). Springer New York

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