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Coronal Ejections and Magnetic Storms

Coronal mass ejections (CMEs) are explosive and violent eruptions of charged, magnetic field-inducing particles and gas (plasma) from the Sun's outer coronal layer. The ejection from the Sun's corona can be massive (e.g., estimates of CME mass often range in the billions of tons. Ejections propel particles in specific directions, some directly crossing Earth's orbital position, at velocities up to 1,200 miles per second (1,931 km per second) or 4,320,000 miles per hour (6,952,366 km/h) in an ionized plasma (also known as the solar wind). Solar CMEs that are Earth directed disrupt and distort Earth's magnetic field and result in geomagnetic storms.

Although the solar wind is continuous, CMEs reflect large-scale increases in wind (i.e., particle) mass and velocity that are capable of generating geomagnetic storms.

Solar coronal ejections and magnetic storms interact with Earth's magnetosphere to produce spectacular auroral displays. Intense storms may interfere with communications and preclude data transfer from Earth orbiting satellites.

Solar coronal ejections and magnetic storms provide the charged particles that result in the northern and southern lights—aurora borealis and aurora australialis—electromagnetic phenomena that usually occur near Earth's polar regions. The auroras result from the interaction of Earth's magnetic field with ionic gas particles, protons, and electrons streaming outward in the solar wind.

The rate of solar coronal ejections is correlated to solar sunspot activity that cycles between maximum levels of activity (i.e., the solar maximum) approximately every 11 years. During solar maximums, it is not uncommon to observe multiple coronal ejections per day. At solar minimum, one solar coronal ejection per day is normal. The last peak of activity occurred in 2001.

Earth's core structure provides it with a relatively strong internal magnetic field (oriented about 10–12 degrees from the polar axis). Earth's magnetosphere protects the Earth from bombardment by Comes by deflecting and modifying the solar wind. At the interface of Earth's magentosphere and the solar wind there is a "bow wave" or magnetic shock wave to form a magnetosheath protecting the underlying magnetosphere that extends into Earth's ionosphere.

Coronal mass ejections not only interact with Earth's magnetic field, they also interact with each other. Stronger or faster ejections may subsume prior weaker ejections directed at the same region of space in a process known as CME cannibalization. Accordingly, the strength of magnetic storms on Earth may not directly correlate to observed coronal ejections. In addition, CME cannibalization can alter predicted arrival time of geomagnetic storms because the interacting CMEs can change the eruption velocity.

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Science EncyclopediaScience & Philosophy: Condensation to Cosh