SWM- Glossary of Terms


Auroras- An aurora (plural: auroras or aurorae) is a natural light display in the sky, particularly in the polar regions, caused by the collision of charged particles directed by the Earth’s magnetic field. An aurora is usually observed at night and typically occurs in the ionosphere. It is also referred to as a polar aurora or, collectively, as polar lights.

Coronal Holes- are areas where the Sun’s corona is darker, colder, and has lower-density plasma than average. These were found when X-ray telescopes in the Skylab mission were flown above the Earth’s atmosphere to reveal the structure of the corona. Coronal holes are linked to unipolar concentrations of open magnetic field lines. During solar minimum, coronal holes are mainly found at the Sun’s polar regions, but they can be located anywhere on the sun during solar maximum. The fast-moving component of the solar wind is known to travel along open magnetic field lines that pass through coronal holes.

Coronal Mass Ejection (CME)- A coronal mass ejection (CME) is a massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona or being released into space.[1]

Coronal mass ejections are often associated with other forms of solar activity, most notably solar flares, but a causal relationship has not been established. Most ejections originate from active regions on Sun’s surface, such as groupings of sunspots associated with frequent flares. CMEs occur during both the solar maxima and the solar minima of sun activity, albeit with decreased frequency during the minima.

Extreme Ultraviolet Radiation- (EUV or XUV) is high-energy ultraviolet radiation, generally defined to be electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths from 120 nm down to 10 nm, and therefore (by the Planck–Einstein equation) having photons with energies from 10 eV up to 124 eV. EUV is naturally generated by the solar corona and artificially by plasma and synchroton light sources.

Geomagnetic Storm- is a temporary disturbance of the Earth‘s magnetosphere caused by a disturbance in space weather. Associated with solar flares and resultant solar coronal mass ejections (CME), a geomagnetic storm is caused by a solar wind shock wave and/or cloud of magnetic field which typically strikes the Earth’s magnetic field 3 days after the event. The solar wind pressure on the magnetosphere and the solar wind magnetic field will increase or decrease depending on the Sun‘s activity. The solar wind pressure changes modify the electric currents in the ionosphere, and the solar wind’s magnetic field interacts with the Earth’s magnetic field causing the entire structure to evolve. Magnetic storms usually last 24 to 48 hours, but some may last for many days.[citation needed] In 1989, an electromagnetic storm disrupted power throughout most of Quebec[1] and caused aurorae as far south as Texas.[2]

Solar Flare- is a large explosion in the Sun‘s atmosphere that can release as much as 6 × 1025 joules of energy[1] (about a sixth of the total energy output of the Sun each second). The term is also used to refer to similar phenomena in other stars, where the term stellar flare applies.

X-rays and UV radiation emitted by solar flares can affect Earth’s ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb operation of radars and other devices operating at these frequencies.

SDO- The Solar Dynamics Observatory (SDO) is a NASA mission which will observe the Sun for over five years. Launched on February 11, 2010, the observatory is part of the Living With a Star (LWS) program.[3] The goal of the LWS program is to develop the scientific understanding necessary to effectively address those aspects of the connected SunEarth system that directly affect life and society. SDO’s goal is to understand the Sun’s influence on Earth and near-Earth space by studying the solar atmosphere on small scales of space and time and in many wavelengths simultaneously. SDO will investigate how the Sun’s magnetic field is generated and structured, how this stored magnetic energy is converted and released into the heliosphere and geospace in the form of solar wind, energetic particles, and variations in the solar irradiance.[4]

STEREO- (Solar TErrestrial RElations Observatory) is a solar observation mission.[1] Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth. This will enable stereoscopic imaging of the Sun and solar phenomena, such as coronal mass ejections.

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