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Moreton Waves
A Moreton wave, Solar Tsunami, or Moreton-Ramsey wave is the chromospheric signature of a large-scale solar corona shock wave. Described as a kind of solar "tsunami", they are generated by solar flares. They are named for American astronomer Gail Moreton, an observer at the Lockheed Solar Observatory in Burbank, and Harry E. Ramsey, an observer who spotted them in 1959 at The Sacramento Peak Observatory. He discovered them in time-lapse photography of the chromosphere in the light of the Balmer alpha transition. There were few follow-up studies for decades. Then the 1995 launch of the Solar and Heliospheric Observatory (SOHO) led to observation of coronal waves, which cause Moreton waves. Moreton waves were a research topic again. (SOHO's EIT instrument discovered another, different wave type called "EIT waves".) The reality of Moreton waves (also known as fast-mode MHD waves) has also been confirmed by the two Solar Terrestrial Relations Observatory (STEREO) spacecraft. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extreme Ultraviolet Imaging Telescope
The Extreme ultraviolet Imaging Telescope (EIT) is an instrument on the SOHO spacecraft used to obtain high-resolution images of the solar corona in the ultraviolet range. The EIT instrument is sensitive to light of four different wavelengths: 17.1, 19.5, 28.4, and 30.4 nm, corresponding to light produced by highly ionized iron (XI)/(X), (XII), (XV), and helium (II), respectively. EIT is built as a single telescope with a quadrant structure to the entrance mirrors: each quadrant reflects a different colour of EUV light, and the wavelength to be observed is selected by a shutter that blocks light from all but the desired quadrant of the main telescope. The EIT wavelengths are of great interest to solar physicists because they are emitted by the very hot solar corona but not by the relatively cooler photosphere of the Sun; this reveals structures in the corona that would otherwise be obscured by the brightness of the Sun itself. EIT was originally conceived as a viewfinder instr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Transition Region
The solar transition region is a region of the Sun's atmosphere between the upper chromosphere and corona. It is important because it is the site of several unrelated but important transitions in the physics of the solar atmosphere: * Below, gravity tends to dominate the shape of most features, so that the Sun may often be described in terms of layers and horizontal features (like sunspots); above, dynamic forces dominate the shape of most features, so that the transition region itself is not a well-defined layer at a particular altitude. * Below, most of the helium is not fully ionized, so that it radiates energy very effectively; above, it becomes fully ionized. This has a profound effect on the equilibrium temperature (see below). * Below, the material is opaque to the particular colors associated with spectral lines, so that most spectral lines formed below the transition region are absorption lines in infrared, visible light, and near ultraviolet, while most lines formed at o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Spicule
In solar physics, a spicule, also known as a fibril or mottle, is a dynamic jet of plasma in the Sun's chromosphere about 300 km in diameter.Quantifying Spicules, Tiago M. D. Pereira, Bart De Pontieu, and Mats Carlsson, ''The Astrophysical Journal'' 759, #1 (October 2012), pp. 18-34, , . They move upwards with speeds between 15 and 110 km/s from the photosphere and last a few minutes each. They were discovered in 1877 by Angelo Secchi, but the physical mechanism that generates them is still hotly debated. Description Spicules last for about 15 minutes; at the solar limb they appear elongated (if seen on the disk, they are known as "mottles" or "fibrils"). They are usually associated with regions of high magnetic flux; their mass flux is about 100 times that of the solar wind. They rise at a rate of 20 km/s (or 72,000 km/h) and can reach several thousand kilometers in height before collapsing and fading away. Prevalence There are about 3,000,000 active spicul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Prominence
A prominence, sometimes referred to as a filament, is a large plasma and magnetic field structure extending outward from the Sun's surface, often in a loop shape. Prominences are anchored to the Sun's surface in the photosphere, and extend outwards into the solar corona. While the corona consists of extremely hot plasma, prominences contain much cooler plasma, similar in composition to that of the chromosphere. Prominences form over timescales of about a day and may persist in the corona for several weeks or months, looping hundreds of thousands of kilometers into space. Some prominences may give rise to coronal mass ejections. Scientists are currently researching how and why prominences are formed. A typical prominence extends over many thousands of kilometers; the largest on record was estimated at over long, roughly a solar radius. History The first detailed description of a solar prominence was in 14th-century Laurentian Codex, describing the Solar eclipse of 1 May 11 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OSO 8
The Orbiting Solar Observatory (abbreviated OSO) Program was the name of a series of American space telescopes primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully into low Earth orbit by NASA between 1962 and 1975 using Delta rockets. Their primary mission was to observe an 11-year sun spot cycle in UV and X-ray spectra. The initial seven (OSO 1–7) were built by Ball Aerospace, then known as Ball Brothers Research Corporation (BBRC), in Boulder, Colorado.Todd Neff (2010From Jars to the Stars: How Ball Came to Build a Comet-Hunting Machine Denver, CO.: Earthview Media. OSO 8 was built by Hughes Space and Communications Company, in Culver City, California. History The basic design of the entire series featured a rotating section, the "Wheel", to provide gyroscopic stability. A second section, the "Sail", was driven electrically against the Wheel's rotation, and stabilized to point at the Sun. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helioseismology
Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology (also coined by Gough), which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The modern field is separated into global helioseismology, which studies the Sun's resonant modes directly, and local helioseismology, which studies the propagation of the component waves near the Sun's surface. Helioseismology has contributed to a number of scientific breakthroughs. The most notable was to show the predicted neutrino flux from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Wave
In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a ''wave orbit''. Gravity waves on an air–sea interface of the ocean are called surface gravity waves (a type of surface wave), while gravity waves that are the body of the water (such as between parts of different densities) are called ''internal waves''. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides. The period of wind-generated gravity waves on the free surface of the Earth's ponds, lakes, seas and oceans are predominantly between 0.3 and 30 secon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroseismology
Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature and chemical composition. Because the resulting oscillation modes are sensitive to different parts of the star, they inform astronomers about the internal structure of the star, which is otherwise not directly possible from overall properties like brightness and surface temperature. Asteroseismology is closely related to helioseismology, the study of stellar pulsation specifically in the Sun. Though both are based on the same underlying physics, more and qualitatively different information is available for the Sun because its surface can be resolved. Theoretical background By linearly perturbing the equations defining the mechanical equilibrium of a star (i.e. mass conservation and hydrostatic equilibrium) and assuming that the pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speed
In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is not the same as velocity. Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel, the knot is commonly used. The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum ''c'' = metres per second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PhysOrg
Phys.org is an online science, research and technology news aggregator offering briefs from press releases and reports from news agencies (a form of journalism sometimes pejoratively called churnalism). The website also produces its own science journalism. Phys.org is one of the most updated science websites, with an average of 98 posts per day. It is part of the Science X network of websites, headquartered on the Isle of Man, United Kingdom. In April 2011, Phys.org launched the Medical Xpress site dedicated to content on medicine and health. See also * EurekAlert! * Science Daily ''Science Daily'' is an American website launched in 1995 that aggregates press releases and publishes lightly edited press releases (a practice called churnalism) about science, similar to Phys.org and EurekAlert!. The site was founded by mar ... References External links * British news websites Technology websites British technology news websites News aggregators British science websit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronal Mass Ejection
A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted theoretical understanding of these relationships has not been established. If a CME enters interplanetary space, it is referred to as an interplanetary coronal mass ejection (ICME). ICMEs are capable of reaching and colliding with Earth's magnetosphere, where they can cause geomagnetic storms, aurorae, and in rare cases damage to electrical power grids. The largest recorded geomagnetic perturbation, resulting presumably from a CME, was the solar storm of 1859. Also known as the Carrington Event, it disabled parts of the at the time newly created United States telegraph network, starting fires and shocking some telegraph operators. Near solar maxima, the Sun produces about three CMEs every day, whereas near solar minima, there is about ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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