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Solar Radio Emission
Solar radio emission refers to radio waves that are naturally produced by the Sun, primarily from the lower and upper layers of the atmosphere called the chromosphere and Stellar corona, corona, respectively. The Sun produces radio emissions through four known mechanisms, each of which operates primarily by converting the energy of moving electrons into radiation. The four emission mechanisms are thermal bremsstrahlung (free-free) emission, gyromagnetic emission, plasma emission, and electron-cyclotron maser emission. The first two are ''incoherent'' mechanisms, which means that they are the summation of radiation generated independently by many individual particles. These mechanisms are primarily responsible for the persistent "background" emissions that slowly vary as structures in the atmosphere evolve. The latter two processes are ''coherent'' mechanisms, which refers to special cases where radiation is efficiently produced at a particular set of frequencies. Coherent mechanisms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Wave
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shorter than a grain of rice); at 30 Hz the corresponding wavelength is (longer than the radius of the Earth). Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects. Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver, which p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paul Wild (Australian Scientist)
Dr John Paul Wild Companion of the Order of Australia, AC Commander of the Order of the British Empire, CBE Master of Arts, MA Doctor of Science, ScD (University of Cambridge, Cantab.) Fellow of the Royal Society, FRS Australian Academy of Technological Sciences and Engineering, FTSE Fellow of the Australian Academy of Science, FAA (17 May 192310 May 2008) was a United Kingdom, British-born Australian scientist. Following service in World War II as a radar officer in the Royal Navy, he became a radio astronomy, radio astronomer in Australia for the Council for Scientific and Industrial Research, the fore-runner of the Commonwealth Scientific and Industrial Research Organisation (CSIRO). In the 1950s and 1960s he made discoveries based on radio observations of the Sun. In the late 1960s and early 1970s his team built and operated the world's first solar radio-spectrographs and subsequently the Culgoora radio-heliograph, near Narrabri, New South Wales. The Paul Wild Observatory at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atacama Large Millimeter Array
The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The array has been constructed on the elevation Chajnantor plateau - near the Llano de Chajnantor Observatory and the Atacama Pathfinder Experiment. This location was chosen for its high elevation and low humidity, factors which are crucial to reduce noise and decrease signal attenuation due to Earth's atmosphere. ALMA provides insight on star birth during the early Stelliferous era and detailed imaging of local star and planet formation. ALMA is an international partnership amongst Europe, the United States, Canada, Japan, South Korea, Taiwan, and Chile. Costing about US$1.4 billion, it is the most expensive ground-based telescope in operation. ALMA began scientific observations in the second half of 2011 and the first images were relea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Very Large Array
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes (twenty-seven of which are operational while one is always rotating through maintenance) deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Each of the massive telescopes is mounted on double parallel railroad tracks, so the radius and density of the array can be transformed to adjust the balance between its angular resolution and its surface brightness sensitivity. Astronomers using the VLA have made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowled ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siberian Solar Radio Telescope
The Siberian Solar Radio Telescope (SSRT) is a radio telescope located in the Russian republic of Buryatia designed for solar observation. It has been in operation since 1983. In 2017 it has been upgraded with the Siberian Radioheliograph. It operates in the microwave range (5.7 GHz) where the processes occurring in the solar corona A corona ( coronas or coronae) is the outermost layer of a star's atmosphere. It consists of plasma. The Sun's corona lies above the chromosphere and extends millions of kilometres into outer space. It is most easily seen during a total solar ... are accessible to observation over the entire solar disk. It is a crossed interferometer, consisting of two arrays of 128x128 parabolic antennas 2.5 meters in diameter each, spaced equidistantly at 4.9 meters and oriented in the E-W and N-S directions. It is located in a wooded valley separating two mountain ridges of the Eastern Sayan Mountains and Khamar-Daban, 220 km from Irkutsk, Russia. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gauribidanur Radio Observatory
The Gauribidanur Radio Observatory is a radio telescope observatory located at Gauribidanur, near Bengaluru. It is operated jointly by Raman Research Institute and the Indian Institute of Astrophysics. The observatory has been in operation since 1976. Location The Gauribidanur Observatory is located at Gauribidanur kolar diatrict (Latitude:13.60° N; Longitude:77.44° E), 100 km north of Bengaluru. Science and observation The Observatory has been used for studying various aspects of the Sun, galaxies and pulsars. A few observations with the array have been the first two-dimensional images of radio emission from slowly varying discrete sources in the outer solar corona, an all-sky survey of radio sources at 34.5 MHz in the declination range -30° S to 60° N, and a low frequency carbon recombination lines in astrophysical sources. Studies have also been done of gaseous remnants of exploding stars and the apparently vacant space between members of a cluster of galaxies. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nançay Radio Observatory
The Nançay Radio Observatory (in French: ''Station de Radioastronomie de Nançay''), opened in 1956, is part of Paris Observatory, and also associated with the University of Orléans. It is located in the department of Cher in the Sologne region of France. The station consists of several instruments. Most iconic of these is the large decimetric radio telescope, which is one of the largest radio telescopes in the world. Long established are also the radio heliograph, a T-shaped array, and the decametric array operating at wavelengths between 3 m and 30 m. History Radio astronomy emerged after the Second World War, when experts and surplus equipment became available for civilian use. The École Normale Superieure was given three 7.5 m diameter Würzburg Riese that the British had seized from the Germans during the war. These were initially deployed at a research centre of the French navy at Marcoussis. It was recognised that radio astronomy required a large, flat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sunspot
Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sunspots appear within active regions, usually in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle. Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from to . Larger sunspots can be visible from Earth without the aid of a telescope. They may travel at relative speeds, or proper motions, of a few hundred meters per second when they first emerge. Indicating intense magnetic activity, sunspots accompany other active region phenomena such as coronal loops, prominences, and reconnection events. Most solar flares and coronal mas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Interferometry
Sea interferometry, also known as sea-cliff interferometry, is a form of radio astronomy that uses radio waves reflected off the sea to produce an interference pattern. It is the radio wave analogue to Lloyd's mirror. The technique was invented and exploited in Australia between 1945 and 1948. Process A radio detecting aerial is placed on top of a cliff, which detects radio propagation coming directly from the source and radio waves reflected off the water surface. The two sets of waves are then combined to form an interference pattern such as that produced by two separate aerials. The reflected wavefront travels an additional distance before reaching the detector where ''h'' and ''i'' are the height of the cliff and the inclination (or altitude angle) of the incoming wavefront respectively. It acts as a second aerial twice the height of the cliff below the first. Sea interferometers are ''drift instruments'', that is, they are fixed and their pointing direction changes with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture Synthesis
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and orientation, the lobe-pattern of the interferometer produces an output which is one component of the Fourier transform of the spatial distribution of the brightness of the observed object. The image (or "map") of the source is produced from these measurements. Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations. For example, the Event Horizon Telescope project derived the first image of a black hole using aperture synthesis. Technical issues Aperture synthesis is possible only if both the amplitude and the phase of the incoming signal are measured by each telescope. For radio frequencies, this is possible by electronics, while for optical frequencies, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interferometry
Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, remote sensing, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms. Interferometers are devices that extract information from interference. They are widely used in science and industry for the measurement of microscopic displacements, refractive index changes and surface irregularities. In the case with most interferometers, light from a single source is split into two beams that travel in different optical paths, which are then combined again to produce interfer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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