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Alfvén Surface
The Alfvén surface is the boundary separating the sun's corona from the solar wind defined as where the coronal plasma's Alfvén speed and the large-scale solar wind speed are equal. It is named after Hannes Alfvén, and is also called Alfvén critical surface or Alfvén point. Parker Solar Probe became the first spacecraft that crossed Alfvén surface of the Sun. Definition The Sun does not have a solid surface. However, it does have a superheated atmosphere, made of solar material bound to the Sun by gravity and magnetic forces. The Sun's corona extends far beyond the solar surface, or photosphere, and is considered the outer boundary of the Sun. It marks the transition to the solar wind which moves through the Solar System. This limit is defined by the distance at which disturbances in the solar wind cannot propagate back to the solar surface. Those disturbances cannot propagate back towards the Sun if the outbound solar wind speed exceeds Mach one, the speed of 'sound' as de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parker Solar Probe Touches The Sun
Parker may refer to: Persons * Parker (given name) * Parker (surname) Places Place names in the United States *Parker, Arizona *Parker, Colorado *Parker, Florida *Parker, Idaho *Parker, Kansas *Parker, Missouri *Parker, North Carolina *Parker, Pennsylvania *Parker, South Carolina *Parker, South Dakota *Parker, Texas in Collin County * Parker, Johnson County, Texas * Parker, Washington *Parker City, Indiana *Parker County, Texas *Parker Dam, at Lake Havasu on the Colorado River between Arizona and California *Parker Road (DART station), a light rail terminal on Parker Road in Plano, Texas *Parker School, Montana *Parker Strip, Arizona *Parker Township, Marshall County, Minnesota *Parker Township, Morrison County, Minnesota *Parker Township, Butler County, Pennsylvania *Parker Center, a former police building in Los Angeles Elsewhere * C. W. Parker Carousel, a Burnaby Village Museum exhibit in British Columbia, Canada * Mount Parker (Philippines), a Mindanao island volcano of the Ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar 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 eclipse, but it is also observable with a coronagraph. Spectroscopic measurements indicate strong ionization in the corona and a plasma temperature in excess of , much hotter than the surface of the Sun, known as the photosphere. The word ''corona'' is , in turn derived . History In 1724, French-Italian astronomer Giacomo F. Maraldi recognized that the aura visible during a solar eclipse belongs to the Sun, not to the Moon. In 1809, Spanish astronomer José Joaquín de Ferrer coined the term 'corona'. Based in his own observations of the 1806 solar eclipse at Kinderhook (New York), de Ferrer also proposed that the corona was part of the Sun and not of the Moon. English astronomer Norman Lockyer identified the first element unknown o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Wind
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the solar wind plasma also includes a mixture of materials found in the solar plasma: trace amounts of heavy ions and atomic nuclei such as C, N, O, Ne, Mg, Si, S, and Fe. There are also rarer traces of some other nuclei and isotopes such as P, Ti, Cr, 54Fe and 56Fe, and 58Ni, 60Ni, and 62Ni. Superposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface. At a distance of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alfvén Speed , an asteroid discovered in 1960, named after Hannes Alfvén
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Alfvén may refer to: People * Hannes Alfvén (1908–1995), Swedish plasma physicist and Nobel Prize in Physics laureate * Hugo Alfvén (1872–1960), Swedish composer, conductor, violinist, and painter * Marie Triepcke Krøyer Alfvén (1867–1940), commonly known as Marie Krøyer, Danish painter, wife of Hugo Other * Alfvén wave, a type of magnetohydrodynamic wave, named after Hannes Alfvén * 1778 Alfvén 1778 Alfvén, also designated , is a carbonaceous Themistian asteroid from the outer region of the asteroid belt, approximately 20 kilometers in diameter. It was discovered on 26 September 1960, by astronomers Cornelis van Houten, Ingrid van Hou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hannes Alfvén
Hannes Olof Gösta Alfvén (; 30 May 1908 – 2 April 1995) was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics (MHD). He described the class of MHD waves now known as Alfvén waves. He was originally trained as an electrical power engineer and later moved to research and teaching in the fields of plasma physics and electrical engineering. Alfvén made many contributions to plasma physics, including theories describing the behavior of aurorae, the Van Allen radiation belts, the effect of magnetic storms on the Earth's magnetic field, the terrestrial magnetosphere, and the dynamics of plasmas in the Milky Way galaxy. Education Alfvén received his PhD from the University of Uppsala in 1934. His thesis was titled "Investigations of High-frequency Electromagnetic Waves." Early years In 1934, Alfvén taught physics at both the University of Uppsala and the Nobel Institute for Physics (late ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parker Solar Probe
The Parker Solar Probe (PSP; previously Solar Probe, Solar Probe Plus or Solar Probe+) is a NASA space probe launched in 2018 with the mission of making observations of the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million km or 4.3 million miles) from the center of the Sun, and by 2025 will travel, at closest approach, as fast as , or 0.064% the speed of light. It is the fastest object ever built. The project was announced in the fiscal 2009 budget year. The cost of the project is US$1.5 billion. Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft, which was launched on 12 August 2018. It became the first NASA spacecraft named after a living person, honoring nonagenarian physicist Eugene Newman Parker, professor emeritus at the University of Chicago. A memory card containing the names of over 1.1 million people was mounted on a plaque and installed below the spacecraft's high-gain antenna on 18 May 2018. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosphere
The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/''phos, photos'' meaning "light" and σφαῖρα/''sphaira'' meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will escape without being scattered. A photosphere is the deepest region of a luminous object, usually a star, that is transparent to photons of certain wavelengths. Temperature The surface of a star is defined to have a temperature given by the effective temperature in the Stefan–Boltzmann law. Stars, except neutron stars, have no solid or liquid surface. Therefore, the photosphere is typically used to describe the Sun's or another star's visual surface. Composition of the Sun The Sun is composed primarily of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar System" and "solar system" structures in theinaming guidelines document. The name is commonly rendered in lower case ('solar system'), as, for example, in the ''Oxford English Dictionary'' an''Merriam-Webster's 11th Collegiate Dictionary''. is the gravity, gravitationally bound system of the Sun and the objects that orbit it. It Formation and evolution of the Solar System, formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The solar mass, vast majority (99.86%) of the system's mass is in the Sun, with most of the Jupiter mass, remaining mass contained in the planet Jupiter. The four inner Solar System, inner system planets—Mercury (planet), Mercury, Venus, Earth and Mars—are terrest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Radii
Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: :1\,R_ = 6.957\times 10^8 \hbox is approximately 10 times the average radius of Jupiter, about 109 times the radius of the Earth, and 1/215th of an astronomical unit, the distance of the Earth from the Sun. It varies slightly from pole to equator due to its rotation, which induces an oblateness in the order of 10 parts per million. Measurements The unmanned SOHO spacecraft was used to measure the radius of the Sun by timing transits of Mercury across the surface during 2003 and 2006. The result was a measured radius of . Haberreiter, Schmutz & Kosovichev (2008) determined the radius corresponding to the solar photosphere to be . This new value is consistent with helioseismic estimates; the same study showed that previous estimates using inflection poin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FIELDS
Fields may refer to: Music *Fields (band), an indie rock band formed in 2006 *Fields (progressive rock band), a progressive rock band formed in 1971 * ''Fields'' (album), an LP by Swedish-based indie rock band Junip (2010) * "Fields", a song by Sponge from ''Rotting Piñata'' (1994) Businesses * Field's, a shopping centre in Denmark * Fields (department store), a chain of discount department stores in Alberta and British Columbia, Canada Places in the United States * Fields, Oregon, an unincorporated community * Fields (Frisco, Texas), an announced planned community Other uses * Fields (surname), a list of people with that name * Fields Avenue (other), various roads * Fields Institute, a research centre in mathematical sciences at the University of Toronto * Fields Medal, for outstanding achievement in mathematics * Caulfield Grammarians Football Club, also known as The Fields * FIELDS, a spacecraft instrument on the Parker Solar Probe See also * Mrs. Fields, an A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SWEAP
SWEAP (Solar Wind Electrons Alphas and Protons) is an instrument on the unmanned space probe to the Sun, the Parker Solar Probe. The spacecraft with SWEAP on board was launched by a Delta IV Heavy on 12 August 2018 from Cape Canaveral, Florida. SWEAP includes two types of instruments, the Solar Probe Cup (SPC) and Solar Probe Analyzers (SPAN). SWEAP has four sensors overall, and is designed to take measurements of the Solar wind including electrons and ions of hydrogen (protons) and helium (these are the main components of the Solar wind and coronal plasma). Design SWEAP consists of the Solar Probe Cup (SPC), a faraday cup which faces the Sun and is designed to measure electrons and ions in the space environment near the Sun; the Solar Probe Analyzers (SPAN-A and SPAN-B); and the SWEAP electronics module (SWEM). The Solar Probe Cup is a Sun facing instrument directly exposed to the Sun, and had to be designed to handle the high temperature conditions at 9-10 Solar radii from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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