Shock waves are common in astrophysical environments. Because of the low ambient density, most astronomical shocks are collisionless. This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system. Such shocks were first theorised by De Hoffmann and Teller, who studied shock waves in magnetized fluids with infinite conductivity. The precise mechanism for energy dissipation and entropy generation at such shocks is still under investigation, but it is widely accepted that the general mechanism driving these shocks consists of wave particle interaction and plasma instabilities, that operate on the scale of plasma skin depth, which is typically much shorter than the mean free path.
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| - Shock waves in astrophysics (en)
- 激波 (天文物理) (zh)
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| - Shock waves are common in astrophysical environments. Because of the low ambient density, most astronomical shocks are collisionless. This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system. Such shocks were first theorised by De Hoffmann and Teller, who studied shock waves in magnetized fluids with infinite conductivity. The precise mechanism for energy dissipation and entropy generation at such shocks is still under investigation, but it is widely accepted that the general mechanism driving these shocks consists of wave particle interaction and plasma instabilities, that operate on the scale of plasma skin depth, which is typically much shorter than the mean free path. (en)
- 激波在天文物理的環境中屢見不鮮。一些在天文物理中的激波例子如下：
* 太陽系的弓形震波（bow shock）：近年來一直在爭議太陽系中是否存在弓形震波。
* 超新星殘骸驅動激波穿越星際物質（interstellar medium，ISM）。
* 當大質量恆星爆炸成為核心塌縮超新星產生激波。
* 星雲的重力塌縮或分子雲之間的碰撞造成星際氣體的衝擊。
* 在星系團邊緣的吸積衝擊。 由於低密度的環境，多數天文學的激波是。這意味著因為平均自由徑太大，經常超過系統的尺度，激波不是由兩個物體的形成的。人們普遍認為驅動這些激波的機制是，這是由電漿表面深度所掌控，因為它通常比自由路徑短得多。 眾所周知無碰撞的激波是非常高能量的高能粒子，雖然觀測上還不能明確證實高能量的光子是由質子、電子或者兩者都是，輻射出來的；一般都認為費米加速機制的加速產生高能粒子。人們通常都認超新星殘骸的激波在星際物質間的擴散造成激波，加速了在地球大氣層觀察到的宇宙射線。 在恆星環境中的激波，像是恆星內部核心塌縮形成的超新星爆炸，往往成為輻射介質激波。這種衝擊是光子與物質的墊子撞擊產生的，並且這種衝擊的下游是由輻射能量木度主導，而不是物質的熱能。 (zh)
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| - HH 1/2 , HH 34 , and HH 47 were numbered in order of their discovery; it is estimated that there are up to 150,000 such objects in the Milky Way. (en)
- The crab nebula supernova remnant. Hubble Space Telescope mosaic image assembled from 24 individual Wide Field and Planetary Camera 2 exposures taken in October 1999, January 2000, and December 2000. (en)
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| - Examples of shock waves found in astrophysics; Herbig-Haro object and supernova remnants . (en)
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| - Crab Nebula.jpg (en)
- HH 47 HH 34 and HH 2.jpg (en)
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| - Shock waves are common in astrophysical environments. Because of the low ambient density, most astronomical shocks are collisionless. This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system. Such shocks were first theorised by De Hoffmann and Teller, who studied shock waves in magnetized fluids with infinite conductivity. The precise mechanism for energy dissipation and entropy generation at such shocks is still under investigation, but it is widely accepted that the general mechanism driving these shocks consists of wave particle interaction and plasma instabilities, that operate on the scale of plasma skin depth, which is typically much shorter than the mean free path. It is known that collisionless shocks are associated with extremely high energy particles, although it has not been definitively established if the high energy photons observed are emitted by protons, electrons or both. The energetic particles are in general believed to be accelerated by the Fermi acceleration mechanism. It is usually agreed that shocks caused by supernova remnants expanding in the interstellar medium accelerate the cosmic rays measured above the Earth's atmosphere. Shock waves in stellar environments, such as shocks inside a core collapse supernova explosion often become radiation mediated shocks. Such shocks are formed by photons colliding with the electrons of the matter, and the downstream of these shocks is dominated by radiation energy density rather than thermal energy of matter. An important type of astrophysical shock is the relativistic shock, in which the shock velocity is a non-negligible fraction of the speed of light. These shocks are unique to astrophysical environments, and can be either collisionless or radiation mediated. Relativistic shocks are theoretically expected in gamma ray bursts, active galactic nucleus jets and in some types of supernovae. (en)
- 激波在天文物理的環境中屢見不鮮。一些在天文物理中的激波例子如下：
* 太陽系的弓形震波（bow shock）：近年來一直在爭議太陽系中是否存在弓形震波。
* 超新星殘骸驅動激波穿越星際物質（interstellar medium，ISM）。
* 當大質量恆星爆炸成為核心塌縮超新星產生激波。
* 星雲的重力塌縮或分子雲之間的碰撞造成星際氣體的衝擊。
* 在星系團邊緣的吸積衝擊。 由於低密度的環境，多數天文學的激波是。這意味著因為平均自由徑太大，經常超過系統的尺度，激波不是由兩個物體的形成的。人們普遍認為驅動這些激波的機制是，這是由電漿表面深度所掌控，因為它通常比自由路徑短得多。 眾所周知無碰撞的激波是非常高能量的高能粒子，雖然觀測上還不能明確證實高能量的光子是由質子、電子或者兩者都是，輻射出來的；一般都認為費米加速機制的加速產生高能粒子。人們通常都認超新星殘骸的激波在星際物質間的擴散造成激波，加速了在地球大氣層觀察到的宇宙射線。 在恆星環境中的激波，像是恆星內部核心塌縮形成的超新星爆炸，往往成為輻射介質激波。這種衝擊是光子與物質的墊子撞擊產生的，並且這種衝擊的下游是由輻射能量木度主導，而不是物質的熱能。 天文物理的激波有一種很重要的是相對論激波，這種激波的速度相較於光速是不能被忽略的。這種激波在天體的實質環境中，是既無碰撞也無輻射物質的一種。相對論激波的理論預期是在活躍星系核、伽瑪射線暴的噴流和某些類型的超新星爆炸的噴流。 (zh)
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