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The optical surface of the Sun (the photosphere) is known to have a temperature of approximately 6,000 K. Above it lies the solar corona at a temperature of 1,000,000 K. The high temperature of the corona shows that it is heated by something other than direct heat conduction from the photosphere.
It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere, and two main mechanisms have been proposed to explain coronal heating. The first is wave heating, in which sound, gravitational and magnetohydrodynamic waves are produced by turbulence in the convection zone. These waves travel upward and dissipate in the corona, depositing their energy in the ambient gas in the form of heat. The other is magnetic heating, in which magnetic energy is continuously built up by photospheric motion and released through magnetic reconnection in the form of large solar flares and myriad similar but smaller events.
Currently, it is unclear whether waves are an efficient heating mechanism. All waves except Alfvén waves have been found to dissipate or refract before reaching the corona. In addition, Alfvén waves do not easily dissipate in the corona. Current research focus has therefore shifted towards flare heating mechanisms. One possible candidate to explain coronal heating is continuous flaring at small scales, but this remains an open topic of investigation.
An Alfvén wave in a plasma is a low-frequency traveling oscillation of the ions and the magnetic field (by low frequency we mean that the wave frequency is well below the ion cyclotron frequency). The ion mass density provides the inertia and the magnetic field line tension provides the restoring force.
The wave propagates in the direction of the magnetic field, although waves exist at oblique incidence and smoothly change into the magnetosonic wave when the propagation is perpendicular to the magnetic field.
The motion of the ions and the perturbation of the magnetic field are in the same direction and transverse to the direction of propagation. The wave is dispersionless.
Originally posted by Trams
reply to post by SevenThunders
We will probably never be sure if were right about how the universe works. I mean whos there to check us? Anyway, I always felt like something is missing, when I am learning something new about space. Like what I am hearing is not the whole truth. There is so many things that need to be discovered about the physics of the universe.
“Rather than learning how to think scientifically, students are generally being told about science and asked to remember facts.” “Their science teachers failed to make it clear that science fundamentally depends on evidence that can be logically and independently verified; instead, they taught science as if it were a form of revealed truth from scientists.” This attitude carries over into the way scientists report their findings and the supine attitude of the media.
Originally posted by eightpoundworld
[SNIP]. Did you know that There are scientists in erope working on plasma fushon? And when they are done they will reach heats over the heat of the son. at least that is what they say. who knows what will happen, maybe we'll all die in a tradic chain reaction. check it out on www.nationalgeographic.com