By Phillips K. J. H., Feldman U., Landi E.

ISBN-10: 0521841607

ISBN-13: 9780521841603

Explores beneficial properties of the Sun's surroundings, for graduate students/researchers in astrophysics and sunlight physics.

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Ultraviolet and X-ray Spectroscopy of the Solar Atmosphere (2008)(en)(360s)

Explores positive factors of the Sun's surroundings, for graduate students/researchers in astrophysics and sunlight physics.

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Fast and slow mode MHD waves are hybrids of Alfv´en and sound waves, with fast waves travelling at nearly the Alfv´en speed, slow waves travelling at approximately the ion sound speed. Sound wave speeds for the solar atmosphere are approximately the most probable thermal speeds which for protons in the quiet Sun corona are ∼ 200 km s−1 . For flare plasmas having Te ∼ 20 MK, they are ∼ 800 km s−1 . The corona’s high temperature is maintained by a non-radiative heating mechanism which may be the dissipation of MHD waves or the occurrence of tiny flares, nanoflares, which produce heated plasma in localized regions that may disperse into larger volumes (Parker (1988)), or some other means.

The rapidly rotating dK and dM stars (their large rotational speeds are a consequence of their relative youth) give rise to considerable stellar activity, including coronae that are strong X-ray emitters, detectable at the Earth, and extremely powerful flares, with visible-light increases that are greater than the total output of the stars in their non-flaring states. In visible light, their spectra are characterized by the Ca ii H and K lines and members of the hydrogen Balmer sequence in emission: stars with the Hα line in emission have designations e after the spectral type (dKe, dMe).

11) where Nm is the number density of X +m ions, Nm+1 that of X +m+1 ions. The quantity Cm is the total ionization rate coefficient, or number of ionizations from stage X +m to X +m+1 per unit density and time (units cm3 s−1 ). Correspondingly, αm+1 is the rate coefficient of recombination from stage X +m+1 to X +m . The number densities of ions in successive stages, Nm /Nm+1 , is thus given by the ratio of the recombination to ionization rate coefficients, αm+1 /Cm . For most coronal ions, the ionization potentials are generally several keV.

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Ultraviolet and X-ray Spectroscopy of the Solar Atmosphere (2008)(en)(360s) by Phillips K. J. H., Feldman U., Landi E.


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