Non-Maxwellian Diagnostics from SDO/EVE Spectra of an X-class Flare
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+ | === Introduction === | ||
+ | |||
+ | Particle acceleration is a common process in solar flares. | ||
+ | Typically, high-energy power-law tails are observed at energies higher than a | ||
+ | few keV in the [https://en.wikipedia.org/wiki/Bremsstrahlung bremsstrahlung] (continuum) radiation. | ||
+ | However, electrons at these energies are also involved in formation of high-temperature flare | ||
+ | lines, i.e., in the bound-bound emission of highly ionized ions. | ||
+ | For example, Fe XXV denotes a helium-like iron ion, one with two electrons; typically an ''ionization equilibrium'' theory, in which collisional stripping | ||
+ | balances recombinations, determines the relative abundances of the different ionic states. | ||
+ | In a tenuous plasma such as the corona, this differs strongly from the well-known [https://en.wikipedia.org/wiki/Saha_ionization_equation Saha equlibrium]. | ||
+ | |||
+ | Both the ionization and excitation of an ion are dominated by collisions with free electrons. | ||
+ | The presence of high-energy electrons strongly influences the rates of both ionization and excitation (e.g., Ref [1], [2]). | ||
+ | The inverse processes of recombination and collisional de-excitation are also affected. | ||
+ | This means that the intensities of flare lines should also be influenced by the high-energy electrons, and in turn, the presence of these | ||
+ | high-energy tails could in principle be derived also from observations of the flare emission lines, such as those of the Fe XVIII-XXIV ionic states of iron. | ||
+ | |||
[[File:317f1.png|932px|thumb|center|Figure 1: The X5.4 | [[File:317f1.png|932px|thumb|center|Figure 1: The X5.4 |
Revision as of 11:06, 16 February 2018
Nugget | |
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Number: | 317 |
1st Author: | Jaroslav Dudik |
2nd Author: | |
Published: | 19 February 2018 |
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Previous Nugget: | MinXSS/RHESSI X-ray Spectra |
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Introduction
Particle acceleration is a common process in solar flares. Typically, high-energy power-law tails are observed at energies higher than a few keV in the bremsstrahlung (continuum) radiation. However, electrons at these energies are also involved in formation of high-temperature flare lines, i.e., in the bound-bound emission of highly ionized ions. For example, Fe XXV denotes a helium-like iron ion, one with two electrons; typically an ionization equilibrium theory, in which collisional stripping balances recombinations, determines the relative abundances of the different ionic states. In a tenuous plasma such as the corona, this differs strongly from the well-known Saha equlibrium.
Both the ionization and excitation of an ion are dominated by collisions with free electrons. The presence of high-energy electrons strongly influences the rates of both ionization and excitation (e.g., Ref [1], [2]). The inverse processes of recombination and collisional de-excitation are also affected. This means that the intensities of flare lines should also be influenced by the high-energy electrons, and in turn, the presence of these high-energy tails could in principle be derived also from observations of the flare emission lines, such as those of the Fe XVIII-XXIV ionic states of iron.
RHESSI Nugget Date | 19 February 2018 + |
RHESSI Nugget First Author | Jaroslav Dudik + |
RHESSI Nugget Index | 317 + |