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Silicon in the solar corona

  • K. G. Widing (a1) and J. R. Porter (a1)

Abstract

Resonance lines of coronal ions of silicon are prominent in the spectral ranges 40–62 Å and 254–356 Å.

An unexpected feature of the soft X-ray spectrum is the weakness or absence of the resonance lines of iron in ionization stages XI through XV.

A second feature is the prominence of lines of the type (3d → 2p) relative to the resonance transitions (3p → 2s) in Li-like and Beryllium-like spectra. It is suggested that the upper levels (3d) are excited by quadrupole collisions from the ground 2s or 2s2 levels.

The intensity of the soft X-ray lines relative to the resonance lines in the 300 Å region seems to be more consistent with temperatures well above one million degrees than with temperatures as low as 700000°K, but the data are not adequate for a precise comparison. The relative intensity of the line emission from the various stages of silicon ionization may be interpreted as indicating that the ionization of silicon peaks in stages IX and X.

The abundances of C, Mg, S, and Al relative to silicon do not seem to be greatly different from the chromospheric abundances reported by Pottasch or with the photospheric abundances.

Dans les régions spectrales 40-62 Å et 256-356 Å, les raies de résonance des ions de Si sont particulièrement visibles dans la Couronne. La faiblesse ou l'absence totale des raies de résonance du fer d'état d'ionisation compris entre XI et XV dans le spectre des rayons X mous coronaux est inattendue. On peut remarquer aussi l'importance des raies de type (3d → 2p) par rapport aux transitions de résonance (3p 2s) dans les spectres du genre de Li ou de Be. On suggère que les niveaux supérieurs (3d) sont excités par collisions quadripolaires ä partir des états fondamentaux 2s ou 2s2.

L'intensité relative des raies X par rapport aux raies de résonance dans la région 300 Å semble plus conciliable avec des températures bien supérieures а 10е К qu'avec des tempéraiures aussi basses que 700000 °K; mais les données disponibles ne permetterU pas une comparaison précise. L'intensité relative de l'émission dans les raies issues de différents états dionisaiion de Si peut signifier que l'ionisation de Si passe par un maximum pmr les états IX ei X. Les abondances de O, Mg, S et Al relativement ά Sine semblent pas trés différentes des abondances chromosphériques données par Pottasch, ni des abondances photosphériques.

Резюме

В спектральных областях 40-62 Å и 256-356 Å резонансные линии ионов Si особенно видимы в короне. Слабость или полное отсутствие резонансных линий железа в ионизированном состоянии, заключенном между XI и XV, в спектре лучей X менее корональных — неожиданы. Можно также отметить значительность линий типа (3d — 2р) по отношению к резонансным переходам (Зр — 25) в спектрах ряда Li или Ве. Выдвинута мысль, что верхние уровни (3d) возбуждены четырехпо- люсными соударениями с основных состояний 2s или 2s2.

Относительная интенсивность линий X по отношению к резонансным линиями в области 300 Å повидимому более согласуема с температурами намного превышающими 10е к°, чем с такими низкими температурами как 700.00 к0; но имеющиеся данные не позволяют точное сравнение. Относительная интенсивность эмиссии в линиях, происшедших, из разных ионизационных состояний Si, может означать, что ионизация Si проходит через максимум для состояний IX и X. Обилия С, Mg, S и Al по отношению к Si повидимому не очень отличны от хромосрефных обилий приведенных Потташем, ни от фотосферных обилий.

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Copyright

References

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Silicon in the solar corona

  • K. G. Widing (a1) and J. R. Porter (a1)

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