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  An overall view of temperature oscillations in the solar chromosphere with ALMA

Jafarzadeh, S., Wedemeyer, S., Fleck, B., Stangalini, M., Jess, D., Morton, R., et al. (2021). An overall view of temperature oscillations in the solar chromosphere with ALMA. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 379(2190): 20200174. doi:10.1098/rsta.2020.0174.

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Jafarzadeh, S., Author
Wedemeyer, S., Author
Fleck, B., Author
Stangalini, M., Author
Jess, D.B., Author
Morton, R.J., Author
Szydlarski, M., Author
Henriques, V.M.J., Author
Zhu, Xiaoshuai1, Author           
Wiegelmann, Thomas1, Author           
Guevara Gómez, J.C., Author
Grant, S.D.T., Author
Chen, B., Author
Reardon, K., Author
White, S.M., Author
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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 Abstract: By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb–Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3–5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1098/rsta.2020.0174
 Degree: -

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Title: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
  Other : Phil. Trans. R. Soc. A
Source Genre: Journal
 Creator(s):
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Publ. Info: London : Royal Society
Pages: - Volume / Issue: 379 (2190) Sequence Number: 20200174 Start / End Page: - Identifier: ISSN: 1364-503X
CoNE: https://pure.mpg.de/cone/journals/resource/954928604111_3