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The First ALMA Observation of a Solar Plasmoid Ejection from an X-ray Bright Point  

Masumi Shimojo   Submitted: 2017-05-22 02:20

Eruptive phenomena such as plasmoid ejections or jets are an important feature of solar activity with the potential for improving our understanding of the dynamics of the solar atmosphere. Such ejections are often thought to be signatures of the outflows expected in regions of fast magnetic reconnection. The 304 Å EUV line of Helium, formed at around 105 K, is found to be a reliable tracer of such phenomena, but the determination of physical parameters from such observations is not straightforward. We have observed a plasmoid ejection from an X-ray bright point simultaneously at millimeter wavelengths with ALMA, at EUV wavelengths with AIA, in soft X-rays with Hinode/XRT. This paper reports the physical parameters of the plasmoid obtained by combining the radio, EUV and X-ray data. As a result, we conclude that the plasmoid can consist either of (approximately) isothermal 105 K plasma that is optically thin at 100 GHz, or else a 104 K core with a hot envelope. The analysis demonstrates the value of the additional temperature and density constraints that ALMA provides, and future science observations with ALMA will be able to match the spatial resolution of space-borne and other high-resolution telescopes.

Authors: M. Shimojo, H. S. Hudson, S. M. White, T. S. Bastian, K. Iwai
Projects: None

Publication Status: Published in Astrophysical Journal Letters. Vol. 481, L5
Last Modified: 2017-05-24 14:23
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Observing the Sun with Atacama Large Millimeter/submillimeter Array (ALMA): High Resolution Interferometric Imaging  

Masumi Shimojo   Submitted: 2017-05-22 02:18

Observations of the Sun at millimeter and submillimeter wavelengths offer a unique probe into the structure, dynamics, and heating of the chromosphere; the structure of sunspots; the formation and eruption of prominences and filaments; and energetic phenomena such as jets and flares. High-resolution observations of the Sun at millimeter and submillimeter wavelengths are challenging due to the intense, extended, low- contrast, and dynamic nature of emission from the quiet Sun, and the extremely intense and variable nature of emissions associated with energetic phenomena. The Atacama Large Millimeter/submillimeter Array (ALMA) was designed with solar observations in mind. The requirements for solar observations are significantly different from observations of sidereal sources and special measures are necessary to successfully carry out this type of observations. We describe the commissioning efforts that enable the use of two frequency bands, the 3 mm band (Band 3) and the 1.25 mm band (Band 6), for continuum interferometric-imaging observations of the Sun with ALMA. Examples of high-resolution synthesized images obtained using the newly commissioned modes during the solar commissioning campaign held in December 2015 are presented. Although only 30 of the eventual 66 ALMA antennas were used for the campaign, the solar images synthesized from the ALMA commissioning data reveal new features of the solar atmosphere that demonstrate the potential power of ALMA solar observations. The ongoing expansion of ALMA and solar-commissioning efforts will continue to enable new and unique solar observing capabilities.

Authors: M. Shimojo, T.S. Bastian, A.S. Hales, S.M. White, K. Iwai, R.E. Hills, A. Hirota, N.M. Phillips, T. Sawada, P. Yagoubov, G. Siringo, S. Asayama, M. Sugimoto, R. Brajsa, I. Skokic, M. Barta, S. Kim, I. de Gregorio, S.A. Corder, H.S. Hudson, S. Wedemeyer, D.E. Gary, B. De Pontieu, M. Loukitcheva, G.D. Fleishman, B. Chen, A. Kobelski, Y. Yan
Projects: ALMA

Publication Status: Accepted for publication in Solar Physics
Last Modified: 2017-05-24 14:23
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The First ALMA Observation of a Solar Plasmoid Ejection from an X-ray Bright Point
Observing the Sun with Atacama Large Millimeter/submillimeter Array (ALMA): High Resolution Interferometric Imaging

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