2024-03-29T08:37:09Z
https://nagoya.repo.nii.ac.jp/oai
oai:nagoya.repo.nii.ac.jp:00024734
2023-01-16T04:45:30Z
879:880:881
ALMA Discovery of Solar Umbral Brightness Enhancement at λ=3mm
Iwai, Kazumasa
Loukitcheva, Maria
Shimojo, Masumi
Solanki, Sami K.
White, Stephen M.
open access
© 2017. The American Astronomical Society
We report the discovery of a brightness enhancement in the center of a large sunspot umbra at a wavelength of 3 mm using the Atacama Large Millimeter/sub-millimeter Array (ALMA). Sunspots are among the most prominent features on the solar surface, but many of their aspects are surprisingly poorly understood. We analyzed a λ = 3 mm (100 GHz) mosaic image obtained by ALMA that includes a large sunspot within the active region AR12470, on 2015 December 16. The 3 mm map has a 300'' × 300'' field of view and 4farcs9 × 2farcs2 spatial resolution, which is the highest spatial resolution map of an entire sunspot in this frequency range. We find a gradient of 3 mm brightness from a high value in the outer penumbra to a low value in the inner penumbra/outer umbra. Within the inner umbra, there is a marked increase in 3 mm brightness temperature, which we call an umbral brightness enhancement. This enhanced emission corresponds to a temperature excess of 800 K relative to the surrounding inner penumbral region and coincides with excess brightness in the 1330 and 1400 Å slit-jaw images of the Interface Region Imaging Spectrograph (IRIS), adjacent to a partial lightbridge. This λ = 3 mm brightness enhancement may be an intrinsic feature of the sunspot umbra at chromospheric heights, such as a manifestation of umbral flashes, or it could be related to a coronal plume, since the brightness enhancement was coincident with the footpoint of a coronal loop observed at 171 Å.
IOP publishing
2017-06-01
eng
journal article
VoR
http://hdl.handle.net/2237/26956
https://nagoya.repo.nii.ac.jp/records/24734
https://doi.org/10.3847/2041-8213/aa71b5
2041-8205
The Astrophysical Journal Letters
841
2
L20
L20
https://nagoya.repo.nii.ac.jp/record/24734/files/Iwai_2017_ApJL_841_L20.pdf
application/pdf
3.6 MB
2018-02-22