MULTI-WAVELENGTH STUDY of TRANSITION REGION PENUMBRAL SUBARCSECOND BRIGHT DOTS USING IRIS and NST

Na Deng, Vasyl Yurchyshyn, Hui Tian, Lucia Kleint, Chang Liu, Yan Xu, Haimin Wang

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Using high-resolution transition region (TR) observations taken by the Interface Region Imaging Spectrograph (IRIS) mission, Tian et al. revealed numerous short-lived subarcsecond bright dots (BDs) above sunspots (mostly located in the penumbrae), which indicate yet unexplained small-scale energy releases. Moreover, whether or not these subarcsecond TR brightenings have any signature in the lower atmosphere and how they are formed are still not fully resolved. This paper presents a multi-wavelength study of the TR penumbral BDs using a coordinated observation of a near disk center sunspot with IRIS and the 1.6 m New Solar Telescope (NST) at the Big Bear Solar Observatory. NST provides high-resolution chromospheric and photospheric observations with narrowband Hα imaging spectroscopy and broadband TiO images, respectively, complementary to IRIS TR observations. A total of 2692 TR penumbral BDs are identified from a 37 minute time series of IRIS 1400 Å slit-jaw images. Their locations tend to be associated more with downflowing and darker fibrils in the chromosphere, and weakly associated with bright penumbral features in the photosphere. However, temporal evolution analyses of the BDs show that there is no consistent and convincing brightening response in the chromosphere. These results are compatible with a formation mechanism of the TR penumbral BDs by falling plasma from coronal heights along more vertical and dense magnetic loops. The BDs may also be produced by small-scale impulsive magnetic reconnection taking place sufficiently high in the atmosphere that has no energy release in the chromosphere.

Original languageEnglish (US)
Article number103
JournalAstrophysical Journal
Volume829
Issue number2
DOIs
StatePublished - Oct 1 2016

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: activity
  • Sun: chromosphere
  • Sun: magnetic fields
  • Sun: photosphere
  • Sun: transition region
  • sunspots

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