Chromospheric impact of an exploding solar granule

Abstract

Observations of multi-wavelength and therefore height-dependent information following events throughout the solar atmosphere and unambiguously assigning a relation between these rapidly evolving layers are rare and difficult to obtain. Yet, they are crucial for our understanding of the physical processes that couple the different regimes in the solar atmosphere. We characterize the exploding granule event with simultaneous observations of Hinode spectroplarimetric data in the solar photosphere and Hinode broadband CaIIH images combined with Interface Region Imaging Spectrograph (IRIS) slit spectra. We follow the evolution of an exploding granule and its connectivity throughout the atmosphere and analyze the dynamics of a magnetic element that has been affected by the abnormal granule. In addition to magnetic flux maps we use a local correlation tracking method to infer the horizontal velocity flows in the photosphere and apply a wavelet analysis on several IRIS chromospheric emission features such as MgIIk2v and MgIIk3 to detect oscillatory phenomena indicating wave propagation. During the vigorous expansion of the abnormal granule we detect radially outward horizontal flows, causing, together with the horizontal flows from the surrounding granules, the magnetic elements in the bordering intergranular lanes to be squeezed and elongated. In reaction to the squeezing, we detect a chromospheric intensity and velocity oscillation pulse which we identify as an upward traveling hot shock front propagating clearly through the IRIS spectral line diagnostics of MgIIh&k. Conclusion: Exploding granules can trigger upward-propagating shock fronts that dissipate in the chromosphere.

arXiv comment5 pages (3 figures)+1 page movie snapshots(2 figures), accepted in A&A letters, movies can be found at http://www.science-media.org/216 and http://www.science-media.org/217

References in corpus (9)

• The Interface Region Imaging Spectrograph (IRIS)
• The Solar Optical Telescope for the Hinode Mission: An Overview
• Numerical simulation of the three-dimensional structure and dynamics of the non-magnetic solar chromosphere
• The formation of IRIS diagnostics II. The formation of the Mg II h&k lines in the solar atmosphere
• The formation of IRIS diagnostics. III. Near-ultraviolet Spectra and Images
• The Formation of IRIS diagnostics. IV. The Mg II triplet lines as a new diagnostic for lower chromospheric heating
• What do iris observations of Mg II k tell us about the solar plage chromosphere?
• The signature of chromospheric heating in Ca II H spectra
• Magnetic field emergence in mesogranular-sized exploding granules observed with SUNRISE/IMaX data

Cited by in corpus (7)

• Observations of solar small-scale magnetic flux-sheet emergence
• Average radial structures of gas convection in the solar granulation
• On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX
• Evolution of exploding granules from coordinated observations by THEMIS, IRIS, SDO/HMI, and HINODE, and a simulation
• Changes in granulation scales over the solar cycle seen with SDO/HMI and Hinode/SOT
• Newly formed downflow lanes in exploding granules in the solar photosphere
• Emergence of magnetic flux sheets in the quiet Sun. I. Statistical properties