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Title: Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks

Abstract

High-resolution observations of the solar chromosphere and transition region often reveal surge-like oscillatory activities above sunspot light bridges (LBs). These oscillations are often interpreted as intermittent plasma jets produced by quasi-periodic magnetic reconnection. We have analyzed the oscillations above an LB in a sunspot using data taken by the Interface Region Imaging Spectrograph . The chromospheric 2796 Å images show surge-like activities above the entire LB at any time, forming an oscillating wall. Within the wall we often see that the core of the Mg ii k 2796.35 Å line first experiences a large blueshift, and then gradually decreases to zero shift before increasing to a redshift of comparable magnitude. Such a behavior suggests that the oscillations are highly nonlinear and likely related to shocks. In the 1400 Å passband, which samples emission mainly from the Si iv ion, the most prominent feature is a bright oscillatory front ahead of the surges. We find a positive correlation between the acceleration and maximum velocity of the moving front, which is consistent with numerical simulations of upward propagating slow-mode shock waves. The Si iv 1402.77 Å line profile is generally enhanced and broadened in the bright front, which might be caused bymore » turbulence generated through compression or by the shocks. These results, together with the fact that the oscillation period stays almost unchanged over a long duration, lead us to propose that the surge-like oscillations above LBs are caused by shocked p-mode waves leaked from the underlying photosphere.« less

Authors:
; ; ;  [1]
  1. School of Earth and Space Sciences, Peking University, 100871 Beijing (China)
Publication Date:
OSTI Identifier:
22661264
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 838; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; CHROMOSPHERE; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CORRELATIONS; EMISSION; MAGNETIC RECONNECTION; MAGNETOACOUSTICS; NONLINEAR PROBLEMS; OSCILLATIONS; PHOTOSPHERE; PLASMA JETS; RED SHIFT; RESOLUTION; SHOCK WAVES; SUN; SUNSPOTS; VELOCITY; VISIBLE RADIATION

Citation Formats

Zhang, Jingwen, Tian, Hui, He, Jiansen, and Wang, Linghua, E-mail: huitian@pku.edu.cn. Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA63E8.
Zhang, Jingwen, Tian, Hui, He, Jiansen, & Wang, Linghua, E-mail: huitian@pku.edu.cn. Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks. United States. doi:10.3847/1538-4357/AA63E8.
Zhang, Jingwen, Tian, Hui, He, Jiansen, and Wang, Linghua, E-mail: huitian@pku.edu.cn. Mon . "Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks". United States. doi:10.3847/1538-4357/AA63E8.
@article{osti_22661264,
title = {Surge-like Oscillations above Sunspot Light Bridges Driven by Magnetoacoustic Shocks},
author = {Zhang, Jingwen and Tian, Hui and He, Jiansen and Wang, Linghua, E-mail: huitian@pku.edu.cn},
abstractNote = {High-resolution observations of the solar chromosphere and transition region often reveal surge-like oscillatory activities above sunspot light bridges (LBs). These oscillations are often interpreted as intermittent plasma jets produced by quasi-periodic magnetic reconnection. We have analyzed the oscillations above an LB in a sunspot using data taken by the Interface Region Imaging Spectrograph . The chromospheric 2796 Å images show surge-like activities above the entire LB at any time, forming an oscillating wall. Within the wall we often see that the core of the Mg ii k 2796.35 Å line first experiences a large blueshift, and then gradually decreases to zero shift before increasing to a redshift of comparable magnitude. Such a behavior suggests that the oscillations are highly nonlinear and likely related to shocks. In the 1400 Å passband, which samples emission mainly from the Si iv ion, the most prominent feature is a bright oscillatory front ahead of the surges. We find a positive correlation between the acceleration and maximum velocity of the moving front, which is consistent with numerical simulations of upward propagating slow-mode shock waves. The Si iv 1402.77 Å line profile is generally enhanced and broadened in the bright front, which might be caused by turbulence generated through compression or by the shocks. These results, together with the fact that the oscillation period stays almost unchanged over a long duration, lead us to propose that the surge-like oscillations above LBs are caused by shocked p-mode waves leaked from the underlying photosphere.},
doi = {10.3847/1538-4357/AA63E8},
journal = {Astrophysical Journal},
number = 1,
volume = 838,
place = {United States},
year = {Mon Mar 20 00:00:00 EDT 2017},
month = {Mon Mar 20 00:00:00 EDT 2017}
}