Abstract

Prominence eruption is closely related to coronal mass ejections and is an important topic in solar physics. Spectroscopic observation is an effective way to explore the plasma properties, but the spectral observations of eruptive prominences are rare. In this paper we will introduce an eruptive polar crown prominence with spectral observations from the Interface Region Imaging Spectrograph (IRIS), and try to explain some phenomena that are rarely reported in previous works. The eruptive prominence experiences a slow-rise and fast-rise phase, while the line-of-sight motions of the prominence plasma could be divided into three periods: 2 hours before the fast-rise phase, opposite Doppler shifts are found at the two sides of the prominence axis; then, red shifts dominate the prominence gradually; in the fast-rise phase, the prominence gets to be blue-shifted. During the second period, a faint component appears in Mg ii k window with a narrow line width and a large red shift. A faint region is also found in AIA 304Å images along the prominence spine, and the faint region gets darker during the expansion of the spine. We propose that the opposite Doppler shifts in the first period is a feature of the polar crown prominence that we studied. The red shifts in the second period are possibly due to mass drainage during the elevation of the prominence spine, which could accelerate the eruption in return. The blue shifts in the third period are due to that the prominence erupts toward the observer. We suggest that the faint component appears due to the decreasing of the plasma density, and the latter results from the expansion of the prominence spine.

Highlights

  • Solar prominences are composed of cold and dense plasma suspended in the hot corona [1,2,3,4]

  • We focus on the spectral evolution of an eruptive polar crown prominence on 2015 April 28th, which erupts successfully with a coronal mass ejections (CMEs)

  • We studied spectral evolution of an eruptive polar crown prominence using its Interface Region Imaging Spectrograph (IRIS) observations in the Mg ii and Si iv lines and AIA extreme ultraviolet (EUV) images

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Summary

Introduction

Solar prominences are composed of cold and dense plasma suspended in the hot corona [1,2,3,4]. Studying the triggering mechanism and evolution of prominence eruptions are important topics in solar physics. Spectroscopic observation is an effective way to reveal plasma properties and line-of-sight (LOS) motions. High-quality spectral data of eruptive prominences are rare due to limited field of view (FOV) of general spectroscopic observations and randomness of prominence eruptions. The Interface Region Imaging Spectrograph (IRIS [5]), is a small explorer spacecraft launched in 2013 June. It provides simultaneous high-resolution spectral and imaging data from the photosphere to the corona. The IRIS especially has an advantage of observing chromosphere and transition region

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