Spectral Evolution of an Eruptive Polar Crown Prominence With IRIS Observations

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.

Launch of a CME-associated eruptive prominence as observed with IRIS and ancillary instruments

Aims. In this paper we focus on the possible observational signatures of the processes which have been put forward for explaining eruptive prominences. We also try to understand the variations in the physical conditions of eruptive prominences and estimate the masses leaving the Sun versus the masses returning to the Sun during eruptive prominences. Methods. As far as velocities are concerned, we combined an optical flow method on the Atmospheric Imaging Assembly (AIA) 304 Å and Interface Region Imaging Spectrograph (IRIS). Mg II h&k observations in order to derive the plane-of-sky velocities in the prominence, and a Doppler technique on the IRIS Mg II h&k profiles to compute the line-of-sight velocities. As far as densities are concerned, we compared the absolute observed intensities with values derived from non-local thermodynamic equilibrium radiative transfer computations to derive the total (hydrogen) density and consequently compute the mass flows. Results. The derived electron densities range from 1.3 × 109 to 6.0 × 1010 cm−3 and the derived total hydrogen densities range from 1.5 × 109 to 2.4 × 1011 cm−3 in different regions of the prominence. The mean temperature is around 1.1 × 104 K, which is higher than in quiescent prominences. The ionization degree is in the range of 0.1–10. The total (hydrogen) mass is in the range of 1.3 × 1014–3.2 × 1014 g. The total mass drainage from the prominence to the solar surface during the whole observation time of IRIS is about one order of magnitude smaller than the total mass of the prominence.

Structure and Dynamics of an Eruptive Prominence on the Quiet Sun

We present preliminary results on the investigation of one polar crown prominence that erupted on 2012 March 11. This prominence is viewed at the east limb by SDO/AIA and displays a simple vertical-thread structure. A bright U-shape (double horn-like) structure is observed surrounding the upper portion of the prominence before the eruption and becomes more prominent during the eruption. When viewed on the disk, STEREO_B shows that this prominence is composed of series of vertical threads and displays a loop-like structure during the eruption. We focus on the magnetic support of the prominence by studying the structure and dynamics before and during the eruption using observations from SDO and STEREO. We will also present preliminary DEM analysis of the cavity surrounding the prominence.