Hinode,TRACE,SOHO, and Ground‐based Observations of a Quiescent Prominence

Abstract

A quiescent prominence was observed by several instruments on 2007 April 25. The temporal evolution was recorded in Hα by Hinode/SOT, in X-rays by Hinode/XRT and in the 195Å channel by TRACE. Moreover, ground-based observatories (GBO) provided calibrated Hα intensities. Simultaneous EUV data were also taken by the Hinode/EIS and SOHO/SUMER-CDS spectrometers. Here we have selected the SOT Hα image taken at 13:19 UT which nicely shows the prominence fine structure. We compare this image with co-temporal ones taken by XRT and TRACE and show the intensity variations along several cuts parallel to the solar limb. EIS spectra were obtained about half an hour later. Dark prominence structure clearly seen in the TRACE and EIS 195Å images is due to the prominence absorption in HI, HeI and HeII resonance continua plus the coronal emissivity blocking due to the prominence void (cavity). The void clearly visible in XRT images is entirely due to X-ray emissivity blocking, since no prominence structure is seen in the XRT images because of negligible absorption at X-ray wavelengths. We use TRACE, EIS and XRT data to estimate the amount of absorption and blocking. Independently, the Hα integrated intensities provide us with an estimate of the Hα opacity and this is related to the opacity of resonance continua as follows from the non-LTE radiative-transfer modeling. Therefore, we have an independent check of the results obtained from TRACE/XRT and EIS/XRT. However, spatial averaging of the Hα and EUV data have quite different natures which must be taken into account when evaluating the true opacities. We demonstrate this important effect here for the first time. Finally, based on this multi-wavelength analysis, we discuss the determination of the column densities and the ionization degree of hydrogen in the prominence.

Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line

“…This corresponds to the findings of previous studies (Berger et al 2010;Berlicki et al 2011;Heinzel et al 2008;Labrosse et al 2011;Schmieder et al 2010;Török et al 2009) of this prominence passing over the limb between April 24 and April 26, 2007. Several of these authors used standard assumptions for the minimum prominence-core temperature of 8000 K , assumed temperatures from 6000 to 8000 K).…”

“…Among them, Heinzel et al (2008) studied the prominence occurring on April 25, 2007 in multiple spectral channels ranging from X-rays to the optical-range Hα line and showed the importance of the emissivity blocking phenomena when analyzing of quiescent prominences and their accompanying cavities. Schmieder et al (2010) and Berger et al (2010) analyzed A&A 543, A93 (2012) emission-measure curves that are also in good agreement with the observations.…”

Total mass of six quiescent prominences estimated from their multi-spectral observations

“…I p is the coronal intensity measured at a prominence, I c in the surrounding cavity, and I c in the adjacent quiet corona. The intensities of radiation emitted by the corona in front of and behind the prominence are denoted I f and I b , respectively (Heinzel et al 2008). …”

“…X-ray images of XRT made with the Al-mesh filter were used in order to eliminate the effect of the coronal emissivity deficit on the decrease of the EUV coronal intensities. As the calculation of the optical thickness along a cut made across a prominence tangentially to the limb has already been explained in Heinzel et al (2008), we give here only a brief description of the method. As it can be seen in Fig.…”

“…Then the intensity, which is in fact the emissivity integrated along the whole line of sight, measured at the prominence and the cavity is lower than the intensity measured at the surrounding corona. To eliminate an effect of the coronal emissivity deficit, both X-ray observations (not absorbed by a prominence; Anzer et al 2007) and a method proposed by Heinzel et al (2008), are used. Moreover, we use two novelties.…”