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Abstract

We present a comprehensive set of spectral data from two quiescent solar prominences observed in parallel from space and ground: with the VTT, simultaneous two-dimensional imaging of Hβ 4862Å and Ca ii 8542Å yields a constant ratio, indicating small spatial pressure variations over the prominence. With the Gregory, simultaneous spectra of Ca ii 8542Å and He i 10830Å were taken, their widths yielding 8000 < T kin < 9000 K and v nth < 8km/s. The intensity ratio of the helium triplet components gives an optical thickness of τ < 1.0 for the fainter and τ ≤ 2.0 for the brighter prominence. The τ 0 values allow to deduce the source function for the central line intensities and thus the relative population of the helium 3 S and 3 P levels with a mean excitation temperature T mean ex = 3750 K. With SUMER, we sequentially observed 6 spectral windows containing higher Lyman lines, 'cool' emission lines from neutrals and singly charged atoms, as well as 'hot' emission lines from ions like O iv, O v, N v, S v and S vi. The EUV lines show pronounced maxima in the main prominence body as well as 'sidelocations' where the 'hot' lines are enhanced with respect to the 'cool' lines. The line radiance of 'hot' lines blue-wards of the Lyman series limit (λ < 912Å) appear reduced in the main prominence body.This absorption is also visible in TRACE images of Fe ix/x 171Å as fine dark structure which covers only parts of the main ('cool') prominence body.The Lyman lines show a smooth decrease of line widths and radiance with increasing upper level k = 5 through 19. For 5 ≤ k ≤ 8 the level population follows a Boltzmann distribution with T ex > 6 · 10 4 K; higher levels k> 8 appear more and more overpopulated. The larger widths of the Lyman lines require high non-thermal broadening close to that of 'hot' EUV lines. In contrast, the He ii emission is more related to the 'cool' lines.

Solar prominences with Na and Mg emissions and centrally reversed Balmer lines

“…For faint emissions, our data perfectly match those from Stellmacher & Wiehr (1994b) Stellmacher & Wiehr (1994b), and follows the curves calculated by Gouttebroze et al (1993; hereafter referred to as GHV) for temperatures of T kin = 4300 K and T kin = 6000 K. The fact that the present observations coincide well with earlier ones of much fainter and more structured prominences, obtained under quite different conditions, indicates that possible influences from "filling" are negligible (in agreement with Stellmacher et al 2003). This is also seen from the independence on the aspect angle: we do not find significant differences between face-on (e.g.…”

Prominence Cavity Regions Observed Using SWAP 174 Å Filtergrams and Simultaneous Eclipse Flash Spectra

“…A quite similar result, based on a diagnostics which uses completely different lines, was deduced in Stellmacher et al 2003.…”

Solar Prominences: Observations

“…The temperature in the prominence core can be derived from H-Ly continuum observations (Parenti et al, 2005) [the color temperature of which is representative of the electron temperature (Gouttebroze et al, 1993)], or by measuring the kinetic temperature from the width of spectral lines (e.g., Stellmacher et al, 2003). Figure 11 shows an example of the application of the first method over about 100Å of a SOHO/SUMER spectrum of a prominence observed on 8 October 1999 .…”

“…In order to infer the magnetic-field amplitude and direction, an inversion method of line flux needs to be used. Because these lines are often optically thick in prominences (e.g., Stellmacher et al, 2003;Wiehr and Bianda, 2003;Labrosse and Gouttebroze, 2004;Léger and Paletou, 2009) the radiative transfer effects have to be taken into account in their modeling. The difficulties in the inversion of the 10830Å triplet are discussed by López Ariste and Casini (2002).…”