Limb prominences seen in UV, EUV and SXR

P. Heinzel (1,2), F. Farnik (1), U. Anzer (2) and I. Dammasch (3)

(1) - Ondrejov Observatory, Czech Republic
(2) - MPA Garching, Germany
(3) - MSSL, Great Britain

We use SOHO/SUMER,EIT and Yohkoh SXT prominence observations to study the absorption and/or volume blocking (see Anzer and Heinzel, ApJ 622, 714, 2005) of UV, EUV and SXR radiation by cool prominence plasma. As an example for his type of behaviour we study the limb prominence observed on 5 Sept. 1996. The SUMER spectrograph has detected two coronal lines, MgX at 625 A which is absorbed by the hydrogen Lyman continuum and blocked within a volume occupied by cool prominence plasma, and FeXII at 1242 A where the prominence appears dark due to blocking only (since there is negligible absorption at this wavelength). A similar behaviour is visible also in the EUV images taken by EIT. We find that a darkening comparable to that detecetd in the FeXII line can be seen in the SXR images obtained by Yohkoh/SXT. Since the absorptions by the Lyman continuum, the resonance continua of HeI and HeII and also by the metals are all small in the energy range of SXT we explain the darkening seen by SXR as being entirely due to volume blocking. Based on a quantitative analysis of these data, we discuss the physical conditions in cool prominences and in their coronal environment. Finally, we propose new high- resolution EUV and SXR observations of prominences and filaments by Solar-B, using the EUV imaging spectrometer (EIS) and the X-ray telescope (XRT) as a basis for a more detailed investgation of such cool structures.

Correspondence

Frantisek Farnik (ffarnik@asu.cas.cz)

presentation

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