11. Commission des Couches Exterieures du Soleil

Abstract

The work of Commission I I touches very closely on that of several other Commissions such as 10, 12, 13, 40 and the Mixed-Commission on solar-terrestrial relations. Where a subject is of interest to Commission n , but is thought more closely related to another Commission it has not normally been included in the following report. Thus white-light solar phenomena are left to Commission 10 (with faculae marginal), purely spectroscopic matters and the reversing layer to Commission 12, and descriptive eclipse observations to Commission 13. However physical interpretations of the chromosphere and corona resulting from eclipse observations are included as a Commission 11 concern. Solar radio observations and solar-terrestrial relations are included only in so far as they bear on the physical study of the chromosphere and corona. The observations and coordination of fast moving chromospheric phenomena are dealt with by Sub-commission 11 a.Since the last General Assembly the work of our Commission has been stimulated by preparation for and participation in the I.G.Y. Many new instruments have been set up and close co-operation in observing programmes has been put into effect. EQUIPMENTThe main technical advances concern the development of instruments that were already under way in 1955. There have been: (a) an increase in the number, variety and scope of bi-refringent filters used for both chromospheric and coronal studies; (6) the development of high resolution grating spectrographs now fed by coronagraphs and used for chromospheric as well as photospheric work; (c) further development of the Lyot photo-electric coronameter; (d) improvement in means to detect electrons in the faint outer corona; and (e) devices to facilitate special observations, calibrations, guiding, and rapid repetition of slightly varying observations.An excellent recent review of the instrumental situation has been made by W. 0 . Roberts [1], and therefore it is only necessary to summarize points of interest.More than 50 bi-refringent narrow band (< 1 A) niters have been put into use for chromospheric studies; most of these are in Ha, but some are available for D 3 of He and H, K of Ca + . Many with an 0 7 A band pass have been built by Optique et Precision de Levallois (Paris), and seven orders are placed for the SECASI (Bordeaux) instrument of standardized design (due to Lyot) suited to automatic flare patrol. Some of these are going into use. Some of the variations from the standard form are as follows: (a) a filter 164 at https://www.cambridge.org/core/terms.