High-resolution photography of the solar chromosphere

Abstract

High-resolution filtergrams of the quiet chromosphere, taken at seven wavelengths in Ha with the aid of a computer-controlled ~ A filter, have been used to derive the contrast of ten bright and dark mottles as functions of wavelength. The contrast profiles of bright and dark mottles are strikingly different. They disagree with Athay's (1970) 'velocity' model but, with an appropriate choice of parameters, can be brought into good agreement with Beckers' (1964) 'cloud' model. Comparison between observation and theory yields values for the source function S, optical thickness to, line broadening parameter d20, and line-of-sight velocity V for both bright and dark mottles. The values of S and to obtained for dark mottles are consistent with Beckers' (1968) spicule model.

Observations Supporting the Role of Magnetoconvection in Energy Supply to the Quiescent Solar Atmosphere

“…The work ofWorrall & Wilson (1972, 1973), van Breda et al (1995, and Worrall (2002) on other chromospheric spectral abnormalities may be considered with the same perspective.…”

High-resolution photography of the solar chromosphere

“…It has been claimed by Grossmann-Doerth and von Uexkfill (1971) and Bray (1973) that the He contrast profiles of individual bright mottles near the disk centre can reasonably be accounted for in terms of the 'cloud' model proposed by Beckers (1964)*. Among other things, their results indicate that bright mottles have vertical velocities ranging in magnitude up to 12km s-l; there appears to be some preponderance of downward as opposed to upward motions (Grossmann-Doerth and yon Uexktill, 1971: Figure 7;Bray, 1973: Table I).…”

“…On the other hand, the possibility cannot be excluded that the bright mottles execute vertical oscillations with velocities comparable to those recently deduced from Hc~ contrast profile analyses by Grossmann-Doerth andvon Uexkfill (1971) andBray (1973) provided the periods do not exceed a few tens of seconds.* This is not true, however, for mottles observed close to the limb (Loughhead, 1973). …”

“…If the latter alternative is correct, the inferred velocities are of sufficient magnitude to be detectable on direct photographs of bright mottles observed beyond the limb (Bray, 1973). If the latter alternative is correct, the inferred velocities are of sufficient magnitude to be detectable on direct photographs of bright mottles observed beyond the limb (Bray, 1973).…”

Chromospheric Evershed flow

“…In order to compute the line-of-sight velocity from only two opposite Hα wing filtergrams, estimations of the optical depth at line center and the Doppler width are further needed (see Georgakilas et al 1990). Bray and others authors successfully applied the method for studying the physical properties of various chromospheric features (Bray 1973a(Bray , 1974Georgakilas et al 1990;Suematsu et al 1995;Malherbe et al 1997;Georgakilas et al 2001). We applied the above method in order to compute line-of-sight velocities from the Hα ± 0.35 Å, Hα ± 0.5 Å and Hα ± 0.75 Å filtergrams.…”