The solar Lyman continuum and the structure of the solar chromosphere
Solar chromosphere structure and Lyman continuum, examining brightness and kinetic temperatures, limb variations, radiative transfer and models
Kalkofen, W.↗
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Mass motion in the solar chromosphere
Solar chromosphere mass motion, studying macroturbulence influences on visible spectrum lines high resolution profiles from rocket spectrograms
Jones, R. A.↗
The manifold structure of the chromosphere and corona
Solar chromosphere and corona manifold structure data, using high resolution filter photography
Zirin, H.↗
Observations of stellar chromospheres
Stellar chromosphere detection through H, K and metastable He lines observation, noting importance for solar physics
Zirin, H.↗
Morphological relationships in the chromospheric H alpha fine structure
Morphological relationships in solar chromospheric H alpha fine structure involving bushes, fibrils, threads and filaments
Foukal, P.↗
Variations of cosmic rays associated with chromospheric flares on the sun
Features of the cosmic-ray variations in the geomagnetic pole region and a smooth decrease in the cosmic rays intensity as a result of increased solar activity are reported. A 66-day variation of the cosmic rays was registered, in agreement with the maximum frequency and power of solar chromospheric flares.
Kozin, I. D.↗
H alpha fine structure and the chromospheric field.
Study of the physical characteristics of the H alpha structures previously defined as fibrils and threads. The interpretation of the fibrils as ends of flux tubes is useful in tracing the behavior of the transverse field component over the solar surface. The observed properties of fibrils and threads are consistent with the hypothesis that they are produced by a shock wave mechanism similar to that advanced by Parker (1963) to explain spicules. It is suggested that the undisturbed magnetic field in the chromosphere of an active region is confined to a thin sheath, while the field of the quiet regions extends into the corona.
Foukal, P.↗
Structure of the chromosphere-corona transition region.
The structure and energy balance of the chromosphere-corona transition region is investigated by means of a static, planar model which is compared with the results of XUV-resonance-line observations. In this model, the transition region is heated by thermal conduction from the corona and cooled by radiative losses. Comparison of the model with observational results implies that this is the dominant process in the energy balance of the transition region, and that the base of the transition region is inherently nonstatic and/or nonplanar. The model explains the observational finding of Noyes et al. (1970) that the number density and the downward heat flux both increase by the same factor from quiet regions to active regions.
Moore, R. L.↗
High resolution spectroscopy of the disk chromosphere. I - Observing procedures.
Review of some of the main features of a high resolution spectroscopy program aimed at the precise photometric observation of chromospheric fine structures using the Sacramento Peak vacuum telescope. The observing procedures are described, and a sample of the first observational results is presented.
Beckers, J. M.↗
Evidence for stellar chromospheres presented by ultraviolet observations of the sun and stars
Observations of emission lines in stellar sources in the ultraviolet region of the spectrum show P Cygni-like evidence of mass outflow as well as many ultraviolet emission lines which cannot be interpreted wholly in terms of geometric effects. These are considered powerful chromospheric indicators.
Doherty, L.↗
Mechanical heating in stellar chromospheres using the sun as a test case
The shock dissipation hypothesis for solar atmospheric heating is extended to stellar chromospheres of late type stars which have significant convective envelopes. Principle wave modes are studied for their generation, propagation, and heating properties in the presence of a magnetic field, and various approximations on when a sound wave becomes strong enough to produce heating in the atmosphere are presented.
Jordan, S. D.↗
Chromospheric activity and stellar evolution
A study of stellar chromospheres based on the internal structure of particular stars is presented. Used are complex flow diagrams of the linkage paths between mass loss, angular momentum loss, magnetic field from the turbulent dynamo and its relations to differential rotations and the convection zone, and stellar evolution.
Kippenhahn, R.↗
The absence of flares in 3835 A and the heating of the chromosphere.
Simultaneous observations of flares in H-alpha and a band 15 A wide centered on 3835 A show no change whatever in 3835 A at the time of several flares, although the chromospheric network is easily visible. Flares are therefore transparent in this wavelength. Since the flare represents a test heat input from above, and no brightening of the network appears, we conclude it is impossible for the corona to produce the bright network by downward convection.
Zirin, H.↗
Further aspects of weak shock theory applied to the solar chromosphere.
The low chromosphere now seems definitely to require mechanical heating, and dissipation of initially acoustic waves by shocking is one of the most promising possibilities. Results of recent calculations indicate that the weak shock theory may be applicable in this case, but discrepancies exist among various applications of this theory, and the explanations offered to date are not completely satisfactory. It is shown that the different approximations used by different authors to evaluate the mechanical flux integral play an important role in producing these discrepancies, in addition to the already well-known effects of the density scale heights and the wave periods. Arguments are presented favoring Ulmschneider's (1970, 1971) method for evaluation of this flux integral.
Jordan, S. D.↗
A short-lived chromospheric flare-point with a lifetime of 20 seconds and rise and fall times of 5 seconds
We have observed a chromospheric brightening in the H alpha and Ca II K lines with a diameter of about 1 arc second. The time structure of this event, obtained with a relative resolution of 1 second, shows the rise time to be 4 seconds, the lifetime (FWHM) to be 20 seconds, and the decay time to be 5 seconds. This imposes new constraints on flare-point models. These restrictions can be accommodated easily by either an infall-impact flare model or a model invoking the precipitation of high-energy particles from the corona.
Hyder, C. L.↗
Line profiles and turbulence generated by acoustic waves in the solar chromosphere. II - Contours of the Ca II and Mg II K lines
Making use of the time-averaged absorption profiles derived by Oster and Ulmschneider, non-LTE line formation in the context of a two-level atom is investigated for an isothermal atmosphere and for the Ca II and Mg II K lines in the solar chromosphere as represented by the Harvard-Smithsonian Reference Atmosphere. Source functions and emergent line profiles are computed for a variety of assumptions concerning the acoustically broadened profiles and the solar velocity fields.
Shine, R. A.↗
A three-component concept of the chromosphere and transition region
It is proposed that present observations of the chromosphere and transition region in EUV, optical and mm wavelengths are best described by a three-component concept. The three components are taken to be the interiors of supergranular cells, the hot plagettes overlying faculae, and the cooler, transient mottles which surround them in the network boundaries. The enhanced emission of the hot plagettes in transition ions is interpreted as a direct result of the increased pressure scale height over faculae relative to the cell interiors.
Foukal, P.↗