Author name code: giovanelli ADS astronomy entries on 2022-09-14 =author:"Giovanelli, R.G." OR =author:"Giovanelli, Ronald G." ------------------------------------------------------------------------ Title: Geheimnisvolle Sonne. Authors: Giovanelli, R. G.; Beck, R. Bibcode: 1987geso.book.....G Altcode: No abstract at ADS Title: Book-Review - Secrets of the Sun Authors: Giovanelli, R. G.; Hill, R. E. Bibcode: 1985S&T....70..562G Altcode: No abstract at ADS Title: Book-Review - Secrets of the Sun Authors: Giovanelli, R. G.; Jakimiec, J. Bibcode: 1985SSRv...41..398G Altcode: No abstract at ADS Title: Book-Review - Secrets of the Sun Authors: Giovanelli, R. G.; Kleczek, J. Bibcode: 1985Ap&SS.112..424G Altcode: No abstract at ADS Title: The sunspot cycle and solar magnetic fields. I - The mechanism as inferred from observation. II - The interaction of flux tubes with the convection zone Authors: Giovanelli, R. G. Bibcode: 1985AuJPh..38.1045G Altcode: The first part of the present work notes that solar magnetic and velocity field observations can be used to derive the course of events in the solar cycle; such observations differ from those of conventional dynamo theories in the matters of polar field reversal, the sunspot cycle, and the torsional oscillation. In the second part, the mechanisms of interaction between flux tubes or ropes and the convection zone are examined for their relevance to the sunspot cycle. The mechanisms encompass floating, transport, and the penetration of gas from outside the tubes. All previous studies are noted to contain one or more major errors, rendering their conclusions invalid. These errors invariably involve the assumption that Archimede's principle is applicable to flux ropes, that gas entry can be disregarded, or, in some cases, that floating criteria substantially depend on local phenomena. Attention is given to: (1) the transport of flux tubes by the slow poleward motions, and to the even slower systems that carry tube extensions downwards to depths of about 150 Mm and then equatorwards; (2) their magnetic field strengths; and (3) the amplitudes of the torsional oscillation. All major cycle observations are concluded to be accounted for by the novel dynamo mechanism discussed. Title: The Sunspot Cycle and Solar Magnetic Fields - Part Two - the Interaction of Flux Tubes with the Convection Zone Authors: Giovanelli, R. G. Bibcode: 1985AuJPh..38.1067G Altcode: Mechanisms of interaction between flux tubes or ropes and the convection zone are examined insofar as they are relevant to the sunspot cycle. These include floating, transport, and the penetration of gas from outside the tubes. It is found that all previous studies contain one or more major errors of physics which render their conclusions invalid. Some of the results presented here are explanations of (1) the transport of flux tubes by the slow observed poleward motions and the even slower systems; (2) their magnetic field strengths (≡104G at a depth 10 Mm to (6 - 12)x104G at ≡150 Mm); and (3) the amplitudes of the torsional oscillation. Title: Book-Review - Secrets of the Sun Authors: Giovanelli, R. G. Bibcode: 1984AExpr...1Q..81G Altcode: No abstract at ADS Title: Some comments on solar reconnection problems Authors: Giovanelli, R. G. Bibcode: 1984GMS....30..357G Altcode: Comments are given on solar reconnection problems, noting that reconnection of magnetic flux tubes is a widespread phenomenon both on and inside the sun. The solar convection zone, some 200,000 km deep, contains vast numbers of flux tubes, all in pressure equilibrium with the nonmagnetic surroundings. Twisted tubes may well be reconnected in a manner resembling spot welding rather than by Petschek's mechanism. By a sequence of processes, flux ropes are built and float to the surface to produce sunspots. This is a vital part of the solar cycle, and the help of theoreticians in studying it is requested. It is belived that reconnection also occurs in prominences and will be easier to study there than in flares. A massive program is recommended for daily observation of quiescent prominences from limb to limb to establish their typical three dimensional structures. Only after the field geometry is any further work justified on the theory of prominences and related reconnection phenomena. Unanswered questions remaining and observations that could help are noted. Title: Some Comments on Solar Reconnection Problems Authors: Giovanelli, Ronald G. Bibcode: 1984mrsl.conf..357G Altcode: No abstract at ADS Title: Secrets of the sun Authors: Giovanelli, Ronald G. Bibcode: 1984sesu.book.....G Altcode: 1984QB521.4.G56.... No abstract at ADS Title: Magnetic canopies in unipolar regions. Authors: Jones, H. P.; Giovanelli, R. G. Bibcode: 1983SoPh...87...37J Altcode: Base-height statistics are presented for magnetic canopies in six unipolar magnetic regions which were observed near the limb with the Kitt Peak Vacuum Telescope and Diode Array Magnetograph during the period 25 April-3 July, 1980. As in earlier studies, extensive areas are found to be covered by low-lying canopies. Title: Observations of Alfven waves simultaneously in H-alpha and K Authors: Giovanelli, R. G.; Beckers, J. Bibcode: 1983IAUS..102..407G Altcode: Simultaneous spectroheliograms of a quiet region at solar disk centre in Hα +0.29 Å, Hα -0.29 Å, K +0.18 Å and K -0.18 Å show much similarity in the asymmetries in the two lines. The fibrils are identical geometrically. Both lines show patterns of line-of-sight motions propagating along the fibrils. Close to the network, the velocity of propagation is of the order of 12 km s-1 towards or away from the network; further away the patterns propagate away from the network at velocities of the order of 75 km s-1. The latter are interpreted as Alfvén waves, the former as due most likely to variations in longitudinal velocities along the fibrils. Title: Sunspot Geometry and Pressure Balance Authors: Giovanelli, R. G. Bibcode: 1982SoPh...80...21G Altcode: Measurements on magnetic canopies extending from sunspots show that, at the outer penumbral edge, heights of the bases are independent of sunspot diameter and average 180 km. This places a lower limit on the outer penumbral base; with an assumed thickness of 250 km, the top is ∼ 430 km above z = 0 (τc = 1) in the photosphere. Title: The Three-Dimensional Structure of Atmospheric Magnetic Fields in Two Active Regions Authors: Giovanelli, R. G.; Jones, H. P. Bibcode: 1982SoPh...79..267G Altcode: The magnetic field above two unrelated active regions on 11 and 12 September, 1974 has been studied using magnetograms obtained in C I 9111, Fe I 8688, Ca II 8542, and Hα. In C I 9111, originating low in the photosphere, the fields are strong and sharply defined. In Ca II 8542 and Hα they are very diffuse, with significant diffuseness also in Fe I 8688, due to the spreading of the field with height to form almost horizontal magnetic canopies over regions free of field at lower levels. Title: Magnetograph Response to Canopy-Type Fields Authors: Jones, H. P.; Giovanelli, R. G. Bibcode: 1982SoPh...79..247J Altcode: The response of longitudinal-field magnetographs to magnetic fields which are semi-infinite or confined to a horizontal layer is discussed with respect to the interpretation of solar diffuse fields, observed towards the limb, in terms of magnetic canopy models. Numerical results are presented for several reference solar models and typical `calibration' curves are shown for the C I 9111 Å, Fe I 8688 Å, and Ca II 8542 Å lines in magnetostatic atmospheres derived from a mean model. A procedure is developed for determining the base heights of magnetic canopies from observations with an uncertainty not exceeding the order of a pressure scale height. Until definitive information regarding atmospheric structure inside flux tubes can be developed from theory or observation, reliable field strengths cannot be derived from the data. Title: On the Relative Roles of Unipolar and Mixed-Polarity Fields Authors: Giovanelli, R. G. Bibcode: 1982SoPh...77...27G Altcode: Away from plages, solar magnetic fields may be classified as unipolar or as of mixed polarity, though the distinction is strictly arbitrary. The dividing line used here is 0.4 ≤ ¦Bminor/Bmajor¦ ≤ 1, where average fields of major and minor polarities are measured over large areas. Some of their statistical properties and cyclical variations are detailed. In unipolar regions, 3 ≲ Bmajor≲ 50 G, Bminor ≈ 0.1 Bmajor, and ¦B¦ ≈ 1.1 Bmajor. In regions of mixed polarity, 3.5 ≲ ¦B¦≲ 10 G. Title: Magnetic Canopies in Unipolar Regions Authors: Jones, H. P.; Giovanelli, R. G. Bibcode: 1981BAAS...13R.881J Altcode: No abstract at ADS Title: An Explanatory Two-Dimensional Study of the Coarse Structure of Network Magnetic Fields Authors: Giovanelli, R. G. Bibcode: 1980SoPh...68...49G Altcode: Magnetograms in lines originating high in the solar atmosphere show, away from disk center, diffuse fringes of reverse polarity on the limbward side and diffuse centerwards extensions of normal polarity wherever the field is strong. Analysis of a Mg b2 magnetogram reveals that, in active regions (and, hence, wherever the magnetic network is well developed) fields cover associated supergranules completely at heights mostly below 500-600 km (zero height is at τ5000 = 1) but possibly up to 700-800 km at great distances (e.g. >104km) from the network. These lie much lower than previously believed, mostly around the solar average temperature minimum. Near plagettes, the low-lying field has been measured out to ∼6000-7000 km. One consequence is that in active regions and plagettes, the chromosphere-corona transition region probably penetrates below 600 km; another is that potential theory is inapplicable at coronal heights below about 15 000 km. Title: Effects of Field Stratification on Magnetographic Measurements in the Infrared Triplet Lines of CaII Authors: Jones, H. P.; Giovanelli, R. G. Bibcode: 1980BAAS...12..807J Altcode: No abstract at ADS Title: The Supergranule Velocity Field Authors: Giovanelli, R. G. Bibcode: 1980SoPh...67..211G Altcode: A study of supergranule motions confirms horizontal velocities with peak values of typically 0.36 km s−1 as observed in Fe I 8688 Å. These show no significant variation with height over the range of formation of C I 9111, Fe I 8688, and Mg I 8806, but there is a substantial reduction to about one-half of this at the level of Ca II 8542. Title: On the probability of clear daytime skies near Kitt Peak National Observatory. Authors: Giovanelli, R. G. Bibcode: 1979PASP...91..577G Altcode: Graphs are given for the probability of getting a required number of clear days at KPNO during an observing period of given length. The probabilities undergo large variations during the year, and are dominated by the persistence of weather patterns. The analysis is based on records from the Tucson International Airport. Title: On radiative dissipation of sinusoidal compressive waves in the chromosphere. Authors: Giovanelli, R. G. Bibcode: 1979SoPh...62..253G Altcode: A first-order theory is developed for the radiative dissipation of compressive waves in the chromosphere above Tmin, where line radiation becomes dominant. The radiative relaxation time, which is the key to dissipation, is shown to depend on wave amplitude, falling greatly for amplitudes ≳ 2 km s−1 or more. For a given amplitude, dissipation is greatest for high frequencies, ω ≳ 0.1 s−1, periods ≲ 1 min. The observed short-period r.m.s. velocities ~2.4 km s−1 at the D1, level are adequate to provide dissipation balancing chromospheric emission losses. Title: The lack of chemical separation during the diffusion of gas into solar magnetic tubes. Authors: Giovanelli, R. G. Bibcode: 1979SoPh...62...51G Altcode: At a temperature well above Tmin, so that hydrogen is mainly ionized and diffuses negligibly into magnetic tubes, helium can still be mainly neutral so that chemical differentiation could occur. Calculation shows that the rate is too small to acccount for variations in chemical abundance found in the solar wind. Title: The radiative relaxation time in the chromosphere. Authors: Giovanelli, R. G. Bibcode: 1978SoPh...59..293G Altcode: The cooling effect of emission in the spectral lines, which dominates over continuous emission in the chromosphere and becomes important first around the temperature minimum, modifies greatly the radiative relaxation timetr in the solar atmosphere. This rises from low photospheric values to a maximum of ∼8 min just aboveTmin, falls in the low chromosphere to ∼1.5 min because of line emission, but rises again to ∼6 min atT ∼ 7000-8400 K in the chromosphere where hydrogen ionization increases the specific heat. Title: Motions in solar magnetic tubes. II: The oscillations. Authors: Giovanelli, R. G.; Livingston, W. C.; Harvey, J. W. Bibcode: 1978SoPh...59...49G Altcode: The method of Giovanelli and Brown (1977) has been used with a variety of spectral lines to study oscillating longitudinal gas velocities inside solar magnetic elements. Oscillations have been found inside all elements observed, the amplitudes increasing with height from typically ±0.27 km s−1 in Fe I 5166 Å (a line of low origin) to ±0.75 km s−1 in Hα. Simultaneous observations in pairs of lines show that a given disturbance occurs later with height, so that disturbances propagate outwards. The period is typically 5 min in all lines originating near or below Mg b1, but is about 3 min in Hα. Title: Motions in solar magnetic tubes. III: Outward wave propagation in sunspot umbras. Authors: Giovanelli, R. G.; Harvey, J. W.; Livingston, W. C. Bibcode: 1978SoPh...58..347G Altcode: The line-centre magnetogram technique has been used to study velocities at spatial scales ≃5″ in several umbras without interference from light scattered from the surrounding non-magnetic photosphere. In addition, more traditional velocity observations of one sunspot were also analysed. The velocities are highly variable within any spot and from one spot to another. Rms velocities in Hα, b1, 5233 and 5166 Å were typically ±0.6, ±0.20, ±0.10, and ±0.17 km s−1 during present observations, but factors of 2 smaller or larger are not uncommon. In 5166 and 5233 Å these velocities are about two-thirds of those in non-magnetic photospheric regions. Title: Motions in solar magnetic tubes. I: The downflow. Authors: Giovanelli, R. G.; Slaughter, C. Bibcode: 1978SoPh...57..255G Altcode: The line-centre-magnetogram technique has been used to measure the average velocity in magnetic elements in plages and isolated magnetic elements (including dipoles) in Ca II 8542, Mg I 5183, Fe I 8688 and C I 9111. The velocities vary from 0.6 km s−1 downflow in the line of deepest origin to zero in the highest. The smooth curve obtained by combining these with the results of other investigators is in conformity with Giovanelli's (1977) theory of inflow in the neighborhood of the temperature minimum. Title: Gas entry into non-spot magnetic tubes. Authors: Giovanelli, R. G. Bibcode: 1977SoPh...52..315G Altcode: Gas penetration into twisted magnetic tubes can occur by the inward diffusion of neutral atoms in the neighbourhood of the temperature minimum between photosphere and chromosphere, where the degree of ionization is low. Again, turbulent buffeting indents tubes in the convection zone and, in particular near the photosphere, provides a larger area where the overall diffusion rate may be enhanced. These processes do not contribute rapidly to the gas content of magnetic tubes, but diffusion near the temperature minimum may well be the source of the observed downflow in magnetic points. Title: Vertical velocity fluctuations in plage-region magnetic points. Authors: Giovanelli, R. G.; Brown, N. Bibcode: 1977SoPh...52...27G Altcode: Observations of line-of-sight velocities of gases in magnetic fields in weak plages near disk centre confirm the systematic downward velocity of 0.5 km s−1, and show fluctuations about this mean by a rather uncertain 0.2 km s−1. Some of the fluctuations show a fairly regular period around 5.5 min. Title: The helium 10830 Å line in the undisturbed chromosphere. Authors: Giovanelli, R. G.; Hall, D. Bibcode: 1977SoPh...52..211G Altcode: A study of the solar spectrum near helium 10 830 Å has shown that, where the line is very weak, the anomalous ratio of the two components is due almost certainly to faint blends. The centre-limb intensity variation over supergranule centres is in good agreement with an optically-thin law. The line is stronger over supergranule boundaries, and the ratio of the two components can be understood only if the absorbing elements have been resolved incompletely (as is probable); using centre-limb intensity variations, we have been unable to distinguish between unresolved horizontal platelets or inclined slabs. Title: Radiation and structure of the solar atmosphere (Radiation et structure de l'atmosphère solaire). Authors: Giovanelli, R. G.; Mein, P.; Bappu, M. K. V.; Jordan, C.; MacQueen, R. M. Bibcode: 1976IAUTA..16b..55G Altcode: No abstract at ADS Title: Heat Transfer in the Corona and Transition Region Authors: Giovanelli, R. G. Bibcode: 1975SoPh...44..315G Altcode: Thermal transfer in closed magnetic tubes in the corona and transition region is described on the basis of a static model in which all heat generated is radiated away, though conduction transfers much of the heat to the transition region prior to emission. Title: A Diffuse Component in the Hα Chromospheric Network Authors: Giovanelli, R. G. Bibcode: 1974SoPh...38..117G Altcode: Observations are described of diffuse material in and around the chromospheric network which lowers the intensity there in the core of Hα, and is detected best at Hα ± 0.5 Å. Title: Chromospheric Granulation Authors: Giovanelli, R. G. Bibcode: 1974SoPh...37..301G Altcode: Photographs obtained in the core of Hα, free of parasitic continuum radiation, reveal a granular structure in supergranule centres wherever not obscured by mottles or fibrils. Granulation is seen well in the wings out to ±0.5 Å from line centre, the contrasts being largely reversed in opposite wings. The granule diameters (from boundary to boundary) are observed down to 800 km, and are typically 1200 km, both probably upper limits imposed by telescope resolution. At 0.25 Å, the intensity fluctuates over a greater range (some 14%) in the blue wing than in the red (about 10%). The fluctuation is only 4% at line centre. This smaller value represents a real variation at the local line centre, whereas the appearance of granulation in the wings reflects to a large extent Doppler shifts due to vertical velocities. There is a tendency for the bright features at line centre to be moving downwards. Title: Book reviews Authors: de Jager, C.; Hartle, James B.; Drawin, H. W.; Giovanelli, R. G.; Freudenthal, Hans; Wittenberg, H.; Tobias, Cornelius A.; van der Laan, H.; Smit, J. A. Bibcode: 1974SSRv...15..741D Altcode: No abstract at ADS Title: Waves and Oscillations in the Chromosphere in Active and Quiet Regions Authors: Giovanelli, R. G. Bibcode: 1974IAUS...56..137G Altcode: No abstract at ADS Title: Oscillations and Waves in a Sunspot Authors: Giovanelli, R. G. Bibcode: 1972SoPh...27...71G Altcode: Observations have been made in Hα of the vertical velocity distribution in a sunspot. Over the umbra the pattern consists of structures of scale-size 2-3″. The velocity distribution undergoes oscillations with a period of about 165 s and typical amplitude ±3 km s−1, but the pattern breaks down after one or two cycles because the period of oscillation varies typically by ±20 s from place to place. Transverse waves develop in the outer 0.1 of the umbral radius and propagate outwards with a velocity of about 20 km s−1, becoming gradually invisible by or before the outer penumbral boundary; the amplitude is about ±1 km s−1 at the umbra-penumbra border. Title: A Comparison between the Helium 10830 Å and the Hydrogen H&alpha Chromospheres Authors: Giovanelli, R. G.; Hall, D. N. B.; Harvey, J. W. Bibcode: 1972SoPh...22...53G Altcode: Spectroheliograms of resolution about 2 arc sec obtained simultaneously in He 10830 Å and Hα show in the network a very close agreement in position of dark Hα mottles and of bright Hα plage remnants with 10830 Å absorption, though there is not a one-to-one relation between the intensities; the typical intensity in 10830 Å, corrected for overlapping lines, is I≈ 0.91 of the continuum. Some parts of the network do not appear in 10830 Å. This line is much weaker over supergranule centres (I≈ 0.98), though near active regions dark Hα fibrils coincide with faint 10830 Å fibrils (I≈0.93-0.98). Title: The Culgoora Magnetograph Authors: Ramsay, J. V.; Giovanelli, R. G.; Gillett, H. R. Bibcode: 1971IAUS...43...24R Altcode: No abstract at ADS Title: Vertical Velocities Associated with Plage Region Magnetic Fields Authors: Giovanelli, R. G.; Ramsay, J. V. Bibcode: 1971IAUS...43..293G Altcode: No abstract at ADS Title: Solar Magnetic Fields. Authors: Giovanelli, R. G. Bibcode: 1971ICRC....8....9G Altcode: 1971ICRC.........9G; 1971ICRC...12h...9G No abstract at ADS Title: Solar Magnetic Fields and Velocities Authors: Giovanelli, R. G. Bibcode: 1970PASA....1..363G Altcode: 1970PASAu...1..363G It has long been known that Fraunhofer lines show variations in intensity from place to place over the Sun’s surface, these being particularly noticeable in spectroheliograms obtained in the strong chromospheric lines. An early account of the weaker Unes was given by d’Azam-buja. McMath, Mohler, Pierce and Goldberg attributed intensity increases in (or decreases in depth of) metallic spectral lines to local temperature increases. Sheeley used high-resolution spectra to study these line weakenings further, finding them where, and only where, strong non-spot magnetic fields occurred. He also reported that in many cases the continuum in such regions was of reduced intensity, suggesting that fields often occur in the dark lanes and pores in the granulation. Spectroheliograms obtained in the cores of the weakened lines (e.g., Fel 6302.5Å) by Chapman and Sheeley showed that the bright network which these weakenings form appears as a sequence of sharp, bright points in the cores of the fainter lines and the wings of stronger lines but is more diffuse in the cores of stronger lines. They found the bright network in Zeeman-insensitive Unes (e.g., 5123.7A) also, indicating that it is due, at least in part, to variations in physical conditions. Lines of low ionization and excitation are weakened more than those of high ionization and excitation, and they attributed this to a temperature increase by 100-200 °K in the region of formation of the line cores ; a similar increase of 250 °K was found by Harvey and Livingston. Title: Solar: Fine Structure of the Flare of 1968 June 9 Authors: Giovanelli, R. G. Bibcode: 1969PASA....1..184G Altcode: 1969PASAu...1..184G A class 2 flare began on 1968 June 9 in the active region near 17°N 40°E, at about 00h15m U.T., maximum 00h37m, terminating about 02h30m. The event was recorded at Culgoora with the 5-inch flare-patrol and 12-inch chromo-spheric telescopes at solar diameters and frame intervals of 16 mm/10 s and 17 cm/3 s respectively. Both telescopes used Halle filters, pass bands about 0.5Å centred on Hα, and Duplopan 35 mm film. The seeing was mediocre, with occasional fairly good frames. Title: The Optical Programme of the Culgoora Solar Observatory Authors: Giovanelli, R. G. Bibcode: 1967PASA....1...39G Altcode: 1967PASAu...1...39G The Sun being a highly ionized gas, the basic physical quantities most needed for understanding solar phenomena are temperature, pressure (or density), velocity and magnetic field, together with their variations in space and time. The general aim at Culgoora is to secure observations from which these quantities may be derived (insofar as is practicable) simultaneously over extended solar regions. To do this has involved the development and use of filters of high spectral and spatial resolution, the study of atmospheric seeing and ways of securing high-resolution observations, and the study of methods of analysing observations to yield the physical quantities needed. Title: Excitation of hydrogen and CaII under chromospheric conditions Authors: Giovanelli, R. G. Bibcode: 1967AuJPh..20...81G Altcode: No abstract at ADS Title: Structure of the Normal Chromosphere Authors: Giovanelli, R. G. Bibcode: 1967sp...conf..353G Altcode: No abstract at ADS Title: Some remarks on spectroscopic observations of chromospheric limb structures Authors: Giovanelli, R. G.; Michard, R.; Mouradian, Z. Bibcode: 1965AnAp...28..871G Altcode: No abstract at ADS Title: The "double Limb" in Ha. Authors: Bhavilai, Rawi; Norton, D. G.; Giovanelli, R. G. Bibcode: 1965ApJ...141..274B Altcode: Photographs of the solar chromosphere in monochromatic light of pass band 1s A centered on Ha show that the well-known "double limb" vanishes on eliminating all traces of the surrounding continuum. The inner limb is spurious and is simply an image of the photosphere in stray light of unwanted wavelengths. Title: Sunspot minima Authors: Giovanelli, R. G. Bibcode: 1964Obs....84...57G Altcode: No abstract at ADS Title: Methods and techniques for the observation of sunspots in white light Authors: Giovanelli, R. G. Bibcode: 1964susp.conf...68G Altcode: No abstract at ADS Title: Sunspot minima Authors: Giovanelli, R. G. Bibcode: 1964susp.conf...57G Altcode: No abstract at ADS Title: A fluctuation theory of cosmology Authors: Giovanelli, R. G. Bibcode: 1964MNRAS.127..461G Altcode: A cosmological model is proposed in which density fluctuations can occur on all observable scales; in particular, our observable universe need not be representative of the universe as a whole. The sole assumption, aimed at achieving a self-perpetuating universe on a statistical rather than a steady-state basis, is that for an infinite uniform universe the gravitational potential is constant throughout. An equlvalent assumption is that the cosmological constant, A, is 4TrGp0, where p0 is the mean density of the universe. Such a system is unstable, as shown by Jeans, who gave detailed consideration to condensing regions; there are also other regions that expand uniformly, and our local part of the universe is identified with one of these. On Newtonian mechanics, the Hubble constant is predicted to be ( irGp0)"2. Some implications are considered briefly, including the regeneration of vArna tI,e er e1enienf i 1 r nre r < Title: The calculation of spectral line profiles with non-coherent scattering Authors: Giovanelli, R. G. Bibcode: 1962MNRAS.124..221G Altcode: A simple and improved method is described for calculating spectral line proffles when scattering is completely non-coherent. Attention is drawn to the difficalty of explaining the depths of strong Fraunhofer lines if scattering is of this type. Title: Some investigations of the optical properties of the atmosphere Authors: Giovanelli, R. G. Bibcode: 1962sose.conf...31G Altcode: No abstract at ADS Title: Seeing problems within telescopes Authors: Giovanelli, R. G. Bibcode: 1962sose.conf...33G Altcode: No abstract at ADS Title: Seeing monitor development Authors: Giovanelli, R. G. Bibcode: 1962sose.conf...65G Altcode: No abstract at ADS Title: Vertical Velocities in the Solar Chromosphere Authors: Giovanelli, R. G.; Jefferies, J. T. Bibcode: 1961AuJPh..14..212G Altcode: No abstract at ADS Title: A 1/8 A Birefringent Filter for Solar Research Authors: Steel, W. H.; Smartt, R. N.; Giovanelli, R. G. Bibcode: 1961AuJPh..14..201S Altcode: No abstract at ADS Title: On the centre-limb variation of granule contrast Authors: Giovanelli, R. G. Bibcode: 1961MNRAS.122..523G Altcode: It is shown that the observed centre-limb changes in granule contrast, and particularly the disappearance of granulation near the limb, are due mainly to foreshortening and finite telescope resolution. Without greatly improved resolution, it is invalid to use such observations for inferring the optical depth of the top of the granulation zone, as has sometimes been done. Title: Radiative Transfer in Non-uniform Media Authors: Giovanelli, R. G. Bibcode: 1959AuJPh..12..164G Altcode: No abstract at ADS Title: Optical observations of solar disturbances causing type II radio bursts Authors: Giovanelli, R. G.; Roberts, J. A. Bibcode: 1959IAUS....9..201G Altcode: No abstract at ADS Title: Flare puffs as a cause of type III radio bursts Authors: Giovanelli, R. G. Bibcode: 1959IAUS....9..214G Altcode: No abstract at ADS Title: Optical Observations of the Solar Disturbances causing Type II Radio Bursts Authors: Giovanelli, R. G.; Roberts, J. A. Bibcode: 1958AuJPh..11..353G Altcode: No abstract at ADS Title: Flare-Puffs as a Cause of Type III Radio Bursts Authors: Giovanelli, R. G. Bibcode: 1958AuJPh..11..350G Altcode: No abstract at ADS Title: The Flare-surge Event Authors: Giovanelli, R. G.; McCabe, Marie K. Bibcode: 1958AuJPh..11..191G Altcode: No abstract at ADS Title: The Distribution of Flare Heights as Derived from Limb Flares Authors: Giovanelli, R. G.; McCabe, Marie K. Bibcode: 1958AuJPh..11..130G Altcode: No abstract at ADS Title: An abrupt flare on 1956 September 6 Authors: Giovanelli, R. G.; McCabe, M. K. Bibcode: 1957Obs....77..238G Altcode: No abstract at ADS Title: The Emission of Radiation from Model Hydrogen Chromospheres. II Authors: Jefferies, J. T.; Giovanelli, R. G. Bibcode: 1954AuJPh...7..574J Altcode: No abstract at ADS Title: The Albedo for the Atomic Scattering of Optical Radiation Authors: Giovanelli, R. G.; Jefferies, J. T. Bibcode: 1954AuJPh...7..570G Altcode: No abstract at ADS Title: The Emission of Radiation from Flares Authors: Giovanelli, R. G. Bibcode: 1949MNRAS.109..337G Altcode: No abstract at ADS Title: The Hydrogen Spectrum of the Sun Authors: Giovanelli, R. G. Bibcode: 1949MNRAS.109..298G Altcode: No abstract at ADS Title: A Note on Heat Transfer in the Upper Chromosphere and Corona Authors: Giovanelli, R. G. Bibcode: 1949MNRAS.109..372G Altcode: No abstract at ADS Title: Hydrogen Atmospheres in the Absence of Thermodynamic Equilibrium. IV. The Solar Chromosphere Authors: Giovanelli, R. G. Bibcode: 1948AuSRA...1..360G Altcode: 1948AuJPh...1..360G No abstract at ADS Title: Hydrogen Atmospheres in the Absence of Thermodynamic Equilibrium. II. The Populations of the Lower Atomic States Authors: Giovanelli, R. G. Bibcode: 1948AuSRA...1..289G Altcode: 1948AuJPh...1..289G No abstract at ADS Title: Chromospheric Flares Authors: Giovanelli, R. G. Bibcode: 1948MNRAS.108..163G Altcode: No abstract at ADS Title: Emission of Enhanced Microwave Solar Radiation Authors: Giovanelli, R. G. Bibcode: 1948Natur.161..133G Altcode: IT is now well known that radiation in the 1-metre wave-length range from the quiescent sun corresponds, to that from a black body at about 106 °K., but that-when large spot groups are present the effective temperature is many times higher, the extra radiation, originating in the neighbourhood of the spot group. The million degree radiation has been explained by Martyn1, who attributes this to thermal emission from the normal corona. Kiepenheuer has suggested2 that the enhanced emission comes from thermal! electrons spiralling around lines of magnetic force. This idea has been attacked by Martyn3, and both he and Shklovsky4 have advanced theories for the-enhanced emission involving radiation by electrons oscillating at the fundamental frequency of the plasma. Title: Magnetic and Electric Phenomena in the Sun's Atmosphere associated with Sunspots Authors: Giovanelli, R. G. Bibcode: 1947MNRAS.107..338G Altcode: No abstract at ADS Title: A Theory of Chromospheric Flares Authors: Giovanelli, R. G. Bibcode: 1946Natur.158...81G Altcode: No abstract at ADS Title: Solar Eruptions. Authors: Giovanelli, R. G. Bibcode: 1940ApJ....91..334G Altcode: Observations of 268 solar eruptions made with a spectroheioscope during the period June, 1937, to December, 1938, have been analyzed to show the relative distributions of intensities and areas. A simple photometer for the measurement of eruption inten- sity is described. The width of the Ha line during eruptions is constant for small intensities but in- creases rapidly when the intensity becomes equal to, and exceeds that of, the continuous spectrum. There appears to be no appreciable vertical velocity of the eruption itself. Approximately 20 per cent of the eruptions eject eruptive prominences, and, assuming that this is caused by La radiation pressure, the width of La is found to be approxi- mately six times that of Ha when measured in velocity units. The position of eruptions in the chromosphere is discussed, and it is concluded that, in general, eruptions are confined to the levels in which the normal bright hydrogen occurs. OBSERVATION Title: The Motion of Eruptive Prominences. Authors: Giovanelli, R. G. Bibcode: 1940ApJ....91...83G Altcode: A theory is suggested for the motion of such eruptive prominences as are associated with solar eruptions, according to which the constant velocities are maintained by radiation pressure of La and changes in velocity may originate in magnetic fields. The La line emitted by a single flocculus is shown to be strongly reversed. The total effect produced by several flocculi with different La widths is equivalent to that of an La con- tour with several maxima and minima. Provided the intensities are of the right order, to each hump in the contour there corresponds one stable velocity. If the prominence is electrically charged, on moving into a horizontal magnetic field it experiences a force which accelerates it along a horizontal direction, but the radiation exerts sufficient pressure to maintain an essentially constant vertical velocity. On mov- ing into a field of the opposite direction, the prominence is deflected toward the vertical with an increased velocity and may again be subjected to a further radiation pressure, thus giving rise to an increase in velocity Title: The Relations Between Eruptions and Sunspots. Authors: Giovanelli, R. G. Bibcode: 1939ApJ....89..555G Altcode: In this paper a preliminary examination is made of the statistical relationships between sunspots and the solar eruptions that are associated with them. The analysis deals with the probability of an eruption in relation to the size, type, and development of the associated spot group. MATERIA Title: The Association of Radio Fade-Outs with Solar Eruptions Authors: Giovanelli, R. G.; Higgs, A. J. Bibcode: 1939TeMAE..44..181G Altcode: 1939JGR....44..181G Since the announcement in 1936 that radio fade-outs were coincident in time with solar eruptions, a large number of observations have confirmed this beyond all doubt, but whether a particular eruption will be accompanied by a fade-out has not, hitherto, received much consideration. This question is examined in detail in the following discussion.Observations of fade-outs at the Commonwealth Solar Observatory, Canberra, Australia, have been made since June 1937 with automatic P‧ - f (multifrequency) equipment. Briefly, this consists of a pulse-transmitter, the frequency of which is automatically varied over a range from 2.3 to 12 mc/sec, and a special receiver, automatically tuned to the frequency of the transmitter. The complete cycle of operations is repeated, in the present instrument, every six minutes, while in the first instrument, which was in use until April 1938, the period was made five or fifteen minutes according to the solar activity. The signals picked up by the receiver are delineated, finally, on the screen of a cathode-ray oscillograph where the “ground-wave” and reflections, or “echoes,” from the E- and F-regions of the ionosphere are separated. The resulting quasi-stationary picture is photographed on a moving film. For the purposes of this paper a fade-out is defined as a period during which no reflections from the E-region can be seen; a “severe” fade-out is one in which, in addition, no echoes from the F-region are visible, while a “minor” fade-out is one in which some F-region echoes, though weakened, are present. It should be emphasized that this criterion for a fade-out is not absolute and refers particularly to the special transmitter and receiver used in the investigation, though it is worth pointing out that such fade-outs observed here invariably coincide with periods of severe disturbance to commercial radio services. Title: Eruptive Prominences and Ionospheric Disturbances. Authors: Giovanelli, R. G. Bibcode: 1938ApJ....88..204G Altcode: No abstract at ADS Title: Recent Solar Eruptions, Auroras, and Magnetic storms Authors: Higgs, A. J.; Giovanelli, R. G. Bibcode: 1938Natur.141..746H Altcode: IN connexion with the aurora of January 25-26, 1938, discussed in detail in NATURE of February 5, p. 232, it may be of interest to report that a brilliant and prolonged solar eruption and an unusually severe radio fade-out were observed at the Commonwealth Solar Observatory, Canberra, on January 24.