explanation blue bibcodes open ADS page with paths to full text
Author name code: giovanelli
ADS astronomy entries on 2022-09-14
=author:"Giovanelli, R.G." OR =author:"Giovanelli, Ronald G."
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Title: Geheimnisvolle Sonne.
Authors: Giovanelli, R. G.; Beck, R.
1987geso.book.....G Altcode:
No abstract at ADS
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Title: Book-Review - Secrets of the Sun
Authors: Giovanelli, R. G.; Hill, R. E.
1985S&T....70..562G Altcode:
No abstract at ADS
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Title: Book-Review - Secrets of the Sun
Authors: Giovanelli, R. G.; Jakimiec, J.
1985SSRv...41..398G Altcode:
No abstract at ADS
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Title: Book-Review - Secrets of the Sun
Authors: Giovanelli, R. G.; Kleczek, J.
1985Ap&SS.112..424G Altcode:
No abstract at ADS
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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.
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.
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Title: The Sunspot Cycle and Solar Magnetic Fields - Part Two -
the Interaction of Flux Tubes with the Convection Zone
Authors: Giovanelli, R. G.
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
(≡10<SUP>4</SUP>G at a depth 10 Mm to (6 - 12)x10<SUP>4</SUP>G at
≡150 Mm); and (3) the amplitudes of the torsional oscillation.
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Title: Book-Review - Secrets of the Sun
Authors: Giovanelli, R. G.
1984AExpr...1Q..81G Altcode:
No abstract at ADS
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Title: Some comments on solar reconnection problems
Authors: Giovanelli, R. G.
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.
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Title: Some Comments on Solar Reconnection Problems
Authors: Giovanelli, Ronald G.
1984mrsl.conf..357G Altcode:
No abstract at ADS
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Title: Secrets of the sun
Authors: Giovanelli, Ronald G.
1984sesu.book.....G Altcode: 1984QB521.4.G56....
No abstract at ADS
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Title: Magnetic canopies in unipolar regions.
Authors: Jones, H. P.; Giovanelli, R. G.
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.
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Title: Observations of Alfven waves simultaneously in H-alpha and K
Authors: Giovanelli, R. G.; Beckers, J.
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<SUP>-1</SUP> towards
or away from the network; further away the patterns propagate away from
the network at velocities of the order of 75 km s<SUP>-1</SUP>. The
latter are interpreted as Alfvén waves, the former as due most likely
to variations in longitudinal velocities along the fibrils.
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Title: Sunspot Geometry and Pressure Balance
Authors: Giovanelli, R. G.
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 (τ<SUB>c</SUB> = 1) in the photosphere.
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Title: The Three-Dimensional Structure of Atmospheric Magnetic Fields
in Two Active Regions
Authors: Giovanelli, R. G.; Jones, H. P.
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.
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Title: Magnetograph Response to Canopy-Type Fields
Authors: Jones, H. P.; Giovanelli, R. G.
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.
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Title: On the Relative Roles of Unipolar and Mixed-Polarity Fields
Authors: Giovanelli, R. G.
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 ≤
¦B<SUB>minor</SUB>/B<SUB>major</SUB>¦ ≤ 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 ≲ B<SUB>major</SUB>≲ 50 G, B<SUB>minor</SUB>
≈ 0.1 B<SUB>major</SUB>, and ¦B¦ ≈ 1.1 B<SUB>major</SUB>. In
regions of mixed polarity, 3.5 ≲ ¦B¦≲ 10 G.
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Title: Magnetic Canopies in Unipolar Regions
Authors: Jones, H. P.; Giovanelli, R. G.
1981BAAS...13R.881J Altcode:
No abstract at ADS
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Title: An Explanatory Two-Dimensional Study of the Coarse Structure
of Network Magnetic Fields
Authors: Giovanelli, R. G.
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 b<SUB>2</SUB>
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 τ<SUB>5000</SUB> = 1) but possibly up to 700-800 km at
great distances (e.g. >10<SUP>4</SUP>km) 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.
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Title: Effects of Field Stratification on Magnetographic Measurements
in the Infrared Triplet Lines of CaII
Authors: Jones, H. P.; Giovanelli, R. G.
1980BAAS...12..807J Altcode:
No abstract at ADS
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Title: The Supergranule Velocity Field
Authors: Giovanelli, R. G.
1980SoPh...67..211G Altcode:
A study of supergranule motions confirms horizontal velocities with
peak values of typically 0.36 km s<SUP>−1</SUP> 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.
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Title: On the probability of clear daytime skies near Kitt Peak
National Observatory.
Authors: Giovanelli, R. G.
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.
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Title: On radiative dissipation of sinusoidal compressive waves in
the chromosphere.
Authors: Giovanelli, R. G.
1979SoPh...62..253G Altcode:
A first-order theory is developed for the radiative dissipation
of compressive waves in the chromosphere above T<SUB>min</SUB>,
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<SUP>−1</SUP> or more. For a
given amplitude, dissipation is greatest for high frequencies, ω ≳
0.1 s<SUP>−1</SUP>, periods ≲ 1 min. The observed short-period
r.m.s. velocities ~2.4 km s<SUP>−1</SUP> at the D<SUB>1</SUB>,
level are adequate to provide dissipation balancing chromospheric
emission losses.
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Title: The lack of chemical separation during the diffusion of gas
into solar magnetic tubes.
Authors: Giovanelli, R. G.
1979SoPh...62...51G Altcode:
At a temperature well above T<SUB>min</SUB>, 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.
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Title: The radiative relaxation time in the chromosphere.
Authors: Giovanelli, R. G.
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 timet<SUB>r</SUB> in the solar atmosphere. This
rises from low photospheric values to a maximum of ∼8 min just
aboveT<SUB>min</SUB>, 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.
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Title: Motions in solar magnetic tubes. II: The oscillations.
Authors: Giovanelli, R. G.; Livingston, W. C.; Harvey, J. W.
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<SUP>−1</SUP> in Fe I 5166 Å (a line of low origin)
to ±0.75 km s<SUP>−1</SUP> 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 b<SUB>1</SUB>, but is
about 3 min in Hα.
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Title: Motions in solar magnetic tubes. III: Outward wave propagation
in sunspot umbras.
Authors: Giovanelli, R. G.; Harvey, J. W.; Livingston, W. C.
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, b<SUB>1</SUB>, 5233
and 5166 Å were typically ±0.6, ±0.2<SUB>0</SUB>, ±0.1<SUB>0</SUB>,
and ±0.1<SUB>7</SUB> km s<SUP>−1</SUP> 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.
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Title: Motions in solar magnetic tubes. I: The downflow.
Authors: Giovanelli, R. G.; Slaughter, C.
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<SUP>−1</SUP> 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.
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Title: Gas entry into non-spot magnetic tubes.
Authors: Giovanelli, R. G.
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.
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Title: Vertical velocity fluctuations in plage-region magnetic points.
Authors: Giovanelli, R. G.; Brown, N.
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<SUP>−1</SUP>, and show fluctuations about this mean by
a rather uncertain 0.2 km s<SUP>−1</SUP>. Some of the fluctuations
show a fairly regular period around 5.5 min.
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Title: The helium 10830 Å line in the undisturbed chromosphere.
Authors: Giovanelli, R. G.; Hall, D.
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.
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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.
1976IAUTA..16b..55G Altcode:
No abstract at ADS
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Title: Heat Transfer in the Corona and Transition Region
Authors: Giovanelli, R. G.
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.
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Title: A Diffuse Component in the Hα Chromospheric Network
Authors: Giovanelli, R. G.
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.
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Title: Chromospheric Granulation
Authors: Giovanelli, R. G.
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.
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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.
1974SSRv...15..741D Altcode:
No abstract at ADS
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Title: Waves and Oscillations in the Chromosphere in Active and
Quiet Regions
Authors: Giovanelli, R. G.
1974IAUS...56..137G Altcode:
No abstract at ADS
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Title: Oscillations and Waves in a Sunspot
Authors: Giovanelli, R. G.
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<SUP>−1</SUP>, 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<SUP>−1</SUP>, becoming gradually invisible by or before the outer
penumbral boundary; the amplitude is about ±1 km s<SUP>−1</SUP>
at the umbra-penumbra border.
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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.
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).
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Title: The Culgoora Magnetograph
Authors: Ramsay, J. V.; Giovanelli, R. G.; Gillett, H. R.
1971IAUS...43...24R Altcode:
No abstract at ADS
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Title: Vertical Velocities Associated with Plage Region Magnetic
Fields
Authors: Giovanelli, R. G.; Ramsay, J. V.
1971IAUS...43..293G Altcode:
No abstract at ADS
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Title: Solar Magnetic Fields.
Authors: Giovanelli, R. G.
1971ICRC....8....9G Altcode: 1971ICRC.........9G; 1971ICRC...12h...9G
No abstract at ADS
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Title: Solar Magnetic Fields and Velocities
Authors: Giovanelli, R. G.
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.
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Title: Solar: Fine Structure of the Flare of 1968 June 9
Authors: Giovanelli, R. G.
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 00<SUP>h</SUP>15<SUP>m</SUP>
U.T., maximum 00<SUP>h</SUP>37<SUP>m</SUP>, terminating about
02<SUP>h</SUP>30<SUP>m</SUP>. 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.
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Title: The Optical Programme of the Culgoora Solar Observatory
Authors: Giovanelli, R. G.
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.
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Title: Excitation of hydrogen and CaII under chromospheric conditions
Authors: Giovanelli, R. G.
1967AuJPh..20...81G Altcode:
No abstract at ADS
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Title: Structure of the Normal Chromosphere
Authors: Giovanelli, R. G.
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.
1965AnAp...28..871G Altcode:
No abstract at ADS
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Title: The "double Limb" in Ha.
Authors: Bhavilai, Rawi; Norton, D. G.; Giovanelli, R. G.
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.
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Title: Sunspot minima
Authors: Giovanelli, R. G.
1964Obs....84...57G Altcode:
No abstract at ADS
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Title: Methods and techniques for the observation of sunspots in
white light
Authors: Giovanelli, R. G.
1964susp.conf...68G Altcode:
No abstract at ADS
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Title: Sunspot minima
Authors: Giovanelli, R. G.
1964susp.conf...57G Altcode:
No abstract at ADS
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Title: A fluctuation theory of cosmology
Authors: Giovanelli, R. G.
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 <
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Title: The calculation of spectral line profiles with non-coherent
scattering
Authors: Giovanelli, R. G.
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.
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Title: Some investigations of the optical properties of the atmosphere
Authors: Giovanelli, R. G.
1962sose.conf...31G Altcode:
No abstract at ADS
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Title: Seeing problems within telescopes
Authors: Giovanelli, R. G.
1962sose.conf...33G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Seeing monitor development
Authors: Giovanelli, R. G.
1962sose.conf...65G Altcode:
No abstract at ADS
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Title: Vertical Velocities in the Solar Chromosphere
Authors: Giovanelli, R. G.; Jefferies, J. T.
1961AuJPh..14..212G Altcode:
No abstract at ADS
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Title: A 1/8 A Birefringent Filter for Solar Research
Authors: Steel, W. H.; Smartt, R. N.; Giovanelli, R. G.
1961AuJPh..14..201S Altcode:
No abstract at ADS
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Title: On the centre-limb variation of granule contrast
Authors: Giovanelli, R. G.
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.
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Title: Radiative Transfer in Non-uniform Media
Authors: Giovanelli, R. G.
1959AuJPh..12..164G Altcode:
No abstract at ADS
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Title: Optical observations of solar disturbances causing type II
radio bursts
Authors: Giovanelli, R. G.; Roberts, J. A.
1959IAUS....9..201G Altcode:
No abstract at ADS
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Title: Flare puffs as a cause of type III radio bursts
Authors: Giovanelli, R. G.
1959IAUS....9..214G Altcode:
No abstract at ADS
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Title: Optical Observations of the Solar Disturbances causing Type
II Radio Bursts
Authors: Giovanelli, R. G.; Roberts, J. A.
1958AuJPh..11..353G Altcode:
No abstract at ADS
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Title: Flare-Puffs as a Cause of Type III Radio Bursts
Authors: Giovanelli, R. G.
1958AuJPh..11..350G Altcode:
No abstract at ADS
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Title: The Flare-surge Event
Authors: Giovanelli, R. G.; McCabe, Marie K.
1958AuJPh..11..191G Altcode:
No abstract at ADS
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Title: The Distribution of Flare Heights as Derived from Limb Flares
Authors: Giovanelli, R. G.; McCabe, Marie K.
1958AuJPh..11..130G Altcode:
No abstract at ADS
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Title: An abrupt flare on 1956 September 6
Authors: Giovanelli, R. G.; McCabe, M. K.
1957Obs....77..238G Altcode:
No abstract at ADS
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Title: The Emission of Radiation from Model Hydrogen Chromospheres. II
Authors: Jefferies, J. T.; Giovanelli, R. G.
1954AuJPh...7..574J Altcode:
No abstract at ADS
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Title: The Albedo for the Atomic Scattering of Optical Radiation
Authors: Giovanelli, R. G.; Jefferies, J. T.
1954AuJPh...7..570G Altcode:
No abstract at ADS
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Title: The Emission of Radiation from Flares
Authors: Giovanelli, R. G.
1949MNRAS.109..337G Altcode:
No abstract at ADS
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Title: The Hydrogen Spectrum of the Sun
Authors: Giovanelli, R. G.
1949MNRAS.109..298G Altcode:
No abstract at ADS
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Title: A Note on Heat Transfer in the Upper Chromosphere and Corona
Authors: Giovanelli, R. G.
1949MNRAS.109..372G Altcode:
No abstract at ADS
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Title: Hydrogen Atmospheres in the Absence of Thermodynamic
Equilibrium. IV. The Solar Chromosphere
Authors: Giovanelli, R. G.
1948AuSRA...1..360G Altcode: 1948AuJPh...1..360G
No abstract at ADS
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Title: Hydrogen Atmospheres in the Absence of Thermodynamic
Equilibrium. II. The Populations of the Lower Atomic States
Authors: Giovanelli, R. G.
1948AuSRA...1..289G Altcode: 1948AuJPh...1..289G
No abstract at ADS
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Title: Chromospheric Flares
Authors: Giovanelli, R. G.
1948MNRAS.108..163G Altcode:
No abstract at ADS
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Title: Emission of Enhanced Microwave Solar Radiation
Authors: Giovanelli, R. G.
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 10<SUP>6</SUP> °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 Martyn<SUP>1</SUP>, who
attributes this to thermal emission from the normal corona. Kiepenheuer
has suggested<SUP>2</SUP> that the enhanced emission comes from
thermal! electrons spiralling around lines of magnetic force. This
idea has been attacked by Martyn<SUP>3</SUP>, and both he and
Shklovsky<SUP>4</SUP> have advanced theories for the-enhanced emission
involving radiation by electrons oscillating at the fundamental
frequency of the plasma.
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Title: Magnetic and Electric Phenomena in the Sun's Atmosphere
associated with Sunspots
Authors: Giovanelli, R. G.
1947MNRAS.107..338G Altcode:
No abstract at ADS
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Title: A Theory of Chromospheric Flares
Authors: Giovanelli, R. G.
1946Natur.158...81G Altcode:
No abstract at ADS
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Title: Solar Eruptions.
Authors: Giovanelli, R. G.
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
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Title: The Motion of Eruptive Prominences.
Authors: Giovanelli, R. G.
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
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Title: The Relations Between Eruptions and Sunspots.
Authors: Giovanelli, R. G.
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
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Title: The Association of Radio Fade-Outs with Solar Eruptions
Authors: Giovanelli, R. G.; Higgs, A. J.
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.
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Title: Eruptive Prominences and Ionospheric Disturbances.
Authors: Giovanelli, R. G.
1938ApJ....88..204G Altcode:
No abstract at ADS
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Title: Recent Solar Eruptions, Auroras, and Magnetic storms
Authors: Higgs, A. J.; Giovanelli, R. G.
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.
