Author name code: plaskett
ADS astronomy entries on 2022-09-14
=author:"Plaskett, H.H." 
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Title: Solar wavelengths and the limb effect.
Authors: Plaskett, H. H.
Bibcode: 1977MNRAS.179..339P
Altcode:
  The possibility is considered that some effect of photospheric velocity
  is contained within the wavelength of the center of gravity of an
  asymmetric solar line measured with a micrometer microscope from a
  grating spectrum of some specified point on the solar disk and within
  the interferometrically known wavelength of the same line at the center
  of the disk. An attempt is made to show that apparent anomalies in
  solar wavelengths are due to a radial current with vertical velocity
  and that the limb effect is probably a consequence of this current. A
  vertical velocity of about 0.39 km/s is obtained from analysis of
  the limb effect, and both photospheric and chromospheric origins of
  the radial current are investigated. It is concluded that there is
  insufficient information to determine whether this current occurs in
  the photosphere or the chromosphere.

Title: Herman Zanstra.
Authors: Plaskett, H. H.
Bibcode: 1974QJRAS..15...57P
Altcode:
  No abstract at ADS

Title: Equatorial currents in the photosphere
Authors: Plaskett, H. H.
Bibcode: 1973MNRAS.163..183P
Altcode:
  From spectra photographed at Oxford in 1966 and 1968 sight-line
  velocities of the equatorial zone of the Sun are tabulated. After
  correction of these for limb effect an axisymmetric solution gives
  the zonal and meridional components of photospheric velocity. In the
  Northern and Southern Hemispheres of an equatorial zone of constant
  angular velocity there occurs at a latitude of some 10 a dominantly
  meridional current. The properties of the current are described, a
  possible origin of its meridional part proposed and some suggestions
  are made on why the current has hitherto escaped detection.

Title: Limb darkening and solar rotation-II
Authors: Plaskett, H. H.
Bibcode: 1970MNRAS.148..149P
Altcode:
  Spectrophotometric measures of surface brightness at A for diametrically
  opposite limbs of the Sun confirm that the poles are at least five
  per cent brighter than the equatorial limb. Solutions by Radau
  integration for the source function and computation of photospheric
  models give temperature as a function of linear height for a
  number of latitudes. The currents due to the resulting meridional
  temperature-gradient occur in a photospheric Ekmanlayer and are of
  the same order of magnitude as those found from velocities measured
  at Oxford in 1953 and 1960. These thermal currents are stable and are
  maintained against viscous loss by heat absorbed in the photosphere. To
  these currents is probably due the observed decrease of angular velocity
  towards the poles of the Sun. The origin of polar heating is however
  as yet unknown.

Title: The polar rotation of the Sun
Authors: Plaskett, H. H.
Bibcode: 1966MNRAS.131..407P
Altcode:
  Spectroscopic measures of the rotation of the Sun are given for 190
  photo- spheric positions in the latitude range 45750 (section 1). After
  a correction for limb effect, made from the measures themselves (section
  2), these velocities show meridional currents directed towards the
  equator and a difference of rotation in the northern and southern
  hemispheres (section 3. i). Interpreting these velocities as the
  result of a balanced motion between a posttilated meridional pressure
  gradient and an inertial Coriolis force, the polar retardation of the
  Sun's rotation appears to be due to zonal currents moving towards the
  apparent east in an otherwise uniformly rotating photo- sphere (section
  3.2). A re-discussion of unconfirmed measures of limb darkening in shows
  differences of polar and equatorial temperature which may be the origin
  of the meridional pressure gradient and which quantitatively describe
  the observed velocities (section 3.3). Moreover from an analysis of
  the meridional components of velocity some evidence is found of Rossby
  waves, a phenomenon characteristic of well-established zonal winds in
  the Earth's atmosphere (section 4). From these zonal currents which
  tend to brake the rotation of the photo sphere and from the suspected
  polar heating, it is speculatively inferred that beneath the hydrogen
  convection zone the Sun may complete a rotation in some I hours
  (section 5).

Title: The physics of the Sun
Authors: Plaskett, H. H.
Bibcode: 1965Obs....85..178P
Altcode:
  No abstract at ADS

Title: Heat flow in stars
Authors: Plaskett, H. H.
Bibcode: 1963Obs....83..236P
Altcode:
  No abstract at ADS

Title: Limb darkening and solar rotation
Authors: Plaskett, H. H.
Bibcode: 1962MNRAS.123..541P
Altcode:
  In finding the darkening to the limb the determination of , the
  position on the disk, must be no less accurate than that of 1(o, it)
  the surface brightness. Both requirements are met by photographic
  spectrophotometry and with this method new measures are made of limb
  darkeriing along east-west and northsouth radii (Table V). From these
  measures photo- spheric models are computed for heliographic latitudes
  o0 and 750 (Table IX). The horizontal temperature-gradient between
  these latitudes produces a heliostrophic wind blowing from apparent
  west to east. A comparison with measures of photospheric velocity
  (Table X) suggests that the hydrogen convection zone is in uniform
  rotation and that the polar retardation of the Sun's rotation is due
  to a purely photospheric circulation driven by polar heating.

Title: Motions in the Sun at the photospheric level, VIII. Solar
    rotation and photospheric circulation
Authors: Plaskett, H. H.
Bibcode: 1959MNRAS.119..197P
Altcode:
  From spectra exposed 1953 April zI-Z3, sight-line velocities have been
  measured at 33z points over the visible surface of the Sun. For any
  point the sight-line velocity can be expressed as a linear function of
  velocity components directed to the west and the nofth. Least-squares
  solutions of such observation equations for various latitudes reveal
  an asymmetry of rotational velocities in the equatorial zone and the
  presence of meridional currents. These motions suggest the existence
  of a circulation in the photosphere similar to that shown in the upper
  atmosphere of the Earth. This hypothesis is examined in the light of an
  investigation by M. J. Lighthill, and an observational test is proposed.

Title: Excitation of chromospheric emission
Authors: Plaskett, H. H.
Bibcode: 1956MNRAS.116..419P
Altcode:
  The presence of the Lyman-alpha line in emission across the whole
  disk of the Sun suggests that the chromosphere is excited by a
  mechanism additional to that g}ven by the absorption of photospheric
  radiation. To find some of the properties of this additional excitation
  the observed intensity of a chromospheric line, as observed at
  the limb of the Sun outside an eclipse, is derived as an integral
  containing the source function. A numerical method of solving this
  integral equation is outlined, and from the solution the excitation
  temperature and the density can be found as functions of radial height
  in the chromosphere. Other applications of the integral equation are
  briefly discussed.

Title: The Oxford 35 m solar telescope
Authors: Plaskett, H. H.
Bibcode: 1955MNRAS.115..542P
Altcode:
  A new telescope for solar work with an equivalent focal length of
  35 2 m is described. It is an ordinary Cassegrain reflector used at
  the coud focus. The optical requirements for satisfactory performance
  are listed and some of the mechanical features briefly described. The
  performance is assessed from a Hartmann test.

Title: Interpretation of Fraunhofer-line profiles
Authors: Plaskett, H. H.
Bibcode: 1955MNRAS.115..256P
Altcode:
  From the experimentally determined cross-sections of the Na atom for
  collisions of the second kind it is shown that the hypothesis of true
  absorption is probably not applicable to the formation of Fraunhofer
  lines in the solar photosphere. Using atomic transition probabilities
  for radiative excitation and ionization, values of the source functions
  and the ratio of the line to the continuous absorption coefficients are
  derived in terms of kinetic, excitation and ionization temperatures. The
  functional dependence of these quantities on the optical depth is such
  as to permit a numerical integration of the exact equation of transfer,
  and the method of effecting this integration is outlined

Title: Physical conditions in the solar photosphere
Authors: Plaskett, H. H.
Bibcode: 1955VA......1..637P
Altcode:
  From the source-function, recently derived by SYKES, the temperature
  is found as a function of optical depth in the solar photosphere. The
  temperature distribution leads in turn to the gas pressure. To find
  these and other physical parameters it is necessary to assume that the
  photosphere is in local thermodynamic equilibrium. The uncertainty
  produced in these quantities by this and other assumptions, as well
  as by observational error, is briefly discussed. The deep layers of
  the photosphere, where ( d ln T/ d ln p) > 0·4, are unstable;
  the steep temperature gradient may arise from boundary cooling. It is
  shown that solar granulation probably originates in the zone of observed
  instability rather than in the deeper-lying hydrogen-convection zone.

Title: Motions in the Sun at the photospheric level. V. Velocities
    of granules and of other localized regions
Authors: Plaskett, H. H.
Bibcode: 1954MNRAS.114..251P
Altcode:
  Velocities and surface brightness in three Oxford spectra, showing
  granulation, have been measured. The results are in good agreement
  with those earlier found by Richardson and Schwarzschild in a Mount
  Wilson spectrum. In two of the three Oxford spectra a significant
  correlation coefficient of r= - has been found between the surface
  brightness and the sight-lin component of the velocity, showing that
  the bright granular matter is moving vertically upwards. Assuming that
  the top of the granulation zone occurs at an optical depth of unity,
  km sec-' is a lower limit to the velocity of ascent of the bright
  granular matter. The smallness, or in one spectrum the absence, of any
  correlation between surface brightness and velocity suggests that the
  granular velocities are being partially or completely maske by some
  other perturbation of velocity. Removing from the observed velocities
  that part due to granulation, the perturbing velocities are found to
  originate in an oscillatory velocity field with an average period of
  5 of arc and an amplitude of the order of 0.5 km sec-'.

Title: The Oxford solar spectroscope
Authors: Plaskett, H. H.
Bibcode: 1952MNRAS.112..177P
Altcode:
  The prismatic spectroscope, used with the Oxford solar telescope,
  has a clear aperture of 15 2 cin and a focal length of 8 96 m. The
  linear dispersion varies from min A-' at A4ooo to min A-' at A . The
  horizontal apparatus function, determined from the Kr.line A , has a
  half-width of A with a marked asynirnetry to the red. The practical
  resolving power at this wave4ength is 93 900, less than one-third of
  that predicted by diffraction theory. Because of the asymmetry in the
  apparatus function the centres of intensity of solar absorption lines
  are displaced to the red by amounts which vary as their equivalent
  widths; precautions must therefore be adopted in the measurement of
  Doppler displacements. The yertical apparatus function (up and down
  the slit) has a half-width of mm. This tends to wash out the spectra of
  fine details on the solar surface, but theory and practical experience
  show that spectra of solar' granules can be obtained. For unanalysed
  white light, incident on a slit with a height of 19 mm, the general
  scattered light in the focal plane is i 6 per cent.

Title: Motions in the Sun at the photospheric level. I. Methods
Authors: Plaskett, H. H.
Bibcode: 1952MNRAS.112..414P
Altcode:
  for determining sight-line velocities at specified points on the
  solar photosphere are described. The portion of the solar image, the
  spectrufl of which is to be pho\ographed, is observed with an angular
  magnification of 390 times. The image may be guided, independently
  of the telescopic controls, and the photograph taken at the instant
  of best seeing. The spectra are measured against a centre spectrum by
  Evershed's positive-on-negative method on a self-recording micrometer;
  possible line displacements due to the asymmetry of the horizontal
  apparatus function of the spectroscope are thus elminated. An equation
  of condition between the three rectangular velocity components of motion
  in the photosphere and the measured sight-line velocity is derived.

Title: Astronomical Spectroscopy (Presidential Address, 1947)
Authors: Plaskett, H. H.
Bibcode: 1947MNRAS.107..117P
Altcode:
  No abstract at ADS

Title: Astronomical telescopes (Presidential Address, 1946)
Authors: Plaskett, H. H.
Bibcode: 1946MNRAS.106...80P
Altcode:
  No abstract at ADS

Title: (Presidential Address) on presenting the Gold Medal to
    Professor J. H. Oort
Authors: Plaskett, H. H.
Bibcode: 1946MNRAS.106..242P
Altcode:
  No abstract at ADS

Title: The observational determination of the line absorption
    coefficient and its variation with depth in the solar atmosphere
Authors: Plaskett, H. H.
Bibcode: 1941MNRAS.101....3P
Altcode:
  No abstract at ADS

Title: The Oxford solar telescope and Hartmann tests of its
    performance
Authors: Plaskett, H. H.
Bibcode: 1939MNRAS..99..219P
Altcode:
  No abstract at ADS

Title: Solar granulation
Authors: Plaskett, H. H.
Bibcode: 1936MNRAS..96..402P
Altcode:
  No abstract at ADS

Title: A Moll-type microphotometer and its performance
Authors: Plaskett, H. H.
Bibcode: 1934MNRAS..95..160P
Altcode:
  No abstract at ADS

Title: Book Reviews: The Place of Observation in Astronomy
Authors: Plaskett, H. H.
Bibcode: 1934PA.....42..173P
Altcode:
  No abstract at ADS

Title: The formation of the magnesium b lines in the solar atmosphere
Authors: Plaskett, H. H.
Bibcode: 1931MNRAS..91..870P
Altcode: 1931HarRe..70....1P
  No abstract at ADS

Title: Hydrogen emission lines in nebulae
Authors: Plaskett, H. H.
Bibcode: 1931Obs....54...49P
Altcode:
  No abstract at ADS

Title: Line Intensities in Nebular Spectra
Authors: Plaskett, H. H.
Bibcode: 1931PDAO....4..188P
Altcode:
  No abstract at ADS

Title: Line intensities in nebular spectra (abstract)
Authors: Plaskett, H. H.
Bibcode: 1931PAAS....6R.149P
Altcode:
  No abstract at ADS

Title: The composite stellar and nebular spectrum of Z Andromedae
Authors: Plaskett, H. H.
Bibcode: 1931PDAO....4..119P
Altcode:
  No abstract at ADS

Title: Line intensities in nebular spectra (abstract)
Authors: Plaskett, H. H.
Bibcode: 1929PA.....37R...9P
Altcode:
  No abstract at ADS

Title: Line Intensities in Nebular Spectra.
Authors: Plaskett, H. H.
Bibcode: 1928HarCi.335....1P
Altcode:
  Includes: Line Intensities in N.G.C. 1976 and 7027 - Line Intensities
  in Six Planetary Nebulae - Physical Interpretation of Line Intensities.

Title: Scientific Books: The Internal Constitution of the Stars
Authors: Plaskett, H. H.
Bibcode: 1927Sci....66...81P
Altcode: 1927Sci....66...81E
  No abstract at ADS

Title: A possible origin of the nebular lines (abstract)
Authors: Plaskett, H. H.
Bibcode: 1927PAAS....5R..77P
Altcode:
  No abstract at ADS

Title: The wedge method and its application to astronomical
    spectrophotometry (abstract)
Authors: Plaskett, H. H.
Bibcode: 1927PAAS....5Q..78P
Altcode:
  No abstract at ADS

Title: Corrections to a List of Spectroscopic Binaries
Authors: Plaskett, H. H.
Bibcode: 1924JRASC..18..367P
Altcode:
  No abstract at ADS

Title: The Nature of Science
Authors: Plaskett, H. H.
Bibcode: 1924JRASC..18..294P
Altcode:
  No abstract at ADS

Title: The spectra of nebulae (abstract)
Authors: Plaskett, H. H.
Bibcode: 1924PA.....32..462P
Altcode:
  No abstract at ADS

Title: A Possible Origin of the Nebular Lines
Authors: Plaskett, H. H.
Bibcode: 1923Natur.112..392P
Altcode:
  THE hypothesis that the lines of unknown origin in the spectra of
  nebulæ are due to the atom of some hitherto undiscovered element (``
  nebulium '') is not the only one that may be advanced. The recently
  developed quantum theory of band spectra makes it at least possible that
  these lines could have their origin in a molecule with small moment of
  inertia composed of atoms of those elements which are known to exist
  in nebulæ. It is proposed in this letter to show that the existing
  astronomical evidence is not in contradiction to this alternative
  hypothesis, and also to indulge in some speculation as to the nature
  of such a molecule.

Title: Spectra of three O-type stars (abstract)
Authors: Plaskett, H. H.
Bibcode: 1923PA.....31R..19P
Altcode:
  No abstract at ADS

Title: The wedge method and its application to astronomical
    spectrophotometry (abstract)
Authors: Plaskett, H. H.
Bibcode: 1923PA.....31Q.659P
Altcode:
  No abstract at ADS

Title: A possible origin of the nebular lines (abstract)
Authors: Plaskett, H. H.
Bibcode: 1923PA.....31R.658P
Altcode:
  No abstract at ADS

Title: The Pickering Series and Bohr's Atom
Authors: Plaskett, H. H.
Bibcode: 1922JRASC..16..137P
Altcode:
  No abstract at ADS

Title: The Intensity Distribution in Typical Stellar Spectra
Authors: Plaskett, H. H.
Bibcode: 1922PAAS....4..226P
Altcode:
  No abstract at ADS

Title: The Radial Velocities of 594 Stars
Authors: Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H.
Bibcode: 1922PAAS....4..277P
Altcode:
  No abstract at ADS

Title: The Spectra of Three O-Type Stars
Authors: Plaskett, H. H.
Bibcode: 1922PAAS....4R.380P
Altcode:
  No abstract at ADS

Title: The Spectroscopic Orbit of Z Vulpeculae
Authors: Plaskett, H. H.
Bibcode: 1922PAAS....4..227P
Altcode:
  No abstract at ADS

Title: The Pickering Series in O Type Stars.
Authors: Plaskett, H. H.
Bibcode: 1921Natur.108..209P
Altcode:
  IF the Pickering series, consisting of the lines 5411, 4542, 4200,
  etc., in stellar spectra, is due to ionised helium, it is known
  from the investigations of Fowler and from Bohr's theory that there
  must be additional lines which appear as violet components of the
  Balmer series of hydrogen. As these components have an average
  separation of 2 Å. they should be readily seen in the spectra of O
  type stars. Unfortunately, there are two unfavourable circumstances:
  first, the O type stars are all faint, and, secondly, the lines of
  both the Balmer and the Pickering series are in general so diffuse as
  to be hopelessly blended.

Title: The Radial Velocities of 600 Stars (Abstract)
Authors: Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H.
Bibcode: 1921PASP...33R.212P
Altcode:
  No abstract at ADS

Title: Radiation from the Carbon Arc
Authors: Plaskett, H. H.
Bibcode: 1921Natur.107..648P
Altcode:
  AN application of Merton and Nicholson's form of the wedge method
  has been made to the study of the intensity distribution in typical
  stellar spectra. In the late type spectra (including the sun), which
  are sufficiently bright at the red end, the energy curves give a marked
  depression from 0.50-0.67µ-a result not obtained by other observers. As
  the spectrum of the carbon arc, assumed to radiate as a black body
  at a temperature of 3750° Abs., is used to remove the colour curve
  of the plate, a possible cause of this depression, which is common to
  all stellar spectra that have been observed in the red, would lie in
  an intensity distribution in the carbon arc differing from that assumed.

Title: The radial velocities of 594 stars.
Authors: Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H.
Bibcode: 1921PDAO....2....1P
Altcode:
  No abstract at ADS

Title: Eighty-eight spectroscopic binaries.
Authors: Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H.
Bibcode: 1921PDAO....1..287P
Altcode:
  No abstract at ADS

Title: The spectra of three O-type stars.
Authors: Plaskett, H. H.
Bibcode: 1921PDAO....1..325P
Altcode:
  No abstract at ADS

Title: The Origin of Spectra (concluded)
Authors: Plaskett, H. H.
Bibcode: 1920JRASC..14..269P
Altcode:
  No abstract at ADS

Title: The Origin of Spectra
Authors: Plaskett, H. H.
Bibcode: 1920JRASC..14..221P
Altcode:
  No abstract at ADS

Title: Spectroscopy, Astronomical, The intensity distribution in
    the continuous spectrum and the intensity of the hydrogen lines in
    γ Cassiopei&aelig
Authors: Plaskett, H. H.
Bibcode: 1920MNRAS..80..771P
Altcode:
  No abstract at ADS

Title: One hundred spectroscopic binaries.
Authors: Plaskett, J. S.; Harper, W. E.; Young, R. K.; Plaskett, H. H.
Bibcode: 1920PDAO....1..163P
Altcode:
  No abstract at ADS

Title: Atmospheric Haze and a Suspected Variation in Solar Rotation
    in 1915
Authors: Plaskett, H. H.
Bibcode: 1919JRASC..13..391P
Altcode:
  No abstract at ADS

Title: The solar rotation in 1913
Authors: Plaskett, H. H.
Bibcode: 1918PAAS....3Q..89P
Altcode:
  No abstract at ADS

Title: A Variation in Solar Rotation
Authors: Plaskett, H. H.
Bibcode: 1917ApJ....45..144P
Altcode:
  No abstract at ADS

Title: The Psychology of Differential Measurements
Authors: Plaskett, H. H.
Bibcode: 1916JRASC..10..220P
Altcode:
  No abstract at ADS

Title: A Variation in the Solar Rotation
Authors: Plaskett, H. H.
Bibcode: 1916ApJ....43..145P
Altcode:
  No abstract at ADS

Title: The Solar Rotation in 1913
Authors: Plaskett, H. H.
Bibcode: 1914JRASC...8..307P
Altcode:
  No abstract at ADS