Author name code: rhodes
ADS astronomy entries on 2022-09-14
author:"Rhodes, Edward J. Jr." OR author:"Rhodes, E.J. Jr." -aff:"Sheffield" -aff:"Earth" -author:"Rhodes, Elizabeth"
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Title: Sub-surface Meridional Flow Results from MWO, GONG, and MDI
during Solar Cycle 23
Authors: Pinkerton, Stephen; Rhodes, Edward J.; Bogart, Richard S.
Bibcode: 2014AAS...22421823P
Altcode:
Time series of full-disk Dopplergrams were acquired at the 60-Foot
Solar tower of the Mount Wilson Observatory every year between 1987
and 2009. Analysis of this archive revealed that the focal plane of
the Tower did experience a small amount of systematic rotation, which
suggested that the alignment of the optics had changed slightly over
the years since its construction in 1907. This has caused some of the
initial daily flow maps to possess a so-called “washing machine”
effect similar to the pattern that was seen in raw GONG flow maps. We
have incorporated a systematic program of ring-diagram analysis in
which we have tracked the raw solar images using five differing assumed
instrumental rotation rates. We have then gone on to compute synoptic
maps of the horizontal flow vectors at several different depths over
much of Solar Cycle 23 in order to study how such an instrumental
rotation might affect both the zonal and meridional flows as functions
of latitude, depth, and time. We compare these results with GONG and MDI
flow measurements to empirically determine the regime within which the
MWO results are reliable and extend our analysis into Solar Cycle 22.
Title: Optically Stimulated Luminescence Dating of Sediments over
the Past 200,000 Years
Authors: Rhodes, Edward J.
Bibcode: 2011AREPS..39..461R
Altcode:
Optical dating of sediment using optically stimulated luminescence
has become important for studying Earth surface processes, and this
technique continues to develop rapidly. A group of closely linked
luminescence methods can be used to estimate the time since grains of
quartz and feldspar were last exposed to daylight by detecting their
subsequent response to environmental ionizing radiation exposure. The
technique is well suited to the dating of deposits as young as one year
to several hundred thousand years. Recent technical developments have
established a dating protocol with improved precision, a high degree
of reliability, and an in-built means to detect incomplete signal
removal during deposition. This approach has been extended to age
estimation for single grains, opening up a wider range of potential
environments and new possibilities for understanding postdepositional
grain movement. Ongoing research offers the possibility of significant
age range extension and novel applications including low-temperature
thermochronology.
Title: Miniature Neutron-Alpha Activation Spectrometer
Authors: Rhodes, Edgar; Holloway, James Paul; He, Zhong; Goldsten, John
Bibcode: 2002AIPC..632..101R
Altcode:
We are developing a miniature neutron-alpha activation spectrometer for
in-situ analysis of chem-bio samples, including rocks, fines, ices,
and drill cores, suitable for a lander or Rover platform for Mars or
outer-planet missions. In the neutron-activation mode, penetrating
analysis will be performed of the whole sample using a γ spectrometer
and in the α-activation mode, the sample surface will be analyzed
using Rutherford-backscatter and x-ray spectrometers. Novel in our
approach is the development of a switchable radioactive neutron source
and a small high-resolution γ detector. The detectors and electronics
will benefit from remote unattended operation capabilities resulting
from our NEAR XGRS heritage and recent development of a Ge γ detector
for MESSENGER. Much of the technology used in this instrument can be
adapted to portable or unattended terrestrial applications for detection
of explosives, chemical toxins, nuclear weapons, and contraband.
Title: Observed and Predicted Ratios of the Horizontal and Vertical
Components of the Solar p-Mode Velocity Eigenfunctions
Authors: Rhodes, Edward J., Jr.; Reiter, Johann; Schou, Jesper;
Kosovichev, Alexander G.; Scherrer, Philip H.
Bibcode: 2001ApJ...561.1127R
Altcode:
We present evidence that the observed ratios of the horizontal
and vertical components of the solar intermediate-degree p-mode
velocity eigenfunctions closely match theoretical predictions of
these ratios. This evidence comes from estimates of the observed
eigenfunction component ratios that were obtained from the fitting
of the p-mode oscillation peaks in low- and intermediate-degree
(l<=200) m-averaged power spectra computed from two different
60.75 day time series of Global Oscillation Network Group (GONG)
project Dopplergrams obtained in late 1996 and early 1998. These fits
were carried out using a peak-fitting method in which we fitted each
observed p-mode multiplet with a model profile that included both the
target mode and its six nearest spatial sidelobes and which incorporated
the effects of the incomplete observational time series through the
convolution of the fitted profiles with the temporal window functions,
which were computed using the two actual GONG observing histories. The
fitted profile also included the effects of the spatial leakage of
the modes of differing degrees into the target spectrum through the
use of different sets of m-averaged spatial leakage matrices. In
order to study the sensitivity of the estimated component ratios to
the details of the computation of the m-averaged power spectra and of
the image-masking schemes employed by the GONG project, we generated
a total of 22 different sets of modal fits. We found that the best
agreement between the predicted and inferred ratios came from the use
of unweighted averaged power spectra that were computed using so-called
n-averaged frequency-splitting coefficients, which had been computed
by cross-correlating the 2l+1 zonal, tesseral, and sectoral power
spectra at each l over a wide range of frequencies. This comparison
yielded a total of 1906 pairs of predicted ct,theory and
fitted ct,fit eigenfunction component ratios. A linear
regression analysis of these pairs of ratios resulted in the following
regression equation: ct,fit=(0.0088+/-0.0013)+(0.9940+/-
0.0044)ct,theory. The resulting correlation coefficient
was 0.9817. This agreement between the predicted and inferred ratios
suggests that the predicted ratios should be used in the fitting of
high-degree power spectra where the ratios cannot be inferred because
of the blending together of individual modal peaks into broad ridges
of power.
Title: Helioseismology: A probe of the solar interior, atmosphere,
and activity cycle
Authors: Rhodes, Edward J.
Bibcode: 1996AIPC..382....3R
Altcode:
Helioseismology began in earnest in the mid-1970s. By 1977
helioseismology had demonstrated that the solar convection zone was
about twice as deep as was previously thought to be the case. Since then
helioseismology has also provided a measurement of the radial profile
of the sound speed in the solar interior and it has also ruled out
solar models which would attempt to solve the solar neutrino problem
through a lowering of the temperature of the core, while at the same
time showing that the effects of the diffusion of helium and other
elements must be incorporated in the computation of the most accurate
models of the solar interior. The field has also provided measurements
of the radial and latitudinal profiles of the sun's angular velocity
over the outer half of the solar interior (as measured by radius). It
has also provided evidence for helical flow patterns in the motions of
the very shallow, sub-photospheric layers. Finally, the frequencies
of the solar p-mode oscillations have also been demonstrated to vary
with changing levels of solar activity.
Title: Confirmation of Solar Cycle--dependent Intermediate-Degree
p-Mode Frequency Shifts
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.; Ulrich, Roger K.
Bibcode: 1993ApJ...406..714R
Altcode:
Results of intercomparisons of seven different sets of frequencies of
intermediate-degree p-modes obtained at several different locations
between 1981 and 1989 are presented. It is shown that the frequency
shifts exhibited by all of these intermediate-degree p-modes are
consistent with the intermediate-degree frequency shifts presented by
Libbrecht and Woodward (1990) and also with the low-degree frequency
shifts presented by Elsworth et al. (1990). It is also shown that these
frequency shifts correlate with solar cycle-dependent changes in sunspot
number, area, and irradiance. Unbinned and binned differences between
1984 Mount Wilson Observatory and revised 1981 South Pole frequencies
are illustrated.
Title: The Supergranulation Spectrum
Authors: Hathaway, David H.; Rhodes, Edward J.; Cacciani, Alessandro;
Korzennik, Sylvain G.
Bibcode: 1991LNP...388..163H
Altcode: 1991ctsm.conf..163H
Full-disk Dopplergram observations obtained at the 60-foot
tower of the Mount Wilson Observatory with the Cacciani sodium
magneto-optical filter were analyzed to determine the spectrum of
the solar supergranulation. Individual Dopplergrams were averaged
together using a weighted average over 20-minute intervals to remove
the p-mode oscillations. The Doppler signals due to the motion of the
observer, the solar rotation, differential rotation, and limb shift
were then removed from the data to produce Dopplergrams dominated
by the supergranular flows. These data were mapped to heliographic
coordinates and projected onto the spherical harmonics. The resulting
spectrum exhibits a peak at spherical harmonic degree } 100, which
corresponds to typical cell diameters of about 40 Mm. Synthetic data
were constructed and passed through the same analysis procedures to
determine the actual spectrum required to reproduce the results. A
good fit was obtained with a kinetic energy spectrum which peaks at }
100 and decreases exponentially out to } 500 with an e-folding range
of } 90. A power law fit to the spectrum over this range in yields an
exponent of about -2.75. No corrections for seeing were included in
the analysis. Although the image was sampled at 8 arcsec resolution,
the effects of seeing may alter the actual slope of the spectrum and
make it somewhat flatter. The spectrum does not exhibit any evidence
for a distinct mesogranulation component out to } 500 (corresponding
to cell diameters of about 8 Mm).
Title: Solar Oscillation Ring Diagrams from Mt. Wilson Full-Disk
Magneto-Optical Dopplergrams
Authors: Hill, Frank; Rhodes, Edward J.; Korzennik, Sylvain G.;
Cacciani, Alessandro; Brown, Timothy M.
Bibcode: 1991LNP...388..271H
Altcode: 1991ctsm.conf..271H
Three-dimensional power spectra of solar oscillations have been
computed from moderate-resolution full disk Doppler images obtained
with the Magneto-Optical Filter at Mt. Wilson. Slices of the spectra
at constant frequency reveal the ring structures that are analogous
to the ridges in two-dimensional spectra. Ring diagrams obtained
at different heliographic positions show large differences in the
structure of the rings. These variations can be attributed to the
changing effective spatial resolution of the observations across the
disk. After correction for this effect, and .for terrestrial seeing,
the rings will be used to map the horizontal flows in the convection
zone as a function of position and depth.
Title: Measurements of Intermediate- and High-Degree (20<1<600)
p-Mode Solar Oscillation Power and Energy
Authors: Rhodes, Edward J.; Brown, Timothy M.; Cacciani, Alessandro;
Korzennik, Sylvain G.; Ulrich, Roger K.
Bibcode: 1991LNP...388..277R
Altcode: 1991ctsm.conf..277R
We present measurements of the total modal power and energy of
both intermediate- and high-degree (20< l <600) solar p-mode
oscillations which have been corrected to first order for the combined
effects of atmospheric seeing, image motion due to imperfect tracking,
and the point spread function of our optics. These power and energy
estimates have been obtained from an average of 20 separate zonal l -
n power spectra, which were obtained from observations obtained at the
60-Foot Solar Tower of the Mt. Wilson Observatory between July 1 and 20,
1988. The raw total power values were obtained from a least-squares
fitting of Lorentzian profiles to the p-mode ridges in the average
zonal power spectrum. As an initial method of correcting the observed
power levels, we adopted the procedure described by Kaufman (1988)
and deconvolved measurements of the observed limb profiles from one
of our images using two slightly different theoretical unblurred limb
profiles in order to obtain two estimates of the modulation transfer
function (mtf) of our experiment. The corrected power values which
resulted show systematic variations with both frequency and degree
which are similar to those obtained by Kaufman. For example, between
l = 100 and 600 our corrected power values drop by a factor of at
least 4.5, although the magnitude of our correction becomes less
certain as the degree is increased above 300. We also convert these
power values into estimates of the total energy of the modes to show
that the modal energies decrease by a factor of at least 15 over the
same range in l. Even given the uncertainty of our correction at the
higher degrees, the consistency of the l-dependent decrease in the
modal energies with similar results by Kaufman (1990) suggests that,
at least above l = 100, the modes are not in energy equipartition with
turbulent convective eddies.
Title: Further Evidence for Radial Variations in the Solar Equatorial
Angular Velocity Profile
Authors: Rhodes, Edward J.; Cacciani, Alessandro; Korzennik, Sylvain
G.; Ulrich, Roger K.
Bibcode: 1991LNP...388..285R
Altcode: 1991ctsm.conf..285R
One year ago we presented evidence that the rotationally-induced
frequency splittings of intermediate- and high-degree sectoral p-mode
oscillations vary systematically as a function of the degree, l,
of the modes (Rhodes, Cacciani, and Korzennik, 1989. Recently, we
confirmed the results presented there in three different ways. First,
we extended our earlier 5-day sequence of Dopplergrams to one of 20 days
which ran from July 1 through 20, 1988. We then repeated our earlier
cross-correlation analysis using the intrinsically higher frequency
resolution sectoral power spectra which resulted from the longer
data string. This analysis also showed the same l-dependence of the
frequency splittings which we had found in our earlier work. Second,
we computed a separate pair of 1024-minute long sectoral power
spectra for each of the 20 days and then averaged the 20 prograde
and 20 retrograde spectra into two average sectoral spectra. We
next computed the frequencies of the centers of both the prograde
and retrograde sectoral ridges at each even-l by fitting Lorentzian
profiles using a standard non-linear least-squares method and we then
simply subtracted the central frequencies of the corresponding prograde
and retrograde ridges at those same values of l. The splittings which
resulted from averaging these frequency differences over both l and
the radial overtone, n, showed the same l-dependence as did those
obtained from the cross-correlation analysis. Thirdly, we computed
Legendre coefficient expansions to the m - v frequency shifts of both
the high- and low-resolution tesseral power spectra. We then normalized
the sums of the odd Legendre expansion coefficients to obtain additional
estimates of the sectoral frequency splittings. Finally, we carried out
an inversion of the sectoral frequency splittings. This inversion shows
a rapid rise in the solar equatorial angular velocity from its surface
value to a value of 476 nHz at a depth of 0.07 to 0.08 solar radii below
the photosphere. The inverted profile also shows that the inner half
of the solar convection zone may be rotating at the magnetic feature
rate and that the equatorial angular velocity decreases inwardly of
the base of the convection zone to a depth of at least 0.50 solar radii.
Title: Summary of the Institute of Theoretical Physics (ITP) program
on helioseismology (Santa Barbara, January-June 1990)
Authors: Däppen, Werner; Rhodes, Ed
Bibcode: 1991AdSpR..11d..15D
Altcode: 1991AdSpR..11...15D
The authors presented their view as participants of the ITP programme
on helioseismology, which was coordinated by D.O. Gough and J. Toomre
(Santa Barbara, Jan 1990 - June 1990). Detailed proceedings can be found
in ``Challenges to theories of the structure of moderate-mass stars''
(eds. D.O. Gough and J. Toomre, Springer, Heidelberg, 1991).
Title: Depth and Latitude Dependence of the Solar Internal Angular
Velocity
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.
Bibcode: 1990ApJ...351..687R
Altcode:
One of the design goals for the dedicated helioseismology observing
state located at Mount Wilson Observatory was the measurement of the
internal solar rotation using solar p-mode oscillations. In this paper,
the first p-mode splittings obtained from Mount Wilson are reported
and compared with those from several previously published studies. It
is demonstrated that the present splittings agree quite well with
composite frequency splittings obtained from the comparisons. The
splittings suggest that the angular velocity in the solar equatorial
plane is a function of depth below the photosphere. The latitudinal
differential rotation pattern visible at the surface appears to persist
at least throughout the solar convection zone.
Title: Contribution of High-Degree Frequency Splittings to the
Inversions of the Solar Rotation Rate
Authors: Korzennik, Sylvain G.; Cacciani, Alessandro; Rhodes, Edward
J.; Ulrich, Roger K.
Bibcode: 1990LNP...367..341K
Altcode: 1990psss.conf..341K
We present the contribution of high degree rotational splittings to
the inversion of the internal rotation rate around the equator. The
extention of the input data set to l of 500, allow us to improve the
resolution of the solution mainly in the outermost 15% of the solar
radius. The rotational profile obtained in the regions below the
surface leads to an attractive picture that could reconcile different
non-seismic estimates of the surface rotation rate.
Title: Evidence for Radial Variations in the Equatorial Profile of
the Solar Internal Angular Velocity
Authors: Rhodes, Edward J.; Cacciani, Alessandro; Korzennik, Sylvain G.
Bibcode: 1990LNP...367..163R
Altcode: 1990psss.conf..163R
We present evidence that the solar internal angular velocity, at least
as measured in the equatorial plane, shows systematic radial variations
in the outer half (by radius of the solar interior. Specifically,
we employ the rotationally-induced frequency splittings of both high-
and intermediate-degree sectoral p-mode oscillations to demonstrate
that the internal angular velocity rises inwardly from the observed
spectroscopic rotation rate of the photospheric gas to a higher value
that is at least equal to the observed rotation rate of sunspots, if
not higher, in the outer third of the convection zone before decreasing
inward of the convection zone to a value which is at least two percent
below the photospheric gas rotation rate. By making the assumption that
the observed splittings are sensitive to solar rotation at the midpoints
of the p-mode eigenfunctions we obtain an angular velocity profile which
rises from 452 nHz at the photosphere to 462 nHz at a depth of about
five percent of the solar radius below the photosphere. A comparison of
this inferred angular velocity profile with that obtained from a formal
inversion of these splittings (which is reported elsewhere in these
proceedings by Korzennik et al.) suggests that the angular velocity
might actually exceed the magnetic rotation rate over much of the
convection zone before decreasing inwardly toward the center of the sun.
Title: Measurement of the rotational frequency splitting of the solar
five-minute oscillations from magneto-optical filter observations.
Authors: Tomczyk, Steven; Cacciani, Alessandro; Korzennik, Sylvain G.;
Rhodes, Edward J., Jr.; Ulrich, Roger K.
Bibcode: 1988ESASP.286..141T
Altcode: 1988ssls.rept..141T
Observations of the solar five-minute oscillations in the photospheric
velocity field were obtained during the summer of 1984 at the 60-foot
solar tower of the Mt. Wilson Observatory with a magneto-optical
filter. The magneto-optical filter employs magneto-optical effects in
an atomic vapor to isolate narrow bandpasses in alternate wings of
a spectral line. Time series of full disk velocity images having a
resolution of about 10 arcseconds and a noise level of 15 m/s/pixel
were obtained on 92 days between the months of May and September of
1984. A subset of two time series from this data of 16 and 19 days
duration having a total of 25744 doppler images were analyzed to provide
estimates of the rotational frequency splitting for spherical harmonic
degrees between 5 and 120. The results of this analysis indicate a
decrease in the rate of solar rotation with increasing depth inside
the sun. Also, a decrease in the rate of differential rotation with
increasing depth is observed.
Title: Inversion of the solar rotation rate versus depth and latitude.
Authors: Korzennik, Sylvain G.; Cacciani, Alessandro; Rhodes, Edward
J., Jr.; Tomczyk, Steven; Ulrich, Roger K.
Bibcode: 1988ESASP.286..117K
Altcode: 1988ssls.rept..117K
The authors have used three different inversion techniques to compute
the internal solar rotation rate from several sets of n-averaged
frequency splittings. They have used an iterative variation of the
spectral expansion method, the optimal averaging kernel method and
a piecewise constant constrained least square method to invert the
data. Each computation was carried out independently. While they
present similar trends, each of the solutions differs in detail. A
consistent feature in all the inversions is the disappearance of
differential rotation below the base of the convection zone. Also,
a strong differential signature in the deeper part of the convection
zone is present in most of the solutions. A slow decrease of the
rotation rate with depth for the equatorial and mid-latitude curves
is significant in the spectral expansion and the least square results
but only marginally apparent in the averaging kernel results.
Title: Acquisition and reduction procedures for MOF
Doppler-magnetograms.
Authors: Cacciani, Alessandro; Ricci, D.; Rosati, P.; Rhodes, Edward
J., Jr.; Smith, E.; Tomczyk, Steven; Ulrich, Roger K.
Bibcode: 1988ESASP.286..185C
Altcode: 1988ssls.rept..185C
The authors analyse defects occurred on the MOF first magnetograms,
particularly they discuss the problem of the apparent contamination
between velocity and magnetic fields. They find that a correct
acquisition and reduction procedure gives cleaner results. The authors
also suggest a new vector magnetograph and compute the vector field
at coronal levels using one MOF longitudinal magnetogram.
Title: Radial and latitudinal gradients in the solar internal
angular velocity.
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.
Bibcode: 1988ESASP.286...73R
Altcode: 1988ssls.rept...73R
The authors recently presented the results of an analysis of the
frequency splittings of intermediate-degree (3 < degree ≤ 170)
p-mode oscillations which were obtained from a 16-day subset of our 1984
Mt. Wilson 60-foot tower observations. These results showed evidence
for both radial and latitudinal gradients in the solar internal
angular velocity. In particular, the results indicated that, from
0.6 Rsun to 0.95 Rsun,
the solar internal angular velocity increases systematically from
440 to 463 nHz, corresponding to a positive radial gradient of ≍66
nHz/Rsun for that portion of the solar interior. A
previous analysis indicated that the latitudinal differential rotation
gradient which is seen at the solar surface persists throughout
the convection zone, although there was some indication that the
differential rotation might disappear entirely below the base of the
convection zone. Here the authors extend their previous analysis to
include comparisons with additional observational studies and they
also present comparisons between our earlier results and the results
of additional inversions of several of the observational datasets. All
of these comparisons reinforce the previous conclusions regarding
the existence of radial and latitudinal gradients in the internal
angular velocity.
Title: Initial high-degree p-mode frequency splittings from the 1988
Mt. Wilson 60-foot tower solar oscillation program.
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik,
Sylvain G.
Bibcode: 1988ESASP.286...81R
Altcode: 1988ssls.rept...81R
The authors present here the initial frequency splitting results
of solar p-mode oscillations which they have obtained from their
1988 helioseismology at the Mt. Wilson Observatory. These frequency
splittings correspond to the rotational splittings of sectoral harmonics
which range in degree between 10 and 598. They were obtained from a
cross-correlation analysis of the prograde and retrograde portions
of a two-dimensional (l-ν) power spectrum. This power spectrum was
computed from an eight-hour sequence of full-disk Dopplergrams which
were obtained on July 2, 1988, at the 60-foot tower telescope with
a Na magneto-optical filter and a 1024×1024 pixel CCD camera. These
frequency splittings have an inherently larger scatter than did the
splittings obtained from earlier 16-day power spectra. Consequently,
the best one can say now is that these splittings are consistent with an
internal solar rotational velocity which is independent of radius along
the equatorial plane. The normalized frequency splittings averaged
449±3 nHz, a value which is very close to the observed equatorial
rotation rate of the photospheric gas of 451.7 nHz.
Title: Full-disk magnetograms obtained with a NA magneto-optical
filter at the Mount Wilson Observatory
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Garneau, Glenn;
Misch, Tony; Progovac, Dusan; Shieber, Tom; Tomczyk, Steve; Ulrich,
Roger K.
Bibcode: 1988fnsm.work...33R
Altcode:
The first full-disk magnetograms to be obtained with the Na
magneto-optical filter (MOF) which is located at the 60 foot solar
tower of the Mount Wilson Observatory are presented. This MOF was
employed as a longitudinal magnetograph on June 18, 19, and July 1,
1987. On those three days the MOF was combined with a large format
(1024 x 1024 pixel) virtual phase change coupled device camera and
a high-speed data acquisition system. The combined system was used
to record both line-of-sight magnetograms and Dopplergrams which
covered the entire visible solar hemisphere. The pixel size of these
magnetograms and Dopplergrams was 2.3 arcseconds. On each of the three
days a time series of nine pairs of magnetograms and Dopplergrams
was obtained at the rate of one pair every two minutes. On the same
three day longitudinal magnetograms have one arcsecond pixels were
obtained with the vacuum telescope at Kitt Peak. The MOF and vacuum
tower magnetograms were compared at both the JPL Multi-Mission Image
Processing Laboratory and at USC and have found the two sets of images
to be well correlated both in spatial distribution and strength of the
measured magnetic field. The simultaneously-obtained MOF Dopplergrams to
remove the crosstalk which was present between the Doppler and Zeeman
shifts of the NaD lines from the magnetograms from all three days and
will also describe recent improvements to the system which allowed the
obtaining of full-disk magnetograms as rapidly as one every 25 seconds.
Title: On the Constancy of Intermediate-Degree p-Mode Frequencies
during the Declining Phase of Solar Cycle 21
Authors: Rhodes, Edward J., Jr.; Woodard, Martin F.; Cacciani,
Alessandro; Tomczyk, Steven; Korzennik, Sylvain G.; Ulrich, Roger K.
Bibcode: 1988ApJ...326..479R
Altcode:
A comparison of two sets of frequencies of intermediate-degree (6 ≤ l
≤ 89) solar p-mode oscillations obtained in late 1981 and in mid-1984
shows agreement at the level of 0.02 μHz, or better than one part in
105. In particular, the frequencies of 573 modes obtained
at the South Pole during 1981 December 24 - 25, (reported by Duvall,
Harvey, and Pomerantz in 1987) were compared with the frequencies of
the same modes as observed at the Mount Wilson Observatory 60 foot
Solar Tower from 1984 July 29 through August 13. It is concluded that
the data are consistent with no change in intermediate-degree p-mode
frequencies between late 1981 and mid-1985.
Title: Estimates of the solar internal angular velocity obtained
with the Mt. Wilson 60-foot solar tower
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Woodard,
Martin; Tomczyk, Steven; Korzennik, Sylvain; Ulrich, R. K.
Bibcode: 1987ASSL..137...75R
Altcode: 1987isav.symp...75R
Estimates are obtained of the solar internal angular velocity from
measurements of the frequency splittings of p-mode oscillations. A
16-day time series of full-disk Dopplergrams obtained during July and
August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory
is analyzed. Power spectra were computed for all of the zonal, tesseral,
and sectoral p-modes from l = 0 to 89 and for all of the sectoral
p-modes from l = 90 to 200. A mean power spectrum was calculated for
each degree up to 89. The frequency differences of all of the different
nonzonal modes were calculated for these mean power spectra.
Title: Full-disk solar dopplergrams observed with a one megapixel
CCD camera and sodium magnetooptical filter
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Tomczyk, Steven
Bibcode: 1987ASSL..137...69R
Altcode: 1987isav.symp...69R
The paper presents here the first two full-disk solar Dopplergrams
obtained with the new 1024 x 1024-pixel CCD camera which has recently
been installed at the 60-Foot Tower Telescope of the Mt. Wilson
Observatory. These Dopplergrams have a spatial resolution of 2.2
arcseconds and were obtained in a total of one minute of time. The
Dopplergrams were obtained with a magnetooptical filter which was
designed to obtain images in the two Na D lines. The filter and the
camera were operated together as part of the development of a solar
oscillations imager experiment which is currently being designed at JPL
for the Joint NASA/ESA Solar and Heliospheric Observatory mission. Two
different images obtained by subtracting two pairs of the Dopplergrams
from the initial time series are also included.
Title: Applications of the magneto-optical filter to stellar pulsation
measurements
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Tomczyk, Steven
Bibcode: 1986ASIC..169..359R
Altcode: 1986ssds.proc..359R
A proposed method of employing the Cacciani magneto-optical filter (MOF)
for stellar seismology studies is described. The method relies on the
fact that the separation of the filter bandpasses in the MOF can be
changed by varying the level of input power to the filter cells. With
the use of a simple servosystem the bandpass of a MOF can be tuned to
compensate for the changes in the radial velocity of a star introduced
by the orbital motion of the earth. Such a tuned filter can then be
used to record intensity fluctuations through the MOF bandpass over
an extended period of time for each given star. Also, the use of a two
cell version of the MOF makes it possible to alternately chop between
the bandpass located in the stellar line wing and a second bandpass
located in the stellar continuum. Rapid interchange between the two
channels makes it possible for atmospheric-introduced noise to be
removed from the time series.
Title: A one-megapixel image acquisition and processing system for
solar oscillation studies.
Authors: Rhodes, Edward J., Jr.; Bursch, Thomas K.; Ulrich, Roger K.;
Tomczyk, Steven
Bibcode: 1986SPIE..627..256R
Altcode:
The 1-Mpixel image acquisition and processing system that has been
installed at the Mt. Wilson observatory as part of the development
effort for the NASA/ESA Solar Oscillations Imager Experiment of the
projected Heliospheric Observatory mission is discussed. The system
encompasses a high speed CCD camera with a 1024 x 1024-pixel virtual
phase chip array, yielding a readout rate of about 800,000 pixels/sec;
this allows the entire Mpixel array to be read out in just over 1
sec. The camera is interfaced with a floating point array processor
that integrates several successive exposures from the CCD camera and
differences selected pairs of integrated images. The system is currently
being used to record and difference narrowband images of the sun.
Title: The 1984 solar oscillation program of the Mt. Wilson 60-foot
tower.
Authors: Rhodes, Edward J., Jr.; Cacciani, Alessandro; Tomczyk,
Steven; Ulrich, Roger K.
Bibcode: 1986ASIC..169..309R
Altcode: 1986ssds.proc..309R
The authors describe the instrumentation, data, and preliminary results
from the summer, 1984, solar oscillation observing program which
was carried out using the 60-foot tower telescope of the Mt. Wilson
Observatory.
Title: Non-radial pressure mode oscillations as a seismic probe of
solar structure
Authors: Rhodes, Edward Joseph, Jr.
Bibcode: 1977PhDT.......159R
Altcode:
No abstract at ADS