Author name code: musman
ADS astronomy entries on 2022-09-14
author:"Musman, Steven"
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Title: Comparison of Local Helioseismic Techniques Applied to MDI
Doppler Data
Authors: Hindman, B. W.; Featherstone, N. A.; Haber, D. A.; Musman,
S.; Toomre, J.
Bibcode: 2004ESASP.559..460H
Altcode: 2004soho...14..460H
No abstract at ADS
Title: Plasmaspheric depletion and refilling associated with the
September 25, 1998 magnetic storm observed by ground magnetometers
at L = 2
Authors: Chi, P. J.; Russell, C. T.; Musman, S.; Peterson, W. K.;
Le, G.; Angelopoulos, V.; Reeves, G. D.; Moldwin, M. B.; Chun, F. K.
Bibcode: 2000GeoRL..27..633C
Altcode:
The plasmaspheric mass density at L ≃ 2 was monitored by two IGPP/LANL
ground magnetometer stations during the magnetic storm on September 25,
1998. Even at this low latitude the plasma density dropped significantly
to ≃ 1/4 of the pre-storm value. The total electron content (TEC)
inferred by GPS signals also shows a sizable decrease during the
storm. The observations suggest that the convection caused by the
strong electric field associated with the magnetic storm eroded the
plasmasphere as low as L = 2, which is a much lower latitude than
that expected from the estimated potential drop across the polar cap
together with a simple model of the magnetospheric convection pattern.
Title: Total electron content changes in the ionosphere during the
January 10, 1997 disturbance
Authors: Musman, Steven; Mader, Gerry; Dutton, C. Everett
Bibcode: 1998GeoRL..25.3055M
Altcode:
We have used the CORS network of GPS receivers to record ionospheric TEC
changes in the continental United States caused by the well observed
geomagnetic disturbance of January 10, 1997. This event produced
numerous worldwide consequences. Although the initial arrival of this
disturbance was before sunrise in the U.S. the TEC levels were most
significantly altered later during the daylight hours. We display
temporal and spatial changes through time series at selected sites
and maps of the entire network. The usual sequence of diurnal changes
was not greatly altered, but most of the TEC values were increased by
about a factor of one and a half to two. Stations in the northeast
and upper north central were exceptions and showed a small decrease
in TEC. We interpret the TEC changes as consequences of changes in
neutral chemical composition resulting from storm heating.
Title: Imaging spread-F structures using GPS observations at
Alcântara, Brazil
Authors: Musman, S.; Jahn, J. -M.; LaBelle, J.; Swartz, W. E.
Bibcode: 1997GeoRL..24.1703M
Altcode:
During October 1994, a dual-frequency GPS receiver was operated in
Alcântara, Brazil, at the same site where the Cornell University
Portable Radar Interferometer (CUPRI) was performing spread-F
measurements for an ongoing rocket campaign. We present data for
two nights during which several spread-F plumes drifted through the
field-of-view of CUPRI. Fluctuations in the total electron content
(TEC) measured with the GPS receiver were correlated with those
plumes. We define a “roughness” measure from a specialized high
frequency filter. Plots of “roughness” in a magnetic longitude
versus time space show initially low activity followed by regions of
dramatic localized onsets and a slower subsequent decline. Features
in the roughness image are well-correlated with plumes in the CUPRI
backscatter power map.
Title: Simultaneous Global Positioning System and radar observations
of equatorial spread F at Kwajalein
Authors: Kelley, Michael C.; Hysell, David; Musman, Steven
Bibcode: 1996JGR...101.2333K
Altcode:
GPS satellites broadcast at two frequencies (L1 of 1575.42 MHz and
L2 of 1227.6 MHz). The dispersive property of the ionosphere is
frequently used to correct positional measurements for ionospheric
effects. Independent measurements at the two frequencies can also
be combined to form a relative ionospheric delay and a measure of
the total electron content (TEC) which is uncertain by an additive
constant. In a previous paper (Musman et al., 1990) estimates
of this offset were utilized in constructing models of the time
history of the equivalent zenith delay at Westford, Massachusetts. An
ionospheric model composed of uniform shells whose electron density
changes slowly in a typical diurnal pattern would produce relative
ionospheric delays with a simple u-shaped or j-shaped curve. Most
of the change in delay would be a result of changes in geometry
between the observer and the satellite. Departures from a simple
pattern are indicative of ionospheric disturbances and the influence
of the protonosphere. From GPS data alone, it is ambiguous whether
these disturbances are due to spatial structures, temporal changes,
or some combination of the two. Equatorial spread F(ESF) refers to
a variety of equatorial ionospheric disturbances, some of which are
associated with rising plasma plumes having low electron density and
a high degree of turbulence. This phenomenon occurs primarily between
local sunset and local midnight at sites within about 15° of the
magnetic equator. In some seasons, disturbances can occur during two
out of three evenings, while at other times it can be much quieter. GPS
observations at Kwajalein (9°N latitude) reported here for August
14, 1990, show severe ionospheric disruption. Two independent and
simultaneous sets of radar observations confirm the presence of ESF
and reveal quite a bit about the spatial and temporal conditions which
affect the system. GPS observations on August 15, 1990, when no ESF
was present are much quieter. We find that tens of minute variations
in the TEC correspond to the motion of large scale features across the
GPS field of view. More severe GPS effects are seen to be collocated
with turbulent low density plumes which rise rapidly to high altitudes
and drift west to east across the GPS line of sight. Severe disruption
can occur in moderately sophisticated GPS systems during such events,
at least near solar maximum.
Title: Statistical tests of ARIES data
Authors: Musman, S.
Bibcode: 1982JGR....87.5553M
Altcode:
Statistical tests are performed on Project ARIES preliminary
baseline measurements in the Southern California triangle formed by
the Jet Propulsion Laboratory, the Owens Valley Radio observatory,
and the Goldstone tracking complex during 1976-1980. In addition
to conventional one-dimensional tests a two-dimensional test which
allows for an arbitrary correlation between errors in individual
components is formulated using the Hotelling statistic. On two out
of three baselines the mean rate of change in baseline vector is
statistically significant. Apparent motions on all three baselines are
consistent with a pure shear with north-south compression and east-west
expansion of 1×10-7/year. The ARIES measurement
are consistent with the USGS geodolite networks in Southern California
and the SAFE laser satellite ranging experiment. All three experiments
are consistent with a 6 cm/year motion between the Pacific and North
American Plates and a band of diffuse shear 300 km wide, except that
corresponding rotation of the entire triangle is not found.
Title: The Evolution of an Average Solar Granule
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1981BAAS...13..879A
Altcode:
No abstract at ADS
Title: Is Granulation a Periodic Phenomenon?
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1980BAAS...12..894A
Altcode:
No abstract at ADS
Title: Physical Development of an Average Solar Granule
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1979BAAS...11..641A
Altcode:
No abstract at ADS
Title: Recurrent geomagnetic disturbances and coronal holes as
observed in Fe XIV λ5303 Å
Authors: Musman, S.; Altrock, R. C.
Bibcode: 1978JGR....83.4817M
Altcode:
We present data obtained with the Fe XIV λ5303-Å coronal photometer of
the Sacramento Peak Observatory for the period October 3 to December 22,
1976. During this period there was a pattern of three coronal holes and
three emission regions near the solar equator. Recurrent geomagnetic
disturbances were associated with two of these three holes. We propose
a simple method for predicting recurrent geomagnetic disturbances
were associated with two of these three holes. We propose a simple
method for predicting recurrent geomagnetic disturbances at times
of low solar activity based on coronal brightness and test it on our
data. We show that the method gives correct results 72% of the time,
compared with 64% for 27 day recurrence.
Title: Time Development of Solar Granulation
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1978BAAS...10..623A
Altcode:
No abstract at ADS
Title: The scale of the solar granulation.
Authors: Nelson, G. D.; Musman, S.
Bibcode: 1978ApJ...222L..69N
Altcode:
The observed scale of granulation is derived as a consequence of a
physical model. At scales smaller than granulation, horizontal radiative
transport reduces temperature fluctuations and the resultant buoyancy
forces in the surface layers. At scales only slightly larger than
granulation, the dynamical pressure required to drive horizontal motions
changes the opacity sufficiently to reduce the apparent contrast. This
raises the possibility that the dark center of an exploding granule
may actually be hot below the surface. The maximum possible horizontal
extent of a surface-driven convective flow is estimated as 4.5 times
granular scale.
Title: The Scale of Granulation.
Authors: Musman, S. A.; Nelson, G. D.
Bibcode: 1977BAAS....9..616M
Altcode:
No abstract at ADS
Title: A dynamical model of solar granulation.
Authors: Nelson, G. D.; Musman, S.
Bibcode: 1977ApJ...214..912N
Altcode:
We construct a steady-state model of solar granulation with a
simplified horizontal structure. As in our previous model the
transfer of radiation dominates the energy balance and determines the
temperature fluctuations. The turbulent drag force which we include
in a simplified form balances the buoyancy created by the temperature
fluctuations. Penetration of velocity and temperature fluctuations
are similar to those observed. The small-scale turbulence generated by
granular motions may be an important contributor to observed unresolved
motions but cannot account for the total.
Title: Global oscillations of the solar brightness.
Authors: Musman, S.; Nye, A. H.
Bibcode: 1977ApJ...212L..95M
Altcode:
The Sacramento Peak Observatory vacuum tower telescope, echelle
spectrograph, and diode array were used to search for global solar
oscillations. The technique employed compares the relative intensity
of a number of points on the solar disk and favors the detection of
nonradial modes. In 6 days of observing, no narrow-band oscillations
with periods between 15 and 90 minutes were found. The sensitivity
per independent frequency interval is 0.0002 in contrast, or 0.3 K
in temperature.
Title: Introduction
Authors: Musman, Steven A.
Bibcode: 1977lsms.procD...3M
Altcode:
No abstract at ADS
Title: Coronal holes as observed in Fe XIV 5303 Å.
Authors: Altrock, R. C.; Musman, S. A.
Bibcode: 1977BAAS....9R.432A
Altcode:
No abstract at ADS
Title: Large-Scale Motions on the Sun
Authors: Musman, Steven A.
Bibcode: 1977lsms.proc.....M
Altcode:
No abstract at ADS
Title: Global Solar Oscillations
Authors: Musman, Steven; Nye, Alan H.
Bibcode: 1976ssp..conf...19M
Altcode:
No abstract at ADS
Title: The energy balance of granulation.
Authors: Musman, S.; Nelson, G. D.
Bibcode: 1976ApJ...207..981M
Altcode:
We construct columnar models of the solar granulation based on the
balance of convective energy carried by a vertical velocity field
and radiation. A specified velocity field and perturbation of the
radiative flux determines the variation of temperature fluctuations
with height. For a nominal model we compute the variation of contrast
with wavelength and heliocentric angle. We conclude that the observed
temperature fluctuations cannot be produced by the observed velocities
alone, but require either a modified radiation field or turbulent
energy transport, or both.
Title: Observations of penumbral wave in the photosphere.
Authors: Musman, S.; Nye, A. H.; Thomas, J. H.
Bibcode: 1976ApJ...206L.175M
Altcode:
Simultaneous observations have been made of velocities in the
chromosphere (in H-alpha) and in the photosphere (in the nonmagnetic
Fe I line at 5526-A) of three sunspots. The results reveal waves
propagating horizontally outward across the penumbra in the photosphere
with about the same period as the running penumbral waves in H-alpha
(250-290 s). The photospheric waves are more intermittent and have
higher horizontal phase velocity (by a factor of 2 or more) than the
chromospheric penumbral waves.
Title: Observations of Penumbral Waves in the Photosphere
Authors: Musman, S.; Nye, A. H.; Thomas, J. H.
Bibcode: 1976BAAS....8..344M
Altcode:
No abstract at ADS
Title: Global Solar Oscillations
Authors: Musman, S.; Nye, A. H.
Bibcode: 1976BAAS....8..299M
Altcode:
No abstract at ADS
Title: Physical conditions in granulation.
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1976ApJ...203..533A
Altcode:
High-resolution spectroheliograms made in the Ti I and Fe I 5016-A lines
with the diode array of a tower telescope are analyzed. Temperature
perturbations (delta T) were introduced into the Harvard-Smithsonian
Reference Atmosphere and varied empirically until the calculated line
profiles matched the observed profiles. It is found that the absolute
value of delta T increases going downward in the low photosphere. In the
middle photosphere, the absolute value does not exceed 70 K. It is also
found that the large buoyant forces implied by the solutions for delta T
are inconsistent with the small observed accelerations in the granular
flow. It is concluded that this incompatibility provides additional
evidence besides line broadening for the existence of microturbulence in
the low photosphere. The convective flux at an optical thickness of 3
(5000 A) is small compared with the total flux. Also, the temperature
fluctuations are much larger than those that would be produced by
the observed convective velocities alone. Thus, the observable low
photosphere appears to be near radiative equilibrium.
Title: Physical condition in granulation
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1976pmas.conf..285A
Altcode:
No abstract at ADS
Title: Coronal Density Distributions from FeXIV λ5303 Data
Authors: Fisher, R.; Musman, S.; Seagraves, P.
Bibcode: 1975BAAS....7..355F
Altcode:
No abstract at ADS
Title: Observations of Velocity and Intensity Fluctuations in Solar
Granulation
Authors: Musman, S.
Bibcode: 1975BAAS....7R.362M
Altcode:
No abstract at ADS
Title: Physical Conditions in Granulation
Authors: Altrock, R. C.; Musman, S.
Bibcode: 1975BAAS....7..362A
Altcode:
No abstract at ADS
Title: Detection of coronal holes from lambda 5303 Fe XIV
observations.
Authors: Fisher, R.; Musman, S.
Bibcode: 1975ApJ...195..801F
Altcode:
Photoelectric measurements of intensity are used to estimate the
distribution of volume emissivity in the coronal green line over the
solar surface. Using this distribution and a calculated dependence
of emissivity as a function of temperature and electron density, it
is possible to estimate a coronal density distribution. An example
is given which shows a region of drastically reduced emissivity -
a coronal hole - which was simultaneously detected by spacecraft.
Title: The Origin of the Solar Five-Minute Oscillation
Authors: Musman, Steven
Bibcode: 1974SoPh...36..313M
Altcode:
Two absorption lines formed in the lower photosphere were used to
study simultaneous velocity and intensity fluctuations. No significant
correspondence was found between the locations of granules and those of
oscillation, even when a time lag was included. This result supports
the explanation of the origin of the oscillations as a self-excited
sound wave rather than the local response to a granule excitation.
Title: The Generation of the Solar Five-Minute Oscillation
Authors: Musman, Steven
Bibcode: 1974BAAS....6S.292M
Altcode:
No abstract at ADS
Title: The Location of Exploding Granules
Authors: Allen, Marc S.; Musman, Steven
Bibcode: 1973SoPh...32..311A
Altcode:
No abstract at ADS
Title: Vertical Phase Variation and Mechanical Flux in the Solar
5-MINUTE Oscillation
Authors: Canfield, Richard C.; Musman, Steven
Bibcode: 1973ApJ...184L.131C
Altcode:
We have made observations of the solar five-minute oscillation that
allow measurement of the difference of phase between absorption
lines formed over a range of almost 1000 km in the photosphere
and chromosphere. We derive phase velocities, group velocities,
and mechanical fluxes. The amount of mechanical flux lost by the
five-minute oscillation matches the estimated chromospheric radiative
loss in quantity but has a different height distribution. This
difference implies that a change in the mode of energy propagation
may take place below 500 km. Subject headings:chromosphere, solar -
solar atmospheric motions
Title: Observation and Interpretation of Phase Lags in the Five-Minute
Oscillation
Authors: Canfield, Richard C.; Musman, Steven
Bibcode: 1973BAAS....5..269C
Altcode:
No abstract at ADS
Title: The Dynamics of Solar Granulation.
Authors: Musman, S.
Bibcode: 1973BAAS....5....2M
Altcode:
No abstract at ADS
Title: A Mechanism for the Exploding Granule Phenomenon
Authors: Musman, Steven
Bibcode: 1972SoPh...26..290M
Altcode:
I suggest that the exploding granule phenomenon is a consequence
of the observed internal granular motions and the conservation of
angular momentum. When a granule rising from the convection zone
penetrates into the overlying stable region it is stretched out
horizontally. Conservation of angular momentum in the internal motions
changes its form into a vortex ring. A time sequence of photographs
showing an exploding solar granule is described. The proposed mechanism
is illustrated by a laboratory simulation and a numerical calculation.
Title: A Mechanism for Exploding Solar Granules
Authors: Musman, Steven
Bibcode: 1972BAAS....4S.388M
Altcode:
No abstract at ADS
Title: Interference in Solar Oscillations
Authors: Reif, R. J.; Musman, Steven
Bibcode: 1971SoPh...20..257R
Altcode:
We have analyzed magnetograph observations of the 5-min oscillations. We
find that most of the oscillatory power is concentrated in space and
frequency. Interference effects where these concentrations overlap
can explain some of the variations in amplitude of the oscillation.
Title: Bright-Dark Asymmetry in Solar Granulation
Authors: Parvey, Michael I.; Musman, Steven
Bibcode: 1971SoPh...18..385P
Altcode:
Although a positive print of solar granulation gives the impression of
bright irregular areas on a dark background, this impression is highly
subjective and depends upon the nature of the photographic process. We
developed an objective method for comparing bright and dark features
and applied it to 40 000 elements from a granulation photograph. Each
element had dimensions of 150 km by 150 km. We found that dark features
were fewer in number, larger, and had larger perimeter-to-area ratios
than the bright features. The statistical confidence level of our
results exceeded 99%. Our results are consistent with the subjective
impression that granulation is composed of bright features separated
by dark lanes.
Title: Interference of solar oscillations.
Authors: Reif, R. J.; Musman, S.
Bibcode: 1971BAAS....3..264R
Altcode:
No abstract at ADS
Title: Bright-dark asymmetry in solar granulation
Authors: Parvey, Michael I.; Musman, Steven Abel
Bibcode: 1971PGLO..120..386P
Altcode:
No abstract at ADS
Title: Observations and Interpretion of Supergranule Velocity and
Magnetic Fields
Authors: Musman, S.
Bibcode: 1971IAUS...43..289M
Altcode:
No abstract at ADS
Title: Bright-Dark Asymmetry in Solar Granulation
Authors: Parvey, Michael I.; Musman, Steven
Bibcode: 1970BAAS....2Q.335P
Altcode:
No abstract at ADS
Title: Vertical Velocities and Horizontal Wave Propagation in the
Solar Photosphere
Authors: Musman, Steven; Rust, David M.
Bibcode: 1970SoPh...13..261M
Altcode:
We used the Sacramento Peak Doppler-Zeeman Analyzer to study the
velocity and magnetic fields in 60″ × 300″ areas on the solar
disk. We map the steady component of the line-of-sight velocity
and longitudinal magnetic fields and compare them with the coarse
Ca+ network. The collective phase behavior of the 5-min
oscillations is studied in detail. We find large scale phase coherence,
including waves with typical horizontal phase velocities of 100 km/sec
which can be followed up to 50 000 km. The important oscillatory
features are interpreted in terms of the properties of modified
sound waves. We find no apparent relationship between the steady and
oscillatory fields.
Title: Mechanical Heating of the Chromosphere and Corona
Authors: Musman, S.
Bibcode: 1969cctr.conf..181M
Altcode:
No abstract at ADS
Title: Two-Dimensional Observations of Solar Oscilating Regions
Authors: Musman, Steven A.; Rust, David M.
Bibcode: 1969BAAS....1S.287M
Altcode:
No abstract at ADS
Title: The Effect of Finite Resolution on Solar Granulation
Authors: Musman, Steven
Bibcode: 1969SoPh....7..178M
Altcode:
Some numerical experiments were performed in order to simulate the
effect of finite resolution on solar granulation. When a two-dimensional
pattern is smeared, another pattern emerges whose nature depends on the
width of the smearing function rather than the original pattern. The
size of the structures present in a typical granulation photograph
is about that which would be expected from the smearing of smaller
structures by the effect of atmospheric `seeing'. Only Stratoscope
photographs appear to have unambiguously determined the nature of
solar granulation.
Title: Solar Convection.
Authors: Musman, Steven
Bibcode: 1968AJS....73...73M
Altcode:
A stringent test of a theory of solar convection is that it must
predict correctly observable convective velocities and temperature
differences at the solar surface. Several convective theories, which
can well describe the structure and heat flux in a convective region
will not do this. Thus, for example, a mixing length model for the
solar convective zone will predict that the temperature gradient
is very near the adiabatic one and that nearly all the heat flux is
carried by convection. However, the velocities predicted near the top
of the zone have little relation to observed velocities. A convective
theory is described which does not employ a mixing length or any other
arbitrary parameter, and can predict physically reasonable velocities
and temperature differences. Preliminary results compare favorably
with laboratory convective experiments. This research was supported by
the Air Force High Altitude Solar Observatory Project under Contract
F19628-67-C-0231.
Title: Effect of Finite Resolution on Solar Granulation.
Authors: Musman, Steven
Bibcode: 1968AJS....73S.194M
Altcode:
Some numerical experiments were performed in order to simulate the
effect of finite resolution on solar granulation. When a two-dimensional
pattern is smeared, another pattern emerges, whose nature depends on
the width of the smearing function. The patterns formed by smearing
fields of random numbers resemble solar granulation, and are about
the size to be expected from atmospheric "seeing."
Title: ALFVÉN Waves in Sunspots
Authors: Musman, Steven
Bibcode: 1967ApJ...149..201M
Altcode:
Some form of non-radiative energy transport appears to be required
in sunspots, and the possibility of Alfve'n waves is examined here. A
simple sunspot model is constructed in which Alfve'n waves generated
in a convectively unstable layer are permitted to propagate upward
into an overlying stable layer. In the model investigated, only a very
narrow range of physical conditions permits the growth of the waves,
and it is concluded that waves of this sort are not likely to contribute
significantly to energy transport in sunspots.
Title: The Stability of Sunspots to the Emission of Alfv n Waves.
Authors: Musman, Steven
Bibcode: 1965AJ.....70R.145M
Altcode:
Several authors (Schliiter and Temesvary, 1958, IA U Symp. No. 6;
Chitre, Monthly Notices Roy. Astron. Soc. 126, 431, 1963) found that
they could not construct models of sunspots using only radiative
transport of energy. One possible mode of nonradiative transport, that
of Alfve'n waves, is examined here. Danielsen (Astrophys. J. 134, 289,
1961) investigated the stability of a layer of sunspot material in a
vertical magnetic field. He found that for a range of five orders of
magnitude in a dimensionless number describing the physical state of
the layer small perturbations could grow in the form of increasing
oscillations. These oscillations can be interpreted as a standing
Alfve'n wave in the layer. However, the boundary conditions used
did not permit the propagation of the wave outside the layer. When
the problem is re-examined by permitting the wave to propagate
upward into a stable layer the properties of the unstable layer are
drastically altered. In this case there is only a narrow range of 20%
in the dimensionless number which allows the growth of the oscillations;
hence it is concluded that it is not likely that Alfv~n waves contribute
substantially to energy transport in sunspots.
Title: An upper limit to a rayleigh scattering atmosphere on mars
Authors: Musman, Steven
Bibcode: 1964P&SS...12..799M
Altcode:
No abstract at ADS
Title: The stability of sunspots to the emission of Alfvén waves
Authors: Musman, Steven Abel
Bibcode: 1964PhDT.........9M
Altcode:
No abstract at ADS