explanation blue bibcodes open ADS page with paths to full text
Author name code: musielak
ADS astronomy entries on 2022-09-14
author:"Musielak, Zdzislaw E."
---------------------------------------------------------
Title: Determining Hill Stability of Triple Stellar Systems with
Confirmed Exoplanets
Authors: Boyle, Lindsey; Rosario-Franco, Marialis; Musielak, Zdzislaw
2021DPS....5321211B Altcode:
The universe contains a multitude of stellar systems with configurations
that range from single star systems up to sextuplet star systems. A
percentage of these multi-star systems contain exoplanets. Out of a
total of 35 multi-stellar systems with exoplanets, 33 are triple-star
systems. This work aims to provide insight into the dynamics of
such systems by determining the topological boundary that forbids
close encounters for an infinite time, otherwise known as Hill
stability. Motivated by this, we apply the criterion established in
Walker (1983) to determine the Hill stability of the triple stellar
components by calculating the stability coefficient and comparing it
with the semi-major axis coefficient of the system. Additionally, we
extend it to corroborate the Hill stability of the planets within. We
found 17 triple stellar systems out of the 18 in our sample to be Hill
stable. Within these 17 systems, 29 planets are shown to be Hill stable
as well. <P />Cross-listed as presentation #403.02.
---------------------------------------------------------
Title: Spatial variation in the periods of ion and neutral waves in
a solar magnetic arcade
Authors: Kuźma, B.; Murawski, K.; Musielak, Z. E.; Poedts, S.;
Wójcik, D.
2021A&A...652A..88K Altcode: 2021arXiv210509882K
Context. We present new insight into the propagation of ion
magnetoacoustic and neutral acoustic waves in a magnetic arcade in the
lower solar atmosphere. <BR /> Aims: By means of numerical simulations,
we (a) study two-fluid waves propagating in a magnetic arcade embedded
in the partially ionised, lower solar atmosphere and (b) investigate the
effect of the background magnetic field configuration on the observed
wave-periods. <BR /> Methods: We considered a 2D approximation of the
gravitationally stratified and partially ionised lower solar atmosphere
consisting of ion plus electron and neutral fluids that are coupled
by ion-neutral collisions. In this model, the convection below the
photosphere causes the excitation of ion magnetoacoustic-gravity and
neutral acoustic-gravity waves. <BR /> Results: We find that in the
solar photosphere, where ions and neutrals are strongly coupled by
collisions, ion magnetoacoustic-gravity and neutral acoustic-gravity
waves have periods ranging from 250 s to 350 s. In the chromosphere,
where the collisional coupling is weak, the wave characteristics
strongly depend on the magnetic field configuration. Above the
footpoints of the considered arcade, the plasma is dominated by a
vertical magnetic field along which ion magnetoacoustic-gravity waves
propagate. These waves exhibit a broad range of periods, and the most
prominent periods are 180 s, 220 s, and 300 s. Above the main loop of
the solar arcade, where mostly horizontal magnetic field lines guide
ion magnetoacoustic-gravity waves, the main spectral power reduces to
the period of about 180 s, and no longer wave-periods exist. <BR />
Conclusions: In photospheric regions, ongoing solar granulation excites
a broad spectrum of wave-periods that undergoes complex interactions:
mode-coupling, refractions through the inhomogeneous atmosphere, real
physical absorption, and conversion of wave power. We found that, in
addition, the magnetic arcade configuration with a partially ionised
plasma drastically changes the image of wave-periods observed in the
upper layers of the chromosphere and corona. Our results agree with
recent observational data.
---------------------------------------------------------
Title: New equation of nonrelativistic physics and theory of dark
matter
Authors: Musielak, Z. E.
2021IJMPA..3650042M Altcode: 2021arXiv210414345M
Two infinite sets of Galilean invariant equations are derived using
the irreducible representations of the orthochronous extended Galilean
group. It is shown that one set contains the Schrödinger equation,
which is the fundamental equation for ordinary matter, and the
other set has a new asymmetric equation, which is proposed to be the
fundamental equation for dark matter. Using this new equation, a theory
of dark matter is developed and its profound physical implications are
discussed. This theory explains the currently known properties of dark
matter and also predicts a detectable gravitational radiation.
---------------------------------------------------------
Title: New cutoff frequency for torsional Alfvén waves propagating
along wide solar magnetic flux tubes
Authors: Routh, Swati; Musielak, Z. E.; Sundar, M. N.; Joshi, Sai
Sravanthi; Charan, Sree
2020Ap&SS.365..139R Altcode: 2020arXiv200803653R
An isolated, isothermal, and wide magnetic flux tube embedded either in
the solar chromosphere or in the lower solar corona is considered, and
the propagation of linear torsional Alfvén waves is investigated. It is
shown that the wideness of the tube leads to a new cutoff frequency,
which is a local quantity that gives the conditions for the wave
propagation at different atmospheric heights. The cutoff is used to
establish the ranges of frequencies for the propagating and reflected
waves in the solar chromosphere and lower solar corona. The obtained
results are compared to those previously obtained for thin magnetic
flux tubes and the differences are discussed. Moreover, the results
are also compared to some current observational data, and used to
establish the presence of propagating waves in the data at different
atmospheric heights; this has profound implications on the energy
and momentum transfer by the waves in the solar atmosphere, and the
role of linear torsional Alfvén waves in the atmospheric heating and
wind acceleration.
---------------------------------------------------------
Title: 3D Numerical Simulations of Solar Quiet Chromosphere Wave
Heating
Authors: Murawski, K.; Musielak, Z. E.; Wójcik, D.
2020ApJ...896L...1M Altcode:
Despite numerous observational and theoretical attempts, the heating
problem of the solar chromosphere still remains unsolved. We develop
a novel 3D two-fluid model that accounts for dynamics of charged
species and neutrals, and use it to perform the numerical simulations
of granulation driven jets and associated waves in a quiet region of
the solar chromosphere. The energy carried by the waves is dissipated
through ion-neutral collisions, which are sufficient to balance
radiative energy losses and to sustain the quasi-stationary atmosphere
whose ion and neutral number densities, ionization fraction, and
temperature profiles are relatively close to the observationally based
semi-empirical model. Additional verification of our results is provided
by a good fit of the numerically predicted waveperiod variations with
height to the recent observational data. These observational validations
of the numerical results demonstrate that the wave heating problem of
a quiet region of the chromosphere may be solved.
---------------------------------------------------------
Title: Orbital Stability of Exomoons and Submoons with Applications
to Kepler 1625b-I
Authors: Rosario-Franco, Marialis; Quarles, Billy; Musielak, Zdzislaw
E.; Cuntz, Manfred
2020AJ....159..260R Altcode: 2020arXiv200506521R
An intriguing question in the context of dynamics arises: could a
moon possess a moon itself? Such a configuration does not exist in
the solar system, although this may be possible in theory. Kollmeier
& Raymond determined the critical size of a satellite necessary
to host a long-lived subsatellite, or submoon. However, the orbital
constraints for these submoons to exist are still undetermined. Domingos
et al. indicated that moons are stable out to a fraction of the host
planet's Hill radius R<SUB>H,p</SUB>, which in turn depend on the
eccentricity of its host's orbit. Motivated by this, we simulate
systems of exomoons and submoons for 10<SUP>5</SUP> planetary
orbits, while considering many initial orbital phases to obtain
the critical semimajor axis in terms of R<SUB>H,p</SUB> or the
host satellite's Hill radius R<SUB>H,sat</SUB>, respectively. We
find that, assuming circular coplanar orbits, the stability limit
for an exomoon is 0.40 R<SUB>H,p</SUB> and for a submoon is 0.33
R<SUB>H,sat</SUB>. Additionally, we discuss the observational
feasibility of detecting these subsatellites through photometric,
radial velocity, or direct imaging observations using the Neptune-sized
exomoon candidate Kepler 1625b-I and identify how stability can shape
the identification of future candidates.
---------------------------------------------------------
Title: Wave heating of the solar atmosphere without shocks
Authors: Wójcik, D.; Kuźma, B.; Murawski, K.; Musielak, Z. E.
2020A&A...635A..28W Altcode:
Context. We investigate the wave heating problem of a solar quiet
region and present its plausible solution without involving shock
formation. <BR /> Aims: We aim to use numerical simulations to
study wave propagation and dissipation in the partially ionized solar
atmosphere, whose model includes both neutrals and ions. <BR /> Methods:
We used a 2.5D two-fluid model of the solar atmosphere to study the
wave generation and propagation. The source of these waves is the
solar convection located beneath the photosphere. <BR /> Results:
The energy carried by the waves is dissipated through ion-neutral
collisions, which replace shocks used in some previous studies as the
main source of local heating in quiet regions. <BR /> Conclusions:
We show that the resulting wave dissipation is sufficient to balance
radiative and thermal energy losses, and to sustain a quasi-stationary
atmosphere whose averaged temperature profile agrees well with the
observationally based semi-empirical model of Avrett & Loeser
(2008, ApJS, 175, 229).
---------------------------------------------------------
Title: Partially Ionized Solar Atmosphere: Two-fluid Waves and
Their Cutoffs
Authors: Wójcik, D.; Murawski, K.; Musielak, Z. E.
2019ApJ...882...32W Altcode:
A novel model of the solar atmosphere that accounts for partially
ionized plasma is developed and used to study the propagation
of magnetoacoustic-gravity waves, which are generated by solar
granulation. The model includes neutrals in otherwise ionized plasma
and therefore the considered waves are two-fluid waves. Numerical
simulations of these waves allow computing their cutoff period and its
variations in the solar atmosphere. The results of these computations
are compared to the observational data collected by Wiśniewska et
al. and Kayshap et al., and a good agreement between the theory and
observations is obtained. This first theoretical confirmation of the
observational data profoundly shows the importance of effects caused
by partially ionized plasma on the behavior of waves in the solar
atmosphere, and on the origin of solar chromospheric oscillations. It
is also suggested that theoretically predicted differences between
the behavior of ions and neutrals can be verified by some currently
operating solar missions.
---------------------------------------------------------
Title: Determining Stability Conditions for Submoons Orbiting Exomoon
Candidate: Kepler 1625-b-I
Authors: Rosario-Franco, Marialis; Quarles, Billy; Musielak, Zdzislaw
E.; Cuntz, Manfred
2019DDA....5030309R Altcode:
An intriguing question in the context of dynamics arises: Could a
moon possess a moon itself? Such a configuration does not exist in
the Solar System, although this may be possible in theory; Kollmeier
& Raymond (2019) showed the critical size of a satellite necessary
to host a long-lived sub-satellite, or submoon. However, the orbital
constraints for these submoons to exist are still undetermined, where a
critical parameter is how far from the host satellite can these submoons
orbit. Previous studies (Domingos et al. 2006) indicate that moons
should be stable out to a fraction of the host planet's Hill sphere,
which in turn will depend on the eccentricity and inclination of its
orbit. Motivated by this, we have performed orbital integrations of the
exomoon candidate Kepler 1625-b-I, a Neptune-sized exomoon candidate
that orbits the Jovian planet Kepler 1625-b (Teachey & Kipping
2018). In our numerical study, we evaluate the orbital parameters
where possible submoons could be stable by varying the eccentricity
and inclination of their orbits. Moreover, we provide discussion on
the observational consequences of observing these satellites through
photometric or radial velocity observations.
---------------------------------------------------------
Title: Cutoff periods of magnetoacoustic waves in the solar atmosphere
Authors: Kraśkiewicz, J.; Murawski, K.; Musielak, Z. E.
2019A&A...623A..62K Altcode:
We perform numerical simulations of magnetoacoustic waves (MAWs) in the
solar atmosphere, which is gravitationally stratified and structured by
either vertical or horizontal uniform magnetic fields. These waves are
excited by a monochromatic driver that operates in the photosphere. We
show that the gradients of the atmospheric parameters lead to filtering
of the waves through the solar atmosphere and to variations of the
dominant wave period with height. We use these variations to determine a
local cutoff period, which shows a good agreement with the previously
obtained analytical and numerical results in an isothermal solar
atmosphere. In our numerical simulations, the propagation of MAWs
in a more realistic model of the solar atmosphere is considered, and
the obtained results demonstrate that the waves with periods higher
than a local cutoff wave period are strongly reflected and become
evanescent with height, while the waves with shorter wave periods
are propagating, and may even reach the solar corona. Some of the
evanescent waves may also tunnel and reach the atmospheric heights that
would not be otherwise accessible to them. An important result of our
study is excitation of chromospheric oscillations with periods equal
to the period that is comparable to the observed solar chromospheric
oscillations. Implications of our theoretical predictions are discussed.
---------------------------------------------------------
Title: Acoustic waves in two-fluid solar atmosphere model: cut-off
periods, chromospheric cavity, and wave tunnelling
Authors: Wójcik, D.; Murawski, K.; Musielak, Z. E.
2018MNRAS.481..262W Altcode: 2018MNRAS.tmp.2189W
We perform numerical simulations of acoustic waves in a two-fluid
model of quiet region of the solar atmosphere. The two-fluid model
describes partially ionized (non-magnetized) solar plasma, whose main
components are neutral atoms, protons, and electrons. The waves are
excited by a monochromatic driver, which operates at the bottom of
the solar photosphere. Our numerical results show that the driver
excites ion and neutral acoustic waves whose propagation is affected
by the gravity. As a result, the acoustic waves with periods higher
than a local acoustic cut-off period are evanescent, while lower
waveperiods are free to reach the solar corona. Acoustic waves, which
are evanescent in the photosphere and low chromosphere, tunnel their
energy into the upper chromosphere and the transition region. The wave
propagation to the solar corona is affected by partial wave reflection
that occurs in the transition region, and is responsible for formation
of a cavity, where the waves are trapped. Fourier power analysis of
temporal characteristic of plasma quantities reveals that a spectrum
of various periods is generated. While oscillations traced in ion and
neutral velocities look very similar, dynamics of mass densities of
ions and neutrals differs a lot. The obtained results clearly show
that the two-fluid model provides new insights into the acoustic wave
propagation in a more realistic (partially ionized) quiet region of
the solar atmosphere.
---------------------------------------------------------
Title: Confined pseudo-shocks as an energy source for the active
solar corona
Authors: Srivastava, Abhishek Kumar; Murawski, Krzysztof; Kuźma,
BlaŻej; Wójcik, Dariusz Patryk; Zaqarashvili, Teimuraz V.;
Stangalini, Marco; Musielak, Zdzislaw E.; Doyle, John Gerard; Kayshap,
Pradeep; Dwivedi, Bhola N.
2018NatAs...2..951S Altcode: 2018NatAs.tmp..138S
The Sun's active corona requires an energy flux of 10<SUP>3</SUP>
W m<SUP>-2</SUP> to compensate for radiative losses and to maintain
its high temperature<SUP>1</SUP>. Plasma moves in the corona through
magnetic loops<SUP>2,3</SUP>, which may be connected with the flows
in and around sunspots<SUP>4-6</SUP>. Global energizing processes
(for example, reconnection) play an important part in heating the
corona<SUP>7-9</SUP>; however, energy and mass transport may also
occur via shocks, waves or flows<SUP>5,10,11</SUP>. A full picture
and the influence of such localized events, which significantly
couple with various layers of the solar upper atmosphere, is still not
clear. Using the Interface Region Imaging Spectrograph temporal image
data of C uc(ii) 1,330 Å, we observed the presence of pseudo-shocks
around a sunspot. Unlike shocks<SUP>12</SUP>, pseudo-shocks exhibit
discontinuities only in the mass density. A two-fluid numerical
simulation reproduces such confined pseudo-shocks with rarefied
plasma regions lagging behind them. We find that these pseudo-shocks
carry an energy of 10<SUP>3</SUP> W m<SUP>-2</SUP>, which is enough
to locally power the inner corona and also generate bulk flows (
10<SUP>-5</SUP> kg m<SUP>-2</SUP> s<SUP>-1</SUP>), contributing to the
localized mass transport. If they are ubiquitous, such energized and
bulky pseudo-shocks above active regions could provide an important
contribution to the heating and mass transport in the overlying
solar corona.
---------------------------------------------------------
Title: Vertical propagation of acoustic waves in the solar
internetworkas observed by IRIS
Authors: Kayshap, P.; Murawski, K.; Srivastava, A. K.; Musielak,
Z. E.; Dwivedi, B. N.
2018MNRAS.479.5512K Altcode: 2018arXiv180701449K; 2018MNRAS.tmp.1776K
We investigate the Interface Region Imaging Spectrograph (IRIS)
observations of the quiet-Sun (QS) to understand the propagation
of acoustic waves in transition region (TR) from photosphere. We
selected a few IRIS spectral lines, which include the photospheric
(Mn I 2801.25 Å), chromospheric (Mg II k 2796.35 Å), and TR (C
II 1334.53 Å), to investigate the acoustic wave propagation. The
wavelet cross-spectrum reveals significant coherence (about 70 per
cent locations) between photosphere and chromosphere. Few minutes
oscillations (i.e. period range from 1.6 to 4.0 min) successfully
propagate into chromosphere from photosphere, which is confirmed by
dominance of positive phase lags. However, in higher period regime
(i.e. greater than ≈4.5 min), the downward propagation dominates
is evident by negative phase lags. The broad spectrum of waves
(i.e. 2.5-6.0 min) propagates freely upwards from chromosphere to
TR. We find that only about 45 per cent locations (out of 70 per cent)
show correlation between chromosphere and TR. Our results indicate that
roots of 3 min oscillations observed within chromosphere/TR are located
in photosphere. Observations also demonstrate that 5 min oscillations
propagate downward from chromosphere. However, some locations within QS
also show successful propagation of 5 min oscillations as revealed by
positive phase lags, which might be the result of magnetic field. In
addition, our results clearly show that a significant power, within
period ranging from 2.5 to 6.0 min, of solar chromosphere is freely
transmitted into TR triggering atmospheric oscillations. Theoretical
implications of our observational results are discussed.
---------------------------------------------------------
Title: Dynamics of a Probable Earth-mass Planet in the GJ 832 System
Authors: Satyal, S.; Griffith, J.; Musielak, Z. E.
2017ApJ...845..106S Altcode: 2016arXiv160404544S
The stability of planetary orbits around the GJ 832 star system, which
contains inner (GJ 832c) and outer (GJ 832b) planets, is investigated
numerically and a detailed phase-space analysis is performed. Special
attention is given to the existence of stable orbits for a planet
less than 15 M <SUB>⊕</SUB> that is injected between the inner and
outer planets. Thus, numerical simulations are performed for three
and four bodies in elliptical orbits (or circular for special cases)
by using a large number of initial conditions that cover the selected
phase-spaces of the planet’s orbital parameters. The results presented
in the phase-space maps for GJ 832c indicate the least deviation of
eccentricity from its nominal value, which is then used to determine its
inclination regime relative to the star-outer planet plane. Also, the
injected planet is found to display stable orbital configurations for
at least one billion years. Then, the radial velocity curves based on
the signature from the Keplerian motion are generated for the injected
planets with masses 1 M <SUB>⊕</SUB> to 15 M <SUB>⊕</SUB> in order
to estimate their semimajor axes and mass limits. The synthetic RV
signal suggests that an additional planet of mass ≤15 M <SUB>⊕</SUB>
with a dynamically stable configuration may be residing between 0.25
and 2.0 au from the star. We have provided an estimated number of RV
observations for the additional planet that is required for further
observational verification.
---------------------------------------------------------
Title: Numerical Simulations of Torsional Alfvén Waves in
Axisymmetric Solar Magnetic Flux Tubes
Authors: Wójcik, D.; Murawski, K.; Musielak, Z. E.; Konkol, P.;
Mignone, A.
2017SoPh..292...31W Altcode: 2017arXiv170104594W
We numerically investigate Alfvén waves propagating along an
axisymmetric and non-isothermal solar flux tube embedded in the solar
atmosphere. The tube magnetic field is current-free and diverges
with height, and the waves are excited by a periodic driver along
the tube magnetic field lines. The main results are that the two
wave variables, the velocity and magnetic field perturbations in the
azimuthal direction, behave differently as a result of gradients of
the physical parameters along the tube. To explain these differences
in the wave behavior, the time evolution of the wave variables and
the resulting cutoff period for each wave variable are calculated and
used to determine regions in the solar chromosphere where strong wave
reflection may occur.
---------------------------------------------------------
Title: Why Theory Fails to Reproduce the Observed Variation of
Acoustic Cutoff in the Solar Atmosphere?
Authors: Musielak, Zdzislaw E.; Murawski, Krzysztof
2017AAS...22932501M Altcode:
Recent observational results by Wisniewska et al. (2016) suggest
that the acoustic cutoff frequency varies with height within the
solar atmosphere, and that the existing theoretical formulas for the
cutoff cannot account for the observed variations. Specifically, five
formulas for acoustic cutoffs commonly used in helioseismology and
asteroseismology failed to reproduce the observations. We present
results of both numerical and analytical studies, and discuss
improvements that may be applied to the theory in order to fully
reproduce the observational results. In addition, we use observational
and theoretical results to seismically probe the physical parameters
of the background solar atmosphere.
---------------------------------------------------------
Title: Improving Habitability of Earth-sized Proxima Centauri b by
an Exomoon
Authors: Garza, Sergio; Rosario Franco, Marialis; Davachi, Niyousha;
Musielak, Zdzislaw E.
2017AAS...22912005G Altcode:
In an unprecedented discovery, an Earth-sized exoplanet was discovered
on a stable, low-eccentricity orbit located in the habitable zone of
our nearest neighbor, Proxima Centauri. While the exoplanet, called
Proxima Centauri b, is located within the region that may support
liquid water on its surface, its habitability has been questioned
because of dangerous flares generated by the M dwarf host star and
also because of possible tidal locking. The main goal of this work
is to understand the constraints under which an exomoon can maintain
stable orbits around the exoplanet and how its presence can improve
the habitability of the exoplanet. We utilize an N-body integrator,
REBOUND, which is a software package that can integrate the motion of
particles under the influence of gravity, to perform exomoon’s orbital
evolution studies. We present the results of numerical simulations
of exomoons of different sizes, determine locations of their stable
orbits around Proxima Centauri b, and discuss the effects caused by
their presence on the exoplanet’s habitability.
---------------------------------------------------------
Title: Effects of exomoon’s magnetic field on generation of radio
emissions
Authors: Griffith, John; Noyola, Joaquin; Satyal, Suman; Musielak,
Zdzislaw E.
2017AAS...22924528G Altcode:
In the recent work by Noyola et al. (2014, 2016), a novel technique
of detection of exomoons through the radio emissions produced by the
magnetic field interactions between exoplanet-exomoon pair is emulated
based upon the processes occurring in the Jupiter-Io system. Their
calculations have shown that the radio signal from the distant
extra-solar planetary systems is detectable by current technology
provided that the systems emanating the radio waves are relatively
closer, have some form of atmosphere, and have larger exomoons. In
this work, we explore the effect of exomoon’s magnetic field on
the radio emission processes by considering a hypothetical magnetic
exomoon and re-calculating the resulting radio flux. Then, a limit
to the exomoon’s magnetic field is proposed based on the signal
amplification versus the dampening effect the magnetic field induces
on the secondary conditions such as the containment of ions within the
exomoon’s magnetic field and the effect of the plasma torus density
that co-orbits with the moon. The energy from the exomoon’s magnetic
field is expected to amplify the radio signal, hence increasing the
probability of detection of the first exomoons.
---------------------------------------------------------
Title: Searching for the First Exomoon in the Radio: A Report on
GMRT Data
Authors: Rosario-Franco, Marialis; Noyola, Joaquin; Satyal, Suman;
Musielak, Zdzislaw E.; Kodilkar, Jitendra
2017AAS...22941502R Altcode:
The field of exoplanetary research has undergone a great deal of
development and growth. Achievements in theoretical studies and
detection techniques have allowed the discovery of over 3,500 exoplanets
in ~2,600 planetary systems to date. Despite this great success,
the detection of the first exomoon is yet to be achieved. Motivated by
this, we have applied a novel radio-detection method, proposed by Noyola
et.al (2014, 2016). The technique is based on a planet-moon interaction
observed in the Jupiter-Io system, and Io-controlled decametric radio
emissions were used to demonstrate how the presence of exomoons around
giant planets might be revealed by the same modulation mechanism. Three
targets, selected as the best candidates for radio detection, were
observed through the Giant Metrewave Radio Telescope (GMRT); located in
India. The results of our data analysis will be presented and discussed.
---------------------------------------------------------
Title: Stable Orbits for Exomoons in Earth’s Cousin (Kepler-452b)
Orbiting a Sun-like Star
Authors: Davachi, Niyousha; Rosario Franco, Marialis; Garza, Sergio;
Musielak, Zdzislaw E.
2017AAS...22912006D Altcode:
Kepler 452b, also nicknamed Earth’s cousin, was discovered orbiting
the habitable zone (HZ) of a G2 Star (Jenkins et al. 2015). This
exoplanet is considered a super Earth, with a mass of 5 ± 2 Mass of
Earth and a radius of 1.11 Radius of Earth; and is arguably the first
rocky, habitable exoplanet to orbit a sun-like star. With a period of
385 days, conditions are prompt to be similar to those of Earth, and
while Kepler-452b orbits the HZ of its parent star, its habitability
could also be affected by the presence of an exomoon. Motivated by the
need to understand conditions of habitability and orbital stability
of Kepler-45b, we have performed a series of N-body integrations to
examine the possibility of the exoplanet hosting an exomoon(s). Our
results give a range of physical parameters leading to stable orbits
for exomoons around this habitable super Earth.
---------------------------------------------------------
Title: Randomly driven acoustic-gravity waves in the solar atmosphere:
cutoff period and its observational verification
Authors: Murawski, K.; Musielak, Z. E.
2016MNRAS.463.4433M Altcode: 2016MNRAS.tmp.1416M
We study the propagation of acoustic-gravity waves in the solar
atmosphere. The waves are excited by a space- and time-dependent random
driver, whose action mimics turbulence in the upper part of the solar
convection zone. Our main goal is to find vertical variations of
wave periods of these waves and compare the obtained results to the
recent observations of Wiśniewska et al. We solve numerically the
hydrodynamic equations in the solar atmosphere whose temperature is
given by the semi-empirical model of Avrett & Loeser. The obtained
numerical results show that wave periods vary along vertical direction
in agreement with the recent observational data. We discuss physical
consequences of our theoretical results.
---------------------------------------------------------
Title: Variation of Acoustic Cutoff Period with Height in the Solar
Atmosphere: Theory versus Observations
Authors: Murawski, K.; Musielak, Z. E.; Konkol, P.; Wiśniewska, A.
2016ApJ...827...37M Altcode: 2016arXiv160802748M
Recently Wiśniewska et al. demonstrated observationally how the
acoustic cutoff frequency varies with height in the solar atmosphere
including the upper photosphere and the lower and middle chromosphere,
and showed that the observational results cannot be accounted for by
the existing theoretical formulas for the acoustic cutoff. In order
to reproduce the observed variation of the cutoff with atmospheric
height, numerical simulations of impulsively generated acoustic waves
in the solar atmosphere are performed, and the spectral analysis of
temporal wave profiles is used to compute numerically changes of the
acoustic cutoff with height. Comparison of the numerical results with
the observational data shows good agreement, which clearly indicates
that the obtained results may be used to determine the structure of
the background solar atmosphere.
---------------------------------------------------------
Title: Dark Energy and Dark Matter: Current Ideas and Their
Implications
Authors: Musielak, Zdzislaw E.
2016pas..conf..207M Altcode:
Astronomical observations show that our Universe is dominated by Dark
Energy (DE) and Dark Matter (DM). Understanding the origin and nature
of DE and DM is one of the most challenging and pressing scientific
problems of modern science. Elucidating its solution requires new ideas
and new approaches. In this paper, standard and non-standard theories
to explain DE and DM are reviewed with a special emphasis on recent
theoretical developments and their far reaching physical consequences.
---------------------------------------------------------
Title: On the Radio Detection of Multiple-exomoon Systems due to
Plasma Torus Sharing
Authors: Noyola, J. P.; Satyal, S.; Musielak, Z. E.
2016ApJ...821...97N Altcode: 2016arXiv160301862N
The idea of single exomoon detection due to the radio emissions
caused by its interaction with the host exoplanet is extended to
multiple-exomoon systems. The characteristic radio emissions are made
possible in part by plasma from the exomoon’s own ionosphere. In this
work, it is demonstrated that neighboring exomoons and the exoplanetary
magnetosphere could also provide enough plasma to generate a detectable
signal. In particular, the plasma-torus-sharing phenomenon is found
to be particularly well suited to facilitate the radio detection of
plasma-deficient exomoons. The efficiency of this process is evaluated,
and the predicted power and frequency of the resulting radio signals
are presented.
---------------------------------------------------------
Title: Observational Evidence for Variations of the Acoustic Cutoff
Frequency with Height in the Solar Atmosphere
Authors: Wiśniewska, A.; Musielak, Z. E.; Staiger, J.; Roth, M.
2016ApJ...819L..23W Altcode:
Direct evidence for the existence of an acoustic cutoff frequency in
the solar atmosphere is given by observations performed by using the
HELioseismological Large Regions Interferometric DEvice operating on the
Vacuum Tower Telescope located on Tenerife. The observational results
demonstrate variations of the cutoff with atmospheric heights. The
observed variations of the cutoff are compared to theoretical
predictions made by using five acoustic cutoff frequencies that
have been commonly used in helioseismology and asteroseismology. The
comparison shows that none of the theoretical predictions is fully
consistent with the observational data. The implication of this finding
is far reaching as it urgently requires either major revisions of the
existing methods of finding acoustic cutoff frequencies or developing
new methods that would much better account for the physical picture
underlying the concept of cutoff frequencies in inhomogeneous media.
---------------------------------------------------------
Title: Stability of a planet in the HD 41004 binary system
Authors: Satyal, S.; Musielak, Z. E.
2016AN....337..300S Altcode:
The Hill stability criterion is applied to analyse the stability of a
planet in the binary star system of HD 41004 AB, with the primary and
secondary separated by 22 AU, and masses of 0.7 M_⊙ and 0.4 M_⊙,
respectively. The primary hosts one planet in an S-type orbit, and the
secondary hosts a brown dwarf (18.64 M_J) on a relatively close orbit,
0.0177 AU, thereby forming another binary pair within this binary
system. This star-brown dwarf pair (HD 41004 B+Bb) is considered a
single body during our numerical calculations, while the dynamics of
the planet around the primary, HD 41004 Ab, is studied in different
phase-spaces. HD 41004 Ab is a 2.6 M_J planet orbiting at the distance
of 1.7 AU with orbital eccentricity 0.39. For the purpose of this
study, the system is reduced to a three-body problem and is solved
numerically as the elliptic restricted three-body problem (ERTBP). The
{Hill stability} function is used as a chaos indicator to configure and
analyse the orbital stability of the planet, HD 41004 Ab. The indicator
has been effective in measuring the planet's orbital perturbation due
to the secondary star during its periastron passage. The calculated
Hill stability time series of the planet for the coplanar case shows the
stable and quasi-periodic orbits for at least ten million years. For the
reduced ERTBP the stability of the system is also studied for different
values of planet's orbital inclination with the binary plane. Also, by
recording the planet's {ejection time} from the system or {collision
time} with a star during the integration period, stability of the
system is analysed in a bigger phase-space of the planet's orbital
inclination, ≤ 90<SUP>o</SUP>, and its semimajor axis, 1.65-1.75
AU. Based on our analysis it is found that the system can maintain
a stable configuration for the planet's orbital inclination as high
as 65<SUP>o</SUP> relative to the binary plane. The results from the
Hill stability criterion and the planet's dynamical lifetime map are
found to be consistent with each other.
---------------------------------------------------------
Title: Theoretical prediction of chromospheric oscillations in
late-type stars
Authors: Fawzy, Diaa E.; Musielak, Z. E.
2016Ap&SS.361...23F Altcode:
Self-consistent, nonlinear and time-dependent numerical computations
of the excitation of chromospheric oscillations in a thin and
non-isothermal magnetic flux tube embedded in magnetic-free atmospheres
of late-type stars are performed. Longitudinal tube waves are considered
and the wave energy spectra and fluxes generated in convective zones of
these stars are calculated. The process of filtering the energy carried
by longitudinal tube waves is investigated and both the local heating
by shock waves as well as the excitation of chromospheric oscillations
are studied. Cutoff frequencies of the resulting oscillations are
computed numerically at different atmospheric heights in stars of
different effective temperatures and gravities, and compared to three
analytically derived cutoff frequencies. The obtained results show
that the oscillation frequency ranges from 4 mHz for F5V stars to 20
MHz for M0V stars. It is pointed out that this frequency range may be
relevant to the recent stellar p-mode observations made by the NASA
space mission Kepler.
---------------------------------------------------------
Title: Exomoon Capture in the Restricted 3-Body Problem and the Role
of Torque in Mechanical Energy Transfer
Authors: Polo Noyola, Joaquin; Rosario Franco, Marialis; Musielak,
Zdzislaw
2015IAUGA..2258136P Altcode:
The discovery of giant exoplanets in habitable zones has raised
the question of how common large habitable exomoons really are
in the universe. Several detection techniques for exomoons have
been developed; however their effectiveness depends largely on the
exomoon’s size. It is commonly believed that large exomoons are
primarily created through a capture processes whereby a terran exoplanet
becomes gravitationally bounded to a nearby Jovian. The efficiency of
this process is investigated within the framework of the restricted
3-body problem. Specifically, we explore how a small particle orbiting
a primary mass can be captured by a secondary mass through cumulative
perturbations over long periods of time, and concentrate on the
transfer of mechanical energy through a gravitational torque from the
secondary mass on the small particle about the barycenter. Conditions
under which the gravitational torque performs net positive work on the
particle are derived, and applied to several astronomical systems known
to have giant exoplanets and which have great potential for hosting
exomoons. The study is used to assess the existence of large exomoons
in these systems.
---------------------------------------------------------
Title: Dynamics of an Earth-Like Planet in GJ 832 System
Authors: Satyal, Suman; Griffith, John; Musielak, Zdzislaw
2015IAUGA..2243278S Altcode:
The dynamics of planetary orbits around GJ 832 is studied with an
emphasis on a potential Earth-like planet. We perform various phase
space analyses of GJ 832c (inner planet) and the long-term orbital
stability of an Earth-mass planet injected in between the inner and
outer (GJ 832b) planets. The stability of the system is defined in
terms of the planet’s lifetime during the orbital integration and
the phase space maps, displaying the maximum eccentricity, generated
in the evolution process. Furthermore, the net deviation in the
planet’s initial eccentricity is used to study perturbation in the
system. Numerical integrations comprising of three and four bodies
in an elliptical orbits (or circular for special cases) are carried
out for a large number of initial conditions that incorporates the
whole phase space of the existing bodies. Our results show that the
orbital elements of the inner planets seem unaffected by addition of
the Earth-like planet. Further analysis of the added planet displays
stable orbital configuration for the relative orbital inclination up
to 40 degrees and semi major axis ranging from 0.2 to 2.2 AU with an
exception of few de-stabilizing resonances between the inner and the
outer planets. Finally, resonance, including Kozai, among the planets
is studied for assertion of the system’s dynamics.
---------------------------------------------------------
Title: Fractal and multifractal analysis of the rise of oxygen in
Earth's early atmosphere
Authors: Kumar, Satish; Cuntz, Manfred; Musielak, Zdzislaw E.
2015CSF....77..296K Altcode: 2014arXiv1402.3243K
The rise of oxygen in Earth's atmosphere that occurred 2.4 to
2.2 billion years ago is known as the Earth's Great Oxidation,
and its impact on the development of life on Earth has been
profound. Thereafter, the increase in Earth's oxygen level persisted,
though at a more gradual pace. The proposed underlying mathematical
models for these processes are based on physical parameters whose
values are currently not well-established owing to uncertainties in
geological and biological data. In this paper, a previously developed
model of Earth's atmosphere is modified by adding different strengths
of noise to account for the parameters' uncertainties. The effects of
the noise on the time variations of oxygen, carbon and methane for
the early Earth are investigated by using fractal and multifractal
analysis. We show that the time variations following the Great Oxidation
cannot properly be described by a single fractal dimension because they
exhibit multifractal characteristics. The obtained results demonstrate
that the time series as obtained exhibit multifractality caused by
long-range time correlations.
---------------------------------------------------------
Title: Nonlinear Wave Coupling of Torsional Alfvén Waves in the
Solar Atmosphere
Authors: Musielak, Zdzislaw; Murawski, Krzysztof
2015IAUGA..2258447M Altcode:
There is strong observational evidence for the existence of torsional
Alfvén waves in the solar atmosphere. The waves propagate inside
solar magnetic flux tubes and transfer energy to thesolar chromosphere
and corona. We present analytical and numerical models that describe
theprocess of nonlinear wave coupling, and use them to determine the
efficiency of the process andits effect on dissipation of energy carried
by the waves. Our numerical models involve the wave propagation along
3D solar magnetic flux tubes, and they are used to identify regions
in the solar atmosphere where maximum amounts of the wave energy can
be dissipated. By comparing ourresults to the heating rates observed
in different parts of the solar atmosphere, are able to determinethe
role played by torsional Alfvén waves in the heating of the solar
chromospheres and corona
---------------------------------------------------------
Title: Multi-shell Magnetic Twisters as a New Mechanism for Coronal
Heating and Solar Wind Acceleration
Authors: Murawski, K.; Srivastava, A. K.; Musielak, Z. E.; Dwivedi,
B. N.
2015ApJ...808....5M Altcode:
We perform numerical simulations of impulsively generated Alfvén waves
in an isolated photospheric flux tube and explore the propagation
of these waves along such magnetic structure that extends from the
photosphere, where these waves are triggered, to the solar corona, and
we analyze resulting magnetic shells. Our model of the solar atmosphere
is constructed by adopting the temperature distribution based on the
semi-empirical model and specifying the curved magnetic field lines
that constitute the magnetic flux tube that is rooted in the solar
photosphere. The evolution of the solar atmosphere is described by 3D,
ideal MHD equations that are numerically solved by the FLASH code. Our
numerical simulations reveal, based on the physical properties of the
multi-shell magnetic twisters and the amount of energy and momentum
associated with them, that these multi-shell magnetic twisters may be
responsible for the observed heating of the lower solar corona and for
the formation of solar wind. Moreover, it is likely that the existence
of these twisters can be verified by high-resolution observations.
---------------------------------------------------------
Title: Theoretical evidence for cutoff frequencies for Alfvén waves
propagating in the solar atmosphere
Authors: Perera, H. K.; Musielak, Z. E.; Murawski, K.
2015MNRAS.450.3169P Altcode:
Propagation of linear Alfvén waves in the isothermal solar atmosphere
is investigated numerically and analytically. It is shown that the two
wave variables, the velocity and magnetic field perturbations, behave
differently and that there is a range of wave frequencies for which
the wave behaviour changes from propagating to non-propagating. The
so-called transition and turning points corresponding to this change
are determined analytically, and their locations in the atmosphere are
calculated and verified against the numerical results. The transition
and turning points are then used to introduce cutoff frequencies,
which are different for different wave variables. The main result of
the paper is that there is no one unique cutoff frequency for Alfvén
waves but instead a number of cutoff frequencies can be introduced
depending upon the method used to define them as well as on the choice
of the wave variable used to describe the waves. Relevance of the
obtained results to recent observations of Alfvén waves in the solar
atmosphere is also briefly discussed.
---------------------------------------------------------
Title: Torsional Alfvén waves in solar magnetic flux tubes of
axial symmetry
Authors: Murawski, K.; Solov'ev, A.; Musielak, Z. E.; Srivastava,
A. K.; Kraśkiewicz, J.
2015A&A...577A.126M Altcode: 2015arXiv150100252M
<BR /> Aims: Propagation and energy transfer of torsional Alfvén waves
in solar magnetic flux tubes of axial symmetry is studied. <BR />
Methods: An analytical model of a solar magnetic flux tube of axial
symmetry is developed by specifying a magnetic flux and deriving
general analytical formulas for the equilibrium mass density and gas
pressure. The main advantage of this model is that it can be easily
adopted to any axisymmetric magnetic structure. The model is used to
numerically simulate the propagation of nonlinear Alfvén waves in such
2D flux tubes of axial symmetry embedded in the solar atmosphere. The
waves are excited by a localized pulse in the azimuthal component of
velocity and launched at the top of the solar photosphere, and they
propagate through the solar chromosphere, the transition region, and
into the solar corona. <BR /> Results: The results of our numerical
simulations reveal a complex scenario of twisted magnetic field lines
and flows associated with torsional Alfvén waves, as well as energy
transfer to the magnetoacoustic waves that are triggered by the Alfvén
waves and are akin to the vertical jet flows. Alfvén waves experience
about 5% amplitude reflection at the transition region. Magnetic
(velocity) field perturbations that experience attenuation (growth)
with height agree with analytical findings. The kinetic energy of
magnetoacoustic waves consists of 25% of the total energy of Alfvén
waves. The energy transfer may lead to localized mass transport in
the form of vertical jets, as well as to localized heating because
slow magnetoacoustic waves are prone to dissipation in the inner corona.
---------------------------------------------------------
Title: Numerical simulations of multi-shell plasma twisters in the
solar atmosphere
Authors: Murawski, K.; Srivastava, A. K.; Musielak, Z. E.; Dwivedi,
B. N.
2015arXiv150503793M Altcode:
We perform numerical simulations of impulsively generated Alfvén waves
in an isolated photospheric flux tube, and explore the propagation
of these waves along such magnetic structure that extends from the
photosphere, where these waves are triggered, to the solar corona, and
analyze resulting magnetic shells. Our model of the solar atmosphere
is constructed by adopting the temperature distribution based on the
semi-empirical model and specifying the curved magnetic field lines
that constitute the magnetic flux tube which is rooted in the solar
photosphere. The evolution of the solar atmosphere is described by 3D,
ideal magnetohydrodynamic equations that are numerically solved by the
FLASH code. Our numerical simulations reveal, based on the physical
properties of the multi-shell magnetic twisters and the amount of
energy and momentum associated with them, that these multi-shell
magnetic twisters may be responsible for the observed heating of the
lower solar corona and for the formation of solar wind. Moreover,
it is likely that the existence of these twisters can be verified by
high-resolution observations.
---------------------------------------------------------
Title: Astronomical constraints on quantum theories of cold dark
matter - II. Supermassive black holes and luminous matter
Authors: Spivey, S. C.; Musielak, Z. E.; Fry, J. L.
2015MNRAS.448.1574S Altcode:
Our previous model of quantum cold dark matter (QCDM) is expanded
to include the influence of supermassive black holes located at
centres of different galaxies and galactic luminous (baryonic) matter
distributions. The inclusion of a black hole to the galactic potential
is shown to produce a more concentrated halo with a cuspier core. The
addition of a small-scale galactic luminous matter distribution also
concentrates the halo, while a large-scale distribution diffuses
it; nevertheless, in either case the smooth core of the halo is
preserved. Effects caused by including a non-linear scattering term are
investigated by solving the Gross-Pitaevskii equation. The obtained
results demonstrate that the scattering term produces a rounder and
more diffuse density profile. Moreover, adding a sufficiently large
black hole in combination with this term results in an even cuspier
profile than the black hole alone. As a result of all these additions,
our extended QCDM model can be applied to a much larger range of dark
matter halo shapes and sizes.
---------------------------------------------------------
Title: Is the Alfvén wave propagation in the solar atmosphere
affected by cutoff frequencies or not?
Authors: Musielak, Zdzislaw E.; Perera, Harsha K.; Murawski, Krzysztof
2015AAS...22511501M Altcode:
The question posed in the title does not have a unique answer. Some
researchers argue that the Alfvén wave propagation in the solar
atmosphere is cutoff-free, while others claim that it is exactly the
opposite! To resolve this longstanding puzzle, we solved numerically
the initial-value problem for the Alfvén wave propagation and
identified a range of wave frequencies for which the wave's behavior
changes from propagating to non-propagating at certain heights in
the solar atmosphere. We determined the locations of these heights
in the atmosphere and identified them with the so-called transition
and turning points, which we use to introduce cutoff frequencies for
Alfvén waves. We find that there is not one unique cutoff frequency
for Alfvén waves but instead the cutoffs depend on the method used to
define them as well as on the choice of the wave variable selected to
describe the waves. Our results provide strong theoretical evidence
for the existence of the cutoff frequencies for the Alfvén wave
propagation in the solar atmosphere. We discuss the relevance of our
results to the current observational data.
---------------------------------------------------------
Title: Propagation of acoustic waves in the non-isothermal solar
atmosphere
Authors: Routh, S.; Musielak, Z. E.
2014AN....335.1043R Altcode:
The acoustic cutoff frequency was originally introduced by Lamb in the
study of the propagation of acoustic waves in a stratified, isothermal
medium. In this paper, we use a new method to generalize Lamb's result
for a stratified, non-isothermal medium and obtain the local acoustic
cutoff frequency, which describes the propagation of acoustic waves in
such a medium. The main result is that the cutoff frequency is a local
quantity and that its value at a given atmospheric height determines
the frequency acoustic waves must have in order to propagate at this
height. Application of this result to specific physical problems like
the solar atmosphere is discussed.
---------------------------------------------------------
Title: Numerical Simulations of Impulsively Generated Alfvén Waves
in Solar Magnetic Arcades
Authors: Chmielewski, P.; Murawski, K.; Musielak, Z. E.; Srivastava,
A. K.
2014ApJ...793...43C Altcode: 2014arXiv1408.0855C
We perform numerical simulations of impulsively generated Alfvén
waves in an isolated solar arcade, which is gravitationally stratified
and magnetically confined. We study numerically the propagation of
Alfvén waves along the magnetic structure that extends from the lower
chromosphere, where the waves are generated, to the solar corona,
and analyze the influence of the arcade size and the width of the
initial pulses on the wave propagation and reflection. Our model
of the solar atmosphere is constructed by adopting the temperature
distribution based on the semi-empirical VAL-C model and specifying
the curved magnetic field lines that constitute the asymmetric magnetic
arcade. The propagation and reflection of Alfvén waves in this arcade
is described by 2.5-dimensional magnetohydrodynamic equations that are
numerically solved by the FLASH code. Our numerical simulations reveal
that the Alfvén wave amplitude decreases as a result of a partial
reflection of Alfvén waves in the solar transition region, and that
the waves that are not reflected leak through the transition region and
reach the solar corona. We also find the decrement of the attenuation
time of Alfvén waves for wider initial pulses. Moreover, our results
show that the propagation of Alfvén waves in the arcade is affected
by the spatial dependence of the Alfvén speed, which leads to phase
mixing that is stronger for more curved and larger magnetic arcades. We
discuss the processes that affect the Alfvén wave propagation in an
asymmetric solar arcade and conclude that besides phase mixing in the
magnetic field configuration, the plasma properties of the arcade, the
size of the initial pulse, and the structure of the solar transition
region all play a vital role in the Alfvén wave propagation.
---------------------------------------------------------
Title: Detection of Exomoons through Observation of Radio Emissions
Authors: Noyola, J. P.; Satyal, S.; Musielak, Z. E.
2014ApJ...791...25N Altcode: 2013arXiv1308.4184N
In the Jupiter-Io system, the moon's motion produces currents along
the field lines that connect it to Jupiter's polar regions. The
currents generate and modulate radio emissions along their paths via
the electron-cyclotron maser instability. Based on this process, we
suggest that such modulation of planetary radio emissions may reveal the
presence of exomoons around giant planets in exoplanetary systems. A
model explaining the modulation mechanism in the Jupiter-Io system is
extrapolated and used to define criteria for exomoon detectability. A
cautiously optimistic scenario of the possible detection of such
exomoons around Epsilon Eridani b and Gliese 876 b is provided.
---------------------------------------------------------
Title: Fast Magnetic Twister and Plasma Perturbations in a
Three-dimensional Coronal Arcade
Authors: Murawski, K.; Srivastava, A. K.; Musielak, Z. E.
2014ApJ...788....8M Altcode: 2014arXiv1404.4176M
We present results of three-dimensional (3D) numerical simulations of
a fast magnetic twister excited above a foot-point of the potential
solar coronal arcade that is embedded in the solar atmosphere with the
initial VAL-IIIC temperature profile, which is smoothly extended into
the solar corona. With the use of the FLASH code, we solve 3D ideal
magnetohydrodynamic equations by specifying a twist in the azimuthal
component of magnetic field in the solar chromosphere. The imposed
perturbation generates torsional Alfvén waves as well as plasma swirls
that reach the other foot-point of the arcade and partially reflect
back from the transition region. The two vortex channels are evident
in the generated twisted flux-tube with a fragmentation near its apex
which results from the initial twist as well as from the morphology of
the tube. The numerical results are compared to observational data of
plasma motions in a solar prominence. The comparison shows that the
numerical results and the data qualitatively agree even though the
observed plasma motions occur over comparatively large spatio-temporal
scales in the prominence.
---------------------------------------------------------
Title: The three-body problem
Authors: Musielak, Z. E.; Quarles, B.
2014RPPh...77f5901M Altcode: 2015arXiv150802312M
The three-body problem, which describes three masses interacting through
Newtonian gravity without any restrictions imposed on the initial
positions and velocities of these masses, has attracted the attention
of many scientists for more than 300 years. In this paper, we present a
review of the three-body problem in the context of both historical and
modern developments. We describe the general and restricted (circular
and elliptic) three-body problems, different analytical and numerical
methods of finding solutions, methods for performing stability analysis
and searching for periodic orbits and resonances. We apply the results
to some interesting problems of celestial mechanics. We also provide a
brief presentation of the general and restricted relativistic three-body
problems, and discuss their astronomical applications.
---------------------------------------------------------
Title: Impulsively Generated Linear and Non-linear Alfven Waves in
the Coronal Funnels
Authors: Chmielewski, P.; Srivastava, A. K.; Murawski, K.; Musielak,
Z. E.
2014AcPPA.125..158C Altcode: 2014arXiv1401.2329C
We present simulation results of the impulsively generated linear
and non-linear Alfvén waves in the weakly curved coronal magnetic
flux-tubes (coronal funnels) and discuss their implications for the
coronal heating and solar wind acceleration. We solve numerically
the time-dependent magnetohydrodynamic equations to find the temporal
signatures of the small and large-amplitude Alfvén waves in the model
atmosphere of open and expanding magnetic field configuration with a
realistic temperature distribution. We compute the maximum transversal
velocity of both linear and non-linear Alfvén waves at different
heights of the model atmosphere, and study their response in the
solar corona during the time of their propagation. We infer that the
pulse-driven non-linear Alfvén waves may carry sufficient wave energy
fluxes to heat the coronal funnels and also to power the solar wind that
originates in these funnels. Our study of linear Alfvén waves shows
that they can contribute only to the plasma dynamics and heating of the
funnel-like magnetic flux-tubes associated with the polar coronal holes.
---------------------------------------------------------
Title: Reflection and Wave Coupling of Torsional Alfven Waves in 3D
Solar Magnetic Flux Tubes
Authors: Musielak, Zdzislaw E.; Murawski, K.; Srivastava, A. K.
2014AAS...22311806M Altcode:
We simulate numerically propagation of nonlinear torsional Alfven waves
in 3D magnetic flux tubes embedded in the solar atmosphere with the
VAL-C temperature profile that is smoothly extended into the solar
corona. The waves are launched at the top of the solar photosphere
and their propagation through the solar chromosphere and transition
region to the solar corona is studied. We investigate wave reflection
in the solar transition region and nonlinear coupling of torsional
Alfven waves to magnetoacoustic waves, and use our numerical results
to determine the efficiency of energy transfer by these waves to the
solar corona and the role played by nonlinear coupling of the waves
in heating of different parts of the solar atmosphere. The obtained
results are compared to the recent observational data that supplied
evidence for the existence of torsional Alfven waves in the solar
atmosphere and to the observationally established heating requirements
in different parts of the solar atmosphere.
---------------------------------------------------------
Title: Astronomical constraints on quantum theories of cold dark
matter - I. Einasto density profile for galactic haloes
Authors: Spivey, S. C.; Musielak, Z. E.; Fry, J. L.
2013MNRAS.428..712S Altcode: 2012MNRAS.tmp...52S
Among different models of dark matter, the so-called quantum (or
`fuzzy') cold dark matter plays an important role as it allows removing
cuspy halo profiles and an abundance of low mass haloes, which are
predicted by cold dark matter models but have never been observed. The
basic idea of the quantum cold dark matter is the existence of extremely
light bosonic particles whose expected masses are of the order of
10<SUP>-22</SUP> eV or even as small as 10<SUP>-24</SUP> eV. With such a
small mass, the particle's behaviour in galactic dark matter haloes is
described by the Schrödinger equation with a gravitational potential
term. In this paper, two previously introduced quantum models of dark
matter are reconsidered and the probability densities predicted by these
models are compared to the astronomically established density profiles
of dark matter haloes of the Milky Way and a dwarf galaxy. By imposing
these astronomical constraints on the quantum models, it is shown
that the models do reproduce well the Einasto profile with index n ≈
0.56. However, the models can neither account for the total masses and
halo shapes of these two galaxies, nor other galaxies, using the same
dark matter elementary particle. Possible improvements of the quantum
models that could potentially remove this deficiency are discussed.
---------------------------------------------------------
Title: Global and Local Cutoff Frequencies for Transverse Waves
Propagating along Solar Magnetic Flux Tubes
Authors: Routh, S.; Musielak, Z. E.; Hammer, R.
2013ApJ...763...44R Altcode: 2013arXiv1301.2736R
It is a well-established result that the propagation of linear
transverse waves along a thin but isothermal magnetic flux tube
is affected by the existence of the global cutoff frequency, which
separates the propagating and non-propagating waves. In this paper,
the wave propagation along a thin and non-isothermal flux tube is
considered and a local cutoff frequency is derived. The effects of
different temperature profiles on this local cutoff frequency are
studied by considering different power-law temperature distributions,
as well as the semi-empirical VAL C model of the solar atmosphere. The
obtained results show that the conditions for wave propagation
strongly depend on the temperature gradients. Moreover, the local
cutoff frequency calculated for the VAL C model gives constraints on
the range of wave frequencies that are propagating in different parts
of the solar atmosphere. These theoretically predicted constraints are
compared to observational data and are used to discuss the role played
by transverse tube waves in the atmospheric heating and dynamics,
and in the excitation of solar atmospheric oscillations.
---------------------------------------------------------
Title: Pulse-driven non-linear Alfvén waves and their role in the
spectral line broadening
Authors: Chmielewski, P.; Srivastava, A. K.; Murawski, K.; Musielak,
Z. E.
2013MNRAS.428...40C Altcode: 2012MNRAS.tmp....5C; 2012arXiv1207.6507C
We study the impulsively generated non-linear Alfvén waves in the
solar atmosphere and describe their most likely role in the observed
non-thermal broadening of some spectral lines in solar coronal holes. We
solve numerically the time-dependent magnetohydrodynamic equations to
find temporal signatures of large-amplitude Alfvén waves in the solar
atmosphere model of open and expanding magnetic field configuration,
with a realistic temperature distribution. We calculate the temporally
and spatially averaged, instantaneous transversal velocity of non-linear
Alfvén waves at different heights of the model atmosphere and estimate
its contribution to the unresolved non-thermal motions caused by the
waves. We find that the pulse-driven non-linear Alfvén waves with the
amplitude A<SUB>v</SUB> = 50 km s<SUP>- 1</SUP> are the most likely
candidates for the non-thermal broadening of Si viii λ1445.75 Å line
profiles in the polar coronal hole as reported by Banerjee et al. We
also demonstrate that the Alfvén waves driven by comparatively smaller
velocity pulse with amplitude A<SUB>v</SUB> = 25 km s<SUP>- 1</SUP>
may contribute to the spectral line width of the same line at various
heights in coronal hole broadening. We conclude that the non-linear
Alfvén waves excited impulsively in the lower solar atmosphere may be
responsible for the observed spectral line broadening in polar coronal
holes. This is an important result as it allows us to conclude that
such large amplitude and pulse-driven Alfvén waves may indeed exist
in solar coronal holes. The existence of these waves may impart the
required momentum to accelerate the solar wind.
---------------------------------------------------------
Title: Study of resonances for the restricted 3-body problem
Authors: Quarles, B.; Musielak, Z. E.; Cuntz, M.
2012AN....333..551Q Altcode: 2012arXiv1205.0950Q
Our aim is to identify and classify mean-motion resonances (MMRs)
for the coplanar circular restricted three-body problem (CR3BP) for
mass ratios between 0.10 and 0.50. Our methods include the maximum
Lyapunov exponent, which is used as an indicator for the location of
the resonances, the Fast Fourier Transform (FFT) used for determining
what kind of resonances are present, and the inspection of the orbital
elements to classify the periodicity. We show that the 2:1 resonance
occurs the most frequently. Among other resonances, the 3:1 resonance
is the second most common, and furthermore both 3:2 and 5:3 resonances
occur more often than the 4:1 resonance. Moreover, the resonances in the
coplanar CR3BP are classified based on the behaviour of the orbits. We
show that orbital stability is ensured for high values of resonance
(i.e., high ratios) where only a single resonance is present. The
resonances attained are consistent with the previously established
resonances for the solar system, i.e., specifically, in regards to the
asteroid belt. Previous work employed digital filtering and Lyapunov
characteristic exponents to determine stochasticity of the eccentricity,
which is found to be consistent with our usage of Lyapunov exponents
as an alternate approach based on varying the mass ratio instead of
the eccentricity. Our results are expected to be of principal interest
to future studies, including augmentations to observed or proposed
resonances, of extra-solar planets in binary stellar systems.
---------------------------------------------------------
Title: Habitability of Earth-mass Planets and Moons in the Kepler-16
System
Authors: Quarles, B.; Musielak, Z. E.; Cuntz, M.
2012ApJ...750...14Q Altcode: 2012arXiv1201.2302Q
We demonstrate that habitable Earth-mass planets and moons can exist
in the Kepler-16 system, known to host a Saturn-mass planet around
a stellar binary, by investigating their orbital stability in the
standard and extended habitable zone (HZ). We find that Earth-mass
planets in satellite-like (S-type) orbits are possible within the
standard HZ in direct vicinity of Kepler-16b, thus constituting
habitable exomoons. However, Earth-mass planets cannot exist in
planetary-like (P-type) orbits around the two stellar components
within the standard HZ. Yet, P-type Earth-mass planets can exist
superior to the Saturnian planet in the extended HZ pertaining to
considerably enhanced back-warming in the planetary atmosphere if
facilitated. We briefly discuss the potential detectability of such
habitable Earth-mass moons and planets positioned in satellite and
planetary orbits, respectively. The range of inferior and superior
P-type orbits in the HZ is between 0.657-0.71 AU and 0.95-1.02 AU,
respectively.
---------------------------------------------------------
Title: The stability of the suggested planet in the ν Octantis
system: a numerical and statistical study
Authors: Quarles, B.; Cuntz, M.; Musielak, Z. E.
2012MNRAS.421.2930Q Altcode: 2012arXiv1201.2313Q; 2012MNRAS.tmp.2692Q
We provide a detailed theoretical study aimed at the observational
finding about the ν Octantis binary system that indicates the
possible existence of a Jupiter-type planet in this system. If a
prograde planetary orbit is assumed, it has earlier been argued that
the planet, if existing, should be located outside the zone of orbital
stability. However, a previous study by Eberle & Cuntz concludes
that the planet is most likely stable if assumed to be in a retrograde
orbit with respect to the secondary system component. In the present
work, we significantly augment this study by taking into account the
observationally deduced uncertainty ranges of the orbital parameters
for the stellar components and the suggested planet. Furthermore,
our study employs additional mathematical methods, which include
monitoring the Jacobi constant, the zero velocity function and the
maximum Lyapunov exponent. We again find that the suggested planet
is indeed possible if assumed to be in a retrograde orbit, but it is
virtually impossible if assumed in a prograde orbit. Its existence
is found to be consistent with the deduced system parameters of the
binary components and of the suggested planet, including the associated
uncertainty bars given by observations.
---------------------------------------------------------
Title: Atmospheric oscillations in late-type stars - I. Non-linear
response to excitation by acoustic wave energy spectra
Authors: Fawzy, Diaa E.; Musielak, Z. E.
2012MNRAS.421..159F Altcode:
The main aim of this paper is to perform first self-consistent numerical
computation of the response of stellar atmospheres to the propagation
of acoustic waves specified by realistic acoustic wave energy
spectra. In the numerical approach, stellar atmospheres are stratified,
non-isothermal and plane-parallel, and only their magnetic-free regions
are considered. The resulting atmospheric heating is calculated and the
time sequence of atmospheric velocities computed by a time-dependent
hydrodynamic numerical code is analysed. All computations are done
adiabatically and Fourier analysis is used in order to determine the
oscillatory properties of stellar atmospheres. The numerical approach
is supplemented by an analytical treatment in which three different
local acoustic cut-off frequencies are selected from the literature;
their values in the stellar atmospheric models are calculated and
compared to the numerical results. The theoretical results obtained
clearly show that atmospheric oscillations do exist in late-type
stars and that their origin and physical properties are similar to
those observed in the solar atmosphere. The oscillation frequency of
stellar atmospheric oscillations ranges from 7.5 mHz for F5V stars to
16.0 mHz for M0V stars. The relevance of this theoretically predicted
range of stellar oscillation in solar-like stars to the recent data
obtained by the NASA space mission Kepler is discussed.
---------------------------------------------------------
Title: The stability of the suggested planet in the ν Octantis
system: a numerical and statistical study
Authors: Quarles, Billy; Cuntz, Manfred; Musielak, Zdzislaw
2012APS..TSS.C1003Q Altcode:
Exoplanets in binary systems have received heightened interest by
the scientific community. Especially with the recent detection of
a circumbinary planet of Kepler-16b (Doyle et al. 2011)[Science
333, 1602] planets in binary systems have warranted second and
even third glances. The system of ν Octantis has been a system
of great controversy since the suggested planet in this system
(Ramm et al. 2009)[MNRAS 394, 1695] appears to be located beyond its
theoretical stability limit. In order to resolve this controversy we
seek to determine whether the proposed planet can exist in the context
of current stability theory. We have performed detailed simulations
by exploiting the uncertainty measurements to determine the short and
long-term stability of a prograde starting configuration. However to
follow up on the previous results by Eberle & Cuntz (2010)[ApJ 721,
L168], we have investigated the hypothesis of a retrograde orbit in more
detail by considering a larger set of possible initial conditions to
determine the possibility of a retrograde configuration with respect
to the motion of the binary system. We will show that a retrograde
configuration is preferred by both stability considerations with
respect to the maximum Lyapunov exponent and numerical statistical
considerations.
---------------------------------------------------------
Title: On The Existence Of Earth-like Planets In The Circumbinary
System Kepler-16
Authors: Quarles, Billy L.; Musielak, Z. E.; Cuntz, M.
2012AAS...21911003Q Altcode:
The newly discovered circumbinary system Kepler-16 contains a pair of
low-mass stars and a Saturn-mass planet (Doyle et al. 2011) [Science
333, 1602]. A truly fascinating problem is to explore whether Earth-like
planets can exist in the habitable zone (HZ) of this unique system. The
HZ of this system is mainly due to the primary star and extends from
0.36 AU to 0.71 AU. We have performed extensive numerical studies
of long-term orbital stability of Earth-like planets in this HZ by
considering both S-type and P-type planetary orbits. The semi-major
axis for S-type orbits has been determined as 0.0675 ± 0.0039 AU
from the stellar primary. This distance is well inside the inner
limit of habitability where the influence of the runaway greenhouse
effect becomes important. Consequently, the existence of a habitable
Earth-like planet in an S-type orbit is highly unlikely. However it
appears possible that such a planet can exist in a P-type orbit inside
the HZ thus providing a realistic possibility for long-term evolution
of life in this type of system. The obtained results are of special
interest because they can assist in the selection process of system
candidates in future terrestrial planet search missions.
---------------------------------------------------------
Title: Astronomical Constraints on Quantum Cold Dark Matter
Authors: Spivey, Shane; Musielak, Z.; Fry, J.
2012AAS...21911202S Altcode:
A model of quantum (`fuzzy') cold dark matter that accounts for both
the halo core problem and the missing dwarf galaxies problem, which
plague the usual cold dark matter paradigm, is developed. The model
requires that a cold dark matter particle has a mass so small that its
only allowed physical description is a quantum wave function. Each such
particle in a galactic halo is bound to a gravitational potential that
is created by luminous matter and by the halo itself, and the resulting
wave function is described by a Schrödinger equation. To solve this
equation on a galactic scale, we impose astronomical constraints that
involve several density profiles used to fit data from simulations of
dark matter galactic halos. The solutions to the Schrödinger equation
are quantum waves which resemble the density profiles acquired from
simulations, and they are used to determine the mass of the cold dark
matter particle. The effects of adding certain types of baryonic matter
to the halo, such as a dwarf elliptical galaxy or a supermassive black
hole, are also discussed.
---------------------------------------------------------
Title: Case studies of habitable Trojan planets in the system of
HD 23079
Authors: Eberle, J.; Cuntz, M.; Quarles, B.; Musielak, Z. E.
2011IJAsB..10..325E Altcode: 2011arXiv1104.3092E
We investigate the possibility of habitable Trojan planets in the HD
23079 star-planet system. This system consists of a solar-type star and
a Jupiter-type planet, which orbits the star near the outer edge of the
stellar habitable zone in an orbit of low eccentricity. We find that
in agreement with previous studies Earth-mass habitable Trojan planets
are possible in this system, although the success of staying within the
zone of habitability is significantly affected by the orbital parameters
of the giant planet and by the initial condition of the theoretical
Earth-mass planet. In one of our simulations, the Earth-mass planet
is captured by the giant planet and thus becomes a habitable moon.
---------------------------------------------------------
Title: The instability transition for the restricted 3-body
problem. III. The Lyapunov exponent criterion
Authors: Quarles, B.; Eberle, J.; Musielak, Z. E.; Cuntz, M.
2011A&A...533A...2Q Altcode: 2011arXiv1106.5062Q
<BR /> Aims: We establish a criterion for the stability of planetary
orbits in stellar binary systems by using Lyapunov exponents and
power spectra for the special case of the circular restricted 3-body
problem (CR3BP). The criterion augments our earlier results given
in the two previous papers of this series where stability criteria
have been developed based on the Jacobi constant and the hodograph
method. <BR /> Methods: The centerpiece of our method is the concept
of Lyapunov exponents, which are incorporated into the analysis
of orbital stability by integrating the Jacobian of the CR3BP and
orthogonalizing the tangent vectors via a well-established algorithm
originally developed by Wolf et al. The criterion for orbital stability
based on the Lyapunov exponents is independently verified by using
power spectra. The obtained results are compared to results presented
in the two previous papers of this series. <BR /> Results: It is
shown that the maximum Lyapunov exponent can be used as an indicator
for chaotic behaviour of planetary orbits, which is consistent with
previous applications of this method, particularly studies for the
Solar System. The chaotic behaviour corresponds to either orbital
stability or instability, and it depends solely on the mass ratio μ
of the binary components and the initial distance ratio ρ<SUB>0</SUB>
of the planet relative to the stellar separation distance. Detailed
case studies are presented for μ = 0.3 and 0.5. The stability
limits are characterized based on the value of the maximum Lyapunov
exponent. However, chaos theory as well as the concept of Lyapunov time
prevents us from predicting exactly when the planet is ejected. Our
method is also able to indicate evidence of quasi-periodicity. <BR />
Conclusions: For different mass ratios of the stellar components, we
are able to characterize stability limits for the CR3BP based on the
value of the maximum Lyapunov exponent. This theoretical result allows
us to link the study of planetary orbital stability to chaos theory
noting that there is a large array of literature on the properties and
significance of Lyapunov exponents. Although our results are given for
the special case of the CR3BP, we expect that it may be possible to
augment the proposed Lyapunov exponent criterion to studies of planets
in generalized stellar binary systems, which is strongly motivated
by existing observational results as well as results expected from
ongoing and future planet search missions.
---------------------------------------------------------
Title: Detection of Moons around Giant Extrasolar Planets
Authors: Musielak, Dora; Musielak, Z. E.
2011AAS...21731805M Altcode: 2011BAAS...4331805M
The fact that Jupiter's radio emission is affected by the presence of
its moon Io has been know for many years and extensively studied both
observationally and theoretically. Since Io moves inside the Jovian
magnetic field, its motion produces currents along the field lines
that connect the moon to the Jupiter's polar regions, where the radio
emission is modulated by the currents. It has been suggested that
such modulation of planetary radio emission may reveal the presence
of moons around giant planets in extrasolar planetary system. With
the first indirect observational evidence for extrasolar planetary
magnetic fields, and with the promise of detecting more such cases
by the upcoming new observations, we seriously consider the idea
and determine the required physical conditions for such detection to
take place. The results of our study will be used to select the most
promising candidates for detection of moons around giant planets in
currently known extrasolar planetary systems.
---------------------------------------------------------
Title: Lyapunov Exponent Criterion for Stability of Planetary Orbits
in Binary Systems
Authors: Musielak, Zdzislaw E.; Quarles, B.; Eberle, J.; Cuntz, M.
2011AAS...21741505M Altcode: 2011BAAS...4341505M
The existence of planets in stellar binary systems is now well-confirmed
by many observations. Stability of planetary orbits in these systems
has extensively been studied and some attempts have been made to
establish stringent stability criteria for the orbits. In this
paper, we contribute to the ongoing work on the stability criteria
in binary systems by introducing a Lyapunov exponent criterion. We
have computed the Lyapunov exponents, the Lyapunov dimension and
the time series spectra for planets in binary system. The obtained
results demonstrate when a system becomes unstable by orbital energy
criterion and the method of Lyapunov exponents provides a quantitative
classification scale to characterize the instability. By applying the
maximum Lyapunov exponent to the parameter space, which covers mass
and distance ratios for the considered binary systems, we determined
regions of stability and used the time series spectra and the Lyapunov
dimension to illustrate the reasons behind the stability. Specific
applications of the criterion to binary systems with known planets
will also be discussed.
---------------------------------------------------------
Title: The great oxidation of Earth's atmosphere
Authors: Musielak, Zdzislaw E.; Cuntz, Manfred; Roy, Dipanjan
2010HiA....15..680M Altcode:
A simplified model of the Earth's atmosphere consisting of three
nonlinear differential equations with a driving force was developed
by Goldblatt et al. (2006). They found a steady-state solution that
exhibits bistability and identified its upper value with the great
oxidation of the Earth's atmosphere. Noting that the driving force in
their study was a step function, it is the main goal of this paper to
investigate the stability of the model by considering two different
more realistic driving forces. The stability analysis is performed
by using Lyapunov exponents. Our results show that the model remains
stable and it does not exhibit any chaotic behavior.
---------------------------------------------------------
Title: Orbital stability of Earth-type planets in stellar binary
systems
Authors: Eberle, Jason; Cuntz, Manfred; Musielak, Zdzislaw E.
2010HiA....15..691E Altcode:
An important factor in estimating the likelihood of life elsewhere
in the Universe is determining the stability of a planet's orbit. A
significant fraction of stars like the Sun occur in binary systems which
often has a considerable effect on the stability of any planets in such
a system. In an effort to determine the stability of planets in binary
star systems, we conducted a numerical simulation survey of several mass
ratios and initial conditions. We then estimated the stability of the
planetary orbit using a method that utilizes the hodograph to determine
the effective eccentricity of the planetary orbit. We found that this
method can serve as an orbital stability criterion for the planet.
---------------------------------------------------------
Title: Linear Alfvén waves in the solar atmosphere
Authors: Murawski, K.; Musielak, Z. E.
2010A&A...518A..37M Altcode:
<BR /> Aims: We aim to analytically and numerically explore
small-amplitude Alfvén waves in the solar atmosphere. <BR /> Methods:
We transform the wave equations to obtain the cutoff-frequency
and wave travel time for strictly linear Alfvén waves. The wave
equations are solved numerically to find out spatial and temporal
signatures of the waves. <BR /> Results: The analytical predictions are
verified by numerically solving the wave equations for linear Alfvén
waves. The waves are impulsively generated and their characteristics
and behavior in the solar atmosphere are investigated by the numerical
simulations. The derived cutoff-frequency is used to determine regions
in the solar atmosphere where strong reflection occurs for Alfvén
waves of different frequencies. <BR /> Conclusions: The numerical
results reveal that impulsively generated small-amplitude waves exhibit
characteristic spatial and temporal signatures which agree with the
predictions of the analytical theory.
---------------------------------------------------------
Title: The origin of cutoff frequencies for torsional tube waves
propagating in the solar atmosphere
Authors: Hammer, R.; Musielak, Z. E.; Routh, S.
2010AN....331..593H Altcode:
Torsional waves supported by magnetic flux tubes have long been thought
to bear a high potential for supplying energy and momentum to the
upper solar atmosphere, thereby contributing to its heating and to
the driving of dynamic events like spicules. This hope rested on the
belief that their propagation is not impeded by cutoff restrictions,
unlike longitudinal and kink waves. We point out that this applies only
to thin, isothermal tubes. When they widen in the chromosphere, and
as a result of temperature gradients, cutoff restrictions arise. We
compare them to recent observational reports of such waves and of
vortex motions and find that their long period components are already
affected by cutoff restrictions. An observational strategy is proposed
that should permit the derivation of better information on vortex
flows from off-center observations with next generation telescopes.
---------------------------------------------------------
Title: Temperature Gradients in the Solar Atmosphere and the Origin
of Cutoff Frequency for Torsional Tube Waves
Authors: Routh, S.; Musielak, Z. E.; Hammer, R.
2010ApJ...709.1297R Altcode:
Fundamental modes supported by a thin magnetic flux tube embedded in the
solar atmosphere are typically classified as longitudinal, transverse,
and torsional waves. If the tube is isothermal, then the propagation
of longitudinal and transverse tube waves is restricted to frequencies
that are higher than the corresponding global cutoff frequency for each
wave. However, no such global cutoff frequency exists for torsional
tube waves, which means that a thin and isothermal flux tube supports
torsional tube waves of any frequency. In this paper, we consider a thin
and non-isothermal magnetic flux tube and demonstrate that temperature
gradients inside this tube are responsible for the origin of a cutoff
frequency for torsional tube waves. The cutoff frequency is used to
determine conditions for the wave propagation in the solar atmosphere,
and the obtained results are compared to the recent observational data
that support the existence of torsional tube waves in the Sun.
---------------------------------------------------------
Title: Generation and Propagation of Torsional Tube Waves in the
Solar Atmosphere
Authors: Musielak, Zdzislaw E.; Routh, S.; Hammer, R.
2010AAS...21532204M Altcode: 2010BAAS...42..324M
Recent observational evidence for the existence of torsional tube waves
in the solar atmosphere (e.g., Bonet et al. 2008; Jess et al. 2009) has
triggered theoretical work on the generation and propagation of these
waves. We modify our previous theory of generation of torsional tubes
waves by the solar turbulent convection and compute the resulting the
wave energy spectra and fluxes. We also demonstrate that tube thickness
and temperature gradients lead to the origin of cutoff frequencies
for torsional tube waves. Using the cutoffs, we calculate a range
of frequencies corresponding to the propagating waves and compare
it to that given by the observations. We use the obtained result
to discuss the role of torsional tube waves in heating of the solar
atmosphere. This work is supported by NSF under grant ATM-0538278.
---------------------------------------------------------
Title: Orbital Stability of Earth-Type Planets in Binary Systems
Authors: Eberle, J.; Cuntz, M.; Musielak, Z. E.
2009ASPC..420..357E Altcode: 2007arXiv0712.3266E
About half of all known stellar systems with Sun-like stars consist of
two or more stars, significantly affecting the orbital stability of any
planet in these systems. Here we study the onset of instability for an
Earth-type planet that is part of a binary system. Our investigation
makes use of previous analytical work allowing to describe the
permissible region of planetary motion. This allows us to establish a
criterion for the orbital stability of planets that may be useful in
the context of future observational and theoretical studies.
---------------------------------------------------------
Title: The Great Oxidation of Earth's Atmosphere: Contesting the
Yoyo Model Via Transition Stability Analysis
Authors: Cuntz, M.; Roy, D.; Musielak, Z. E.
2009ApJ...706L.178C Altcode:
A significant controversy regarding the climate history of the Earth
and its relationship to the development of complex life forms concerns
the rise of oxygen in the early Earth's atmosphere. Geological records
show that this rise occurred about 2.4 Gyr ago, when the atmospheric
oxygen increased from less than 10<SUP>-5</SUP> present atmospheric
level (PAL) to more than 0.01 PAL and possibly above 0.1 PAL. However,
there is a debate whether this rise happened relatively smoothly or
with well-pronounced ups and downs (the Yoyo model). In our study,
we explore a simplified atmospheric chemical system consisting of
oxygen, methane, and carbon that is driven by the sudden decline of
the net input of reductants to the surface as previously considered
by Goldblatt et al. Based on the transition stability analysis for the
system equations, constituting a set of non-autonomous and non-linear
differential equations, as well as the inspection of the Lyapunov
exponents, it is found that the equations do not exhibit chaotic
behavior. In addition, the rise of oxygen occurs relative smoothly,
possibly with minor bumps (within a factor of 1.2), but without major
jumps. This result clearly argues against the Yoyo model in agreement
with recent geological findings.
---------------------------------------------------------
Title: Novel explanation for the shape of the lenticular galaxy
bulge and its implication for red spiral galaxy evolution
Authors: Schachar, R. A.; Liao, G. G.; Kirby, R. D.; Kamangar, F.;
Musielak, Z. E.; Rosensteel, G.
2009A&A...505..613S Altcode:
Aims: According to Hubble's classification scheme, lenticular galaxies
represent an intermediate evolutionary step between elliptical and
spiral galaxies. This evolutionary path predicts that the aspect
ratios of both lenticular and spiral galaxies should be smaller
than the aspect ratios of their E6 or E7 elliptical predecessors. In
contradiction to this prediction, observation has demonstrated that
the aspect ratio of lenticular galaxies is larger than its immediate
elliptical predecessor. In this paper, we suggest a novel explanation
for this inconsistency. <BR />Methods: The approach described in this
paper is primarily based on analytical methods; however, some numerical
methods are also used. <BR />Results: Our idea comes from theoretical
and experimental results, which show that a small increase in the
equatorial diameter of an oblate spheroid with an aspect ratio ≤0.6
surprisingly causes its minor axis to also increase. We demonstrate that
the same phenomenon occurs in the isodensity contours of elliptical
galaxies given by Miyamoto & Nagai (Miyamoto M., & Nagai R.,
1975, PASJ, 27, 533) and in a Maclaurin spheroidal mass in response
to the gravitational force generated by a circumferential equatorial
disk. <BR />Conclusions: The result of this paper is our explanation
for the transformation of a disky elliptical galaxy into a lenticular
galaxy which in response to rotation and equatorial diameter expansion
evolves into a red spiral galaxy. This evolutionary path is consistent
with the common environmental location of disky ellipticals, lenticular
and red spiral galaxies and explains why elliptical galaxies are
generally ≤E4. The proposed evolutionary path is opposite to the
generally accepted formation of lenticular galaxies from the merger
of spiral galaxies.
---------------------------------------------------------
Title: Propagation of Waves in Solar Non-Isothermal Atmosphere
Authors: Routh, Swati; Musielak, Z.; Hammer, R.
2009SPD....40.1001R Altcode:
Fundamental modes supported by a thin and isothermal magnetic flux
tube embedded in the solar atmosphere are typically identified as
longitudinal, transverse and torsional waves. The propagation of
longitudinal and transverse tube waves is restricted to frequencies
that are higher than the corresponding global cutoff frequency for
each wave. No such global cutoff frequency exists for torsional tube
waves, which means that the flux tube supports torsional tube waves
of any frequency. The situation becomes different when a 'wide’ and
isothermal flux tube is concerned; in this case, a cutoff frequency
for torsional tube waves arises naturally and it becomes a local
quantity. Since the solar atmosphere is not isothermal, the effects
of different temperature gradients on the cutoff are investigated. A
method to determine these effects is presented and applied to specific
models of solar magnetic flux tubes. An interesting result is that the
resulting cutoff frequency is a local quantity in the model, and that
its value at a given height determines the frequency that transverse
and torsional tube waves must have in order to be propagating at this
height. The obtained results are applied to the VAL C model of the
solar atmosphere.
---------------------------------------------------------
Title: The instability transition for the restricted 3-body
problem. I. Theoretical approach
Authors: Eberle, J.; Cuntz, M.; Musielak, Z. E.
2008A&A...489.1329E Altcode:
Aims: We study the onset of orbital instability for a small object,
identified as a planet, that is part of a stellar binary system
with properties equivalent to the restricted three body problem. <BR
/>Methods: Our study is based on both analytical and numerical means
and makes use of a rotating (synodic) coordinate system keeping both
binary stars at rest. This allows us to define a constant of motion
(Jacobi's constant), which is used to describe the permissible region
of motion for the planet. We illustrate the transition to instability
by depicting sets of time-dependent simulations with star-planet
systems of different mass and distance ratios. <BR />Results: Our
method utilizes the existence of an absolute stability limit. As the
system parameters are varied, the permissible region of motion passes
through the three collinear equilibrium points, which significantly
changes the type of planetary orbit. Our simulations feature various
illustrative examples of instability transitions. <BR />Conclusions:
Our study allows us to identify systems of absolute stability, where
the stability limit does not depend on the specifics or duration of
time-dependent simulations. We also find evidence of a quasi-stability
region, superimposed on the region of instability, where the planetary
orbits show quasi-periodic behavior. The analytically deduced onset of
instability is found to be consistent with the behavior of the depicted
time-dependent models, although the manifestation of long-term orbital
stability will require more detailed studies.
---------------------------------------------------------
Title: Spicules: Energetics and the Role of Magnetic Waves
Authors: Hammer, R.; Musielak, Z. E.; Routh, S.; Nesis, A.
2008ESPM...12.3.11H Altcode:
The class of spicule-like processes comprises a variety of phenomena
that were given different names, depending on how and where on the
Sun they can be observed - including (classical limb) spicules,
macrospicules, FUV spicules, mottles, fibrils, and the "type
II spicules" recently discovered with Hinode. The relationships
between these phenomena are not fully clarified. We point out that
the reported observed properties cannot all be reconciled with a
single driving mechanism. Indeed, many different mechanisms have been
suggested in the past, all with some success. We argue that this was
ultimately possible because the observed properties are consistent
with an approximate equipartition between enthalpy, kinetic energy,
and presumably also magnetic energy. One of the most popular driving
mechanisms of the last few years invokes the guiding of global p-mode
oscillations along magnetic field lines that are sufficiently inclined
against the vertical, so that the cutoff frequency for longitudinal
waves drops below the excitation frequency. We show that in such a
situation transverse, and perhaps also torsional, waves are much more
promising, because of their weaker cutoff restrictions even for the
small inclinations that are typical for limb spicules. Indeed there is
now growing observational evidence for transverse waves. We point out
the need to understand better the cutoff properties of various kinds
of magnetic waves.
---------------------------------------------------------
Title: Local Cutoff Frequencies for Transverse Waves Propagating
Along Thin and Non-Isothermal Magnetic Flux Tubes
Authors: Musielak, Z. E.; Subramaniam, S.; Routh, S.; Hammer, R.
2008ESPM...12.3.25M Altcode:
Propagation of transverse waves along thin magnetic flux tubes embedded
in an isothermal atmosphere is affected by the cutoff frequency, which
is a global quantity that restricts the wave propagation to only those
frequencies that are higher than the cutoff. Since the solar atmosphere
is not isothermal, the effects of different temperature gradients
on the cutoff are investigated. A method to determine these effects
is presented and applied to specific models of solar magnetic flux
tubes. An interesting result is that the resulting cutoff frequency
is a local quantity in the model, and that its value at a given height
determines the frequency that transverse tube waves must have in order
to be propagating at this height. The obtained results are applied to
the solar atmospheric oscillations.
---------------------------------------------------------
Title: Orbital stability of planets in binary systems: A new look
at old results
Authors: Eberle, J.; Cuntz, M.; Musielak, Z. E.
2008IAUS..249..507E Altcode: 2007IAUS..249..507E; 2007arXiv0712.3239E
About half of all known stellar systems with Sun-like stars consist
of two or more stars, significantly affecting the orbital stability of
any planet in these systems. This observational evidence has prompted
a large array of theoretical research, including the derivation of
mathematically stringent criteria for the orbital stability of planets
in stellar binary systems, valid for the “coplanar circular restricted
three-body problem”. In the following, we use these criteria to
explore the validity of results from previous theoretical studies.
---------------------------------------------------------
Title: Stability of planetary orbits in binary systems
Authors: Musielak, Z. E.; Cuntz, M.; Marshall, E. A.; Stuit, T. D.
2008A&A...480..573M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Waves in Inclined Solar Magnetic Flux Tubes
Authors: Routh, Swati; Musielak, Z.; Hammer, R.
2007AAS...211.8001R Altcode: 2007BAAS...39..870R
The solar chromosphere shows numerous needle-shaped extensions into
the overlying corona, in which plasma shoots up at high speeds. These
phenomena are variously called spicules, mottles, or dynamic fibrils,
depending on where and how they are observed on the Sun. Many different
explanations have been suggested for how these phenomena might be
generated in the dynamic solar atmosphere. The currently most popular
suggestion is that global solar oscillations propagate as longitudinal
waves along magnetic flux tubes. These long-period waves suffer from
a cutoff restriction, but if the flux tubes are sufficiently inclined
to the vertical they can propagate nevertheless. We will analyze the
cutoff behavior of longitudinal and also other wave modes, namely kink
flux tube waves inside these inclined tubes and show that they have
better chances to transport energy upward. Such waves must therefore
be taken into account in order to understand spicules. <P />This work
is supported by NSF grant ATM 05-38278
---------------------------------------------------------
Title: Conditions for Propagation of Torsional Waves in Solar Magnetic
Flux Tubes
Authors: Routh, S.; Musielak, Z. E.; Hammer, R.
2007SoPh..246..133R Altcode:
Propagation of torsional waves along isothermal and initially-untwisted
magnetic-flux tubes embedded in the solar atmosphere is studied
analytically. Conditions for wave propagation along thin and
wide magnetic-flux tubes are determined, and it is shown that the
propagation along thin tubes is cutoff free; however, for wide tubes the
propagation is affected by a cutoff frequency. A method to determine
the cutoff frequency is presented and applied to a specific model of
solar magnetic flux tubes. An interesting result is that the cutoff
frequency is a local quantity in the model and that its value at a
given height determines the frequency that torsional tube waves must
have to propagate at this height.
---------------------------------------------------------
Title: Stringent Criteria for Stable and Unstable Planetary Orbits
in Stellar Binary Systems
Authors: Cuntz, M.; Eberle, J.; Musielak, Z. E.
2007ApJ...669L.105C Altcode:
The existence of planets in stellar binary (and higher order) systems
has now been confirmed by many observations. The stability of planetary
orbits in these systems has been extensively studied, but no precise
stability criteria have so far been introduced. Therefore, there is an
urgent need for developing stringent mathematical criteria that allow
us to precisely determine whether a planetary orbit in a binary system
is stable or unstable. In this Letter, such criteria are defined using
the concept of Jacobi's integral and Jacobi's constant. These criteria
are used to contest previous results on planetary orbital stability
in binary systems.
---------------------------------------------------------
Title: Propagation Characteristics of Waves in Solar Magnetic
Flux Tubes
Authors: Hammer, Reiner; Musielak, Zdzislaw E.; Routh, Swati
2007AN....328..704H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Multiple Time Scales of Solar Granulation
Authors: Hammer, Reiner; Musielak, Zdzislaw E.; Nesis, Anastasios;
Routh, Swati; Schleicher, Helmold
2007AN....328..703H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Cutoff-free Propagation of Torsional Alfvén Waves along Thin
Magnetic Flux Tubes
Authors: Musielak, Z. E.; Routh, S.; Hammer, R.
2007ApJ...659..650M Altcode: 2007astro.ph..1720M
Propagation of torsional Alfvén waves along magnetic flux tubes has
been extensively studied for many years, but no conclusive results
regarding the existence of a cutoff frequency for these waves have
been obtained. The main purpose of this paper is to derive new wave
equations that describe the propagation of linear torsional Alfvén
waves along thin and isothermal magnetic flux tubes and to use these
wave equations to demonstrate that the torsional wave propagation
is not affected by any cutoff frequency. It is also shown that this
cutoff-free propagation is independent of the different choices of
coordinate system and wave variables adopted in previous studies. A
brief discussion of the implications of this cutoff-free propagation
of torsional tube waves on theories of wave heating of the solar and
stellar atmospheres is also given.
---------------------------------------------------------
Title: Acoustic Heating of the Solar Chromosphere: Present Indeed
and Locally Dominant
Authors: Cuntz, M.; Rammacher, W.; Musielak, Z. E.
2007ApJ...657L..57C Altcode:
We investigate the physical reality of acoustic heating in the
solar chromosphere. Evidence is provided that contrary to previous
claims by Fossum & Carlsson, high-frequency acoustic waves are
indeed sufficient to heat the nonmagnetic solar chromosphere. This
assessment is based on three different lines of evidence, which are
(1) a discussion of the inherent problems of the limited sensitivity of
TRACE when assessing the three-dimensional solar chromospheric topology,
(2) a study of the acoustic chromospheric wave energy flux, and (3)
a new look at the heating and emission of chromospheric basal flux
stars such as τ Ceti.
---------------------------------------------------------
Title: Case Studies of the Restricted Three Body Problem
Authors: Eberle, Jason; Cuntz, Manfred; Musielak, Zdzislaw
2006APS..TSF.P1005E Altcode:
Are we alone in the universe? Nobody can give an answer yet. However,
one step on the way to find out is to inquire how many planets in the
universe could harbor life. An important feature a planet should have
for life to exist is that the planet shouldn't crash into the star
or fly off into interstellar space. In regard to our own solar system
this is a non-issue as all planets are known to have orbited the Sun
for billons of years. The unfortunate truth is that most planets don't
have it as nice as Earth does. In fact, about half of all known stellar
systems harbor two or more stars, thus affecting orbital stability of
any planets in the systems. It is found that when a system harbors
two stars, the planet may orbit one or both stars, depending on the
physical conditions, or may even be kicked out of the neighborhood
of the stars completely, and lost in space forever. In this poster,
we provide detailed case studies for planets in binary systems.
---------------------------------------------------------
Title: Role of analyticity and covariance in determining laws of
mechanics
Authors: Fry, John; Musielak, Zdzislaw; Swift, L. D.
2006APS..TSFOT2006F Altcode:
We impose two postulates for state functions in our universe and
use them to obtain dynamical equations of mechanics for isolated
elementary particles. The first postulate is that the state function
is analytic on its carrier space. The second postulate is that any
equation defining the state function must be written in covariant form
for the metric of its carrier space. This implies Wigner's definition
of an elementary particle, which we adopt. Using a Minkowski metric
we obtain equations for isolated elementary particles which resemble
the Dirac and Klein-Gordon equations. We introduce a quantum action
operator and observe that the state function must be an eigenfunction
of the operator. It must have eigenvalue to obtain the quantum theory
of our universe. We identify the origin of Hamilton's principle for
quantum systems as a consequence of the first two postulates and the
definition of a particle. Dynamical equations in non-relativistic and
classical limits will also be discussed.
---------------------------------------------------------
Title: On the Validity of Acoustically Heated Chromosphere Models
Authors: Ulmschneider, P.; Rammacher, W.; Musielak, Z. E.; Kalkofen, W.
2005ApJ...631L.155U Altcode:
Theoretical models of solar and stellar chromospheres heated by
acoustic waves have so far been constructed by using time-dependent,
one-dimensional, radiation-hydrodynamic numerical codes that are
based on the approximation of plane-parallel geometry. The approach
seems to be justified by the fact that the chromospheres of most
stars extend over very narrow height ranges compared to the stellar
radius. It is demonstrated that this commonly used assumption may lead
to unrealistic shock mergings, to the artificial formation of unusually
strong shocks and the artificial destruction of high-frequency acoustic
wave power. Comparing one-dimensional calculations with observations may
lead to severe misjudgment about the nature of chromospheric heating.
---------------------------------------------------------
Title: Fast Method for Calculating Chromospheric Ca II and Mg II
Radiative Losses
Authors: Rammacher, W.; Fawzy, D.; Ulmschneider, P.; Musielak, Z. E.
2005ApJ...631.1113R Altcode:
A fast and reasonably accurate method for calculating the total
radiative losses by Ca II and Mg II ions for time-dependent
chromospheric wave calculations has been developed. The method is
based on a two-level atom procedure with pseudo-partial frequency
redistribution (pseudo-PRD). The speed of the method is due to
scaling of the total losses from single-line results. Acceleration of
computation speeds by factors of roughly 10<SUP>2</SUP>-10<SUP>3</SUP>
can be achieved. The method is tested against the results from a
modified version of the multilevel atom code MULTI.
---------------------------------------------------------
Title: Atmospheric Oscillations in White Dwarfs: A New Indicator of
Chromospheric Activity
Authors: Musielak, Z. E.; Winget, D. E.; Montgomery, M. H.
2005ApJ...630..506M Altcode:
A new type of oscillation, the so-called atmospheric oscillations
resulting from the response of stellar atmospheres to propagating
acoustic waves, must be present in white dwarfs with chromospheric
activity. Since these oscillations exist only in atmospheres with an
outward temperature increase, they can be used as a new indicator of
chromospheric activity in white dwarfs. Theoretical predictions of
periods and amplitudes of the oscillations are given for selected DA
and DB stars. The best candidates for detection of these oscillations
are also identified.
---------------------------------------------------------
Title: Stability of planetary orbits in binary systems
Authors: Musielak, Z. E.; Cuntz, M.; Marshall, E. A.; Stuit, T. D.
2005A&A...434..355M Altcode:
Stability of S-type and P-type planetary orbits in binary systems
of different mass and separation ratios is investigated. Criteria
for stable, marginally stable and unstable planetary orbits are
specified. These criteria are used to determine regions of stability
of planetary orbits in different binary systems with Jupiter-type
planets. The obtained results show that the regions of stability for
S-type orbits depend on the distance ratio between the star and planet,
and the stellar companions, in the range of 0.22 and 0.46, depending
on the mass ratio. For P-type orbits, the regions of stability also
depend on that distance ratio, in the range of 1.75 and 2.45, again
depending on the the mass ratio. Applications of these results to three
observed binary systems with giant planets, namely, τ Boo, HD 195019
and GJ 86, show that the orbits of the giant planets in those systems
can be classified as stable, as expected.
---------------------------------------------------------
Title: Heating of Stellar Chromospheres and Transition Regions
Authors: Musielak, Z. E.
2004IAUS..219..437M Altcode: 2003IAUS..219E..45M
To explain the heating of stellar chromospheres and transition regions
two classes of heating mechanisms have been considered: (1) dissipation
of acoustic and magnetic waves generated in stellar convection
zones; and (2) dissipation of currents generated by photospheric
motions of surface magnetic fields. I will review both classes of
heating mechanisms and discuss recent results which demonstrate that
theoretical models of stellar chromospheres based on the wave heating
(1) can explain the ""basal flux"" and the observed Ca II emission
in most stars but cannot account for the observed Mg II emission in
active stars. I will also present theoretical arguments which imply
that the base of stellar chromospheres is heated by acoustic waves
the heating of the middle and upper chromospheric layers is dominated
by magnetic waves associated with magnetic flux tubes and that other
non-wave (2)heating mechanisms are required to explain the structure
of the highest layers of stellar chromospheres and transition regions.
---------------------------------------------------------
Title: Torsional magnetic tube waves in stellar convection
zones. I. Analysis of wave generation and application to the Sun
Authors: Noble, M. W.; Musielak, Z. E.; Ulmschneider, P.
2003A&A...409.1085N Altcode:
An analytic approach to the generation of torsional magnetic tube waves
in stellar convection zones is presented. The waves are produced in
a thin, vertically oriented magnetic flux tube embedded in a magnetic
field-free, turbulent and compressible external medium and are excited
by external turbulent flows. A theory for this interaction is developed
and used to compute the wave energy spectra and fluxes carried by
torsional tube waves in the solar atmosphere. We find that these tube
waves have a characteristic cutoff frequency.
---------------------------------------------------------
Title: Atmospheric oscillations in solar magnetic flux
tubes. II. Excitation by transverse tube waves and random pulses
Authors: Musielak, Z. E.; Ulmschneider, P.
2003A&A...406..725M Altcode:
The response of an exponentially diverging magnetic flux tube embedded
in an isothermal solar atmosphere to the propagation of transverse tube
waves and random transverse pulses generated in the solar convection
zone is studied analytically. General solutions are presented and
applied to solar flux tubes located in the interior region and at
the boundary of supergranulation cells. It is shown that the period
of the free oscillations driven by transverse waves and pulses ranges
from 7 to 10 min for the considered values of the tube magnetic field,
and that these oscillations decay in time as t<SUP>-3/2</SUP>. Since
the observational signatures of these transverse oscillations are hard
to detect, we also consider the generation of longitudinal tube waves
by nonlinear mode coupling and the excitation of free atmospheric
oscillations by longitudinal waves. Our results show that the basic
properties of oscillations driven by transverse and longitudinal tube
waves are different. While transverse waves excite oscillations with
7-10 min periods, oscillations by longitudinal waves have periods near
3 min. This is consistent with the observed 3-min oscillations inside
the supergranule cells but inconsistent with the 7-min oscillations
observed in the chromospheric network. We suggest that an explanation of
the observed 7-min oscillations might be found by taking into account a
more realistic structure of flux tubes located in the magnetic network.
---------------------------------------------------------
Title: Chandra Observations of Magnetic White Dwarfs and Their
Theoretical Implications
Authors: Musielak, Z. E.; Noble, M.; Porter, J. G.; Winget, D. E.
2003ApJ...593..481M Altcode:
Observations of cool DA and DB white dwarfs have not yet been successful
in detecting coronal X-ray emission, but observations of late-type
dwarfs and giants show that coronae are common for these stars. To
produce coronal X-rays, a star must have dynamo-generated surface
magnetic fields and a well-developed convection zone. There is some
observational evidence that the DA star LHS 1038 and the DB star GD 358
have weak and variable surface magnetic fields. It has been suggested
that such fields can be generated by dynamo action, and since both
stars have well-developed convection zones, theory predicts detectable
levels of coronal X-rays from these white dwarfs. However, we present
analysis of Chandra observations of both stars showing no detectable
X-ray emission. The derived upper limits for the X-ray fluxes provide
strong constraints on theories of formation of coronae around magnetic
white dwarfs. Another important implication of our negative Chandra
observations is the possibility that the magnetic fields of LHS 1038
and GD 358 are fossil fields.
---------------------------------------------------------
Title: Atmospheric oscillations in solar magnetic flux
tubes. I. Excitation by longitudinal tube waves and random pulses
Authors: Musielak, Z. E.; Ulmschneider, P.
2003A&A...400.1057M Altcode:
The response of exponentially spreading magnetic flux tubes embedded in
an isothermal solar atmosphere to the propagation of longitudinal tube
waves and random pulses produced in the solar convection zone is studied
analytically. General solutions are presented and applied to solar tube
models. It is shown that free atmospheric oscillations inside these
flux tubes are generated with oscillation periods near 3 min, which
are essentially identical to the oscillation periods observed in the
interior regions of supergranulation cells. The observed oscillations
are therefore consistent with processes in magnetic tubes as well as
in nonmagnetic regions. Stochastic perpetual excitation is expected
to keep these flux tube oscillations present at all times. These
oscillations are inconsistent with the observed 7-min oscillations in
the chromospheric network.
---------------------------------------------------------
Title: Mechanisms of Chromospheric and Coronal Heating (Invited
review)
Authors: Ulmschneider, P.; Musielak, Z.
2003ASPC..286..363U Altcode: 2003ctmf.conf..363U
No abstract at ADS
---------------------------------------------------------
Title: On the Generation of Flux-Tube Waves in Stellar Convection
Zones. IV. Longitudinal Wave Energy Spectra and Fluxes for Stars
with Nonsolar Metallicities
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
2002ApJ...573..418M Altcode:
In the previous papers of this series, we developed an analytical
method describing the generation of longitudinal tube waves in
stellar convection zones and used it to compute the wave energy
spectra and fluxes for late-type stars with the solar metal abundance
(Population I). We now extend these calculations to Population II
stars with effective temperatures ranging from T<SUB>eff</SUB>=2500
to 10,000 K, gravities logg=3-5, and with three different metal
abundances: 1/10, 1/100, and 1/1000 of solar metallicity. The obtained
results are valid for a single magnetic flux, and they show that
the effects of metallicity are important only for cool stars with
T<SUB>eff</SUB><6000 K and that the amount of the generated wave
energy decreases roughly by an order of magnitude for every decrease
of the metallicity by an order of magnitude. The maximum wave energy
flux generated in Population II stars is 7×10<SUP>8</SUP> ergs
cm<SUP>-2</SUP> s<SUP>-1</SUP>, and it is practically the same for
stars of different gravities and metallicities. The computed spectra
and fluxes can be used to construct theoretical models of magnetic
regions in chromospheres of Population II stars.
---------------------------------------------------------
Title: Orbital Stability of Terrestrial Planets inside the Habitable
Zones of Extrasolar Planetary Systems
Authors: Noble, M.; Musielak, Z. E.; Cuntz, M.
2002ApJ...572.1024N Altcode:
We investigate orbital stability of terrestrial planets inside the
habitable zones of three stellar systems, i.e., 51 Peg, 47 UMa, and
HD 210277, with recently discovered giant planets. These systems have
similar habitable zones; however, their giant planets have different
masses and significantly different orbital parameters. It is shown that
stable orbits of terrestrial planets exist in the entire habitable
zone of 51 Peg as well as in the inner part of the habitable zone of
47 UMa, but no stable orbits are found in the habitable zone of HD
210277. The obtained results allow us to draw general conclusions on
the existence of stable orbits in the habitable zones of newly found
extra-solar planetary systems.
---------------------------------------------------------
Title: Acoustic and magnetic wave heating in stars . I. Theoretical
chromospheric models and emerging radiative fluxes
Authors: Fawzy, D.; Rammacher, W.; Ulmschneider, P.; Musielak, Z. E.;
Stȩpień, K.
2002A&A...386..971F Altcode:
We describe a method to construct theoretical, time-dependent,
two-component and wave heated chromosphere models for late-type
dwarfs. The models depend only on four basic stellar parameters:
effective temperature, gravity, metallicity and filling factor, which
determines the coverage of these stars by surface magnetic fields. They
consist of non-magnetic regions heated by acoustic waves and vertically
oriented magnetic flux tubes heated by longitudinal tube waves with
contributions from transverse tube waves. Acoustic, longitudinal
and transverse wave energy spectra and fluxes generated in stellar
convection zones are computed and used as input parameters for the
theoretical models. The waves are allowed to propagate and heat both
components by shock dissipation. We compute the time-dependent energy
balance between the dissipated wave energy and the most prominent
chromospheric radiative losses as function of height in the stellar
atmosphere. For the flux tube covered stars, the emerging radiative
fluxes in the Ca II and Mg II lines are computed by using a newly
developed multi-ray radiative transfer method.
---------------------------------------------------------
Title: Torsional Tube Waves in the Solar Atmosphere
Authors: Noble, M.; Musielak, Z. E.
2002AAS...200.8803N Altcode: 2002BAAS...34..789N
Recent results presented by Ulmschneider et al. (2001) imply that
the energy carried by acoustic waves and magnetic (longitudinal and
transverse) tube waves from the solar convection zone to the solar
atmosphere is insufficient to heat the uppermost chromospheric layers,
the transition region and corona. Since torsional tube waves are not
included in their study, we have developed a theory of generation
of these waves in the solar convection zone and use it to compute
the resulting wave energy spectra and fluxes. We show the dependence
of these spectra and fluxes on the strength of the magnetic field and
various models of the solar convection zone, and discuss the role played
by torsional tube waves in the heating of different layers of the solar
atmosphere. This work is supported by NSF under grant ATM-0087184,
NATO under grant CRG-910058 and The Alexander von Humboldt Foundation.
---------------------------------------------------------
Title: Excitation of transverse magnetic tube waves in stellar
convection zones. II. Wave energy spectra and fluxes
Authors: Musielak, Z. E.; Ulmschneider, P.
2002A&A...386..606M Altcode:
The wave energy spectra and fluxes for transverse magnetic tube
waves generated in stellar convection zones are computed by using the
analytical method developed in the previous paper of this series. The
main physical process responsible for the generation of these waves is
shaking of a thin and vertically oriented magnetic flux tube by the
external turbulent convection. The approach includes the correlation
effects, which occur when the tube is shaken over a significant fraction
of its length, but is limited to linear waves. The calculations are
performed for population I stars with effective temperatures ranging
from T<SUB>eff</SUB> = 2000 K to 10 000 K, and with gravities log g =
3-5. It is shown that the fluxes carried by linear transverse waves
along a single flux tube are approximately one order of magnitude
higher than those carried by linear longitudinal tube waves. The
obtained results can be used to construct theoretical models of stellar
chromospheres and winds.
---------------------------------------------------------
Title: Excitation of transverse magnetic tube waves in stellar
convection zones . III. Effects of metallicity on wave energy spectra
and fluxes
Authors: Musielak, Z. E.; Ulmschneider, P.
2002A&A...386..615M Altcode:
In the previous two papers of this series, we developed an analytical
method describing the generation of transverse tube waves in stellar
convection zones and used it to compute the wave energy spectra and
fluxes for late-type stars with the solar metal abundance (population
I stars). We now extend these calculations to population II stars
with effective temperatures ranging from T<SUB>eff</SUB> = 2500 K
to 10 000 K, gravities log g = 3 - 5, and with three different metal
abundances: 1/10, 1/100 and 1/1000 of solar metallicity. The obtained
results are valid only for a single magnetic flux tube and they show
that the effects of metallicity are important only for cool stars with
T<SUB>eff</SUB> < 6000 K and that the amount of the generated wave
energy decreases roughly by an order of magnitude for every decrease
of the metallicity by an order of magnitude. The maximum wave energy
flux generated in population II stars is 3 x 10<SUP>9</SUP> erg
cm<SUP>-2</SUP> s<SUP>-1</SUP> and it is practically the same for
stars of different gravities and metallicities.
---------------------------------------------------------
Title: Chromospheric Heating
Authors: Musielak, Z. E.
2002AAS...200.5302M Altcode: 2002BAAS...34..729M
It is now well-established that the Sun and all other late-type stars
show chromospheric activity, which is typically identified with
the presence of emission in the cores of Ca II and Mg II spectral
lines. This activity varies significantly for a given spectral type
and a star is more active when a larger portion of its surface is
covered by magnetic fields. For stars of very low activity, a minimum
core emission flux ("basal flux") has been observed. To explain the
required heating and the observed range of activity, two classes of
heating mechanisms have been considered: (1) dissipation of acoustic
and magnetic waves generated in stellar convection zones; and (2)
dissipation of currents generated by photospheric motions of surface
magnetic fields. I will review both classes of heating mechanisms and
discuss recent results which demonstrate that theoretical models of
stellar chromospheres based on the wave heating (1) can explain the
"basal flux" and the observed Ca II emission in most stars but cannot
account for the observed Mg II emission in active stars. I will also
present theoretical arguments which imply that the base of stellar
chromospheres is heated by acoustic waves, the heating of the middle
and upper chromospheric layers is dominated by magnetic waves associated
with magnetic flux tubes, and that other non-wave (2) heating mechanisms
are required to explain the structure of the highest layers of stellar
chromospheres in active stars. This work was supported by NSF under
grant ATM-0087184, NATO under grant CRG-910058 and The Alexander von
Humboldt Foundation.
---------------------------------------------------------
Title: Acoustic and magnetic wave heating in stars . II. On the
range of chromospheric activity
Authors: Fawzy, D.; Ulmschneider, P.; Stȩpień, K.; Musielak, Z. E.;
Rammacher, W.
2002A&A...386..983F Altcode:
In the first paper of this series we developed a method to construct
theoretical, time-dependent and two-component chromosphere models
for late-type main sequence stars. The models consist of non-magnetic
regions heated by acoustic waves and magnetic flux tube regions heated
by magnetic tube waves. By specifying the magnetic filling factor,
theoretical models of stellar atmospheres with different chromospheric
activity can be calculated. Here, these models are used to simulate the
emerging Ca II and Mg II chromospheric emission fluxes and compare them
with observations. The comparison shows that the wave heating alone
can explain most but not all of the observed range of chromospheric
activity. In addition, the results obtained clearly imply that the base
of stellar chromospheres is heated by acoustic waves, the heating of
the middle and upper chromospheric layers is dominated by magnetic
waves associated with magnetic flux tubes, and that other non-wave
(e.g., reconnective) heating mechanisms are required to explain the
structure of the highest layers of stellar chromospheres.
---------------------------------------------------------
Title: Acoustic and magnetic wave heating in stars . III. The
chromospheric emission-magnetic filling factor relation
Authors: Fawzy, D.; Stȩpień, K.; Ulmschneider, P.; Rammacher, W.;
Musielak, Z. E.
2002A&A...386..994F Altcode:
Theoretical chromospheric models described in the two previous
papers of this series are used to study the relationship between the
chromospheric emission and the filling factor. This theoretically
determined relationship shows that the chromospheric emission flux
in Ca II (H+K) is approximately proportional to the square root of
the magnetic filling factor at the stellar surface. To relate the
filling factor to stellar rotation rate, we compare the theoretical
fluxes with observations of stars with known rotation period. The
comparison shows that the Rossby number is probably a more appropriate
measure of the rotation influence on activity of main-sequence stars
than the rotation period. Our theoretical Mg II (h+k) and Ca II (H+K)
emission fluxes are also found to be well correlated, which is in a
good agreement with the observational data.
---------------------------------------------------------
Title: Main Heating Mechanisms in Stellar Atmospheres
Authors: Musielak, Z. E.; Fawzy, D.; Ulmschneider, P.; Rammacher,
W.; Stepien, K.
2001AAS...19914302M Altcode: 2001BAAS...33.1522M
To identify the main heating mechanisms operating in atmospheres of
late-type stars, we have constructed purely theoretical, two-component
and time-dependent models of stellar chromospheres. Our models depend
only on four basic stellar parameters: effective temperature, gravity,
metallicity, and filling factor, which determines the coverage of
these stars by surface magnetic fields and is treated as a free
parameter. They consist of non-magnetic regions heated by acoustic
waves and magnetic flux tubes heated by longitudinal and transverse
tube waves. At each height in stellar atmospheres, the time-dependent
energy balance between the dissipated wave energy and the most prominent
radiative losses is calculated. By specifying the filling factor,
theoretical models of stellar atmospheres with different chromospheric
activity are computed. We have used these models to simulate the
emerging Ca II and Mg II chromospheric emission fluxes and compare them
with observations. The comparison shows that the wave heating alone
can explain most but not all of the observed range of chromospheric
activity. In addition, the obtained results clearly imply that the base
of stellar chromospheres is heated by acoustic waves, the heating of the
middle and upper chromospheric layers is dominated by magnetic waves
associated with magnetic flux tubes, and that other non-wave (e.g.,
reconnective) heating mechanisms are required to explain the structure
of the highest layers of stellar chromospheres. This work was supported
by NSF, NATO, DFG, KBN and The Alexander von Humboldt Foundation.
---------------------------------------------------------
Title: Orbital Stability of Earth-like Planets in Stellar Habitable
Zones
Authors: Noble, M.; Musielak, Z. E.; Cuntz, M.
2001AAS...199.0310N Altcode: 2001BAAS...33.1304N
Long-term orbital stability of Earth-like planets in stellar habitable
zones (HZs) is necessary for the evolution of any form of life. It is
then interesting to ask whether Earth-like planets can exist in stable
orbits around single stars with giant planets and in multiple stellar
systems? The main conclusion from previous studies is that orbits
of terrestrial planets in the HZs of 70 Vir, ρ CrB and 47 UMa are
stable over the length of time required for the biological evolution,
however, no long-term stability was found for Gl 876 and υ And. We
have investigated orbital stability of terrestrial planets inside the
HZs of three stellar systems, 51 Peg, 47 UMa and HD 210277, with known
giant planets. The chosen systems have similar HZs, however, their
planets have significantly different masses and orbital parameters. It
is shown that stable orbits of terrestrial planets exist in the entire
HZ of 51 Peg and in the inner part of the HZ of 47 UMa, but no stable
orbits are found in the HZ of HD 210277. In addition, we have studied
stability of orbits of Earth-like planets in one binary system (ζ
Her) and in one triple system (ξ UMa). The obtained results allow us
to draw general conclusions on the existence of stable orbits in the
HZs of newly detected extra-solar planetary systems. This work was
supported by NSF, NATO and The Alexander von Humboldt Foundation.
---------------------------------------------------------
Title: Habitability and Orbital Stability of Terrestrial Planets
around 47 UMa
Authors: Cuntz, M.; Noble, M.; Musielak, Z. E.
2001AAS...199.3305C Altcode: 2001BAAS...33R1356C
We investigate the orbital stability and habitability of terrestrial
planets around 47 UMa. This planetary system shows striking similarities
to the Solar System by hosting two Jupiter-mass planets in nearly
circular orbits at distances where respectable giant planets should
be present and with its inner region free of gas giants. Orbits of
terrestrial planets at different positions in the habitable zone (HZ)
of 47 UMa are simulated numerically taking into account an updated
definition of habitability. We show that habitable planets can in
principle exist in the inner part of the HZ of 47 UMa, but not in
its outer part owing to gravitational disturbances by the inner giant
planet. Our study, which has meanwhile been extended to other stars
as well, allows general conclusions about the existence of habitable
planets around host stars, which may assist in the selection process
of system candidates for future terrestrial planet search missions.
---------------------------------------------------------
Title: Wave Heating and Range of Stellar Activity in Late-Type Dwarfs
Authors: Ulmschneider, P.; Fawzy, D.; Musielak, Z. E.; Stępień, K.
2001ApJ...559L.167U Altcode:
Theoretical time-dependent and two-component chromospheric models for
late-type dwarfs are constructed based on acoustic and magnetic wave
heating mechanisms. The models are used to predict the theoretical range
of chromospheric activity for these stars. Comparison of this range with
the one established observationally shows that the wave heating alone
can explain most but not all of the observed range of stellar activity.
---------------------------------------------------------
Title: Magnetic wave energy fluxes for late-type
stars. I. Longitudinal tube waves
Authors: Ulmschneider, P.; Musielak, Z. E.; Fawzy, D. E.
2001A&A...374..662U Altcode:
The wave energy fluxes carried by longitudinal tube waves along thin
vertical magnetic flux tubes embedded in atmospheres of late-type
stars are computed. The main physical process responsible for the
generation of these waves is the nonlinear time-dependent response of
the flux tubes to continuous and impulsive external turbulent pressure
fluctuations, which are represented here by an extended Kolmogorov
spatial and modified Gaussian temporal energy spectrum. Both the wave
energy fluxes and spectra are calculated for population I stars with
effective temperatures ranging from T<SUB>eff</SUB> = 3500 K to 7000
K, and with gravities in the range log g = 3-5. The obtained results
show that the computed wave energy may significantly contribute to
the enhanced heating observed in magnetic regions of late-type stars.
---------------------------------------------------------
Title: Excitation of transverse magnetic tube waves in stellar
convection zones. I. Analytical approach
Authors: Musielak, Z. E.; Ulmschneider, P.
2001A&A...370..541M Altcode:
Analytical treatment of the excitation of transverse magnetic tube
waves in stellar convection zones is presented. The waves are produced
by the interaction between thin and vertically oriented magnetic flux
tubes embedded in stellar convection zones and the external turbulent
motions. A general theory describing this interaction is developed
and used to compute the wave energy spectra and fluxes for the Sun.
---------------------------------------------------------
Title: Self-Consistent Magnetic/Acoustic Chromosphere Models of
Late-Type Stars (CD-ROM Directory: contribs/cuntz1)
Authors: Cuntz, M.; Ulmschneider, P.; Rammacher, W.; Musielak, Z. E.;
Saar, S. H.
2001ASPC..223..913C Altcode: 2001csss...11..913C
No abstract at ADS
---------------------------------------------------------
Title: Analyzing the Effects of Planets and Brown Dwarfs on Stellar
Chromospheric and Coronal Activity (CD-ROM Directory: contribs/cuntz2)
Authors: Cuntz, M.; Musielak, Z. E.; Saar, S. H.
2001ASPC..223.1528C Altcode: 2001csss...11.1528C
No abstract at ADS
---------------------------------------------------------
Title: Time-dependent analytical solutions for MHD surface waves
propagating in a compressible plasma
Authors: Musielak, Z. E.; Huang, P.; Ulmschneider, P.
2000A&A...362..359M Altcode:
The propagation of linear MHD surface waves in a compressible plasma
with a discontinuous interface in the magnetic field and temperature
is considered. The initial perturbation is applied only to a vorticity
line, which is located on the RHS of the discontinuity. Two different
surface waves exist in this model, one associated with the vorticity
line and the other confined to the discontinuity. Time-dependent
analytical solutions for the wave velocity perturbations are obtained
for both surface waves by applying Laplace transforms. The solutions
are used to investigate the effects caused by compressibility on the
propagation of these waves. It is shown that the compressibility effects
are most important in the vicinity of the vorticity line and at the
magnetic interface, and that they affect differently the behavior of
the surface waves.
---------------------------------------------------------
Title: a Search for Coronal X-Rays from White Dwarfs by Chandra
Authors: Musielak, Zdzislaw
2000cxo..prop..541M Altcode: 2000chan.prop..410M; 2000cxo..prop..410M
Observations of DA and DB white dwarfs have not been successful in
detecting coronal X-ray emission, but observations of late-type dwarfs
and giants show that coronae are common for these stars. To produce
coronal X-rays, a star has to have a well-developed convection zone and
a dynamo-generated magnetic field. There is strong evidence that the
DB star GD 358 and the DA star LHS 1038 have weak and variable surface
magnetic fields. Theory suggests that these fields are generated by
dynamo action, and that both stars have well-developed convection
zones. These stars are among the most promising white dwarf candidates
for having coronal X-ray emission at level detectable by CHANDRA. Its
discovery would confirm the existence of a new class of objects with
convection-dynamo driven X-rays.
---------------------------------------------------------
Title: On the Generation of Flux-Tube Waves in Stellar Convection
Zones. III. Longitudinal Tube Wave-Energy Spectra and Fluxes for
Late-Type Stars
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
2000ApJ...541..410M Altcode:
The wave-energy spectra and fluxes for longitudinal tube waves
generated in stellar convection zones are computed by using analytical
methods developed in the two previous papers of this series. The main
physical process responsible for the generation of these waves is the
interaction between a thin and vertically oriented magnetic flux tube
and the external turbulent convection. The spatial component of the
turbulent convection is represented by an extended Kolmogorov turbulent
energy spectrum, and its temporal component by a modified Gaussian
frequency factor. The calculations are performed for Population I
stars with effective temperatures ranging from T<SUB>eff</SUB>=2000 K
to 10,000 K, and with gravities logg=3-5. The obtained results can be
used to construct theoretical models of magnetic regions in stellar
chromospheres.
---------------------------------------------------------
Title: On Stellar Activity Enhancement Due to Interactions with
Extrasolar Giant Planets
Authors: Cuntz, Manfred; Saar, Steven H.; Musielak, Zdzislaw E.
2000ApJ...533L.151C Altcode:
We present a first attempt to identify and quantify possible
interactions between recently discovered extrasolar giant planets
(and brown dwarfs) and their host stars, resulting in activity
enhancement in the stellar outer atmospheres. Many extrasolar planets
have masses comparable to or larger than Jupiter and are within a
distance of 0.5 AU, suggesting the possibility of their significant
influence on stellar winds, coronae, and even chromospheres. Beyond
the well-known rotational synchronization, the interactions include
tidal effects (in which enhanced flows and turbulence in the tidal
bulge lead to increased magnetoacoustic heating and dynamo action)
and direct magnetic interaction between the stellar and planetary
magnetic fields. We discuss relevant parameters for selected systems
and give preliminary estimates of the relative interaction strengths.
---------------------------------------------------------
Title: On the Origin and Evolution of Stellar Chromospheres, Coronae
and Winds
Authors: Musielak, Z. E.
2000STIN...0038209M Altcode:
This grant was awarded by NASA to The University of Alabama in
Huntsville (UAH) to construct state-of-the-art, theoretical,
two-component, chromospheric models for single stars of different
spectral types and different evolutionary status. In our proposal,
we suggested to use these models to predict the level of the "basal
flux", the observed range of variation of chromospheric activity for
a given spectral type, and the decrease of this activity with stellar
age. In addition, for red giants and supergiants, we also proposed
to construct self-consistent, purely theoretical wind models, and
used these models to investigate the origin of "dividing lines" in
the H-R diagram. In the following, we describe our completed work. We
have accomplished the first main goal of our proposal by constructing
first purely theoretical, time-dependent and two-component models of
stellar chromospheres.1 The models require specifying only three basic
stellar parameters, namely, the effective temperature, gravity and
rotation rate, and they take into account non-magnetic and magnetic
regions in stellar chromospheres. The non-magnetic regions are heated
by acoustic waves generated by the turbulent convection in the stellar
subphotospheric layers. The magnetic regions are identified with
magnetic flux tubes uniformly distributed over the entire stellar
surface and they are heated by longitudinal tube waves generated by
turbulent motions in the subphotospheric and photospheric layers. The
coverage of stellar surface by magnetic regions (the so-called filling
factor) is estimated for a given rotation rate from an observational
relationship. The constructed models are time-dependent and are based
on the energy balance between the amount of mechanical energy supplied
by waves and radiative losses in strong Ca II and Mg II emission
lines. To calculate the amount of wave energy in the non-magnetic
regions, we have used the Lighthill-Stein theory for sound generation.
---------------------------------------------------------
Title: Two-Component Theoretical Chromosphere Models for K Dwarfs
of Different Magnetic Activity: Exploring the Ca II Emission-Stellar
Rotation Relationship
Authors: Cuntz, M.; Rammacher, W.; Ulmschneider, P.; Musielak, Z. E.;
Saar, S. H.
1999ApJ...522.1053C Altcode:
We compute two-component theoretical chromosphere models for K2 V
stars with different levels of magnetic activity. The two components
are a nonmagnetic component heated by acoustic waves and a magnetic
component heated by longitudinal tube waves. The filling factor for the
magnetic component is determined from an observational relationship
between the measured magnetic area coverage and the stellar rotation
period. We consider stellar rotation periods between 10 and 40
days. We investigate two different geometrical distributions of
magnetic flux tubes: uniformly distributed tubes, and tubes arranged
as a chromospheric network embedded in the nonmagnetic region. The
chromosphere models are constructed by performing state-of-the-art
calculations for the generation of acoustic and magnetic energy in
stellar convection zones, the propagation and dissipation of this
energy at the different atmospheric heights, and the formation of
specific chromospheric emission lines that are then compared to the
observational data. In all these steps, the two-component structure of
stellar photospheres and chromospheres is fully taken into account. We
find that heating and chromospheric emission is significantly increased
in the magnetic component and is strongest in flux tubes that spread
the least with height, expected to occur on rapidly rotating stars with
high magnetic filling factors. For stars with very slow rotation, we
are able to reproduce the basal flux limit of chromospheric emission
previously identified with nonmagnetic regions. Most importantly,
however, we find that the relationship between the Ca II H+K emission
and the stellar rotation rate deduced from our models is consistent
with the relationship given by observations.
---------------------------------------------------------
Title: Acoustic wave energy fluxes for late-type stars. II. Nonsolar
metallicities
Authors: Ulmschneider, P.; Theurer, J.; Musielak, Z. E.; Kurucz, R.
1999A&A...347..243U Altcode:
Using the Lighthill-Stein theory with modifications described by
Musielak et al. (1994), the acoustic wave energy fluxes were computed
for late-type stars with the solar metal abundance (population I stars)
by Ulmschneider et al. (1996). We now extend these computations to
stars with considerably lower metal content (population II stars
with 1/10 to 1/1000 of solar metallicity) and find that the acoustic
fluxes calculated for stars of different spectral types and different
luminosities are affected differently by the metallicity. It is found
that the Hertzsprung-Russel diagram can be subdivided into three domains
(labeled I, II and III) representing a different dependence of the
generated acoustic fluxes on the stellar metal abundance. For the
high T_eff stars of domain I there is no dependence of the generated
acoustic fluxes on metallicity. In domain III are stars with low
T_eff. Here the generated acoustic fluxes are lowered roughly by an
order of magnitude for every decrease of the metal content by an order
of magnitude. Finally, domain II represents the transition between the
other two domains and the generated acoustic fluxes strongly depend
on T_eff. The boundaries between the domains I and II, and II and
III can be defined by simple relationships between stellar effective
temperatures and gravities.
---------------------------------------------------------
Title: Numerical simulations of nonlinear MHD body and surface waves
in magnetic slabs
Authors: Huang, P.; Musielak, Z. E.; Ulmschneider, P.
1999A&A...342..300H Altcode:
The behavior of MHD waves propagating in magnetically structured plasmas
has been extensively investigated in the literature. In most of these
studies, the wave treatment was restricted to the linear regime. This
paper presents the results of time-dependent and nonlinear numerical
simulations of MHD body and surface waves propagating along magnetic
slabs. Both longitudinal and transverse waves are computed, and the wave
behavior in the linear and nonlinear regime is compared. Two physical
processes are investigated in detail. The first is the energy leakage
from the magnetic slab to the field-free external medium. It is found
that the energy leakage is 62% for transverse slab waves, which means
that the efficiency of energy transfer along the slab by these waves
is significantly reduced. The second process is the excitation of MHD
waves in two adjacent magnetic slabs by large amplitude acoustic waves
from the external medium. The slabs have physical parameters typical
for photospheric magnetic flux tubes. It is shown that only 1-3%
of the energy carried by these acoustic waves is transferred to the
slabs, and that the efficiency of this process strongly depends on the
location of the slabs relative to the source of acoustic waves and on
the amplitude of these waves. Both physical processes are important
for the problem of heating of magnetically structured regions in the
solar and stellar atmospheres.
---------------------------------------------------------
Title: The Generation of Longitudinal Tube Waves in Late Type Stars
Authors: Fawzy, D. E.; Musielak, Z. E.; Ulmschneider, P.
1999RoAJ....9S.149F Altcode:
The aim of the present work is to compute the generated nonlinear
tube wave energy fluxes carried by longitudinal waves as a result of
the interaction between a vertically directed thin magnetic flux tube
and the turbulent medium in the stellar convection zone of late type
stars. The computations are based on work by Ulmschneider and Musielak
(1998). The current computations are for stars of gravities log g =
3,4,5 and temperature range from Teff = 3500 to 7000 K.
---------------------------------------------------------
Title: Acoustic wave propagation in the solar
atmosphere. III. Analytic solutions for adiabatic wave excitations
Authors: Sutmann, G.; Musielak, Z. E.; Ulmschneider, P.
1998A&A...340..556S Altcode:
The response of an isothermal solar type atmosphere to adiabatic
excitations by various small amplitude acoustic disturbances is studied
analytically. Both continuous and pulse excitations are discussed. It
is shown that wavetrains of random pulses may be responsible for the
excitation of the 3-min solar oscillations.
---------------------------------------------------------
Title: Theoretical Models of Stellar Chromospheres
Authors: Musielak, Z. E.; Cuntz, M.; Ulmschneider, P.
1998AAS...193.2204M Altcode: 1998BAAS...30.1283M
To identify the basic physical processes that underlie stellar
chromospheric activity, we have taken a novel theoretical approach and
constructed first purely theoretical, two-component and time-dependent
models of stellar chromospheres. Our models require specifying only four
basic stellar parameters, namely, the effective temperature, gravity,
metallicity and rotation rate, and they take into account non-magnetic
and magnetic regions in stellar chromospheres. The non-magnetic regions
are heated by acoustic waves generated by the turbulent convection in
the stellar subphotospheric layers. The magnetic regions are identified
with magnetic flux tubes uniformly distributed over the entire
stellar surface and are heated by longitudinal tube waves generated by
turbulent motions in the subphotospheric and photospheric layers. The
coverage of stellar surface by magnetic regions (the so-called filling
factor) is estimated for a given rotation rate from an observational
relationship. The constructed models are based on the energy balance
between the amount of mechanical energy supplied by waves and radiative
losses in strong Ca II and Mg II emission lines. We have already
used our chromospheric models to predict the level of “basal flux”
and the decrease of chromospheric activity with stellar rotation in
selected late-type dwarfs. We present these new results and discuss how
to include stellar transition regions, coronae and winds in our models.
---------------------------------------------------------
Title: On Wave Processes in the Solar Atmosphere
Authors: Musielak, Z. E.
1998STIN...9945903M Altcode:
This grant was awarded by NASA/MSFC to The University of Alabama in
Huntsville (UAH) to investigate the physical processes responsible for
heating and wind acceleration in the solar atmosphere, and to construct
theoretical, self-consistent and time-dependent solar wind models
based on the momentum deposition by finite amplitude and nonlinear
Alfven waves. In summary, there are three main goals of the proposed
research: (1) Calculate the wave energy spectra and wave energy
fluxes carried by magnetic non- magnetic waves. (2) Find out which
mechanism dominates in supplying the wave energy to different parts
of the solar atmosphere. (3) Use the results obtained in (1) and (2)
to construct theoretical, self-consistent and time- dependent models
of the solar wind. We have completed the first goal by calculating the
amount of non-radiative energy generated in the solar convection zone
as acoustic waves and as magnetic tube waves. To calculate the amount of
wave energy carried by acoustic waves, we have used the Lighthill-Stein
theory for sound generation modified by Musielak, Rosner, Stein &
Ulmschneider (1994). The acoustic wave energy fluxes for stars located
in different regions of the Hertzsprung-Russell (H-R) diagram have
also been computed. The wave energy fluxes carried by longitudinal and
transverse waves along magnetic flux tubes have been calculated by using
both analytical and numerical methods. Our analytical approach is based
a theory developed by Musielak, Rosner & Ulmschnelder and Musielak,
Rosner, Gall & Ulmschneider, which allows computing the wave energy
fluxes for linear tube waves. A numerical approach has been developed
by Huang, Musielak & Ulmschneider and Ulmschneider & Musielak
to compute the energy fluxes for nonlinear tube waves. Both methods
have been used to calculate the wave energy fluxes for stars located in
different regions of the HR diagram (Musielak, Rosner & Ulmschneider
1998; Ulmschneider, Musielak & Fawzy 1998). Having obtained the wave
energy fluxes for acoustic and magnetic tube waves, we have investigated
the behavior of these waves in the solar and stellar atmospheres. The
results of our extensive studies have been published in many papers
and presented at numerous scientific meetings. In these studies we have
investigated different aspects of propagation of acoustic and magnetic
waves, the efficiency of energy transfer along magnetic structures
in the solar atmosphere, and behavior of Alfven waves in stgeady and
expanding solar and stellar atmospheres. Recently, we have used some
of these results to construct first purely theoretical, two component
and time-dependent models of solar and stellar chromospheres. Finally,
to address the third goal, we have constructed first fully theoretical,
self-consistent and time dependent wind models based on the momentum
deposition by non-linear Alfven waves. The full set of single-fluid MHD
equations with the background flow has been solved by using a modified
version of the ZEUS MHD code. The constructed wind models are radially
symmetric with the magnetic field decreasing radially and the initial
outflow is described by the standard Parker wind solution. In contrast
to previous studies, no assumptions regarding wave linearity, wave
damping, and wave-flow interaction are made; the models thus naturally
account for the backreaction of the wind on the waves as well as for
the nonlinear interaction between different types of MHD waves. The
models have been used to explain the origin of fast speed streams in
solar coronal holes. The obtained results clearly demonstrate that the
momentum deposition by Alfven waves in the solar wind can be sufficient
to explain the origin of fast stream components of the solar wind. The
range of wave amplitudes required to obtain the desired results seems
to be in good agreement with recent observations.
---------------------------------------------------------
Title: Two-Component Chromosphere Models for K Dwarf Stars: The
Chromospheric Emission --- Stellar Rotation Relationship
Authors: Cuntz, M.; Musielak, Z. E.; Ulmschneider, P.; Rammacher,
W.; Saar, S. H.
1998AAS...193.4402C Altcode: 1998BAAS...30.1315C
We present two-component theoretical chromosphere models for K dwarf
stars with different levels of magnetic activity. The two components
are: a nonmagnetic component heated by acoustic waves, and a magnetic
component heated by longitudinal tube waves. The filling factor for
the magnetic component is determined from an observational relationship
between the stellar rotation rate and the measured coverage of stellar
surface by magnetic fields. The chromosphere models are constructed by
performing state-of-the-art calculations of the generation of acoustic
and magnetic energy in stellar convection zones, the propagation and
dissipation of this energy at the different atmospheric heights,
and the formation of specific chromospheric emission lines, which
are then compared to the observational data. In all these steps, the
two-component structure of stellar photospheres and chromospheres is
fully taken into account. We find that due to the presence of magnetic
flux tubes, the heating and chromospheric emission is significantly
increased in the magnetic component. The heating and chromospheric
emission is found to be the strongest in flux tubes with small
spreading factors which are expected to be present in fast rotating
stars. For stars with very slow rotation we are able to reproduce
the basal flux limit of chromospheric emission previously identified
as due to pure acoustic heating. Most importantly, however, we find
that the relationship between the Ca II H+K emission and the stellar
rotation rate deduced from our models is consistent with the empirical
relationship given by observations.
---------------------------------------------------------
Title: On the generation of nonlinear magnetic tube waves in the
solar atmosphere. II. Longitudinal tube waves
Authors: Ulmschneider, P.; Musielak, Z. E.
1998A&A...338..311U Altcode:
The nonlinear time-dependent response to external pressure fluctuations
acting on a thin vertical magnetic flux tube embedded in the solar
atmosphere is investigated numerically. The continuous and impulsive
fluctuations are imposed on the tube at different atmospheric heights
and the resulting longitudinal tube wave energy fluxes are calculated
for an observationally established range of velocity amplitudes and
tube magnetic fields. The obtained results show that typical wave
energy fluxes carried by nonlinear longitudinal tube waves are of the
order of 2*10(8) erg/cm(2) s, which is roughly a factor of 30 less than
the flux for transverse waves. In contrast to our linear analytical
results the generated nonlinear longitudinal tube wave fluxes can be
up to an order of magnitude higher.
---------------------------------------------------------
Title: Self-Consistent and Time-Dependent Magnetohydrodynamic
Chromosphere Models for Magnetically Active Stars
Authors: Cuntz, Manfred; Ulmschneider, Peter; Musielak, Zdzislaw E.
1998ApJ...493L.117C Altcode:
We present self-consistent and time-dependent MHD heating models
for chromospheres of magnetically active stars. We investigate the
propagation and dissipation of longitudinal flux-tube waves in K2 V
stars with different rotation rates implying different photospheric
and chromospheric magnetic filling factors. These filling factors
are critical for determining the number of flux tubes on the stellar
surface and the spreading of the tubes with height, which is relevant
for the propagation and dissipation of the magnetic energy as well as
the generated radiative emission losses. The filling factors used in
this Letter are estimated using a relationship between the photospheric
values for B<SUB>0</SUB>f<SUB>0</SUB> and P<SUB>rot</SUB> in accord
with very recent magnetic field measurements by Rüedi et al. We also
consider revised computations of magnetic energy fluxes by Ulmschneider
& Musielak generated by turbulent motions. Our models show increased
shock strengths and energy dissipation rates in stars of faster rotation
because of the narrower spreading of the tubes. This also leads to
increased chromospheric emission, particularly in Mg II in stars of
faster rotation. We consider these results as a first step toward a
theoretical derivation of chromospheric emission--stellar rotation
relationships for stars of different masses and evolutionary status.
---------------------------------------------------------
Title: Reflection Coefficient and Non-WKB Effects for Alfven Waves
Propagating in the Solar Wind
Authors: Krogulec, M.; Musielak, Z. E.
1998AcA....48...77K Altcode:
The propagation of Alfven waves in spherically symmetric, isothermal
solar wind models with two different temperatures T_0=2.85 times 10^6
K and T_0=8.2 times 10^5 K is considered. The steady-state Alfven
wave equations are solved numerically and the resulting reflection
coefficient and non-WKB effects are calculated. The obtained results
show that the reflection coefficient is practically zero in the
high-temperature wind model, where wave reflection and non-WKB
effects are essentially absent, and that it can also be zero in the
low-temperature model, where wave reflection and non-WKB effects are
present. A physical explanation of these results is given.
---------------------------------------------------------
Title: MHD Waves and Turbulence in the Solar Wind
Authors: Musielak, Z. E.
1998asct.conf..339M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Acoustic and MHD Wave Energy Fluxes for Late-Type Stars
Authors: Musielak, Z. E.; Cuntz, M.; Ulmschneider, P.; Theurer, J.;
Kurucz, R.
1997AAS...191.1206M Altcode: 1997BAAS...29.1228M
The vast amount of observational data collected at wavelengths
ranging from X-rays to radio waves have indicated the ubiquity of
stellar chromospheres among late-type stars. In addition, there is
growing observational evidence for inhomogeneous and locally strong
magnetic fields in stellar atmospheres. It is reasonable to assume that
stellar magnetic inhomogeneities may be similar to the `flux tube'
structures observed in the solar atmosphere outside sunspots. If so,
two distinct components of stellar chromospheres must be recognized,
namely, non-magnetic component, where acoustic waves are responsible
for the heating, and magnetic component, where MHD tube waves supply
energy for the heating. To construct theoretical models of stellar
chromospheres (see paper by Cuntz et al. presented at this meeting),
it is necessary to know the amount of non-radiative energy generated
in stellar convective zones and carried by acoustic and MHD tube
waves through stellar photospheres. In this paper, we discuss the
correct status of computing acoustic and MHD wave energy fluxes for
the Sun and late-type dwarfs. Our calculations are based on grey LTE
mixing-length convection zone models and both linear and non-linear
theories of wave generation are used. New acoustic and MHD wave
energy fluxes are presented for stars of population I and II in the
range of effective temperatures T_eff 2000 - 10000 K and gravities
log g = 1 - 8. The turbulent flow field is represented by an extended
Kolmogorov spatial and modified Gaussian temporal energy spectrum. The
mixing-length parameter is varied in the range alpha = 1 - 2. We find
that the obtained acoustic wave energy strongly depend on stellar
chemical composition and that MHD fluxes show wide variations for a
given spectral type, variations which can be attributed to changes
in the stellar flux tube filling factor. We discuss the range of the
filling factor for which the calculated MHD fluxes may account for
the observed levels of chromospheric activity.
---------------------------------------------------------
Title: Self-Consistent and Time-Dependent MHD Heating Models for
Chromospheres of Magnetically Active Stars
Authors: Cuntz, M.; Musielak, Z. E.; Ulmschneider, P.
1997AAS...191.1205C Altcode: 1997BAAS...29.1228C
We present self-consistent and time-dependent MHD heating models
for chromospheres of magnetically active stars. We investigate the
propagation and dissipation of longitudinal flux tube waves in K2V
stars with different rotation rates implying different photospheric
and chromospheric magnetic filling factors. These filling factors are
critical for determining the number of flux tubes on the stellar surface
and the spreading of the tubes with height, which is relevant for the
propagation and dissipation of the magnetic energy. The photospheric
filling factors are estimated using a relationship between the magnetic
field strength B_o multiplied by the photospheric magnetic filling
factor f_o and the stellar rotation P_rot in accord with very recent
magnetic field measurements. We also consider revised computations
for the initial magnetic energy fluxes generated by turbulent motions
(Ulmschneider & Musielak 1997, A&A, submitted). Our models
show increased shock strengths and energy dissipation rates in stars of
faster rotation due to the narrower spreading of the tubes. This also
leads to increased chromospheric emission particularly in Mg II in stars
of faster rotation. We consider these results as a first step toward a
theoretical derivation of chromospheric emission --- stellar rotation
relations for stars of different masses and evolutionary status.
---------------------------------------------------------
Title: On the Origin and Evolution of Stellar Chromospheres, Coronae
and Winds
Authors: Musielak, Z. E.
1997STIN...9731037M Altcode:
The final report discusses work completed on proposals to construct
state-of-the-art, theoretical, two-component, chromospheric models for
single stars of different spectral types and different evolutionary
status. We suggested to use these models to predict the level of
the "basal flux", the observed range of variation of chromospheric
activity for a given spectral type, and the decrease of this activity
with stellar age. In addition, for red giants and supergiants,
we also proposed to construct self-consistent, purely theoretical,
chromosphere-wind models, and investigate the origin of "dividing
lines" in the H-R diagram. In the report, we list the following
six specific goals for the first and second year of the proposed
research and then describe the completed work: (1) To calculate
the acoustic and magnetic wave energy fluxes for stars located in
different regions of the H-R diagram; (2) To investigate the transfer
of this non-radiative energy through stellar photospheres and to
estimate the amount of energy that reaches the chromosphere; (3) To
identify major sources of radiative losses in stellar chromospheres
and calculate the amount of emitted energy; (4) To use (1) through (3)
to construct purely theoretical, two-component, chromospheric models
based on the local energy balance. The models will be constructed for
stars of different spectral types and different evolutionary status;
(5) To explain theoretically the "basal flux", the location of stellar
temperature minima and the observed range of chromospheric activity for
stars of the same spectral type; and (6) To construct self-consistent,
time-dependent stellar wind models based on the momentum deposition
by finite amplitude Alfven waves.
---------------------------------------------------------
Title: A Study of Magnetic Complexity Using HURST`S Rescaled Range
Analysis
Authors: Adams, M.; Hathaway, D. H.; Stark, B. A.; Musielak, Z. E.
1997SoPh..174..341A Altcode:
A fractal analysis using the classical Hurst method has been
applied to artificial data, simulated sunspot magnetic field data,
and to data acquired with NASA/Marshall Space Flight Center's
vector magnetograph. The main goals of this study are to quantify
the complexity of an active region and to determine if significant
changes in complexity are associated with flare activity. We tested the
analysis using three basic types of two-dimensional synthetic data: (1)
data composed of gaussians with various types of superimposed features,
(2) random data, and (3) synthetic sunspots created from a basic, simple
configuration on which are placed increasingly smaller structures. Our
results confirm that the Hurst method of analysis is sensitive to the
presence of large-scale structures within a two-dimensional image. When
the large-scale structure has been removed, the value of the Hurst
exponent is inversely proportional to increasing complexity in the
image. The Hurst exponent of magnetograph data with the large-scale
structure of the sunspot removed, shows a tantalizing variation in
the shear parameter five minutes prior to a flare.
---------------------------------------------------------
Title: Self-consistent and Time-dependent Solar Wind Models
Authors: Ong, K. K.; Musielak, Z. E.; Rosner, R.; Suess, S. T.;
Sulkanen, M. E.
1997ApJ...474L.143O Altcode:
We describe the first results from a self-consistent study of Alfvén
waves for the time-dependent, single-fluid magnetohydrodynamic (MHD)
solar wind equations, using a modified version of the ZEUS MHD code. The
wind models we examine are radially symmetrical and magnetized; the
initial outflow is described by the standard Parker wind solution. Our
study focuses on the effects of Alfvén waves on the outflow and is
based on solving the full set of the ideal nonlinear MHD equations. In
contrast to previous studies, no assumptions regarding wave linearity,
wave damping, and wave-flow interaction are made; thus, the models
naturally account for the back-reaction of the wind on the waves,
as well as for the nonlinear interaction between different types of
MHD waves. Our results clearly demonstrate when momentum deposition
by Alfvén waves in the solar wind can be sufficient to explain the
origin of fast streams in solar coronal holes; we discuss the range
of wave amplitudes required to obtained such fast stream solutions.
---------------------------------------------------------
Title: Acoustic wave energy fluxes for late-type stars.
Authors: Ulmschneider, P.; Theurer, J.; Musielak, Z. E.
1996A&A...315..212U Altcode:
We revisit the problem of acoustic wave generation by turbulent
convection in late-type stellar atmospheres. Using the Lighthill-Stein
theory with modifications described in our recent paper Musielak
et al. (1994ApJ...423..474M), we compute both acoustic frequency
spectra and total acoustic fluxes on basis of grey LTE mixing-length
convection zone models for population I stars, in the range of effective
temperatures T_eff_=2000-10000K and gravities logg=0-8. The turbulent
flow field is represented by an extended Kolmogorov spatial and modified
Gaussian temporal energy spectrum. The mixing-length parameter was
varied in the range α=1-2. Particularly for M-dwarf stars we find large
discrepancies between our fluxes and those of Bohn (1981 (Ph.D. Thesis,
Univ. Wuerzburg, Germany), 1984A&A...130..202B). Except for very
cool dwarf stars our total fluxes are well reproduced by the simple
Lighthill-Proudmann formula already developed in the 1950's.
---------------------------------------------------------
Title: Alfvén wave resonances and flow induced by nonlinear Alfvén
waves in a stratified atmosphere
Authors: Stark, B. A.; Musielak, Z. E.; Suess, S. T.
1996AIPC..382..153S Altcode:
A nonlinear, time-dependent, ideal MHD code has been developed and used
to compute the flow induced by nonlinear Alfvén waves propagating
in an isothermal, stratified, plane-parallel atmosphere. The code is
based on characteristic equations solved in a Lagrangian frame. Results
show that resonance behavior of Alfvén waves exists in the presence
of a continuous density gradient and that the waves with periods
corresponding to resonant peaks exert considerably more force on
the medium than off-resonance periods. If only off-peak periods are
considered, the relationship between the wave period and induced
longitudinal velocity shows that short period WKB waves push more on
the background medium than longer period, non-WKB, waves. The results
also show the development of the longitudinal waves induced by finite
amplitude Alfvén waves. Wave energy transferred to the longitudinal
mode may provide a source of localized heating.
---------------------------------------------------------
Title: On Complexity of Solar Magnetic Fields
Authors: Musielak, Z. E.
1996alab.rept.....M Altcode:
Observational data collected by solar magnetographs from different
places around the world seem to clearly indicate that the onset of
flares is related to the structure of sunspot magnetic fields. The
simple, but not necessarily always valid, rule is that the more complex
the structure of the field the more flares are produced. Until now,
estimates of the magnetic field complexity were mostly subjective. An
important problem is how to quantify the field complexity by using
rigorous methods of data analysis. In the completed research we have
used several fractal techniques to address the problem. We have adopted
the well=-known concept of fractal dimension, to quantify the field
complexity and to search for temporal variations of this complexity. We
have calculated the fractal dimension for a chosen magnetic field
data set acquired by the NASA/MSFC vector magnetograph and searched
for temporal changes in the computed fractal dimension which may be
related to the onset of solar flares. The analysis was performed on
magnetic field data collected from solar active regions that showed
different levels of flare activity as well as from non-flaring regions.
---------------------------------------------------------
Title: Propagation of MHD Body and Surface Waves in Magnetically
Structured Regions of the Solar Atmosphere
Authors: Wu, S. T.; Xiao, Y. C.; Musielak, Z. E.; Suess, S. T.
1996SoPh..163..291W Altcode:
The fact that magnetically structured regions exist in the solar
atmosphere has been known for a number of years. It has been suggested
that different kinds of magnetohydrodynamic (MHD) waves can be
efficiently damped in these regions and that the dissipated wave
energy may be responsible for the observed enhancement in radiative
losses. From a theoretical point of view, an important task would be
to investigate the propagation and dissipation of MHD waves in these
highly structured regions of the solar atmosphere. In this paper,
we study the behavior of MHD body and surface waves in a medium
with either a single or double (slab) magnetic interface by use of
a nonlinear, two-dimensional, time-dependent, ideal MHD numerical
model constructed on the basis of a Lagrangean grid and semi-implicit
scheme. The processes of wave confinement and wave energy leakage
are discussed in detail. It is shown that the obtained results depend
strongly on the type of perturbations imposed on the interface or slab
and on the plasma parameter, β. The relevance of the obtained results
to the heating problem of the upper parts of the solar atmosphere is
also discussed.
---------------------------------------------------------
Title: New acoustic wave energy computations for late-type stars
Authors: Theurer, J.; Ulmschneider, P.; Musielak, Z.
1996ASPC..109..169T Altcode: 1996csss....9..169T
No abstract at ADS
---------------------------------------------------------
Title: Generation of Linear and Nonlinear Magnetic Tube Waves in
the Solar Atmosphere
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1996mpsa.conf..427M Altcode: 1996IAUCo.153..427M
No abstract at ADS
---------------------------------------------------------
Title: ROSAT Pointed Observations of Cool Magnetic White Dwarfs
Authors: Musielak, Z. E.; Porter, J. G.; Davis, J. M.
1995ApJ...453L..33M Altcode:
Observational evidence for the existence of a chromosphere on the
cool magnetic white dwarf GD 356 has been reported. In addition,
there have been theoretical speculations that cool magnetic white
dwarfs may be sources of coronal X-ray emission. This emission, if
it exists, would be distinct from the two types of X-ray emission
(deep photospheric and shocked wind) that have already been observed
from hot white dwarfs. We have used the PSPC instrument on ROSAT to
observe three of the most prominent DA white dwarf candidates for
coronal X-ray emission: GD 356, KUV 2316+123, and GD 90. The data show
no significant emission for these stars. The derived upper limits for
the X-ray luminosities provide constraints for a revision of current
theories of the generation of nonradiative energy in white dwarfs.
---------------------------------------------------------
Title: Klein-Gordon Equation and the Local Critical Frequency for
Alfven Waves Propagating in an Isothermal Atmosphere
Authors: Musielak, Z. E.; Moore, R. L.
1995ApJ...452..434M Altcode:
A Klein-Gordon equation approach developed by Musielak, Fontenla,
and Moore for assessing reflection of Alfvén waves in a smoothly
nonuniform medium is reexamined. In this approach, the local critical
frequency for strong reflection is simply found by transforming the wave
equations into their Klein-Gordon forms and then choosing the largest
positive coefficient of the zeroth-order term to be the square of the
local critical frequency. In this paper, we verify this approach for
a particular atmosphere and show that the local critical frequency
can be alternatively defined by using the turning-point property of
Euler's equation. Our results are obtained specifically for steady
state, linear Alfvén waves in an isothermal atmosphere with constant
gravity and uniform vertical magnetic field. The upward Alfvén waves
(those above the wave source) are standing waves and the downward waves
(those below the wave source) are propagating waves. We demonstrate that
for any given wave frequency both upward and downward waves have the
same turning point or critical height. This height is determined by the
condition ω = Ω<SUB>A</SUB> = V<SUB>A</SUB>/2H, where V<SUB>A</SUB>
is the Alfvén velocity and H is the scale height; Ω<SUB>A</SUB>
can be taken as the local critical frequency for strong reflection
for the upward waves and as the local critical frequency for free
propagation for the downward waves. Our turning-point analysis also
yields another interesting result: for our particular model atmosphere
the magnetic field perturbation wave equation yields the local critical
frequency but the velocity-perturbation wave equation does not. Thus,
for this model atmosphere, we find that the Klein-Gordon equation
approach of Musielak, Fontenla, and Moore is correct in (1) its choice
of the magnetic-field-perturbation wave equation for finding the local
critical frequency, and (2) its assumption that the upward and downward
waves have the same critical frequency.
---------------------------------------------------------
Title: On the physical processes underlying the existence and
origin of X-ray and mass loss 'dividing lines' for cool giants
and supergiants
Authors: Musielak, Z. E.
1995alab.rept.....M Altcode:
The necessity of magnetic confinement for hot coronal material and
the large reflection efficiency for Alfven waves in cool exponential
atmospheres are considered. The joint problem is addressed, namely, how
one can account for the coincidence of the relatively sudden onset of
large mass loss rates with the equally sudden disappearance of emission
associated with high temperature (greater than 10<SUP>6</SUP> K) plasma
emitting X-rays as one moves along the giant and supergiant branches
in the H-R diagram. A model is constructed for the transition from
solar-like coronal and transition region behavior to strong, cool mass
outflows as evolved stars move across the locus of 'dividing lines'
in the H-R diagram. This model favors Alfven waves as a main source
of heating the atmospheres to coronal temperatures and as a source
of the wind acceleration. Analytical and numerical methods are used
to investigate reflection and trapping of linear and nonlinear Alfven
waves in highly inhomogeneous and expanding stellar atmospheres.
---------------------------------------------------------
Title: On the Generation of Flux-Tube Waves in Stellar Convection
Zones. II. Improved Treatment of Longitudinal Tube Wave Generation
Authors: Musielak, Z. E.; Rosner, R.; Gail, H. P.; Ulmschneider, P.
1995ApJ...448..865M Altcode:
We have previously considered the generation of purely longitudinal
magnetohydrodynamic tube waves by external turbulent convection and
derived general formulas for the source function and for the wave
energy fluxes. In this paper, we present an improved treatment of the
generation of such tube waves, based on a more sophisticated description
of the turbulence and more refined calculations. These improvements
allow us to compute and discuss in greater detail the spectra and fluxes
of longitudinal tube waves generated in the solar convective zone.
---------------------------------------------------------
Title: Magnetospheric filter effect for Pc 3 Alfvén mode waves
Authors: Zhang, X.; Comfort, R. H.; Gallagher, D. L.; Green, J. L.;
Musielak, Z. E.; Moore, T. E.
1995JGR...100.9585Z Altcode:
We present a ray-tracing study of the propagation of Pc 3 Alfvén
mode waves originating at the dayside magnetopause. This study
reveals interesting features of a magnetospheric filter effect
for these waves. Pc 3 Alfvén mode waves cannot penetrate to low
Earth altitudes unless the wave frequency is below approximately 30
mHz. Configurations of the dispersion curves and the refractive index,
show that the gyroresonance and pseudo-cutoff introduced by the heavy
ion O<SUP>+</SUP> block the waves. When the O<SUP>+</SUP> concentration
is removed from the plasma composition, the barriers caused by the
O<SUP>+</SUP> no longer exist, and waves with much higher frequencies
than 30 mHz can penetrate to low altitudes. The result that the 30-mHz
or lower frequency Alfvén waves can be guided to low altitudes agrees
with ground-based power spectrum observations at high latitudes.
---------------------------------------------------------
Title: Alfven wave resonances and flow induced by non-linear Alfven
waves in a stratified atmosphere
Authors: Stark, B. A.; Musielak, Z. E.; Suess, S. T.
1995sowi.confR..66S Altcode:
A nonlinear, time-dependent, ideal MHD code has been developed and used
to compute the flow induced by nonlinear Alfven waves propagating in
an isothermal, stratified, plane-parallel atmosphere. The code is based
on characteristic equations solved in a Lagrangian frame and is highly
accurate. Results show that resonance behavior of Alfven waves exists
in the presence of a continuous density gradient and that the waves with
periods corresponding to resonant peaks exert considerably more force on
the medium than off-resonance periods; this leads to enhanced flow. If
only off-peak periods are considered, the relationship between the wave
period and induced longitudinal velocity shows that short period WKB
waves push more on the background medium than longer period, non-WKB,
waves. The results also show the development of the longitudinal waves
produced by the finite amplitude of the Alfven waves. The longitudinal
wave becomes strong as the Alfven wave relative amplitude grows above
10 percent and will lead to strong damping of the Alfven waves.
---------------------------------------------------------
Title: On the generation of nonlinear magnetic tube waves in the
solar atmosphere.
Authors: Huang, P.; Musielak, Z. E.; Ulmschneider, P.
1995A&A...297..579H Altcode:
The nonlinear time-dependent response to purely transverse shaking of
a thin vertical magnetic flux tube embedded in the solar atmosphere
is investigated numerically. The shaking is imposed on the tube
at different heights in the solar atmosphere and the resulting
magnetic wave energy fluxes are calculated for the observationally
established range of velocity amplitudes and tube magnetic fields. The
obtained results clearly demonstrate that typical wave energy fluxes
carried by nonlinear transverse tube waves are of the order of
10^9^erg/cm2/s. This, in contrast to previous analytical studies,
seems to indicate that there is enough wave energy to account for
the enhanced heating observed in the chromospheric network, and that
magnetic tube waves may also play some role in the heating of other
regions of the solar atmosphere.
---------------------------------------------------------
Title: Evolution of the Fractal Dimension in a Flaring Active Region
Authors: Adams, M.; Hathaway, D. H.; Musielak, Z. E.
1995SPD....26.1016A Altcode: 1995BAAS...27..980A
No abstract at ADS
---------------------------------------------------------
Title: On the Origin of “Dividing Lines” for Late-Type Giants
and Supergiants
Authors: Rosner, R.; Musielak, Z. E.; Cattaneo, F.; Moore, R. L.;
Suess, S. T.
1995ApJ...442L..25R Altcode:
We show how a change in the nature of the stellar dyanmo can lead to
a transition in the topological character of stellar magnetic fields
of evolved stars, from being mainly closed on the blueward side of the
giant tracks in the Hertzsprung-Russell (H-R) diagram to being mainly
open on their redward side. If such a topological transition occurs,
then these stars naturally segregate into two classes: those having hot
coronae on the blueward side, and those having massive cool winds on the
redward side, thus leading naturally to the so-called dividing lines.
---------------------------------------------------------
Title: Klein-Gordon Equations for Acoustic Waves and Their
Applications in Helioseismology
Authors: Neergaard, L. F.; Musielak, Z. E.; Hathaway, D. H.
1995SPD....26..401N Altcode: 1995BAAS...27..954N
No abstract at ADS
---------------------------------------------------------
Title: Klein-Gordon Equation and Reflection of Alfvén Waves
Authors: Musielak, Z. E.; Moore, R. L.
1995SPD....26..910M Altcode: 1995BAAS...27R.975M
No abstract at ADS
---------------------------------------------------------
Title: Self-Consistent Models of the Solar Wind Accelerated by
Alfvén Waves
Authors: Ong, K. K.; Krogulec, M.; Musielak, Z. E.
1995SPD....26..904O Altcode: 1995BAAS...27..973O
No abstract at ADS
---------------------------------------------------------
Title: Propagating Alfven Waves, Intermittent Magnetic Levitation,
and Coronal Heating in Coronal Holes
Authors: Moore, R. L.; Musielak, Z. E.; Krogulec, M.; Suess, S. T.
1995SPD....26..908M Altcode: 1995BAAS...27Q.975M
No abstract at ADS
---------------------------------------------------------
Title: Reflection of Alfvén waves in the solar wind
Authors: Krogulec, M.; Musielak, Z. E.; Suess, S. T.; Nerney, S. F.;
Moore, R. L.
1994JGR....9923489K Altcode:
We have revisited the problem of propagation of toroidal and linear
Alfvén waves formulated by Heinemann and Olbert (1980) to compare WKB
and non-WKB waves and their effects on the solar wind. They considered
two solar wind models and showed that reflection is important for
Alfvén waves with periods of the order of one day and longer and
that non-WKB Alfvén waves are no more effective in accelerating
the solar wind than WKB waves. There are several recently published
papers that seem to indicate that Alfvén waves with periods of
the order of several minutes should be treated as non-WKB waves
and that these non-WKB waves exert a stronger acceleration force
than WKB waves. The purpose of this paper is to study the origin of
these discrepancies by performing parametric studies of the behavior
of the waves under a variety of different conditions. In addition,
we want to investigate two problems that have not been addressed by
Heinemann and Olbert, namely, calculate the efficiency of Alfvén wave
reflection by using the reflection coefficient and identify the region
of strongest wave reflection in different wind models. To achieve
these goals, we investigated the influence of temperature, electron
density distribution, wind velocity,and magnetic field strength on
the waves. <P />The obtained results clearly demonstrate that Alfvén
wave reflection is strongly model dependent and that the strongest
reflection can be expected in the models with the base temperatures
higher than 10<SUP>6</SUP> K and with the base densities lower than 7
× 10<SUP>7</SUP> cm<SUP>-3</SUP>. In these models as well as in the
models with lower temperatures and higher densities, Alfvén waves
with periods as short as several minutes have negligible reflection so
that they can be treated as WKB waves; however, for Alfvén waves with
periods of the order of one hour or longer reflection is significant,
requiring a non-WKB treatment. We also show that non-WKB, linear
Alfvén waves are always less effective in accelerating the plasma
than WKB Alfvén waves. Finally, it is evident from our results that
the region of strongest wave reflection is usually located at the base
of the models and hence that interpretation of wave reflection based
solely on the reflection coefficient can be misleading.
---------------------------------------------------------
Title: The Role of Alfven Waves in Solar Wind Acceleration
Authors: Krogulec, M.; Musielak, Z. E.; Suess, S. T.; Nerney, S. F.;
Moore, R. L.
1994AAS...185.9206K Altcode: 1994BAAS...26.1472K
The fact that Alfven waves may play a significant role in the
energy balance in solar coronal holes has been known for a number
of years. A special attention has been given to these waves because
they can transfer energy to large distances and deposit efficiently
momentum in the background medium. It has been shown that non-WKB
effects are important for Alfven waves with periods of the order
of one day and longer, and that non-WKB Alfven waves are no more
effective in acceleration of the solar wind than WKB waves. There are,
however, some recently published papers which seem to indicate that
Alfven waves with periods of the order of several minutes should
be treated as non-WKB waves and that these waves exert a stronger
acceleration force than WKB waves. To investigate the origin of these
discrepancies, we have performed a series of parametric studies of
the behavior of the waves under a variety of different conditions
in solar coronal holes. The obtained results demonstrate that both
Alfven wave reflection and the acceleration force due to the waves are
strongly model dependent. The strongest reflection can be expected
in models with the base temperatures higher than 10(6) K and with
the base densities lower than 7 times 10(7) cm(-3) . However, the
strongest acceleration force is expected in the models with the weakest
reflection. This clearly indicates that linear non-WKB Alfven waves
are always less effective in accelerating the plasma than WKB Alfven
waves. Implications of this result for the heating in solar coronal
holes and for the acceleration of the solar wind will be discussed.
---------------------------------------------------------
Title: Fractal Techniques Applied to a Flaring Active Region
Authors: Adams, Mitzi; Musielak, Z. E.
1994AAS...185.9203A Altcode: 1994BAAS...26.1472A
Fractal techniques have been used extensively to characterize data
from the fields of atmospheric physics, geophysics, astrophysics, and
recently to identify fractal clusters in sunspot penumbrae and solar
active regions. Using data acquired with NASA/Marshall Space Flight
Center's vector magnetograph, we apply fractal techniques to identify
temporal changes of the Hurst coefficient by applying Hurst's modified
“Range over Standard Deviation" analysis to 30 sets of data taken
at five minute intervals. These data were obtained over a period of
three hours, during which time one of two M-class flares occured. To
determine the correlation with solar flares, we compare the evolution
of Hurst coefficients from this active region (NOAA AR 6659) June 10,
1991 to a simple, non-flaring sunspot (NOAA AR 6484).
---------------------------------------------------------
Title: Klein-Gordon Equation and Reflection of Alfven Waves
Authors: Musielak, Z. E.; Moore, R. L.
1994AAS...18512106M Altcode: 1994BAAS...26.1520M
It is of some interest to know the physical conditions that lead
to efficient reflection of Alfven waves in the solar and stellar
atmospheres. The problem seems to be important because these waves
may play some role in non-radiative heating of the solar and stellar
chromosphere and coronae, and may also be responsible for acceleration
of the solar and cool massive stellar winds. A significant effort
has been made by a number of authors to understand the behavior of
these waves in highly inhomogeneous stellar atmospheres. The simplest
treatment of the problem seems to be the so-called Klein-Gordon
equation approach, which allows obtaining local critical frequencies by
transforming the wave equations into their Klein-Gordon forms and then
choosing the largest positive coefficient to be the square of the local
critical frequency. In this paper, we show that the local critical
frequency can be alternatively defined by using the turning-point
property of Euler's equation. Our results are obtained specifically
for Alfven waves propagating in an isothermal atmosphere with constant
gravity and uniform vertical magnetic field. We demonstrate that
Alfven waves in the upper (above the wave source) part of our model
always form a standing wave pattern and that the waves in the lower
(below the wave source) part of the model are always propagating
(but partially reflected) waves. We also show that the turning point
for the upward and downward waves is located at the height where
the condition omega = Omega_A is satisfied and that Omega_A = V_A /
2 H, where V_A is the Alfven velocity and H is the scale height,
can be taken as a local critical frequency because the waves undergo
strong reflection in this region of the atmosphere where omega <=
Omega_A . By applying our turning-point analysis to the Alfven
wave equations for the velocity and magnetic field perturbation, we
obtain an interesting result: for our particular model atmosphere the
magnetic-field-perturbation wave equation yields the local critical
frequency but the velocity-perturbation wave equation does not. A
physical interpretation of the obtained results will be given.
---------------------------------------------------------
Title: Limits to Extensions of Burgers Equation
Authors: Nerney, Steven; Schmahl, Edward J.; Musielak, Z. E.
1994solv.int.11005N Altcode:
The vector Burgers equation is extended to include pressure gradients
and gravity. It is shown that within the framework of the Cole-Hopf
transformation there are no physical solutions to this problem. This
result is important because it clearly demonstrates that any extension
of Burgers equation to more interesting physical situations is strongly
limited.
---------------------------------------------------------
Title: On the physics of waves in the solar atmosphere: Wave heating
and wind acceleration
Authors: Musielak, Z. E.
1994alab.reptQ....M Altcode:
New calculations of the acoustic wave energy fluxes generated in the
solar convective zone have been performed. The treatment of convective
turbulence in the sun and solar-like stars, in particular, the precise
nature of the turbulent power spectrum has been recognized as one
of the most important issues in the wave generation problem. Several
different functional forms for spatial and temporal spectra have been
considered in the literature and differences between the energy fluxes
obtained for different forms often exceed two orders of magnitude. The
basic criterion for choosing the appropriate spectrum was the maximal
efficiency of the wave generation. We have used a different approach
based on physical and empirical arguments as well as on some results
from numerical simulation of turbulent convection.
---------------------------------------------------------
Title: On the origin and evolution of stellar X-ray emission
Authors: Musielak, Z. E.
1994pas..conf...41M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On Sound Generation by Turbulent Convection: A New Look at
Old Results
Authors: Musielak, Z. E.; Rosner, R.; Stein, R. F.; Ulmschneider, P.
1994ApJ...423..474M Altcode:
We have revisited the problem of acoustic wave generation by turbulent
convection in stellar atmospheres. The theory of aerodynamically
generated sound, originally developed by Lighthill and later modified
by Stein to include the effects of stratification, has been used
to estimate the acoustic wave energy flux generated in solar and
stellar convection zones. We correct the earlier computations by
incorporating an improved description of the spatial and temporal
spectrum of the turbulent convection. We show the dependence of the
resulting wave fluxes on the nature of the turbulence, and compute the
wave energy spectra and wave energy fluxes generated in the Sun on
the basis of a mixing-length model of the solar convection zone. In
contrast to the previous results, we show that the acoustic energy
generation does not depend very sensitively on the turbulent energy
spectrum. However, typical total acoustic fluxes of order F<SUB>A</SUB>
= 5 x 10<SUP>7</SUP> ergs/sq cm/s with a peak of the acoustic frequency
spectrum near omega = 100 mHz are found to be comparable to those
previously calculated. The acoustic flux turns out to be strongly
dependent on the solar model, scaling with the mixing-length parameter
alpha as alpha<SUP>3.8</SUP>. The computed fluxes most likely constitute
a lower limit on the acoustic energy produced in the solar convection
zone if recent convection simulations suggesting the presence of shocks
near the upper layers of the convection zone apply to the Sun.
---------------------------------------------------------
Title: On the physics of waves in the solar atmosphere: Wave heating
and wind acceleration
Authors: Musielak, Z. E.
1994STIN...9425264M Altcode:
This paper presents work performed on the generation and physics
of acoustic waves in the solar atmosphere. The investigators have
incorporated spatial and temporal turbulent energy spectra in a
newly corrected version of the Lighthill-Stein theory of acoustic
wave generation in order to calculate the acoustic wave energy fluxes
generated in the solar convective zone. The investigators have also
revised and improved the treatment of the generation of magnetic
flux tube waves, which can carry energy along the tubes far away from
the region of their origin, and have calculated the tube wave energy
fluxes for the sun. They also examine the transfer of the wave energy
originated in the solar convective zone to the outer atmospheric layers
through computation of wave propagation and dissipation in highly
nonhomogeneous solar atmosphere. These waves may efficiently heat the
solar atmosphere and the heating will be especially significant in
the chromospheric network. It is also shown that the role played by
Alfven waves in solar wind acceleration and coronal hole heating is
dominant. The second part of the project concerned investigation of
wave propagation in highly inhomogeneous stellar atmospheres using an
approach based on an analytic tool developed by Musielak, Fontenla,
and Moore. In addition, a new technique based on Dirac equations has
been developed to investigate coupling between different MHD waves
propagating in stratified stellar atmospheres.
---------------------------------------------------------
Title: Fractal dimension: a predictor for solar flares.
Authors: Adams, M.; Musielak, Z. E.; Jaenisch, H. M.
1994BAAS...26..794A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: ROSAT observations of cool magnetic white dwarfs.
Authors: Musielak, Z. E.; Davis, J. M.; Porter, J. G.; Trimble, V. L.
1994BAAS...26R.792M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation characteristics of Pc 3 compressional waves
generated at the dayside magnetopause
Authors: Zhang, X.; Comfort, R. H.; Musielak, Z. E.; Moore, T. E.;
Gallagher, D. L.; Green, J. L.
1993JGR....9815403Z Altcode:
New, three-dimensional ray tracing of Pc 3 compressional waves
from the magnetosheath reveals that the magnetosphere can present
a major propagation barrier to the penetration of these waves to
the plasmasphere. This barrier is the ion-ion cutoff between the
He<SUP>+</SUP> and O<SUP>+</SUP> gyroresonances. As a result of the
frequency-dependent location of this cutoff, the magnetosphere behaves
like a filter for Pc 3 compressional waves, and only low-frequency
components of Pc 3 compressional waves can penetrate to inner
magnetosphere. Results are in agreement with previous satellite
observations. This “filter action” strongly depends on the relative
concentration of He<SUP>+</SUP> and O<SUP>+</SUP> and is therefore
sensitive to solar and magnetic activity. Ray-tracing results are based
on a cold plasma dispersion relation, a semi-empirical model of plasma
density, and the Mead-Fairfield magnetic field model.
---------------------------------------------------------
Title: On the physics of waves in the solar atmosphere: Wave heating
and wind acceleration
Authors: Musielak, Z. E.
1993alab.reptS....M Altcode:
This paper presents work performed on the generation and physics
of acoustic waves in the solar atmosphere. The investigators have
incorporated spatial and temporal turbulent energy spectra in a
newly corrected version of the Lighthill-Stein theory of acoustic
wave generation in order to calculate the acoustic wave energy fluxes
generated in the solar convective zone. The investigators have also
revised and improved the treatment of the generation of magnetic
flux tube waves, which can carry energy along the tubes far away
from the region of their origin, and have calculated the tube energy
fluxes for the sun. They also examine the transfer of the wave energy
originated in the solar convective zone to the outer atmospheric layers
through computation of wave propagation and dissipation in highly
nonhomogeneous solar atmosphere. These waves may efficiently heat the
solar atmosphere and the heating will be especially significant in
the chromospheric network. It is also shown that the role played by
Alfven waves in solar wind acceleration and coronal hole heating is
dominant. The second part of the project concerned investigation of
wave propagation in highly inhomogeneous stellar atmospheres using an
approach based on an analytic tool developed by Musielak, Fontenla,
and Moore. In addition, a new technique based on Dirac equations has
been developed to investigate coupling between different MHD waves
propagating in stratified stellar atmospheres.
---------------------------------------------------------
Title: Excitation of Nonlinear Magnetic Flux Tube Waves in the
Solar Atmosphere
Authors: Huang, P.; Musielak, Z. E.; Ulmschneider, P.
1993BAAS...25.1213H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Heating of Solar Coronal Holes by Means of Non-Linear
Alfven Wave Coupling
Authors: Stark, B.; Musielak, Z. E.; Suess, S. T.; Ulmschneider, P.
1993BAAS...25R1212S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Cutoff Frequency for Fast-Mode Magnetohydrodynamic Waves
in an Isothermal Atmosphere with a Uniform Horizontal Magnetic Field
Authors: Stark, B. A.; Musielak, Z. E.
1993ApJ...409..450S Altcode:
This study analytically examines conditions for reflection of MHD
fast-mode waves propagating upward in an isothermal atmosphere. A new
method of transforming the linearized wave equation into Klein-Gordon
form is utilized to calculate a local cutoff (critical) frequency
for these waves. This critical frequency determines the height in
the atmosphere at which reflection dominates and above which wave
propagation is effectively cut off. Comparison of our results to those
previously obtained shows that earlier calculations of the critical
frequency for MHD fast mode waves were done incorrectly. The results
may be helpful in explaining the short-period end of the spectrum of
the solar global p-mode oscillations. They may also be important in
studies of wave propagation and wave trapping in highly magnetized
stellar atmospheres.
---------------------------------------------------------
Title: On the Heating Mechanism of Coronal Holes
Authors: Hammer, R.; Moore, R. L.; Musielak, Z. E.; Suess, S. T.
1993ASSL..183..587H Altcode: 1993pssc.symp..587H
No abstract at ADS
---------------------------------------------------------
Title: On reflection of Alfven waves in the solar wind
Authors: Krogulec, M.; Musielak, Z. E.; Suess, S. T.; Moore, R. L.;
Nerney, S. F.
1993STIN...9530582K Altcode:
We have revisited the problem of propagation of toroidal and linear
Alfven waves formulated by Heinemann and Olbert (1980) to compare WKB
and non-WKB waves and their effects on the solar wind. They considered
two solar wind models and showed that reflection is important for Alfven
waves with periods of the order of one day and longer, and that non-WKB
Alfven waves are no more effective in accelerating the solar wind than
WKB waves. There are several recently published papers which seem to
indicate that Alfven waves with periods of the order of several minutes
should be treated as non-WKB waves and that these non-WKB waves exert
a stronger acceleration force than WKB waves. The purpose of this paper
is to study the origin of these discrepancies by performing parametric
studies of the behavior of the waves under a variety of different
conditions. In addition, we want to investigate two problems that
have not been addressed by Heinemann and Olbert, namely, calculate
the efficiency of Alfven wave reflection by using the reflection
coefficient and identify the region of strongest wave reflection in
different wind models. To achieve these goals, we investigated the
influence of temperature, electron density distribution, wind velocity
and magnetic field strength on the waves. The obtained results clearly
demonstrate that Alfven wave reflection is strongly model dependent and
that the strongest reflection can be expected in models with the base
temperatures higher than 10<SUP>6</SUP> K and with the base densities
lower than 7 x 10<SUP>7</SUP> cm<SUP>-3</SUP>. In these models as
well as in the models with lower temperatures and higher densities,
Alfven waves with periods as short as several minutes have negligible
reflection so that they can be treated as WKB waves; however, for Alfven
waves with periods of the order of one hour or longer reflection is
significant, requiring a non-WKB treatment. We also show that non-WKB,
linear Alfven waves are always less effective in accelerating the
plasma than WKB Alfven waves. Finally, it is evident from our results
that the region of strongest wave reflection is usually located at the
base of the models, and hence that interpretation of wave reflection
based solely on the reflection coefficient can be misleading.
---------------------------------------------------------
Title: On Sound Generation by Turbulent Convection: A New Look at
Old Results
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Gail, P.;
Wang, A.
1992AAS...181.9403M Altcode: 1992BAAS...24.1269M
No abstract at ADS
---------------------------------------------------------
Title: A New Way to Convert Alfven Waves into Heat in Solar Coronal
Holes: Intermittent Magnetic Levitation
Authors: Moore, R. L.; Hammer, R.; Musielak, Z. E.; Suess, S. T.;
An, C. -H.
1992ApJ...397L..55M Altcode:
In our recent analysis of Alfven wave reflection in solar coronal
holes, we found evidence that coronal holes are heated by reflected
Alfven waves. This result suggests that the reflection is inherent to
the process that dissipates these Alfven waves into heat. We propose
a novel dissipation process that is driven by the reflection, and that
plausibly dominates the heating in coronal holes.
---------------------------------------------------------
Title: On the physics of waves in the solar atmosphere: Wave heating
and wind acceleration
Authors: Musielak, Z. E.
1992STIN...9233947M Altcode:
In the area of solar physics, new calculations of the acoustic wave
energy fluxes generated in the solar convective zone was performed. The
original theory developed was corrected by including a new frequency
factor describing temporal variations of the turbulent energy
spectrum. We have modified the original Stein code by including this
new frequency factor, and tested the code extensively. Another possible
source of the mechanical energy generated in the solar convective
zone is the excitation of magnetic flux tube waves which can carry
energy along the tubes far away from the region. The problem as to
how efficiently those waves are generated in the Sun was recently
solved. The propagation of nonlinear magnetic tube waves in the solar
atmosphere was calculated, and mode coupling, shock formation, and
heating of the local medium was studied. The wave trapping problems
and evaluation of critical frequencies for wave reflection in the
solar atmosphere was studied. It was shown that the role played by
Alfven waves in the wind accelerations and the coronal hole heating is
dominant. Presently, we are performing calculations of wave energy
fluxes generated in late-type dwarf stars and studying physical
processes responsible for the heating of stellar chromospheres and
coronae. In the area of physics of waves, a new analytical approach
for studying linear Alfven waves in smoothly nonuniform media was
recently developed. This approach is presently being extended to study
the propagation of linear and nonlinear magnetohydrodynamic (MHD) waves
in stratified, nonisothermal and solar atmosphere. The Lighthill theory
of sound generation to nonisothermal media (with a special temperature
distribution) was extended. Energy cascade by nonlinear MHD waves and
possible chaos driven by these waves are presently considered.
---------------------------------------------------------
Title: A Regularization Method for Extrapolation of Solar Potential
Magnetic Fields
Authors: Gary, G. A.; Musielak, Z. E.
1992ApJ...392..722G Altcode:
The mathematical basis of a Tikhonov regularization method for
extrapolating the chromospheric-coronal magnetic field using
photospheric vector magnetograms is discussed. The basic techniques
show that the Cauchy initial value problem can be formulated for
potential magnetic fields. The potential field analysis considers a
set of linear, elliptic partial differential equations. It is found
that, by introducing an appropriate smoothing of the initial data
of the Cauchy potential problem, an approximate Fourier integral
solution is found, and an upper bound to the error in the solution is
derived. This specific regularization technique, which is a function
of magnetograph measurement sensitivities, provides a method to
extrapolate the potential magnetic field above an active region into
the chromosphere and low corona.
---------------------------------------------------------
Title: Intermittent Magnetic Levitation and Heating by Alfven Waves
in Solar Coronal Holes
Authors: Moore, R. L.; Hammer, R.; Musielak, Z. E.; Suess, S. T.;
An, C. -H.
1992AAS...180.5506M Altcode: 1992BAAS...24R.819M
No abstract at ADS
---------------------------------------------------------
Title: ROSAT guest investigator program (AO-1). On a search for
coronal X ray emissions from white dwarfs
Authors: Musielak, Z. E.
1992STIN...9413171M Altcode:
We have suggested that cool magnetic white dwarfs may be sources of
X-ray coronal emission and proposed several prominent candidates for
this emission. One of these candidates (EG 250) was approved for the
C-category observation by the National and International Committee and
was observed by ROSAT on April 17, 1991. Unfortunately, the granted
exposure time (1071 s) was much shorter than that which was required
by theoretical predictions to observe coronal X-ray emission from
this object. The tape containing the data was send to us in November
1991. Since then we have analyzed the data visiting the ROSAT Science
Center at NASA Goddard Space Flight Center. The analysis of the data
taken during this short observation show, as expected, no X-rays. It
is our hope that EG 250 will be observed again during the AO-2 phase
of pointed observations, as 10,000 s of observing time was granted to
V. Trimble for the C-category observation of this star. We have a close
contact with Dr. Trimble regarding this matter. Because our all targets
(GD 90, KUV 2316-123 and GD 356) proposed for the observation during the
AO-2 phase of pointed observations have been approved by the National
and International Committee, we have installed the required software at
NASA/MSFC to be able to carry out the data analysis in Huntsville. Two
of our targets have already been observed (KUV 2316-123 was observed on
Dec. 3, 1991 with 10,000 s of the exposure time, and GD 356 was observed
on Jan 4, 1992 with 5,000 s of the exposure time). We just received
the data and will begin the analysis soon. The results of our analysis
will be reported to the scientific community by publishing papers in
the Astrophysical Journal Letters. Our intention is to submit a paper
when the analysis of the data taken during AO2 is completed. The data
taken during the observation of EG 250 will be a part of this paper.
---------------------------------------------------------
Title: Why the Winds from Late-Type Giants; Supergiants are Cool
Authors: Moore, R. L.; Musielak, Z. E.; An, C. -H.; Rosner, R.; Suess,
S. T.
1992ASPC...26..464M Altcode: 1992csss....7..464M
No abstract at ADS
---------------------------------------------------------
Title: Heating of solar coronal holes by reflected Alfven waves
Authors: Moore, R. L.; Musielak, Z. E.; Suess, S. T.; An, C. -H.
1992MmSAI..63..777M Altcode:
As a continuation of the work of Moore et al. (1991), who found evidence
that coronal holes are heated by Alfven waves that are reflected back
down within the coronal holes, this paper shows that to demonstrate
this evidence, it is only necessary to consider a subset of the Moore
et al. models, namely, those having radial magnetic field. Using
these models, it is shown that the Alfven velocity is not constant in
the atmosphere of coronal holes, but changes with height (or radius),
causing downward reflection of all upward Alfven waves of sufficiently
long wavelength (or period).
---------------------------------------------------------
Title: Heating of solar and stellar chromospheres and coronae by
MHD waves
Authors: Musielak, Z. E.
1992HiA.....9..665M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Klein-Gordon equation and reflection of Alfvén waves in
nonuniform media
Authors: Musielak, Z. E.; Fontenla, J. M.; Moore, R. L.
1992PhFlB...4...13M Altcode:
A new analytical approach is presented for assessing the reflection
of linear Alfven waves in smoothly nonuniform media. The general
one-dimensional case in Cartesian coordinates is treated. It is
shown that the wave equations, upon transformation into the form
of the Klein-Gordon equation, display a local critical frequency for
reflection. At any location in the medium, reflection becomes strong as
the wave frequency descends past this characteristic frequency set by
the local nonuniformity of the medium. This critical frequecy is given
by the transformation as an explicit function of the Alfven velocity
and its first and second derivatives, and hence as an explicit spatial
function. The transformation thus directly yields, without solution
of the wave equations, the location in the medium at which an Alfven
wave of any given frequency becomes strongly reflected and has its
propagation practically cut off.
---------------------------------------------------------
Title: Alfven wave reflection and heating in coronal holes - Theory
and observation
Authors: Suess, S. T.; Moore, R. L.; Musielak, Z. E.; An, C. -H.
1992sws..coll..117S Altcode:
We present evidence for significant reflection of Alfven waves in an
isothermal, hydrostatic model corona and that heating in coronal holes
is provided by Alfven waves. For Alfven waves with periods of 5 min,
upward propagating waves are reflected if the temperature is less
than 10 exp 6 K, but escape into the solar wind if the temperature
is greater than 10 exp 6 K. This sensitive temperature dependence
may provide the self-limiting mechanism that has been suspected to
exist because the reflected waves result in heating which raises the
temperature which, in turn, decreases the reflection. The reflection
occurs mostly inside of about 6 solar radii, depending on temperature,
wave period, and magnetic field strength and geometry. The importance of
this process has often been overlooked due to a poor choice of coronal
Alfven speed and temperature. SOHO is well-suited to measure whether
the required properties for reflection exist. Solar Probe, however,
is the only definitive experiment to show if the waves actually exist
to the degree necessary.
---------------------------------------------------------
Title: Heating of solar and stellar chromospheres and coronae by
MHD waves
Authors: Musielak, Z. E.
1992MmSAI..63..635M Altcode:
The two general classes of models that deal with the required heating of
stellar chromospheres and coronae assume that outer stellar atmospheres
are heated by hydrodynamic or by magnetohydrodynamic (MHD) waves and
that these waves are generated by turbulent motions in the stellar
convection zones. This paper considers the types of MHD waves and
the source of these waves in stars like sun, the efficiency of the
generation of MHD waves, and the manner of propagation and energy
dissipation of MHD waves. It is shown that the basic criteria for
the validity of any theory of MHD wave heating must account for the
mean level of heating observed in stellar chromospheres and coronae,
and for the range of radiative losses observed for a given spectral
type. It is also required that the MHD wave heating theory accounts for
the existence of inhomogeneities in stellar atmospheres. The results
obtained indicate that magnetic tube waves might supply enough energy
for the chromospheric and coronal heating and might also account for
the observed range of variations of stellar radiative losses for a
given spectral type.
---------------------------------------------------------
Title: Alfven Wave Trapping, Network Microflaring, and Heating in
Solar Coronal Holes
Authors: Moore, R. L.; Musielak, Z. E.; Suess, S. T.; An, C. -H.
1991ApJ...378..347M Altcode:
Fresh evidence that much of the heating in coronal holes is provided
by Alfven waves is presented. This evidence comes from examining the
reflection of Alfven waves in an isothermal hydrostatic model coronal
hole with an open magnetic field. Reflection occurs if the wavelength
is as long as the order of the scale height of the Alfven velocity. For
Alfven waves with periods of about 5 min, and for realistic density,
magnetic field strength, and magnetic field spreading in the model,
the waves are reflected back down within the model hole if the coronal
temperature is only slightly less than 1.0 x 10 to the 6th K, but
are not reflected and escape out the top of the model if the coronal
temperature is only slightly greater than 1.0 x 10 to the 6th K. Because
the spectrum of Alfven waves in real coronal holes is expected to peak
around 5 min and the temperature is observed to be close to 1.0 x 10
to the 6th K, the sensitive temperature dependence of the trapping
suggests that the temperature in coronal holes is regulated by heating
by the trapped Alfven waves.
---------------------------------------------------------
Title: Why the Winds from Late-Type Giants and Supergiants are Cool
Authors: Moore, R. L.; Musielak, Z. E.; An, C. -H.; Rosner, R.; Suess,
S. T.
1991BAAS...23Q1385M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Generation of Magnetic Tube Waves in the Solar
Convection Zone
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Gail, P.
1991BAAS...23.1442M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On Reflection of Fast Mode Waves in the Solar Atmosphere
Authors: Stark, B. A.; Musielak, Z. E.
1991BAAS...23.1442S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Confinement, Alfven Wave Reflection, and the Origins
of X-Ray and Mass-Loss “Dividing Lines” for Late-Type Giants
and Supergiants
Authors: Rosner, R.; An, C. -H.; Musielak, Z. E.; Moore, R. L.; Suess,
S. T.
1991ApJ...372L..91R Altcode:
A simple qualitative model for the origin of the coronal and mass-loss
dividing lines separating late-type giants and supergiants with and
without hot, X-ray-emitting corona, and with and without significant
mass loss is discussed. The basic physical effects considered are
the necessity of magnetic confinement for hot coronal material on the
surface of such stars and the large reflection efficiency for Alfven
waves in cool exponential atmospheres. The model assumes that the
magnetic field geometry of these stars changes across the observed
'dividing lines' from being mostly closed on the high effective
temperature side to being mostly open on the low effective temperature
side.
---------------------------------------------------------
Title: On the generation of magnetic tube waves in the solar
convection zone.
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Gail, P.
1991BAAS...23.1037M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Regularization Method for the Extrapolation of Solar
Magnetic Fields
Authors: Gary, G. A.; Musielak, Z.
1991BAAS...23.1031G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Critical Frequencies and Reflection of Fast Mode Waves in an
Isothermal Atmosphere
Authors: Stark, B. A.; Musielak, Z. E.
1991BAAS...23.1060S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Generation of Magnetic Tube Waves in the Solar
Convection Zone
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Gail, P.
1991BAAS...23Q1037M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation of nonlinear longitudinal-transverse waves along
magnetic flux tubes in the solar atmosphere. I - Adiabatic waves
Authors: Ulmschneider, P.; Zaehringer, K.; Musielak, Z. E.
1991A&A...241..625U Altcode:
The nonlinear time-dependent response to purely transverse foot point
shaking of a vertical magnetic flux tube in the solar atmosphere
was studied. The adiabatic calculations show the generation of a
longitudinal wave mode which has twice the frequency of the transverse
wave. The amplitude of the longitudinal wave increases with the wave
period and with the magnitude of the shaking. Due to the action of
centrifugal forces significant lifting of the tube gas was found. A
forced oscillator type resonance occurs which depends on the tube
length.
---------------------------------------------------------
Title: Recent Developments in Theories of Wave Generation (With
5 Figures)
Authors: Musielak, Z. E.
1991mcch.conf..369M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Confinement, Alfvén Wave Reflection, and the Origin
of X-ray and Mass Loss "Dividing Lines"
Authors: An, C. -H.; Rosner, R.; Musielak, Z. E.; Moore, R. L.; Suess,
S. T.
1991mcch.conf..445A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reflection of Alfvén Waves and Heating in Solar Coronal Holes
(With 1 Figure)
Authors: Moore, R. L.; Musielak, Z. E.; Suess, S. T.; An, C. -H.
1991mcch.conf..435M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Conditions for Vertical Propagation of Magnetoacoustic Waves
in an Isothermal Atmosphere
Authors: Musielak, Z. E.
1990ApJ...351..287M Altcode:
The propagation of magnetoacoustic waves in an isothermal atmosphere
with constant gravity and uniform magnetic field of an arbitrary
direction is considered. The conditions for the vertical propagation
of these waves are determined by characteristic frequencies that
arise in the MHD wave equation which is considered here in the limit
of low-beta plasma. The obtained steady state solutions to the wave
equation describe the behavior of fast and slow magnetoacoustic waves
and allow defining the characteristic frequencies that separate
domains of wave frequency where the sinusoidal and nonsinusoidal
wave solutions are found. The particular problem of dependence of the
characteristic frequencies on the density gradient as well as on the
strength and direction of the uniform magnetic field are discussed. The
obtained results may have important consequences on the behavior of
magnetoacoustic waves in stellar atmospheres and may be found useful
in studying stellar p-mode oscillations.
---------------------------------------------------------
Title: Reflection and Trapping of Alfven Waves in a Spherically
Symmetric Stellar Atmosphere
Authors: An, C. -H.; Suess, S. T.; Moore, R. L.; Musielak, Z. E.
1990ApJ...350..309A Altcode:
Alfven wave propagation in a spherically symmetric isothermal and
stratified stellar atmosphere are analzyed using a time-dependent MHD
numerical model. Particular consideration is given to wave reflection
and the resultant trapping of the wave due to a peak in the Alfven speed
in the atmosphere. Resonance frequencies in the trapping region and the
effect of trapping on Alfven wave pressure force and propagation are
examined. The data reveal that Alfven wave trapping has a potentially
important role in accelerating winds from cool stars.
---------------------------------------------------------
Title: Effect of Radiative Transfer on Convection in the Deep
Photosphere of Late-Type Dwarfs
Authors: Fontenla, J. M.; Musielak, Z. E.; Moore, R. L.
1990ASPC....9...82F Altcode: 1990csss....6...82F
A method is proposed to eliminate the compressional instability of a
shallow layer in the upper part of stellar convective zones in standard
mixing-length models. By equating the radiative cooling time of mixing
eddies to their convective turnover time, the effective sizes of the
eddies are assumed to be the smallest of those which are not eliminated
by radiative transfer. Computations of the models with this assumption
leads to smooth temperature profiles in the previously unstable layers
and reductions of the convective velocity above its maximum value.
---------------------------------------------------------
Title: Generation of Transverse Magnetic Tube Waves and X-Ray
Emissions from Late-Type Dwarfs
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1990ASPC....9...79M Altcode: 1990csss....6...79M
The X-ray emissions observed in late-type stars are shown to be
associated with transverse magnetic tube waves generated in stellar
convective zones. The heating theory is examined to insure that it
accounts for the mechanical energy flux associated with the wide range
of X-ray emissions for each spectral type, and the inhomogeneous and
locally strong magnetic fields in stellar atmospheres. The values of
the free parameters from the wave-heating model developed agree with
observational data, and the tube waves can account for the observed
X-ray emissions of F, G, and K dwarfs.
---------------------------------------------------------
Title: Longitudinal-Transverse Magnetic Tube Waves in the Solar
Atmosphere
Authors: Ulmschneider, P.; Musielak, Z.
1990ASPC....9..116U Altcode: 1990csss....6..116U
The propagation of nonlinear adiabatic magnetohydrodynamic waves in
a thin magnetic flux tube is studied. The waves are excited by purely
transverse shaking. Due to nonlinear coupling there is a significant
energy transfer to the longitudinal wave. This transfer is largest for
long period waves and increases with the shaking amplitude. Lifting
of the tube mass is found due to the increased swaying with height.
---------------------------------------------------------
Title: A Mechanism for the Increase in Stellar Wind Mass Loss from
Giants across the Dividing Line
Authors: An, C. H.; Musielak, Z. E.; Rosner, R.; Moore, R. L.; Suess,
S. T.
1990ASPC....9...70A Altcode: 1990csss....6...70A
No abstract at ADS
---------------------------------------------------------
Title: Why DA and DB White Dwarfs Do Not Show Coronal Activity and
p-Mode Oscillations
Authors: Musielak, Z. E.; Fontenla, J. M.
1989ApJ...346..435M Altcode:
The problems of nonradiative heating of outer atmospheric layers and
p-mode oscillations in white dwarfs caused by acoustic waves generated
in convective zones are discussed. These effects have been studied
by calculating the cutoff periods for adiabatic and isothermal waves
propagating in atmospheres of DA and DB stars with Teff greater than
or equal 20,000 K and log g = 6-9. The obtained cutoff periods are
approximately bounded by 0.01 and 40 sec for high- and low-gravity
white dwarfs, respectively. Expected amplitudes of p-mode oscillations
corresponding to trapped acoustic waves with small angular wave numbers
are estimated, indicating that the amplitudes could be observed
as Doppler shifts of spectral lines which might be detectable if
adequate spectral resolution were available. The luminosity variations
corresponding to these amplitudes are unlikely to be observable when
all damping processes are accounted for. Results also indicate that
the present theory of convection predicts some irregularities in the
behavior of physical parameters.
---------------------------------------------------------
Title: Reflection and trapping of transient Alfven waves propagating
in an isothermal atmosphere with constant gravity and uniform
magnetic field
Authors: An, C. -H.; Musielak, Z. E.; Moore, R. L.; Suess, S. T.
1989ApJ...345..597A Altcode:
A time-dependent linear magnetohydrodynamic numerical model was used
to investigate the propagation of Alfven waves in an isothermal and
stratified atmosphere with constant gravity and uniform vertical
magnetic field. Results show that the Alfven wave transit time for
the wave source to infinity is finite and that the wave exhibits
continuous partial reflection which becomes total reflection as the
front approaches infinity. The total reflection causes the waves to be
trapped in the cavity that extends from the wave source to infinity
and in which the wave energy is stored. The results suggest that the
reflection of Alfven waves (of sufficiently long period) from the
outer corona is an intrinsic phenomenon for any stellar atmosphere
stratified by gravity and an open magnetic field, and that, therefore,
such waves may be trapped in the stellar atmosphere.
---------------------------------------------------------
Title: Alfven Speed and Heating in Solar Coronal Holes
Authors: Moore, R. L.; An, C. H.; Suess, S. T.; Musielak, Z. E.
1989BAAS...21.1180M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagating and Nonpropagating Compression Waves in an
Isothermal Atmosphere with Uniform Horizontal Magnetic Field
Authors: Musielak, Z. E.; An, C. -H.; Moore, R. L.; Suess, S. T.
1989ApJ...344..478M Altcode:
Full analytical solutions to the wave equations for steady vertical
compression waves in an isothermal hydrostatic atmosphere with a uniform
horizontal magnetic field are presented. It is shown that, in the steady
state approach, the behavior of upward waves and downward waves is very
different. It is shown that the finding of Thomas (1983), indicating
that the cutoff frequency for vertically propagating magnetoacoustic
waves in an isothermal atmosphere with a horizontal magnetic field
is the same for isothermal atmosphere with no magnetic field, is true
only for the downward waves.
---------------------------------------------------------
Title: Do Any White Dwarfs Have X-ray Coronae?
Authors: Musielak, Z. E.; Fontenla, J. M.; Moore, R. L.
1989BAAS...21.1222M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: MHD surface waves in high- and low-beta plasmas. Part
1. Normal-mode solutions
Authors: Musielak, Z. E.; Suess, S. T.
1989JPlPh..42...75M Altcode:
Since the first paper by Barston (1964) on electrostatic oscillations
in inhomogeneous cold plasmas, it has been commonly accepted that
all finite layers with a continuous profile in pressure, density
and magnetic field cannot support normal surface waves but instead
the waves always decay through phase mixing (also called resonant
absorption). Here we reanalyse the problem by studying a compressible
current sheet of a general structure with rotation of the magnetic
field included. We find that all inhomogeneous layers considered
in the high-β plasma limit do not support normal modes. However,
in the limit of a low-β plasma there are some cases when normal-mode
solutions are recovered. The latter means that the process of resonant
absorption is not common for all inhomogeneous layers.
---------------------------------------------------------
Title: The generation of MHD waves by forced turbulence in a weakly
magnetized fluid
Authors: Rosner, R.; Musielak, Z. E.
1989A&A...219L..27R Altcode:
The effect of the fluctuating buoyancy force on wave generation in a
weakly magnetized plasma is considered. As expected, the efficiency of
MHD wave generation is enhanced by including this force. However, it
remains true that the observed variation of coronal emission at fixed
spectral type cannot be accounted for by a wave generation process of
the type discussed here.
---------------------------------------------------------
Title: Wave energy leakage and heating of white dwarf atmospheres.
Authors: Fontenla, J. M.; Musielak, Z. E.
1989BAAS...21.1021F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Role of Alfven Wave Trapping in the Acceleration of
Stellar Winds from Late-Type Giants and Supergiants
Authors: An, C. -H.; Musielak, Z. E.; Rosner, R.; Suess, S. T.; Moore,
R. L.
1989BAAS...21..792A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Reflection and Trapping of Alfven Waves in Coronal Holes
Authors: An, C. -H.; Suess, S. T.; Moore, R. L.; Musielak, Z. E.
1989BAAS...21..844A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Can Magnetic Tube Waves Account for X-ray Emissions Observed
from Late-Type Dwarfs
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1989BAAS...21..796M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Subphotospheric Excitation of Alfven Waves and Their Role in
the Solar Atmosphere
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Moore, R. L.
1989BAAS...21R.830M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation of Nonlinear Longitudinal-Transverse Waves Along
Magnetic Flux Tubes in the Solar Atmosphere
Authors: Ulmschneider, P.; Zahringer, K.; Musielak, Z. E.
1989BAAS...21..844U Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Alfven Wave Trapping and Heating in Coronal Holes
Authors: Moore, R. L.; An, C. -H.; Suess, S. T.; Musielak, Z. E.
1989BAAS...21Q.830M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interaction Between Forced Turbulent Flow Field and Intense
Magnetic Flux Tubes
Authors: Rosner, R.; Musielak, Z. E.; Ulmschneider, P.
1989BAAS...21..844R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Generation of Flux Tube Waves in Stellar Convection
Zones. I. Longitudinal Tube Waves Driven by External Turbulence
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1989ApJ...337..470M Altcode:
The source functions and the energy fluxes for wave generation in
magnetic flux tubes embedded in an otherwise magnetic field-free,
turbulent, and compressible fluid are derived. The calculations
presented here assume that the tube interior is not itself turbulent,
e.g., that motions within the flux tube are due simply to external
excitation. Specific results for the generation of longitudinal tube
waves are presented.
---------------------------------------------------------
Title: Surface waves on a generalized current sheet.
Authors: Suess, S. T.; Musielak, Z. E.
1989GMS....54..413S Altcode: 1989opss.conf..413S; 1989sspp.conf..413S
The authors extend the theory for MHD surface waves in a non-isothermal
layer of finite thickness in two different examples. The first is a
tangential "discontinuity" in which the magnetic field undergoes a
rotational change in direction parallel to the layer with no change
in amplitude. The second is a sheet pinch across which the field
undergoes a change in amplitude with no rotation or reversal. Bound,
normal mode surface wave solutions are found to be supported by both
the sheet pinch and tangential discontinuities in which the field
vector undergoes a limited rotation of less that 90°. However, field
rotation does not always remove singularities in the wave equations
and wave decay through mode coversion can then occur.
---------------------------------------------------------
Title: Magnetohydrodynamic Bending Waves in a Current Sheet
Authors: Musielak, Z. E.; Suess, S. T.
1988ApJ...330..456M Altcode:
The physical properties of MHD bending waves in an isothermal,
compressible, low-beta, three-dimensional current sheet of finite
thickness in which the magnetic field direction and strength varies are
considered. The case of the wavenumber (k) to circular frequency ratio
being greater than the Alfven velocity outside the layer (V<SUB>A)</SUB>
corresponds to one-sided surface waves, and it is suggested that
the heliospheric current sheet ripples are not this type of bending
wave. The case of k/omega of less than V<SUB>A</SUB> describes the
interaction of freely and obliquely propagating MHD waves with the
layer, while the case of k/omega = V<SUB>A</SUB> describes an Alfven
wave propagating parallel to but having no interaction with the layer.
---------------------------------------------------------
Title: On the Generation of Magnetohydrodynamic Waves in a Stratified
and Magnetized Fluid. II. Magnetohydromagnetic Energy Fluxes for
Late-Type Stars
Authors: Musielak, Z. E.; Rosner, R.
1988ApJ...329..376M Altcode:
Magnetohydrodynamic (MHD) wave energy fluxes for late-type stars are
calculated, using previously obtained formulae for the source functions
for the generation of MHD waves in a stratified, but otherwise uniform,
turbulent atmosphere; the magnetic fields in the wave generation
region are assumed to be homogeneous. In contradiction to previous
results, it is shown that in this uniform magnetic field case there is
no significant increase in the efficiency of MHD wave generation, at
least within the theory's limits of applicability. The major results are
that the MHD energy fluxes calculated for late-type stars are less than
those obtained for compressible modes in the magnetic field-free case,
and that these MHD energy fluxes do not vary enough for a given spectral
type to explain the observed range of UV and X-ray fluxes from such
stars. It is therefore concluded that MHD waves in stellar atmospheres
with homogeneous magnetic fields in the wave generation region cannot
explain the observed stellar coronal emissions; if such MHD waves are
responsible for a significant component of stellar coronal heating,
then nonuniform fields within the generation region must be appealed to.
---------------------------------------------------------
Title: Trapping of Magnetoacoustic Waves in an Isothermal Atmosphere
Authors: Musielak, Z. E.; Moore, R. L.; Suess, S. T.
1988BAAS...20..683M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic Modulation of the Short-Period Cutoff for Solar
Global p-Mode Oscillations
Authors: Moore, R. L.; Musielak, Z. E.
1988BAAS...20Q.684M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interaction of Freely and Obliquely Propagating MHD Wave
Trains with the Heliospheric Current Sheet
Authors: Suess, S. T.; Musielak, Z. E.
1988BAAS...20S.714S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A Numerical MHD Simulation Model for the Study of Flux
Tube Waves
Authors: Xiao, Y. C.; Wu, S. T.; Musielak, Z. E.; Suess, S. T.
1988BAAS...20..716X Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Generation of MHD Waves by Convective Turbulence
Authors: Rosner, R.; Musielak, Z. E.
1988BAAS...20..715R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Wave Energy in White Dwarf Atmospheres. I. Magnetohydrodynamic
Energy Spectra for Homogeneous DB and Layered DA Stars
Authors: Musielak, Zdzislaw E.
1987ApJ...322..234M Altcode:
The radiative damping of acoustic and MHD waves that propagate
through white dwarf photospheric layers is studied, and other damping
processes that may be important for the propagation of the MHD waves are
calculated. The amount of energy remaining after the damping processes
have occurred in different types of waves is estimated. The results
show that lower acoustic fluxes should be expected in layered DA and
homogeneous DB white dwarfs than had previously been estimated. Acoustic
emission manifests itself in an enhancement of the quadrupole term,
but this term may become comparable to or even lower than the dipole
term for cool white dwarfs. Energy carried by the acoustic waves is
significantly dissipated in deep photospheric layers, mainly because
of radiative damping. Acoustically heated corona cannot exist around
DA and DB white dwarfs in a range T(eff) = 10,000-30,000 K and for log
g = 7 and 8. However, relatively hot and massive white dwarfs could
be exceptions.
---------------------------------------------------------
Title: Theoretical Energy Spectrum for Solar p-Modes
Authors: Musielak, Z. E.
1987BAAS...19.1132M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Excitation of Solar p-Modes by Monopole and Dipole Sources
of Acoustic Waves
Authors: Musielak, Z. E.
1987BAAS...19..934M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Generation of Magnetohydrodynamic Waves in a Stratified
and Magnetized Fluid. I. Vertical Propagation
Authors: Musielak, Z. E.; Rosner, R.
1987ApJ...315..371M Altcode:
The generation of MHD waves by turbulent motions in a stratified medium
with an embedded uniform magnetic field, a topic which is relevant to
the study of the solar atmosphere, is considered. Both compressible
and incompressible MHD waves are treated in a one-dimensional approach;
however, the direction of the background magnetic field is permitted to
vary in an arbitrary direction. Theoretical expressions for MHD energy
fluxes are obtained as a function of wave frequency and multipole
coefficients. It is shown that monopole, dipole, and quadrupole
emissions are responsible for the generation of the compressible
components of the fast and slow modes. However, the incompressible
components and the Alfven modes can be generated by the dipole emission
only. Specific results obtained for special magnetic field geometries
are discussed for the fast and slow modes.
---------------------------------------------------------
Title: MHD Wave Energy Fluxes for Late-Type Dwarfs
Authors: Rosner, R.; Musielak, Z. E.
1987LNP...291...69R Altcode: 1987csss....5...69R
We calculate the efficiency of MHD wave generation by turbulent motions
in the stratified stellar atmospheres of late-type main sequence
stars, under the assumption that the embedded magnetic fields are
uniform. In contradiction with previous results, we show that there is
no significant increase in the efficiency of wave generation because of
the presence of magnetic fields, at least within the theory's limits
of applicability. Thus, we show that MHD energy fluxes for late-type
stars whose surface magnetic fields are uniform are less than those
obtained for acoustic waves in a magnetic field-free atmosphere,
and do not vary enough for a given spectral type in order to explain
observed UV and X-ray fluxes. Thus, our results show that MHD energy
fluxes obtained if stellar surface magnetic fields are uniform cannot
explain the observed stellar coronal emissions.
---------------------------------------------------------
Title: Magnetic Flux Tubes as Sources of Wave Generation
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1987LNP...291...66M Altcode: 1987csss....5...66M
Because solar (and, most likely, stellar) surface magnetic fields
are highly inhomogeneous, and show concentration into `flux tube'
structures, the wave energy generated in stellar convection zones
may be largely carried away by flux tube waves, which then become
important sources for the heating of the outer atmospheric layers. We
report calculations for longitudinal tube waves generated in magnetic
flux tubes embedded in an otherwise magnetic field-free, turbulent,
and stratified medium; we find that such waves are generated by dipole
emission, and that the generation efficiency is a strong function of
the magnetic field strength. We also present wave flux calculations
for magnetic flux tubes embedded in the solar convective zone; the
main result is that the longitudinal tube wave fluxes are at least 2
orders of magnitude too low to play a significant role in the heating
of the solar chromosphere.
---------------------------------------------------------
Title: Generation of flux tube waves in stellar convection zones. 1:
Longitudinal tube waves
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.
1987STIN...8824561M Altcode:
The source functions and the energy fluxes are derived for wave
generation in magnetic flux tubes embedded in an otherwise magnetic-
field free, turbulent, and compressible fluid. Specific results for
the generation of longitudinal tube waves are presented.
---------------------------------------------------------
Title: Fine-Scale Waves on the Heliospheric Current Sheet
Authors: Musielak, Z. E.; Suess, S. T.
1987sowi.conf..340M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relationship between directions of wave and energy propagation
for cold plasma waves
Authors: Musielak, Zdzislaw E.
1986JPlPh..36..341M Altcode:
The dispersion relation for plasma waves is considered in the ‘cold’
plasma approximation. General formulae for the dependence of the
phase and group velocities on the direction of wave propagation with
respect to the local magnetic field are obtained for a cold magnetized
plasma. The principal cold plasma resonances and cut-off frequencies
are defined for an arbitrary angle and are used to establish basic
regimes of frequency where the cold plasma waves can propagate or can
be evanescent. The relationship between direction of wave and energy
propagation, for cold plasma waves in hydrogen atmosphere, is presented
in the form of angle diagrams (angle between group velocity and
magnetic field versus angle between phase velocity and magnetic field)
and polar diagrams (also referred to as ‘Friedrich's diagrams’ ) for
different directions of wave propagation. Morphological features of the
diagrams as well as some critical angles of propagation are discussed.
---------------------------------------------------------
Title: Efficiency of Flux Tube Wave Generation in Late Type Stars
Authors: Musielak, Z. E.; Rosner, R.; Ulmschneider, P.; Bohn, H. U.
1986BAAS...18.1002M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Heating of intense magnetic flux tubes by magnetohydrodynamic
waves
Authors: Musielak, Z.; Bielicz, E.
1983IAUS..102..413M Altcode:
Theoretical models of intense magnetic flux tubes
embedded in the photospheres of late-type stars have been
calculated. Magnetohydrodynamic waves generated in the convective
zone are radiatively damped in the lower part of the flux tube and
then dissipated. The authors discuss how the presence of flux tubes
in stellar photospheres influences the temperature minimum and the
chromospheric activity. They suggest a possible interpretation of the
Wilson-Bappu effect in stars with strong chromospheric activity.
---------------------------------------------------------
Title: Physical processes determining the structure of stellar
chromospheres. II
Authors: Musielak, Z.
1983PoAst..30..269M Altcode:
Observational data pertaining to physical processes in stellar
chromospheres are presented, and correlations between chromospheric and
other atmospheric parameters are examined. The development of models
of the solar chromosphere and stellar chromospheres is described,
the models being based on the balance between radiative losses and
dissipated mechanical energy. Questions relating to the inhomogeneity
of the theoretical models and evolution effects are considered.
---------------------------------------------------------
Title: Physical processes determining the structure of stellar
chromospheres. I
Authors: Musielak, Z.
1982PoAst..30..123M Altcode:
The principal sources of radiative losses in the chromospheres of F,
G, and K stars are indicated, with particular attention given to the
hydrogen continuum and intense and faint lines formed by different
elements. Mechanisms of the heating of stellar chromospheres are
examined, with emphasis on heating via the dissipation of acoustic
and magnetohydrodynamic waves.
---------------------------------------------------------
Title: Generation of magnetohydrodynamic waves in white dwarfs
Authors: Musielak, Z.
1982AcA....32..233M Altcode:
Mechanical energy fluxes generated in H-rich and He-rich convective
zones of white dwarfs were calculated for a wide range of effective
temperatures. In these computations the author assumes that convection
and turbulent spectrum are independent of the magnetic field. The
presence of the magnetic field causes an important change in the
generation of an acoustic flux in the convective zone and introduces new
energy carrying modes - the #agnetohydrodynamic waves. New estimates
of the mechanical energy fluxes give significantly higher values than
those previously given for the white dwarf. Consequently, the author
predicts higher X-ray luminosities that should be observed with the
present-day techniques. It is also shown that the mechanism of X-ray
generation plays a negligible role in the white dwarf companion in a
cataclysmic binary system.
---------------------------------------------------------
Title: Waves in stellar atmospheres. II - Heating of flux tubes by
magnetohydrodynamic waves
Authors: Bielicz, E.; Musielak, Z.
1982AcA....32..251B Altcode:
The authors assume that the active regions are closely connected with
the presence of intense magnetic flux tubes. They also consider the
changes of flux tube models in the upper photosphere which are caused by
propagation and dissipation of magnetohydrodynamic waves. The presence
of a magnetic field leads to a higher value of temperature minimum
and to the increase of chromospheric activity in the flux tube. The
treatment of energy balance in a strong magnetic field is presented.
---------------------------------------------------------
Title: Connection between chromospheric activity of F, G, K type
stars and their magnetic field
Authors: Musielak, Z.; Bielicz, E.
1982AcA....32..263M Altcode:
The appearance of bright emission in the cores of strong resonance lines
is used to define active regions in the solar chromosphere. In the
present study, attention is given to the dependence of chromospheric
activity on the number of the intense magnetic flux tubes. It is
suggested that the strong chromospheric activity found in the case of
some stars can be caused by the appearance of a greater number of flux
tubes in these stars. Theoretical inhomogeneous models of chromospheres
are considered along with aspects of chromospheric activity in dwarfs
and giants, and the Wilson-Bappu effect. The interpretation of the
Wilson-Bappu relation provided for stars with strong chromospheric
activity indicates the important role of flux tubes in explanation of
the strong activity.
---------------------------------------------------------
Title: Theoretical models of homogeneous chromospheres for main
sequence stars.
Authors: Musielak, Z.
1982A&A...105...23M Altcode:
It is shown that the structure of the chromosphere is determined by
three parameters: (1) the dissipating wave period; (2) the energy flux
spectrum provided to the chromosphere; and (3) the magnetic field; where
these parameters are mutually dependent, with the greatest dependency
being between the energy flux spectrum value and the magnetic field. The
analysis presented demonstrates that it is impossible to reconstruct the
semi-empirical models considered when short-period waves are adopted
for heating. The range of energy flux spectrum values given is from
10 million erg/sq cm per sec, for the case of stars cooler than the
sun, to 100 million erg/sq cm per sec for the case of stars that are
hotter. The results contradict theoretical estimates of convective
zone-generated mechanical energy flux, especially for cooler stars. It
is concluded that the strength of the average magnetic field determines
the division of stars into those with weak, and those with strong,
chromospheric activity.
---------------------------------------------------------
Title: Chromospheres of F, G, K type stars. VIII. Energy balance in
transition region.
Authors: Prominski, M.; Musielak, Z.; Sikorski, J.
1982AcA....32..111P Altcode:
Radiative losses, thermal conductivity from the corona, the convective
energy flux, and the dissipation, refraction, and reflection of MHD
waves are calculated for known empirical and theoretical models of
the transition region for the quiet and active (flare) sun and Epsilon
Eri. Emissions of bound-free and free-free transitions for hydrogen and
helium and bound-bound transitions for more than 350 of the strongest
lines identified in that region are allowed for in computing the
radiative losses. It is confirmed that some mechanisms for heating from
below are required to form the lower layers of the transition region. It
is believed that thermal conductivity may compensate radiative losses
only for the upper part of the transition region of the quiet sun model.
---------------------------------------------------------
Title: Chromospheres of F, G, K Type Stars. VII. Upper Chromosphere
and Transition Region
Authors: Musielak, Z. E.; Sikorski, J.
1981AcA....31..494M Altcode:
Basing on detailed energy balance between radiative losses and
amount of mechanical energy (with different flux spectra) we made
an attempt to reconstruct conditions for the formation of transition
region chromosphere-corona. We confirmed that the shape of mechanical
energy spectrum may be different for stars with different effective
temperatures and we found that the gradient of microturbulence
velocity in the chromosphere has a significant influence on formation
of the transition region. Calculations show that transition regions are
present in main sequence stars and absent for alpha Boo and alpha Tau,
in agreement with observations.
---------------------------------------------------------
Title: Chromospheres of F G K Type Stars - Part Seven - Upper
Chromosphere and Transition Region
Authors: Musielak, Z.; Sikorski, J.
1981AcA....31..493M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Waves in stellar atmospheres. I. Heating of upper photosphere
by short period acoustic waves.
Authors: Bielicz, E.; Musielak, Z.; Sikorski, J.
1981AcA....31...51B Altcode:
Theoretical models of upper photosphere and low chromosphere for
ten main sequence stars are calculated. Short period acoustic waves
generated in the convective zone are radiatively damped in the
lower photosphere and then converted into weak shocks which heat the
medium by dissipation processes. The obtained models are compared with
semiempirical ones. It is shown that the temperature minimum region can
be reconstructed using acoustic fluxes different from those predicted
by the Lighthill-Proudman and mixing length theories, especially for
cool stars.
---------------------------------------------------------
Title: Chromospheres of F, G, K type stars. IV - The zone model
of heating
Authors: Musielak, Z.; Sikorski, J.
1980AcA....30..167M Altcode:
The paper proposes the so called 'zone model' of heating in which the
chromosphere is divided into three regions corresponding to dissipation
of energy by acoustic, fast, and slow plus Alfven waves, respectively. A
phenomenological chi parameter is introduced simulating a development
of wave into shock over a finite distance. The influence of magnetic
field, wave period, and chi parameter on the amount of dissipated
energy is investigated for known semiempirical chromospheric models.
---------------------------------------------------------
Title: Chromospheres of F, G K type stars. V. Radiative losses in
spectral lines.
Authors: Glebocki, R.; Musielak, Z.; Sikorski, J.
1980AcA....30..259G Altcode:
Radiative losses in weak and strong lines are compared with losses in
continua. In spite of large number of weak lines (more than 20,000 in
visible region) their total energy losses are small in comparison to
losses in continua.
---------------------------------------------------------
Title: Chromospheres of F, G, K type stars. VI - Theoretical
homogeneous models of solar chromosphere
Authors: Musielak, Z.; Sikorski, J.
1980AcA....30..479M Altcode:
Theoretical models of the chromosphere were developed on the basis
of the energy balance between radiative losses and the amount of
dissipated mechanical energy. The influence of boundary conditions
in the temperature minimum as well as that of free parameters
is examined. Particular attention is given to the effect of the
dissipating-wave period, the amount of mechanical energy provided for
dissipation, and the magnetic field strength on the resulting model. The
influence of these parameters on the Mg II h and k line profiles is
also discussed. It is shown that the monochromatic wave approximation
cannot explain the structure of the highest layers of the chromosphere.
---------------------------------------------------------
Title: Chromospheres of F, G, K type stars. III. Dissipation of
mechanical energy by waves of acoustic, fast and slow modes.
Authors: Musielak, Z.; Sikorski, J.
1979AcA....29..609M Altcode:
Mechanisms of dissipation of acoustic, fast and slow mode waves were
applied for five F, G, K type stars with known semiempirical models
of chromospheres and the sun. The rates of dissipation of energy
for constant and variable period waves with geometrical height were
calculated. The total amount as well as variations with height of
dissipated energy are compared with the radiative losses which were
obtained in a previous paper. It is concluded that heating of the
chromosphere only by the acoustic waves is an oversimplification. The
regions where various magnetohydrodynamic waves should be applied
are discussed.
---------------------------------------------------------
Title: Chromospheres of F, G, K type stars. II - Radiative losses
in continuum
Authors: Musielak, Z.; Sikorski, J.
1979AcA....29..381M Altcode:
Radiative losses for six F, G, K type stars with known semi-empirical
models of the chromospheres and for the sun are calculated. The total
losses as well as the variation of the radiative loss with height are
discussed. Calculated radiative fluxes are compared with predicted
values of mechanical energy supplied in the form of acoustic waves by
the convective zone. In some cases considerable discrepancies between
these fluxes are found.
---------------------------------------------------------
Title: Physical properties of asteroids. Part II.
Authors: Musielak, Z.
1978PoAst..25..161M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Physical properties of asteroids. Part I.
Authors: Musielak, Z.
1977PoAst..25..115M Altcode:
The paper reviews some of the more important methods of observing
asteroids and studying their physical properties. The principles of
photoelectric observations are examined. Examples of light curves
are discussed. The dependence of brightness on phase angle and the
variation of color indices are also considered.
