Author name code: holzer
ADS astronomy entries on 2022-09-14
author:"Holzer, Thomas E."
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Title: Application of a New Technique for Deriving Prominence Mass
from SOHO EIT Fe XII (19.5 nm) Absorption Features
Authors: Gilbert, Holly R.; Falco, Lauren E.; Holzer, Thomas E.;
MacQueen, R. M.
Bibcode: 2006ApJ...641..606G
Altcode:
In a previous study we developed a new technique for deriving prominence
mass by observing how much coronal radiation in the Fe XII (19.5 nm)
spectral line is absorbed by prominence material. In the present work
we apply this new method, which allows us to consider the effects
of both foreground and background radiation in our calculations,
to a sample of different types of prominences (eruptive, quiescent,
and surging) observed during the period 1999 July through 2004
July. The masses of prominences involved in CMEs are not generally
measured, but the accurate determination of such masses may help in
assessing the dynamical importance of prominences in CME events. In
the present study, we find the average mass of our sample of quiescent
prominences to be 4.18×1014 g, while the average mass
of the eruptive prominences is 9.09×1014 g, and that of
surges is 1.53×1014 g.
Title: Heating and Acceleration of the Solar Plasma (Tutorial Talk)
Authors: Holzer, T. E.
Bibcode: 2005ESASP.592..115H
Altcode: 2005soho...16E..18H; 2005ESASP.592E..18H
No abstract at ADS
Title: Multialtitude Observations of a Coronal Jet during the Third
Whole Sun Month Campaign
Authors: Ko, Y. -K.; Raymond, J. C.; Gibson, S. E.; Alexander, D.;
Strachan, L.; Holzer, T.; Gilbert, H.; Cyr, O. C. St.; Thompson, B. J.;
Pike, C. D.; Mason, H. E.; Burkepile, J.; Thompson, W.; Fletcher, L.
Bibcode: 2005ApJ...623..519K
Altcode:
On 1999 August 26, a coronal jet occurred at the northwest limb near
a sigmoid active region (AR 8668) that was the target for a joint
observation plan (SOHO joint observing program 106) during the third
Whole Sun Month Campaign. This jet was observed by several instruments
at the limb (SOHO/CDS, SOHO/EIT, TRACE, and Mauna Loa Solar Observatory
CHIP and PICS) and at 1.64 Rsolar (SOHO/UVCS). At the limb,
this jet event displayed both low- and high-temperature components. Both
high- and low-temperature components were evident during the early phase
(first 20 minutes) of the event. However, the low-temperature component
is maintained for ~1 hr after the higher temperature component is
gone. There is a second brightening (a possible second jet) seen by
EIT and TRACE about 50 minutes after the onset of the first jet. The
line-of-sight motion at the limb began with a 300 km s-1
redshift and evolved to a 200 km s-1 blueshift. At
1.64 Rsolar, the intensities of Lyα and Lyβ in the jet
increased by a factor of several hundred compared with the background
corona. The C III λ977 line also brightened significantly. This
indicates low-temperature [~(1-2)×105 K] emission in the
jet, while the intensities of O VI λ1032 and O VI λ1037 increased
by as much as a factor of 8. The UVCS data show evidence of heating at
the early phase of the event. The Doppler shift in the lines indicates
that the line-of-sight (LOS) velocity in the jet started from ~150
km s-1 in blueshift and ended at ~100 km s-1
in redshift. This LOS motion seen at 1.64 Rsolar was
apparently opposite to what was observed when the jet emerged from the
limb. The Doppler dimming analysis indicates that the radial outflow
speed correlates with the magnitude of the LOS speed. Interestingly,
UVCS observations at 2.33 and 2.66 Rsolar show no trace of
the jet and SOHO/LASCO observations also yield no firm detection. We
find that a simple ballistic model can explain most of the dynamical
properties of this jet, while the morphology and the thermal properties
agree well with reconnection-driven X-ray jet models.
Title: Transient Coronal Holes as Seen in the He I 1083 nm MLSO
Observations
Authors: de Toma, G.; Holzer, T. E.; Burkepile, J. T.; Gilbert, H. R.
Bibcode: 2005ApJ...621.1109D
Altcode:
Observations from Yohkoh SXT and SOHO EIT have shown that dimming
regions often appear on the solar disk near the location of a
coronal mass ejection (CME). We now can see brightenings in He I
1083 nm observations made at the Mauna Loa Solar Observatory (MLSO)
that form at the same time and are cospatial with the EUV intensity
dimmings observed from space. The He I 1083 nm brightenings are
induced by a decrease of the overlying coronal radiation. The EUV and
X-ray dimmings and He I 1083 nm brightenings can thus be interpreted
as different manifestations of the decreased coronal density caused
by the ejection of coronal material during the eruption, i.e., as
transient coronal holes. In this paper we present examples of transient
coronal holes that form during the CME onset as seen in He I 1083 nm
data and compare them with simultaneous observations in the Fe XII
19.5 nm line. We find that there is good agreement in both shape and
size of the transient coronal holes at these two wavelengths. The
3 minute cadence of the He I 1083 nm observations taken at MLSO is
used to determine the appearance and evolution of transient coronal
holes with high temporal accuracy. Additional data in the Hα line
and in broadband visible light are used to investigate the relation of
transient coronal holes to the flare, filament eruption, and CME. The
cases presented here illustrate how the higher time cadence of the MLSO
observations can complement space data to establish the chronology of
the various manifestations of solar activity associated with a CME.
Title: A New Technique for Deriving Prominence Mass from SOHO/EIT
Fe XII (19.5 Nanometers) Absorption Features
Authors: Gilbert, Holly R.; Holzer, Thomas E.; MacQueen, R. M.
Bibcode: 2005ApJ...618..524G
Altcode:
It is presently unclear what role prominences play in the initiation and
dynamics of coronal mass ejections (CMEs), although erupting prominences
are strongly correlated with CMEs. The masses of prominences involved in
CMEs are not generally measured, but the accurate determination of such
masses may help in assessing the dynamical importance of prominences in
CME events. In the technique for deriving prominence mass introduced in
the present work, we use observations of coronal radiation in the Fe XII
(19.5 nm) spectral line, which is absorbed by prominence material. This
new method allows us to consider the effects of both foreground and
background radiation in our calculations, and it can be applied to
both quiescent and erupting prominences by using two versions of the
method, which we label the ``spatial-interpolative'' version and the
``temporal-interpolative'' version. When both versions can be applied
to the same event, we find that the temporal-interpolative approach
yields the more accurate results. We have applied both versions to
an erupting prominence observed on 1999 July 12 (this prominence has
an associated CME), and we find that the two approaches result in
similar mass determinations: (6.0+/-2.5)×1014g for the
temporal-interpolative approach and (7.4+/-4.6)×1014g for
the spatial-interpolative approach.
Title: Transient Coronal Holes: EUV and IR HeI 1083nm Observations
Authors: de Toma, G.; Holzer, T. E.; Gilbert, H. R.; Burkepile, J. T.
Bibcode: 2004AGUFMSH53B0328D
Altcode:
We present cases of transient coronal holes following a CME observed
simultaneously by SOHO/EIT and the instruments at Mauna Loa Solar
Observatory (MLSO). We describe the formation of the transient coronal
holes and their relationship to the flare evolution, filament eruption,
and CME taking advantage of the high 3-minute temporal cadence of the
MLSO observations. We find that transient coronal holes in HeI 1083nm
correspond well to the EUV ones, both spatially and temporally
Title: Chromospheric Waves Observed in the He I Spectral Line (λ =
10830 Å): A Closer Look
Authors: Gilbert, Holly R.; Holzer, Thomas E.
Bibcode: 2004ApJ...610..572G
Altcode:
Although ``Moreton'' waves have historically been observed in Hα data,
more recently waves have also been observed in chromospheric He I
(λ=10830 Å) images. In a previous study, we found that chromospheric
waves observed in He I data (from the Mauna Loa Solar Observatory)
in two events (occurring on 2000 November 25 and 2001 January 20)
are cospatial with the corresponding coronal waves observed by EIT
(Fe XII λ=195 Å). In an effort to better understand the nature of
chromospheric waves, we focus on these two wave events observed in
He I in which two interesting phenomena occur: the waves are visible
in the He I velocity data, and multiple waves are observed for each
event. We suggest that the velocity signal is a result of slow-mode
wave compression followed by a slow-mode wave rarefaction propagating
downward from the corona into the upper chromosphere. We also suggest
that the observed multiple waves indicate that more than one driving
mechanism may be involved.
Title: A Comparison of CME-Associated Atmospheric Waves Observed in
Coronal (Fe XII 195 Å) and Chromospheric (He I 10830 Å) Lines
Authors: Gilbert, Holly R.; Holzer, Thomas E.; Thompson, Barbara J.;
Burkepile, Joan T.
Bibcode: 2004ApJ...607..540G
Altcode:
Although ``Moreton'' waves have historically been observed in Hα
data, more recently waves have also been observed in chromospheric
He I λ10830 images obtained at the Mauna Loa Solar Observatory. In
an effort to better understand the nature of chromospheric waves and
their relationship to coronal waves observed in EUV Imaging Telescope
(EIT) data, we focus on two events in which waves are observed
simultaneously in He I λ10830 and Fe XII λ195, lines that are formed
in the chromosphere and the corona, respectively. Comparing the waves
observed in these two lines allows the determination of the spatial
relationship between coronal and chromospheric waves and thus aids
in the understanding of the underlying physics of waves in the solar
atmosphere. The main goal of this work is to begin an investigation
into whether both coronal and chromospheric waves are mechanical
(e.g., MHD waves) by looking at their spatial relationship. We find
that the chromospheric waves in these two events are cospatial with
their coronal counterparts, indicating that they are not mechanical in
nature but are chromospheric imprints of mechanical waves propagating
through the corona. This conclusion is based on the nature of the
formation of the He I absorption line.
Title: Multi-Altitude Observations of a Coronal Jet
Authors: Ko, Y. -K.; Raymond, J. C.; Gibson, S. E.; Alexander, D.;
Strachan, L.; Holzer, T.; Gilbert, H.; St. Cyr, O. C.; Thompson,
B. J.; Pike, C. D.; Burkepile, J.; Thompson, W.; Fletcher, L.
Bibcode: 2004AAS...204.5413K
Altcode: 2004BAAS...36..759K
A coronal jet occurred on August 26, 1999 at the NW limb near a sigmoid
active region (AR8668). This jet was observed by several instruments
at the limb (SOHO/CDS, SOHO/EIT, TRACE, MLSO/CHIP, MLSO/PICS) and
at 1.64 Ro (SOHO/UVCS). At the limb, this jet event has both low and
high temperature components. The high temperature component appeared
at the early phase (first 20 minutes) of the event along with the low
temperature component while the latter seems to last long ( ∼ 1 hour)
after the higher temperature component was gone. The line-of-sight
motion at the limb started with red-shifted (by as much as 300 km/s)
and turned blue-shifted (by as much as 200 km/s). At 1.64 Ro, the
intensities of Lyα , Lyβ in the jet increased by a factor of several
hundreds compared with the background corona. C III λ 977 line also
brightened significantly. This indicates low temperature ( ∼ 1-2×
105 K) emission in the jet, while the intensities of O VI
λ 1032 and O VI λ 1037 increased by a factor of as large as 8. Both
UVCS and CDS data show evidence of heating at the early phase of the
event. The line-of-sight velocity seen at 1.64 Ro started with ∼ 150
km/sec in blue shift and ended at ∼ 100 km/sec in red shift. This is
apparently opposite to what were observed when the jet emerged from
the limb. The Doppler dimming analysis indicates that the radial
outflow speed correlates with the magnitude of the line-of-sight
speed. Interestingly, UVCS observations at 2.33 and 2.66 Ro show no
trace of the jet and LASCO observations also yield no firm sight of the
jet. In this paper, we present the observations by these instruments
and discuss the dynamical structure and physical properties of this
jet. Y.-K. Ko acknowledges the support by NASA grant NAG5-12865.
Title: Helmet Streamers Gone Unstable: Two-Fluid Magnetohydrodynamic
Models of the Solar Corona
Authors: Endeve, Eirik; Holzer, Thomas E.; Leer, Egil
Bibcode: 2004ApJ...603..307E
Altcode:
The equations of magnetohydrodynamics (MHD) are used to study heating
of electrons and protons in an axially symmetric model of the solar
corona, extending from the coronal base to 15 solar radii. To study
heating of electrons and protons separately, as well as the collisional
coupling between the particle species, we use a two-fluid description
of the electron-proton plasma. A steady coronal heat input, uniform base
pressure, and dipole field boundary conditions produce a magnetic field
configuration similar to that seen with white-light coronagraphs during
quiet-Sun conditions: a helmet streamer is formed in the inner corona
around the equator, surrounded by coronal holes at higher latitudes. The
plasma inside the helmet streamer is in hydrostatic equilibrium, while
in the coronal holes a transonic solar wind is accelerated along the
field. The collisional coupling between electrons and protons becomes
weak close to the coronal base. In the case of proton heating, the
thermal structure along open and closed field lines is very different,
and there is a large pressure jump across the streamer-coronal hole
boundary. When the equations are integrated on a long timescale, the
helmet streamer becomes unstable, and massive plasmoids are periodically
released into the solar wind. These plasmoids contribute significantly
to the total mass and energy flux in the solar wind. The mass of the
plasmoids is reduced when electrons are heated.
Title: Three-dimensional coronal density structure: 1. Model
Authors: Gibson, S. E.; Foster, D. J.; Guhathakurta, M.; Holzer, T.;
St. Cyr, O. C.
Bibcode: 2003JGRA..108.1444G
Altcode:
The three-dimensional (3-D) density structure of the solar corona is a
fundamental boundary condition on the solar wind. Most easily applied
models of the global coronal density have been restricted to date
to axisymmetric 2-D cases. We present here a 3-D model made up of a
superposition of multiple streamers, having distinct gaussian widths in
longitude and latitude and both longitudinal and latitudinal dependence
of the neutral lines implicit beneath the streamer cores. Nonradiality
of streamers and solar B-angle tilt are also explicitly treated. We
show how this simple model can capture many of the general properties
of coronal white light observations and demonstrate how such a model
can assist in the interpretation of the multiple views on coronal
structures such as will be provided by the upcoming STEREO mission.
Title: Time Evolution of Coronal Holes and Their Impact on the
Solar Wind
Authors: Holzer, T. E.; de Toma, G.; Arge, C. N.; Burkepile, J. T.
Bibcode: 2003AGUFMSH42B0529H
Altcode:
Coronal holes, which can be defined as open magnetic field regions on
the Sun, are the source of high-speed streams and possibly slow wind
and thus play an important role in nature and structure of the solar
wind/heliosphere. Over the last decade, significant progress has been
made in our ability to predict ambient solar wind conditions days in
advance using a number of different models that vary widely in their
sophistication (e.g., MHD and Potential Magnetic Field Source Surface
Models) but all of which are driven by observations of the photospheric
magnetic field in the form of synoptic maps. These ambient solar models
based on extrapolation from photospheric magnetic fields are limited
and cannot duplicate the complexity of the solar wind during periods
of transient wind. However, a very recent comprehensive study by Arge
et al. has shown that significant discrepancies often occur between
model predictions and observations after transient wind has completed
its passage past Earth and the observed solar wind has returned to
ambient/background conditions (i.e., when the model is expected to
resume performing well). Such discrepancies can persist for 2 to 3
days after the passage of the transient. To understand the origin of
these differences, we will use coronal observations at time of CMEs to
study variations in the pattern of coronal holes at the Sun. Our goal
is to investigate if changes in coronal holes (probably not visible in
photospheric field synoptic maps) can be responsible for the changes
seen at 1AU.
Title: Acceleration of Prominences in the Low Corona
Authors: de Toma, G.; Burkepile, J. T.; Gilbert, H. R.; Holzer, T. E.
Bibcode: 2003AGUFMSH22A0181D
Altcode:
We show examples of prominence eruptions as observed in the low corona
and present preliminary results of an observational study aimed to
investigate the relationship between the acceleration of eruptive
prominences and the speed of their associated CMEs. For this study,
we have selected events near the limb when we can identify eruptive
prominences in Mauna Loa ground based observations that show a clear
association with CMEs during the period 1998-present. MLSO/CHIP
images in the HeI 1083nm line and the MLSO/PICS images in the Hα
656.3nm line are used to identify the eruptive prominences and to
determine its projected radial velocity and acceleration. SOHO/LASCO
and MLSO/MK4 observations are used to determine the trajectory of the
corresponding CME.
Title: Development of 2D MHD Self-Consistent Empirical Model of the
Corona and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Holzer, T.; Davila,
J.; Guhathakurta, M.
Bibcode: 2003AGUFMSH42D..07S
Altcode:
We are developing a 2D MHD self-consistent empirical model of
the solar corona and solar wind. We constrain the solution using
empirically determined estimates of the effective pressure for the
momentum equation and effective heat flux for the energy equation
provided from coronagraph data and Ulysses plasma and magnetic field
data. Our solutions are steady state and do not use a polytrope which
we know is not valid in the solar corona. We have been able to achieve
preliminary convergence. We will present the results of an error
analysis. Our results are presently only valid during solar minimum,
but are generalizing so it can be used during the transition toward
solar maximum (i.e., three current sheets). We will also present some
preliminary results which will allow us to apply our solutions to
solar maximum conditions.
Title: 2D MHD Models of the Large Scale Solar Corona
Authors: Endeve, Eirik; Holzer, Thomas E.; Leer, Egil
Bibcode: 2003AIPC..679..331E
Altcode:
By solving the equations of ideal MHD the interaction of an isothermal
coronal plasma with a dipole-like magnetic field is studied. We vary the
coronal temperature and the magnetic field strength to investigate how
the plasma and the magnetic field interact to determine the structure
of the large scale solar corona. When our numerical calculations are
initiated with an isothermal solar wind in a dipole magnetic field,
the equations may be integrated to a steady state. Open and closed
regions are formed. In the open regions the atmosphere expands into a
super-sonic wind, and in the closed regions the plasma is in hydrostatic
equilibrium. We find that the magnetic field configuration in the
outer corona is largely determined by the equatorial current sheet.
Title: Development of Multidimensional MHD Model for the Solar Corona
and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Guhathakurta, M.;
Davila, J.; Skoug, R.; Fludra, A.; Holzer, T.
Bibcode: 2003AIPC..679..113S
Altcode:
We are developing a time stationary self-consistent 2D MHD model of
the solar corona and solar wind that explicitly solves the energy
equation, using a semi-empirical 2D MHD model of the corona to provide
an empirically determined effective heat flux qeff (i.e., the term
effective means the possible presence of wave contributions). But,
as our preliminary results indicate, in order to achieve high
speed winds over the poles we also need to include the empirically
determined effective pressure Peff as a constraint in the momentum
equation, which means that momentum addition by waves above 2 RS are
required to produce high speed winds. At present our calculations do
not include the Peff constraint. The estimates of Peff and qeff come
from the semi-empirical 2D MHD model of the solar corona by Sittler
and Guhathakurta (1999a,2002) which is based on Mk-III, Skylab and
Ulysses observations. For future model development we plan to use SOHO
LASCO, CDS, EIT, UVCS and Ulysses data as constraints for our model
calculations. The model by Sittler and Guhathakurta (1999a, 2002) is
not a self-consistent calculation. The calculations presented here is
the first attempt at providing a self-consistent calculation based on
empirical constraints.
Title: Two-dimensional Magnetohydrodynamic Models of the Solar Corona:
Mass Loss from the Streamer Belt
Authors: Endeve, Eirik; Leer, Egil; Holzer, Thomas E.
Bibcode: 2003ApJ...589.1040E
Altcode:
The equations of magnetohydrodynamics (MHD) are used to study an axially
symmetric model of the large-scale solar corona, extending from the
coronal base to 15 solar radii. We use a uniform heating of the inner
corona to investigate the energy output when the magnetic field is given
as a dipole at the coronal base. The heat input produces a large-scale
magnetic field structure similar to that found by Pneuman and Kopp,
with coronal holes in the polar regions and a helmet streamer around the
equator. We pay special attention to the energy balance in the system,
and find that the role of heat conduction is important in determining
the thermal structure in magnetically closed regions. Insufficient
energy loss to the transition region leads to a high temperature inside
the closed region. In the coronal holes a solar wind is accelerated into
interplanetary space, and the temperature is lower. As the difference
in pressure scale height along open and closed flux tubes is large, the
helmet streamer does not relax to a steady state; it opens periodically
to eject mass into interplanetary space. These mass ejections may
contribute significantly to the mass and energy flux in the solar wind.
Title: Multi-Wavelength Synoptic Study of Coronal Holes and Magnetic
Fields
Authors: de Toma, G.; Arge, C. N.; Holzer, T. E.; Mayer, L. R.
Bibcode: 2003SPD....34.0410D
Altcode: 2003BAAS...35..812D
Using a combination of photospheric field and irradiance data (such
as Hα, HeI 1083nm, and EUV wavelengths) in the form of solar synoptic
maps along with potential field source surface (PFSS) extrapolations,
we study the morphology and evolution of large-scale structures such
as coronal holes and filament channels over the course of a few solar
rotations. Multiple wavelengths are useful to correctly distinguish such
features, that may have similar contrast at EUV wavelengths. We select
the time period between January and March 2002, during the maximum phase
of solar cycle 23, because of the relevant changes in coronal holes and
active regions distribution. We compare the observational data with
the results of a potential field source surface model calculation to
assess how well the model captures the large scale structure as well
as its ability to identify coronal holes versus filament channels.
Title: Empirically Constrained Multidimensional MHD Model for the
Solar Corona and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Guthathakurta, M.;
Skoug, R.; Fludra, A.; Davila, J.; Holzer, T.
Bibcode: 2002AGUFMSH21A0502S
Altcode:
We are developing a time stationary self-consistent 2D MHD model of
the solar corona and solar wind that explicitly solves the energy
equation, using a semi-empirical 2D MHD model of the corona to provide
an empirically determined effective heat flux qeff (i.e.,
the term effective means the possible presence of wave contributions)
for the energy equation and effective pressure Peff
for the momentum equation. Preliminary results indicated that in
order to achieve high speed winds over the poles we not only needed
to use qeff in the energy equation, but also needed to
include the empirically determined effective pressure Peff
as a constraint in the momentum equation, which means that momentum
addition by waves above 2 RS are required to produce high
speed winds. A solution which only included qeff showed high
acceleration over the poles below 2 RS, but then drooped
above that radial distance indicating we needed momentum addition above
that height to get high speed flows over the poles. We will show new
results which include the added constraint of Peff in the
momentum equation. This method will allows us to estimate the momentum
addition term due to waves as a function of height and latitude within
the corona. The estimates of Peff and qeff come
from the semi-empirical 2D MHD model of the solar corona by Sittler and
Guhathakurta (1999, 2002) which is based on Mk-III, Skylab and Ulysses
observations. For future model development we plan to use SOHO LASCO,
CDS, EIT, UVCS, Spartan 201-05 and Ulysses data as constraints for
our model calculations. The model by Sittler and Guhathakurta (1999,
2002) is not a self-consistent calculation. The calculations presented
here are a continuing effort to provide a self-consistent calculation
based on empirical constraints.
Title: Chromospheric Waves Observed in HeI (1083 nm)- a Closer Look
Authors: Gilbert, H. R.; Holzer, T. E.
Bibcode: 2002AGUFMSH52A0438G
Altcode:
Although "Moreton" waves have historically been observed in H-alpha
data, more recently waves have also been observed in chromospheric He
I (1083 nm) images. In a previous study, we found that chromospheric
waves observed in He I data (from the Mauna Loa Solar Observatory) in
two events are co-spatial with the corresponding coronal waves observed
by EIT (Fe XII 19.5 nm). In an effort to better understand the nature of
chromospheric waves, we focus on these two wave events observed in He I
in which two interesting phenomena occur: the waves are visible in the
He I velocity data, and multiple waves are observed for each event. We
suggest the velocity signal is a result of slow-mode wave compression
followed by a slow-mode wave rarefaction in the chromosphere. We also
suggest the observed multiple waves indicate more than one driving
mechanism may be involved .
Title: An Improved Calibration for Obtaining Intensity and
Line-of-Sight Velocity Using MLSO/CHIP He I 1083 nm Observations.
Authors: Darnell, J. A.; Stanger, A. L.; Holzer, T. E.; Elmore, D. F.;
Gilbert, H. R.; Detoma, G.; Burkepile, J. T.
Bibcode: 2002AGUFMSH52A0445D
Altcode:
A calibration technique has been developed utilizing normalized
intensities measured at seven different He I filter positions which
are used to infer the line-of-sight velocity of structures observed
with the MLSO CHIP He I filter. To obtain He I intensity, the output
from each of the seven filter positions are normalized to reflect only
the photosheric continuum radiation and the He I 1083 nm absorption
or emission line. Velocity is inferred from an application of these
normalized intensities to an algorithm derived from an empirical
analysis of synthetic spectra. Both the normalization technique
and the application of the algorithm are presented as well as some
example events.
Title: 3-Dimensional Density Model of the Solar Corona
Authors: Foster, D.; Gibson, S. E.; Holzer, T.; Guhathakurta, M.
Bibcode: 2002AGUFMSH52A0448F
Altcode:
We present a 3-D density model of the solar corona, determined
from synoptic maps of Carrington Rotations 1942-3 (22 Oct. 1998 -
18 Nov. - 15 Dec. 1998). The rotations we have chosen include the
time period of the SPARTAN 201-05 flight (Nov. 1-3, 1998), which
had unprecedented spatial and temporal coverage of the white light
corona. These rotations are also useful because they occur at a point
in the solar cycle (ascending phase) that is complex enough to exhibit
interesting 3-D structure, yet not so dynamic that a meaningful density
model cannot be constructed using the rotation of the sun to provide
the 3-D information. Along with SPARTAN data, we consider observations
made by the Mark IV instrument in the Mauna Loa Observatory, and also
SOHO/LASCO and EIT observations. Our analytic model, an extension
of the axisymmetric model of Guhathakurta et al (1996), allows
for multiple streamers varying in both latitude and longitude, and
explicitly treats nonradial streamers. Our 3-D model will be useful
for testing analysis techniques for the upcoming STEREO mission. We
will also compare its structure to magnetic field extrapolation models,
coronal hole boundaries, and magnetic neutral lines.
Title: Neutral Atom Diffusion in a Partially Ionized Prominence Plasma
Authors: Gilbert, Holly R.; Hansteen, Viggo H.; Holzer, Thomas E.
Bibcode: 2002ApJ...577..464G
Altcode:
The support of solar prominences is normally described in terms of
a magnetic force on the prominence plasma that balances the solar
gravitational force. Because the prominence plasma is only partially
ionized, this support needs to be understood in terms of the frictional
coupling between the neutral and ionized components of the prominence
plasma, the efficacy of which depends directly on the ion density. More
specifically, the frictional force is proportional to the relative
flow of neutral and ion species, and for a plasma with a sufficiently
small vertical ion column density, this flow must be relatively large
to produce a frictional force that balances gravity. A large relative
flow, of course, implies significant draining of neutral particles from
the prominence. We evaluate the importance of this draining effect for
a hydrogen-helium plasma and consider the variation of the draining
with a variety of prominence parameters. Our calculations show that
the loss timescale for hydrogen is much longer than that for helium,
which for typical prominence parameters is about one day.
Title: The Structure and Evolution of a Sigmoidal Active Region
Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.;
Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile,
J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder,
B.; Thompson, B. J.
Bibcode: 2002ApJ...574.1021G
Altcode:
Solar coronal sigmoidal active regions have been shown to be precursors
to some coronal mass ejections. Sigmoids, or S-shaped structures,
may be indicators of twisted or helical magnetic structures, having
an increased likelihood of eruption. We present here an analysis of a
sigmoidal region's three-dimensional structure and how it evolves in
relation to its eruptive dynamics. We use data taken during a recent
study of a sigmoidal active region passing across the solar disk
(an element of the third Whole Sun Month campaign). While S-shaped
structures are generally observed in soft X-ray (SXR) emission, the
observations that we present demonstrate their visibility at a range of
wavelengths including those showing an associated sigmoidal filament. We
examine the relationship between the S-shaped structures seen in SXR
and those seen in cooler lines in order to probe the sigmoidal region's
three-dimensional density and temperature structure. We also consider
magnetic field observations and extrapolations in relation to these
coronal structures. We present an interpretation of the disk passage
of the sigmoidal region, in terms of a twisted magnetic flux rope
that emerges into and equilibrates with overlying coronal magnetic
field structures, which explains many of the key observed aspects of
the region's structure and evolution. In particular, the evolving flux
rope interpretation provides insight into why and how the region moves
between active and quiescent phases, how the region's sigmoidicity is
maintained during its evolution, and under what circumstances sigmoidal
structures are apparent at a range of wavelengths.
Title: Ionospheric response to the interplanetary magnetic field
southward turning: Fast onset and slow reconfiguration
Authors: Lu, G.; Holzer, T. E.; Lummerzheim, D.; Ruohoniemi, J. M.;
Stauning, P.; Troshichev, O.; Newell, P. T.; Brittnacher, M.; Parks, G.
Bibcode: 2002JGRA..107.1153L
Altcode:
This paper presents a case study of ionospheric response to an
interplanetary magnetic field (IMF) southward turning. It is based
on a comprehensive set of observations, including a global network
of ground magnetometers, global auroral images, and a SuperDARN HF
radar. There is a clear evidence for a two-stage ionospheric response
to the IMF southward turning, namely, fast initial onset and slow final
reconfiguration. The fast onset is manifested by nearly simultaneous
(within 2 min) rise of ground magnetic perturbations at all local times,
corroborated by a sudden change in the direction of line-of-sight
velocity near local midnight and by the simultaneous equatorward shift
of the auroral oval. The slow reconfiguration is characterized by
the different rising rate of magnetic perturbations with latitudes:
faster at high latitude than at lower latitudes. Furthermore, a
cross-correlation analysis of the magnetometer data shows that the
maximum magnetic perturbation is reached first near local noon, and then
spread toward the nightside, corresponding to a dayside-to-nightside
propagation speed of ~5 km/s along the auroral oval. Global ionospheric
convection patterns are derived based on ground magnetometer data
along with auroral conductances inferred from the Polar UV images,
using the assimilative mapping of ionospheric electrodynamics (AMIE)
procedure. The AMIE patterns, especially the residual convection
patterns, clearly show a globally coherent development of two-cell
convection configuration following the IMF southward turning. While the
foci of the convection patterns remain nearly steady, the convection
flow does intensify with time and the cross-polar-cap potential drop
increases. The overall changes as shown in the AMIE convection patterns
therefore are fully consistent with the two-stage ionospheric response
to the IMF southward turning.
Title: Self-consistent 2D MHD modeling of multi-streamer coronal
structures
Authors: Ofman, L.; Sittler, E. C.; Gibson, S.; Holzer, T. E.;
Guhathakurta, M.
Bibcode: 2002AGUSMSH21B..02O
Altcode:
Recently, a semi-empirical 2D MHD model of the solar corona was
constructed by Sittler and Guhathakurta [1999]. The model uses an
empirical electron density and empirical magnetic field during solar
minimum as input to the conservation equations of mass, momentum,
and energy to derive an empirical effective heat flux, or empirical
heating function. This semi-empirical model is not a self-consistent
calculation. We explore the possibility of developing a self-consistent
model that uses the empirical heating function as a constraint for the
calculations. This allows us to solve the energy equation without use of
a polytrope which we know does not apply near the Sun. For our initial
attempt we use the empirically derived magnetic field model obtained
from observed streamer topologies and Ulysses boundary conditions to
initialize our self-consistent 2D MHD model of the solar corona. We
solve the thermally conductive energy equations with an empirical
heating function, and obtain 3-streamer structure with self-consistent
magnetic field, current-sheets, solar wind outflow, density, and
temperature. We compare the results of the thermally conductive model
to the polytropic model, and to the empirical model. We find that
the self-consistent magnetic field structure is more realistic then
the empirical model. We find that the thermally conductive streamers
result in more diffuse current-sheets than in the polytropic model. We
also find that the heating function reduces the heliocentric distance
of the streamers' cusp, and produces more rapid acceleration of the
solar wind in the thermally conductive model then in the polytropic
model, consistent with observations. We investigate the effect of
various forms of the heating function, and of an empirically derived
heat flux on the solutions.
Title: An Improved Calibration for Obtaining Intensity and
Line-of-Sight Velocity Using MLSO/CHIP He I 1083 nm Observations
Authors: Darnell, J. A.; Stanger, A. L.; Holzer, T. E.; Elmore, D.;
Gilbert, H. R.; Detoma, G.; Burkepile, J. T.
Bibcode: 2002AAS...200.5512D
Altcode: 2002BAAS...34..733D
A calibration technique has been developed utilizing normalized
intensities measured at seven different He I filter positions which are
used to infer the line-of-sight velocity of structures observed with
the Mauna Loa Solar Observatory (MLSO) CHIP He I filter. To obtain He
I intensity, the outputs from each of the seven filter positions are
normalized to reflect only the photospheric continuum radiation and
the He I 1083 nm absorption or emission line. Velocity is inferred from
an application of these normalized intensities to an algorithm derived
from an empirical analysis of synthetic spectra. Both the normalization
technique and the application of the algorithm are presented as well
as some example events. The High Altitude Observatory is a division of
the National Center for Atmospheric Research operated by the University
Corporation for Atmospheric Research under sponsorship of the National
Science Foundation.
Title: Towards an Operational Sun-to-Earth Model for Space Weather
Forecasting
Authors: Gombosi, T. I.; Clauer, C. R.; De Zeeuw, D. L.; Hansen,
K. C.; Manchester, W. B.; Powell, K. G.; Ridley, A. J.; Roussev, I.;
Sokolov, I. V.; Toth, G.; Wolf, R. A.; Sazykin, S.; Holzer, T. E.;
Low, B. C.; Richmond, A. D.; Roble, R. G.
Bibcode: 2002AGUSMSH51B..06G
Altcode:
We are presently developing a physics based, modular, large-scale
model of the solar-terrestrial environment simulating space weather
phenomena and providing a framework to test theories and explore the
possibility of operational use in space weather forecasting. This talk
will describe the main components of the model (a global MHD code,
an upper atmosphere and ionosphere model, and the inner magnetosphere
drift physics model). We will also discuss the testing and transitioning
the model through CCMC to operational use by NOAA SEC and the Air
Force. Particular attention will be paid to the need of validation
and metrics studies.
Title: Transient Coronal Holes as seen in the HeI 1083nm Observations
Authors: de Toma, G.; Holzer, T. E.; Gilbert, H. R.; Burkepile, J. T.;
Harvey, K. L.
Bibcode: 2002AAS...200.3813D
Altcode: 2002BAAS...34R.700D
Observations from Yohkoh/SXT and SOHO/EIT have shown that dimming
regions often appear on the solar disk near the location of a Coronal
Mass Ejection (CME). We can now see in HeI observations made at Mauna
Loa Solar Observatory (MLSO) brightenings that form at the time of a
CME and are co-spatial with the ultraviolet and X-ray dimmings. Both
dimmings and brightenings can be interpreted as different manifestations
of the decreased density of the overlying corona caused by the ejection
of coronal material during the eruption, i.e. as transient coronal
holes. Because of the 3-minute cadence of the HeI 1083nm observations
at MLSO, we can now determine the appearance and evolution of transient
coronal holes with high accuracy. In this paper, we present examples
of transient coronal holes as seen in HeI data and compare them with
simultaneous observations in the H alpha line and in the ultraviolet.
Title: A Comparison of CME-associated Atmospheric Waves Observed in
Coronal (Fe XII 19.5 nm) and Chromospheric (He I 1083 nm) Lines
Authors: Gilbert, H. R.; Thompson, B. J.; Holzer, T. E.; Burkepile,
J. T.
Bibcode: 2002AAS...200.3808G
Altcode: 2002BAAS...34..699G
In an effort to better understand the relationship between coronal waves
(EIT waves) and chromospheric waves, we study two events in which waves
are observed simultaneously in both Fe XII (19.5 nm) and He I (1083 nm):
lines formed in the corona and chromosphere, respectively. Comparing
the waves observed in these two lines allows the determination of the
spatial relationship between coronal and chromospheric waves, and thus
aids in the understanding of the underlying physics of waves. The main
goal of this work is to begin an investigation into whether coronal
and chromospheric waves are both mechanical waves (e.g., MHD waves),
or whether chromospheric waves are simply "reflections" of mechanical
waves propagating in the corona.
Title: The Effect of Transition Region Heating on the Solar Wind
from Coronal Holes
Authors: Lie-Svendsen, Øystein; Hansteen, Viggo H.; Leer, Egil;
Holzer, Thomas E.
Bibcode: 2002ApJ...566..562L
Altcode:
Using a 16 moment solar wind model extending from the chromosphere to
1 AU, we study how the solar wind is affected by direct deposition
of energy in the transition region, in both radially expanding
geometries and rapidly expanding coronal holes. Energy is required
in the transition region to lift the plasma up to the corona, where
additional coronal heating takes place. The amount of energy deposited
determines the transition region pressure and the number of particles
reaching the corona and, hence, how the solar wind energy flux is
divided between gravitational potential and kinetic energy. We find that
when only protons are heated perpendicularly to the magnetic field in a
rapidly expanding coronal hole, the protons quickly become collisionless
and therefore conduct very little energy into the transition region,
leading to a wind much faster than what is observed. Only by additional
deposition of energy in the transition region can a reasonable mass flux
and flow speed at 1 AU be obtained. Radiative loss in the transition
region is negligible in these low-mass flux solutions. In a radially
expanding geometry the same form of coronal heating results in a
downward heat flux to the transition region substantially larger
than what is needed to heat the upwelling plasma, resulting in a
higher transition region pressure, a slow, massive solar wind, and
radiative loss playing a dominant role in the transition region energy
budget. No additional energy input is needed in the transition region
in this case. In the coronal hole geometry the solar wind response to
transition region heating is highly nonlinear, and even a tiny input of
energy can have a very large influence on the asymptotic properties of
the wind. By contrast, the radially expanding wind is quite insensitive
to additional deposition of energy in the transition region.
Title: Development of an Integrated Predictive MHD Space Weather
Model from the Solar Surface to the Earth's Upper Atmosphere
Authors: Clauer, C. R.; Gombosi, T. I.; Powell, K. G.; Stout, Q. F.;
Toth, G.; Dezeeuw, D.; Ridley, A. J.; Wolf, R. A.; Roble, R. G.;
Holzer, T. E.
Bibcode: 2002swsm.conf..149C
Altcode:
No abstract at ADS
Title: A Comparison of CME-associated atmospheric waves observed in
coronal (19.5 nm) and chromospheric (He I 1083 nm and H-alpha 656
nm) lines
Authors: Gilbert, H. R.; Thompson, B. J.; Holzer, T. E.; Burkepile,
J. T.
Bibcode: 2001AGUFMSH12B0746G
Altcode:
Coronal Mass Ejections (CMEs) are frequently associated with wave
phenomena observed in the corona, and sometimes with wave phenomena
observed in the chromosphere. We have studied CME-associated waves
observed in both coronal (19.5 nm) and chromospheric (He I 1083 nm and
H-alpha 656 nm) lines. Comparison of the coronal and chromospheric
signatures allows us to understand better the relationship between
the two wave phenomena.
Title: Neutral Atom Diffusion in a Paritially Ionized Prominence
Plasma
Authors: Gilbert, H. R.; Hansteen, V. H.; Holzer, T. E.
Bibcode: 2001AGUSM..SP61A09G
Altcode:
The support of solar prominences is normally described in terms of
a magnetic force on the prominence plasma that balances the solar
gravitational force. Because the prominence plasma is only partially
ionized, it is necessary to consider in addition the support of
the neutral component of the prominence plasma. This support is
accomplished through a frictional interaction between the neutral and
ionized components of the plasma, and its efficacy depends strongly
on the degree of ionization of the plasma. More specifically, the
frictional force is proportional to the relative flow of neutral and ion
species, and for a sufficiently weakly ionized plasma, this flow must be
relatively large to produce a frictional force that balances gravity. A
large relative flow, of course, implies significant draining of neutral
particles from the prominence. We evaluate the importance of this
draining effect for a hydrogen-helium plasma, and consider the variation
of the draining with the degree of heat input to the prominence plasma,
which determines the ionization state of the prominence.
Title: The Relationship Between Eruptive Prominence Acceleration
and CME Speed
Authors: de Toma, G.; Gilbert, H. R.; Holzer, T. E.; Burkepile, J. T.
Bibcode: 2001AGUSM..SH22B04D
Altcode:
We present an observational study of the relationship between the
acceleration of eruptive prominences and the speed of their associated
CMEs during the period 1998--2001 using observations from the Mauna Loa
Solar Observatory (MLSO) and the SOHO satellite. We have used MLSO/CHIP
data in the HeI 1083 nm line and the MLSO/PICS in the Hα 656.3 nm
line to identify eruptive prominences that show a clear association
to CMEs seen by the MLSO/MarkIV and SOHO/LASCO coronagraphs. Events
occurring at the limb, or near the limb have been selected for this
study to minimize projection effects. Ground based observations have
been used to determine the projected radial velocity and acceleration
of the eruptive prominences, while SOHO/LASCO observations have been
used to determine the same parameters of the corresponding CMEs. The
principal goal of this study is to allow the use of line--of--sight
velocity (and acceleration) measurements of erupting filaments obtained
by the MLSO/CHIP instrument to infer the speeds of earth--directed
CMEs. In particular, we are interested in determining whether the
faster, and more geoeffective CMEs can be associated with a specific
class of eruptive prominences/filaments. It is also hoped that this
study will shed light on the acceleration mechanisms of CMEs.
Title: Narrow Coronal Mass Ejections
Authors: Gilbert, Holly R.; Serex, Elizabeth C.; Holzer, Thomas E.;
MacQueen, R. M.; McIntosh, Patrick S.
Bibcode: 2001ApJ...550.1093G
Altcode:
Narrow coronal mass ejections (CMEs), defined arbitrarily as events
whose apparent angular width is 15° or less, are a small subset of
all CMEs. Little is known of the properties of these events and whether
these properties differ from those of the larger, more typical CMEs. We
have included in this study 15 narrow CMEs observed in the period from
1999 March through December, and we have examined their structure,
angular size, projected radial velocity (speed), and likely surface
associations. We find it useful to break these events into two classes:
structured and unstructured. Unstructured narrow events are generally
narrower and slower than the structured events, but both classes of
narrow CMEs exhibit speeds similar to those of larger CMEs. We found
that 11 of 15 events studied may be traced to regions on the solar
surface near a relatively sharp bend in a polarity-reversal line,
as revealed from Hα synoptic maps. We contrast the properties of the
narrow CMEs with those of the larger CME population.
Title: Observational Interpretation of an Active Prominence on 1999
May 1
Authors: Gilbert, Holly R.; Holzer, Thomas E.; Burkepile, Joan T.
Bibcode: 2001ApJ...549.1221G
Altcode:
This paper presents an observational study of an active prominence
observed in He I 1083 nm intensity and velocity data obtained at the
Mauna Loa Solar Observatory, which provide physical insight into
dynamical processes associated with prominences. We compare these
observations with existing theoretical prominence models, which fall
into two main classes: dip models and flux rope models. Dip models
use sagging magnetic arches to explain prominence support, while flux
rope models are characterized by helical magnetic field lines that
trap prominence material at the bottom of the rope. The prominence on
which we focus in the present paper has four interesting components
of activity, all of which we attempt to explain using each of three
different prominence models: the normal and inverse polarity flux rope
models and the dip model. Our objective is to test the viability of
each of these models in describing this type of activity. The model
that appears consistent with the observed activity in this particular
prominence is the inverse polarity flux rope model. We suggest that
the process of vertical reconnection between an inverse polarity flux
rope and an underlying magnetic arcade may best describe the observed
prominence activity.
Title: Solar Coronal Brightness Changes and Mass Ejections during
Solar Cycle 22
Authors: MacQueen, R. M.; Burkepile, J. T.; Holzer, T. E.; Stanger,
A. L.; Spence, K. E.
Bibcode: 2001ApJ...549.1175M
Altcode:
Observations of the brightness of the outer solar corona from the
Solar Maximum Mission (SMM) coronagraph during solar cycle 22 (1980,
then 1984-1989) are compared with the occurrence rate and the mass of
coronal mass ejections (CMEs) observed during this period. We find that
the brightness and, hence, mass of the outer corona increased by more
than a factor of 4 from solar minimum (1986) to late 1989, when the
SMM ceased operation. The peak brightness (mass) in 1989 was roughly
equivalent to that observed in the latter part of 1980. Accompanying a
sharp increase in brightness (mass) of the corona in early 1989 was a
concomitant increase in both the occurrence rate and the average mass
of CMEs.
Title: Active and Eruptive Prominences and Their Relationship to
Coronal Mass Ejections
Authors: Gilbert, Holly R.; Holzer, Thomas E.; Burkepile, Joan T.;
Hundhausen, Arthur J.
Bibcode: 2000ApJ...537..503G
Altcode:
In order to understand better the dynamical processes in the
solar atmosphere that are associated with coronal mass ejections
(CMEs), we have carried out a study of prominence activity using Hα
observations obtained at the Mauna Loa Solar Observatory (MLSO). After
developing clear definitions of active prominences (APs) and eruptive
prominences (EPs), we examined 54 Hα events to identify distinguishing
characteristics of APs and EPs and to study the relationship between
prominence activity and CMEs. The principal characteristics we found
to distinguish clearly between APs and EPs are maximum projected radial
height, projected radial velocity, and projected radial acceleration. We
determined CME associations with Hα events by using white-light data
from the Mk III K-Coronameter at MLSO and the LASCO C2 Coronagraph on
SOHO. We found that EPs are more strongly associated with CMEs than
are APs and that the CMEs associated with EPs generally have cores,
while those associated with APs do not. A majority of the EPs in the
study exhibit separation of escaping material from the bulk of the
prominence-the latter initially lifting away from and then returning
toward the solar surface. This separation tends to occur in the height
range from 1.20 to 1.35 R0, and we infer that it involves
the formation of an X-type neutral line in this region, which allows
disconnection of part of the prominence material. This disconnection
view of prominence eruption seems most consistent with flux rope models
of prominence support.
Title: SOHO/UVCS Observations of a Coronal Jet During the Third
Whole Sun Month Campaign
Authors: Ko, Y. -K.; Raymond, J.; Gibson, S.; Strachan, L.; Alexander,
D.; Fletcher, L.; Holzer, T.; Gilbert, H.; Burkepile, J.; St. Cyr,
C.; Thompson, B.
Bibcode: 2000SPD....31.0271K
Altcode: 2000BAAS...32R.823K
On August 26 1999, a coronal jet occurred at the north west limb
near a sigmoid active region which has been the target for a joint
observation plan during the third Whole Sun Month Campaign. This jet
was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT,
TRACE, MLSO/CHIP, MLSO/PICS), at 1.7 Ro (SOHO/UVCS), and at the outer
corona (SOHO/LASCO). At 1.7 Ro, the intensities of Lyman alpha, Lyman
beta in the jet increased by as large a factor of 100 compared with the
background corona, while those for O VI 1032 and O VI 1037 increased
by a factor of 2. C III 977 line also brightened significantly. The
line shift in the lines indicates that the line-of-sight velocity in
the jet started from 150 km/sec blue shift and ended at 120 km/sec
red shift. This line-of-sight motion seen at 1.7 Ro apparently was
opposite that observed when the jet emerged from the limb. In this
paper, we present the observation by SOHO/UVCS and discuss the dynamic
structure and physical properties of this jet as it passed through
1.7 Ro. Comparisons will be shown with the observations from other
instruments. This work is supported by NASA Grant number NAG5-7822.
Title: A New Method of Determining Line-of-Sight Velocity Using
MLSO/CHIP He I 1083 nm Observations
Authors: Holzer, T. E.; Gilbert, H. R.; Elmore, D. F.; MacQueen, R. M.
Bibcode: 2000SPD....3102107H
Altcode:
A new method for determining line-of-sight velocity has been developed
for the MLSO/CHIP He I 1083 nm instrument. The method involves tuning
the Lyot-type spectral filter to seven different positions during
each observing sequence (lasting about 3 minutes). The algorithm for
line-of-sight velocity determination using these seven filter positions
yields an accuracy of better than 10 km/s over a line-of-sight velocity
range from -100 km/s to +100 km/s. The method is applicable to the
observation of filaments, surges, sprays, and other features exhibiting
sufficiently strong absorption or emission in the 1083 nm line. It
therefore will be particularly useful in the study of eruptive events
seen against the solar disk, such as filament eruptions associated with
earthward-directed coronal mass ejections. The High Altitude Observatory
(HAO) is part of the National Center for Atmospheric Research (NCAR),
which is sponsored by the National Science Foundation under the
management of the University Corporation for Atmospheric Research.
Title: Multispecies Treatment of Abundance and Temperature Variations
due to Mass Flows in the Solar Transition Region
Authors: Woods, D. T.; Holzer, T. E.
Bibcode: 2000SPD....31.0220W
Altcode: 2000BAAS...32..814W
We compute the density and temperature of a multicomponent plasma
consisting of electrons, protons, ionized, helium, and a trace minor
ion species (carbon). The equations of force and energy balance
are developed allowing for the possibility that the velocity and
temperature of each species are different. For the case of downflows,
we find that the minor ion temperature can be significantly hotter
than the electron temperature, and significant abundance enhancements
can occur due to the slow down of the minor ions from the effect of
the thermal force. The minor ion temperature enhancements relative to
the electron temperature can have implications for the computation of
detailed line profiles. Also, the effect of the thermal force may be of
importance to studies of the emission from asymetrically heated loops
in which the minor ion abundance will be enhanced in the downflowing
leg and diminished in the upward flowing leg. This would tend to make
the downflowing side appear brighter in a given line, and therefore
contribute to the production of a net redshift in a spatially unresolved
loop. This research is supported in part by NASA grant NAG5-7929.
Title: Prominence Densities as Derived from SOHO/EIT Fe XII (195
Angstrom) Absorption Features
Authors: Gilbert, H.; Mize, L.; Holzer, T.; MacQueen, R.
Bibcode: 2000SPD....31.0218G
Altcode: 2000BAAS...32..814G
Prominences often appear in absorption when the sun is viewed in EUV
emission lines formed at coronal temperatures. The coronal EUV radiation
at wavelengths less than 504 anstroms undergoes Lyman continuum
absorption by both hydrogen and helium (i.e., the coronal radiation
ionizes hydrogen and helium atoms from their ground states). We can
thus infer prominence column densities by measuring the amount of
coronal radiation absorbed by prominence material along the line of
sight, and by making assumptions concerning the ionization state and
the helium abundance characterizing the prominence plasma. We do so
by measuring 195 angstrom intensity along lines of sight inside and
outside prominences, both just on the disk and just off the limb. Our
absorption measurements are made using Fe XII (195 angstroms) data
from the Extreme Ultraviolet Imaging Telescope (EIT) on board the
SOHO spacecraft. Initial results using our technique yield prominence
densities on the order of 1010 cm-3. This is
the first step in reaching our ultimate objective of attaining a
quantitative measure of total prominence mass, which may be important
in the dynamical processes involved in Coronal Mass Ejection initiation
and evolution.
Title: Solar Wind Theory
Authors: Holzer, Thomas
Bibcode: 2000APS..APRH14001H
Altcode:
Our understanding of the acceleration of the solar wind is based largely
on E. N. Parker’s work more than three decades ago. With steadily
improving observations (and concomitant theoretical research) of the
outer solar atmosphere and the solar wind, however, this understanding
has progressed significantly. Nevertheless, we have yet to answer
certain fundamental questions concerning the origin, transport, and
dissipation of energy required to heat the solar corona and drive the
solar wind. This talk will outline our present understanding of solar
wind acceleration and some of the questions that remain to be answered.
Title: Dynamics of polar plumes observed at the 1998 February
26 eclipse
Authors: Lites, B. W.; Card, G.; Elmore, D. F.; Holzer, T.; Lecinski,
A.; Streander, K. V.; Tomczyk, S.; Gurman, J. B.
Bibcode: 1999SoPh..190..185L
Altcode:
This paper presents first observations of dynamics of the white-light
solar corona detected during the few minutes of totality of a solar
eclipse. Perturbations of a polar plume associated with an embedded
`jet' structure observed simultaneously at 195 Å with the EUV
Imaging Telescope (EIT) aboard the SOHO spacecraft lead to estimates
of the electron density fluctuations accompanying the jet: ±15%. The
morphological behavior of the jet, its apparent upward propagation speed
of ≈200 km s−1, and the inferred density perturbations
suggest that the jet is led by a weak, outward-propagating shock
resulting from the injection of material at high velocity at the base of
the corona. Smaller perturbations of the white-light corona are apparent
at many other locations, sustaining hope that propagating Alfvén waves
may be measurable in the solar corona. Density perturbations associated
with the jet follow from empirical electron density models of the polar
inter-plume and plume regions, as derived from the ground-based eclipse
measurements of coronal polarization brightness. These models indicate
polar plume densities 4-6 times that of the interplume low corona.
Title: Electron Heat Conduction in the Solar Transition Region:
Validity of the Classical Description
Authors: Lie-Svendsen, Øystein; Holzer, Thomas E.; Leer, Egil
Bibcode: 1999ApJ...525.1056L
Altcode:
We have studied the transport of energy in the solar transition region,
with the aim of finding out whether classical transport theory is
applicable in this region. We use a test particle approximation,
where test electrons move in a prescribed, background Maxwellian
electron-proton plasma. This approximation is validated by comparing
with the Spitzer-Härm result in the collision-dominated limit,
where the Spitzer-Härm result should be valid. We find that the test
particle approximation yields velocity distribution functions in good
agreement with Spitzer and Härm, and the test particle energy flux
is only 25% lower than the correct result. Then, applying the model
to conditions believed to be found in the solar transition region, we
obtain essentially the same good agreement with the classical result,
showing that classical transport theory is sufficient to describe heat
transport in the solar transition region. When the transition region
pressure (density) is reduced to unrealistically low values, while the
temperature profile is kept unchanged, a significant fraction of the
energy flux is carried by nonthermal electrons from the corona. But
the total energy flux is never larger than the classical Spitzer-Härm
value. The heat flux is independent of density at high densities (the
classical result), and decreases monotonically as the transition region
pressure is reduced.
Title: The origin of the high speed solar wind
Authors: Hansteen, Viggo H.; Leer, Egil; Holzer, Thomas E.
Bibcode: 1999AIPC..471...17H
Altcode: 1999sowi.conf...17H
The outflow of coronal plasma into interplanetary space is a
consequence of the coronal heating process. Therefore the formation
of the corona and the acceleration of the solar wind should be
treated as a single problem. The deposition of energy into the corona
through some mechanical or electromagnetic energy flux is balanced
by the various sinks available to the corona, and the sum of these
processes determines the coronal structure, i.e. its temperature and
density. Heating of the extended solar corona leads to high proton and
ion temperatures and relatively low electron temperatures. This is due
to the low heat conductivity in the proton (ion) gas as compared to
the electrons. To a fairly good approximation we can say that most of
the energy flux deposited in the protons and ions is lost as kinetic
and gravitational energy flux in the solar wind flow, whereas a large
fraction of the energy flux added to the electrons is conducted back
into the transition region and lost as radiation. In order to drive
high speed wind most of the energy must be deposited in the ions.
Title: Measuring Coronal Mass Ejection Masses from the Low through
the Outer Corona
Authors: Burkepile, J. T.; Bagenal, F.; Darnell, J. A.; Elmore, D.;
Holzer, T.; Hundhausen, A. J.; Stanger, A. L.
Bibcode: 1999AAS...194.1702B
Altcode: 1999BAAS...31..853B
Estimates have been made of the masses contained in coronal mass
ejections (CMEs) in the middle and outer corona [Howard et al. (1985),
Howard et al. (1986) and Hundhausen et al. (1994)]. It is our goal to
determine the flow of mass with height as the CME moves outward through
the corona and to distinguish the outflow of material from brightenings
due to deflections and compression created by the CMEs motion through
the ambient coronal material. Coronal mass ejection measurements
in the low corona are made using the Mauna Loa K-Coronameter. The
K-Coronameter has recorded a few hundred CMEs that were also visible
in the Solar Maximum Mission Coronagraph and in the Large Angle and
Spectrometric Coronagraph experiment (LASCO) that image the middle
and outer corona. The mass of each CME is plotted as a function of
height and compared with estimates for the amount of mass swept up
by a CME moving with average speed through a typical coronal helmet
streamer. For those events where the classic loop, cavity structure is
apparent, the masses of the loop front and legs are recorded separately
to better determine the amount of material propagating outward and
the amount of material maintained in the legs following the passage of
the CME. The masses are combined with speeds of the CMEs to determine
the kinetic energy of the CME as a function of height. As an example
we report on a CME which occurred on September 9, 1997 and appeared
over the northwest limb in both the MK3 and LASCO data. The mass of
the CME appeared to increase from 1.5x10(15) grams in the MK3 field to
6.2x10(15) grams in the LASCO field of view. The CME was continuing to
accelerate and the kinetic energy increased by an order of magnitude
from the low corona value of 2.5x10(30) ergs in MK3 to 2.0x10(31) ergs
in the LASCO field of view. References: Howard, R.A., N.R. Sheeley,
Jr., M.J. Koomen, and D.J. Michels, 'Coronal Mass Ejections: 1979-1981',
(1985), J. Geophys. Res., 90, 8173-8191 Howard, R.A., N.R. Sheeley, Jr.,
D.J. Michels, M.J. Koomen, ' The Solar Cycle Dependence of Coronal Mass
Ejections', (1986) in: The Sun and the Heliosphere in Three Dimensions,
Marsden, R.G. (ed)., 1986, p 107-111 Hundhausen, A.J., A.L. Stanger,
and S.A. Serbicki,'Mass and Energy Contents of Coronal Mass Ejections:
SMM Results from 1980 and 1984-1988.', (1994) in: Proc. of the Third
SOHO Workshop, Estes Park Colorado, p 409.
Title: Correction to «Land subsidence caused by the East Mesa
Geothermal Field, California, observed using SAR interferometry»
Authors: Massonnet, D.; Holzer, T.; Vadon, H.
Bibcode: 1998GeoRL..25.3213M
Altcode:
No abstract at ADS
Title: Understanding the Solar Wind
Authors: Leer, E.; Hansteen, V. H.; Holzer, T. E.
Bibcode: 1998cvsw.conf..263L
Altcode:
No abstract at ADS
Title: First Results from SWAN Lyman α solar wind mapper on SOHO
Authors: Bertaux, J. L.; Quémerais, E.; Lallement, R.; Kyrölä,
E.; Schmidt, W.; Summanen, T.; Goutail, J. P.; Berthé, M.; Costa,
J.; Holzer, T.
Bibcode: 1997SoPh..175..737B
Altcode:
After one year of almost flawless operation on board the SOHO
spacecraft poised at L1 Lagrange point, we report the main features
of SWAN observations. SWAN is mainly dedicated to the monitoring of
the latitude distribution of the solar wind by the Lα method. Maps
of sky Lα emissions were recorded througout the year. The region of
maximum emission, located in the upwind hemisphere, deviates strongly
from the pattern that could be expected from a solar wind constant
with latitude. It is divided into two lobes by a depression aligned
with the solar equatorial plane called the Lyα groove already noted
in 1976 Prognoz data. The north lobe is much brighter than the south
lobe. These two characteristics can be explained qualitatively by an
enhanced ionization along the neutral sheet where the slow solar wind
is concentrated, which results from the higher low-latitude solar wind
mass flux as measured by Ulysses. The groove is the direct imprint on
the sky of the enhanced carving by the slow solar wind, at this time of
solar minimum, when the tilt angle of the neutral sheet is small. The
question is still pending to predict what will happen with the ascending
phase of the solar cycle. Observations of comets are briefly mentioned,
with the ability of SWAN to monitor the H2O production
of many comets. Operations of the instrument are briefly described,
including some instrumental problems which could be solved by software
modifications sent to the instrument.
Title: The Role of Helium in the Outer Solar Atmosphere
Authors: Hansteen, V. H.; Leer, E.; Holzer, T. E.
Bibcode: 1997ApJ...482..498H
Altcode:
We construct models of the outer solar atmosphere comprising the region
from the mid-chromosphere and into the solar wind in order to study
the force and energy balance in models with a significant helium
abundance. The corona is created by dissipation of an energy flux
from the Sun. The energy flux is lost as radiation from the top of the
chromosphere and as gravitational and kinetic solar wind energy flux. We
find that in models with significant ion heating of the extended corona
most of the energy flux is lost in the solar wind. The ion temperatures
are higher than the electron temperature in these models, and the
α-particle temperature is much higher than the proton temperature,
so there is energy transfer from the α-particle fluid to the protons
and electrons, but this energy exchange between the different species
is relatively small. To a fairly good approximation we can say that the
energy flux deposited in the protons and α-particles is lost as kinetic
and gravitational energy flux in the proton and α-particle flow. How
this energy flux is divided between gravitational and kinetic energy
flux (i.e., how large the particle fluxes and flow speeds are) depends
upon details of the heating process. We also find that mixing processes
in the chromosphere play an important role in determining the coronal
helium abundance and the relative solar wind proton and α-particle
fluxes. Roughly speaking, we find that the relative α-particle and
proton fluxes are set by the degree of chromospheric mixing, while
the speeds are set by the details of the coronal heating process.
Title: The Coronal Helium Abundance and the Solar Wind
Authors: Hansteen, Viggo H.; Hassler, Donald M.; Leer, Egil; Holzer,
Thomas E.; Woods, Thomas N.
Bibcode: 1997SPD....28.0154H
Altcode: 1997BAAS...29Q.889H
The coronal Helium abundance depends on the rate Helium is brought into
the corona via the transition region from the chromosphere and on the
rate that Helium is removed from the corona in the Solar wind. Recent
multi-fluid models of the combined chromosphere, corona, solar wind
system show that the corona may have a significant Helium abundance;
perhaps even exceeding 50% of the Hydrogen number density. These models
also indicate that in order to reproduce the Solar wind at 1AU ions
(alpha -particles as well as protons) may be required to be the most
important recipient of the coronal heating process. In these models the
role of electrons in the energetics of the Solar wind is much reduced
compared to the standard thermally driven winds. A measurement of the
coronal Helium abundance will serve to fix these theoretical ideas and
may give important clues as to mixing processes in the chromosphere as
well as to coronal heating processes. Consequently, we will discuss the
current state of observations (i.e. SOHO), and their limitations, as
well as plans for future observations (i.e. sounding rocket, Spartan).
Title: Land subsidence caused by the East Mesa Geothermal Field,
California, observed using SAR interferometry
Authors: Massonnet, Didier; Holzer, Thomas; Vadon, Hélène
Bibcode: 1997GeoRL..24..901M
Altcode:
Interferometric combination of pairs of synthetic aperture radar
(SAR) images acquired by the ERS-1 satellite maps the deformation
field associated with the activity of the East Mesa geothermal plant,
located in southern California. SAR interferometry is applied to
this flat area without the need of a digital terrain model. Several
combinations are used to ascertain the nature of the phenomenon. Short
term interferograms reveal surface phase changes on agricultural
fields similar to what had been observed previously with SEASAT radar
data. Long term (2 years) interferograms allow the study of land
subsidence and improve prior knowledge of the displacement field, and
agree with existing, sparse levelling data. This example illustrates
the power of the interferometric technique for deriving accurate
industrial intelligence as well as its potential for legal action,
in cases involving environmental damages.
Title: The First 1. 5 Year of Observations from SWAN Lyman-Alpha
Solar Wind Mapper on SOHO
Authors: Bertaux, J. L.; Quémerais, E.; Lallement, R.; Kyrölä,
E.; Schmidt, W.; Summanen, T.; Mäkinen, T.; Holzer, T.
Bibcode: 1997ESASP.404...29B
Altcode: 1997cswn.conf...29B; 1997soho....5...29B
No abstract at ADS
Title: Coronal Hole Structure and the High Speed Solar Wind
Authors: Holzer, T. E.; Leer, E.
Bibcode: 1997ESASP.404...65H
Altcode: 1997cswn.conf...65H; 1997soho....5...65H
No abstract at ADS
Title: Helium in the outer solar atmosphere
Authors: Hansteen, V. H.; Leer, E.; Holzer, T. E.
Bibcode: 1997AIPC..385..197H
Altcode: 1997recs.conf..197H
We construct models of the outer solar atmosphere comprising the
region from the mid chromosphere and into the solar wind in order
to study the force and energy balance in models with a significant
helium abundance. The corona is created by dissipation of an energy
flux from the Sun. The energy flux is lost as radiation from the
top of the chromosphere and as gravitational and kinetic solar wind
energy flux. We find that in models with significant ion heating of the
extended corona most of the energy flux is lost in the solar wind. The
ion temperatures are higher than the electron temperature in these
models, and the α-particle temperature is much higher than the proton
temperature. Roughly speaking we find that the relative α-particle
and proton fluxes are set by the degree of chromospheric mixing while
the speeds are set by the details of the coronal heating process.
Title: Acceleration of the Solar Wind
Authors: Holzer, T. E.; Hansteen, V. H.; Leer, E.
Bibcode: 1997cwh..conf..239H
Altcode: 2006mslp.conf..239H
No abstract at ADS
Title: The Large-Scale Density Structure of the Solar Corona and
the Heliospheric Current Sheet
Authors: Guhathakurta, Madhulika; Holzer, Thomas E.; MacQueen, R. M.
Bibcode: 1996ApJ...458..817G
Altcode:
We have investigated the three-dimensional distribution of the
polarization-brightness product (PB) and then quantitatively
determined the electron density distribution relative to the
inferred heliographic current sheet during the declining phase
of solar cycle 20 (1973-1976). The current sheet is taken as the
center of the bright, dense structures from combined synoptic
pB data from ground-based K-coronameter and the white- light
coronagraph aboard Skylab. Analyses of pB scans as a function of
minimum distance from the current sheet (θmin) over the
radial distance range 1.13 to 5.0 Rsun (from Sun center)
led to the following new results: (1) a quantitative description
of pB obtained around the inferred neutral line is given by the
following equation: pB(p,θmin) = pBp(p)
+ [pBcs(p)-pBp(p)]e-θmin2/w2(r), where p is the shortest distance to the line of sight from
the Sun center, pBcs(p) and pBp(P) are the
observed polarized brightness at the current sheet and the poles,
respectively, and w(r) is the half-width of the distribution;
(2) the electron density obtained by inverting the pB data
is given by N(r,θmg) = Np(r) +
[Np(r)-Np(r)]e-θmg2/w2(r)d ,
where N(r,θmg) is the number of free electrons
per cm3, Ncs(r) and Np(r) are the
electron densities at the current sheet and the poles, respectively,
and θmg is the magnetic latitude. Here θmg is
given by θmg = [-cos θ sin α sin (φ-φ0)
+ sin θ cos α] where θ and φ are heliographic latitude and
longitude, α is the tilt angle of the dipole axis with the rotation
axis, and φ0 is the intersection of the heliomagnetic and
heliographic equators; (3) during the period studied (the last third
of the solar cycle), the mean pB at the current sheet and above the
polar holes is approximately independent of the phase of the solar
cycle; and (4) the organization of pB data about the neutral line
allows inference of the boundary of the polar coronal holes. The
usefulness of one-dimensional white-light density constraint in solar
wind modeling has already been demonstrated by Habbal et al. The
present three-dimensional model should prove very useful in better
understanding of the global hydromagnetic structure of the corona
and the solar wind, relating as it does to the magnetic structure
of the corona, as opposed to heliocentric coordinates. For example,
the density model could provide constraints on coronal temperature,
flow velocity, and magnetic structure subject to a suitable analysis
of geometric effects, which in turn would provide constraints on energy
balance in the coronal expansion.
Title: Understanding and Predicting Solar-Terrestrial
Relations:Counterpoint and Debate
Authors: Holzer, Thomas E.
Bibcode: 1996ASPC...95..408H
Altcode: 1996sdit.conf..408H
No abstract at ADS
Title: SWAN: A Study of Solar Wind Anisotropies on SOHO with Lyman
Alpha Sky Mapping
Authors: Bertaux, J. L.; Kyrölä, E.; Quémerais, E.; Pellinen, R.;
Lallement, R.; Schmidt, W.; Berthé, M.; Dimarellis, E.; Goutail,
J. P.; Taulemesse, C.; Bernard, C.; Leppelmeier, G.; Summanen,
T.; Hannula, H.; Huomo, H.; Kehlä, V.; Korpela, S.; Leppälä,
K.; Strömmer, E.; Torsti, J.; Viherkanto, K.; Hochedez, J. F.;
Chretiennot, G.; Peyroux, R.; Holzer, T.
Bibcode: 1995SoPh..162..403B
Altcode:
On board the SOHO spacecraft poised at L1 Lagrange point, the
SWAN instrument is mainly devoted to the measurement of large scale
structures of the solar wind, and in particular the distribution with
heliographic latitude of the solar wind mass flux. This is obtained from
an intensity map of the sky Lymanα emission, which reflects the shape
of the ionization cavity carved in the flow of interstellar H atoms
by the solar wind. The methodology, inversion procedure and related
complications are described. The subject of latitude variation of the
solar wind is shortly reviewed: earlier Lymanα results from Prognoz in
1976 are confirmed by Ulysses. The importance of the actual value of the
solar wind mass flux for the equation of dynamics in a polar coronal
hole is stressed. The instrument is composed of one electronic unit
commanding two identical Sensor Units, each of them allowing to map
a full hemisphere with a resolution of 1°, thanks to a two-mirrors
periscope system. The design is described in some details, and the
rationale for choice between several variants are discussed. A hydrogen
absorption cell is used to measure the shape of the interplanetary
Lymanα line and other Lyman α emissions. Other types of observations
are also discussed : the geocorona, comets (old and new), the solar
corona, and a possible signature of the heliopause. The connexion
with some other SOHO instruments, in particular LASCO, UVCS, SUMER,
is briefly discussed.
Title: Acceleration of the Solar Wind
Authors: Holzer, T. E.
Bibcode: 1995SPD....26..905H
Altcode: 1995BAAS...27Q.974H
No abstract at ADS
Title: The Solar Wind and Suprathermal Ion Composition Investigation
on the Wind Spacecraft
Authors: Gloeckler, G.; Balsiger, H.; Bürgi, A.; Bochsler, P.; Fisk,
L. A.; Galvin, A. B.; Geiss, J.; Gliem, F.; Hamilton, D. C.; Holzer,
T. E.; Hovestadt, D.; Ipavich, F. M.; Kirsch, E.; Lundgren, R. A.;
Ogilvie, K. W.; Sheldon, R. B.; Wilken, B.
Bibcode: 1995SSRv...71...79G
Altcode:
The Solar Wind and Suprathermal Ion Composition Experiment (SMS)
on WIND is designed to determine uniquely the elemental, isotopic,
and ionic-charge composition of the solar wind, the temperatures
and mean speeds of all major solar-wind ions, from H through Fe,
at solar wind speeds ranging from 175 kms-1 (protons)
to 1280 kms-1 (Fe+8), and the composition,
charge states as well as the 3-dimensional distribution functions of
suprathermal ions, including interstellar pick-up He+, of
energies up to 230 keV/e. The experiment consists of three instruments
with a common Data Processing Unit. Each of the three instruments
uses electrostatic analysis followed by a time-of-flight and, as
required, an energy measurement. The observations made by SMS will make
valuable contributions to the ISTP objectives by providing information
regarding the composition and energy distribution of matter entering
the magnetosphere. In addition SMS results will have an impact on
many areas of solar and heliospheric physics, in particular providing
important and unique information on: (i) conditions and processes in
the region of the corona where the solar wind is accelerated; (ii) the
location of the source regions of the solar wind in the corona; (iii)
coronal heating processes; (iv) the extent and causes of variations in
the composition of the solar atmosphere; (v) plasma processes in the
solar wind; (vi) the acceleration of particles in the solar wind; and
(vii) the physics of the pick-up process of interstellar He as well
as lunar particles in the solar wind, and the isotopic composition of
interstellar helium.
Title: Coupling of the coronal He abundance to the solar wind
Authors: Hansteen, V. H.; Leer, E.; Holzer, T. E.
Bibcode: 1994SSRv...70..347H
Altcode:
Models of the transition region — corona — solar wind system are
investigated in order to find the coronal helium abundance and to
study the role played by coronal helium in controlling the the solar
wind proton flux. The thermal force on α-particles in the transition
region sets the flow of helium into the corona. The frictional coupling
between α-particles and protons and/or the electric polarization field
determines the proton flux in the solar wind as well as the fate of
the coronal helium content.
Title: Coupling of the Coronal Helium Abundance to the Solar Wind
Authors: Hansteen, Viggo H.; Leer, Egil; Holzer, Thomas E.
Bibcode: 1994ApJ...428..843H
Altcode:
Models of the transition region-corona-solar wind system are
investigated in order to find the coronal helium abundance and to
study the role played by coronal helium in controlling the solar wind
proton flux. The thermal force on alpha-particles in the transition
region sets the flow of helium into the corona. The frictional coupling
between alpha-particles and protons and/or the electric polarization
field determines the proton flux in the solar wind as well as the fate
of the coronal helium content. The models are constructed by solving
the time-dependent population and momentum equations for all species
of hydrogen and helium in an atmosphere with a given temperature
profile. Several temperature profiles are considered in order to very
the roles of frictional coupling and electric polarization field in the
solar wind, and the thermal force in the transition region. Steady-state
solutions are found for coronae with a hydrogen flux at 1 AU of 1.0
x 109/cm2/sec or larger. For coronae with
lower hydrogen fluxes, the helium flux into the corona is larger
than the flux 'pulled out' by the solar wind protons, and solutions
with increasing coronal helium content are found. The timescale for
forming a helium-filled corona, that may allow for a steady outflow,
is long compared to the mixing time for the corona.
Title: Density Structure inside a Polar Coronal Hole
Authors: Guhathakurta, M.; Holzer, T. E.
Bibcode: 1994ApJ...426..782G
Altcode:
Analysis of white-light coronagraph observations of a polar coronal
hole during 1973 June 29 - July 13 led Munro and Jackson (1977)
to infer that the density inside the hole varied as a function of
heliocentric radial distance, r, and colatitude theta. However recent
analysis of the white-light data during 1973 December 3 - 1974 January
24, by Guhathakurta et al. (1993) indicates that the density inside
a polar coronal hole, within limits of uncertainties inherent in the
coronal white-light observations, can equally well be described as a
function of r only. In this study we reexamine the data from the Munro
and Jackson period and draw the conclusion that within the limits of
observational uncertainties, electron density in the polar coronal
hole is independent of magnetic latitude and longitude.
Title: Modelling the low-latitude boundary layer with reconnection
entry
Authors: Song, P.; Holzer, T. E.; Russell, C. T.; Wang, Z.
Bibcode: 1994GeoRL..21..625S
Altcode:
We develop a one-dimensional Low-Latitude Boundary Layer (LLBL) model
for northward IMF. The boundary layer in this model is uniform in the
direction normal to the magnetopause, a “plateautype” boundary
layer. The boundary layer motion is decoupled from the magnetosheath
motion and driven by the plasma pressure associated with the incoming
solar wind plasma near local noon, which has become entrained on closed
field lines as a result of reconnection in the cusp region. Dissipation
in the ionosphere at the feet of the boundary layer field lines opposes
this motion. There are two physical solutions for the model. In one, the
boundary layer reaches a terminal velocity in the tail as the boundary
layer plasma effectively joins the solar wind flow. In the other
solution, the flow is nearly stopped in the far tail. In combination
with other mechanisms, this latter solution may correspond to the
case in which the boundary layer plasma participates in magnetospheric
convection and returns sunward. The density, velocity, and thickness
as functions of distance from local noon are studied, assuming that
the magnetopause has elliptical shape and the magnetospheric field
is dipolar.
Title: Gasdynamic models of the solar wind/interstellar medium
interaction
Authors: Steinolfson, R. S.; Pizzo, V. J.; Holzer, T.
Bibcode: 1994GeoRL..21..245S
Altcode:
The interaction between the solar wind and the interstellar medium
is modeled self-consistently using numerical solutions of the
time-dependent gasdynamic equations in spherical and cylindrical
coordinates. For the results presented here it is assumed that the
solar system moves through the surrounding medium with a supersonic
velocity. After an initial (nonequilibrium) state has been specified,
the numerical solution follows the evolution in time until the
interaction relaxes to a dynamic equilibrium. As would be expected, the
solutions show the formation of a bow shock upstream of the traveling
solar system to deflect the interstellar plasma around the cavity
created by the solar wind. A termination shock also forms to slow
and compress the solar wind plasma. For the simulation in spherical
coordinates, the downstream portion of the termination shock reaches
equilibrium more than three times further from the Sun than the
equilibrium distance to the termination shock on the upstream side.
Title: Neutral Hydrogen in the Solar Wind Acceleration Region
Authors: Olsen, Espen Lyngdal; Leer, Egil; Holzer, Thomas E.
Bibcode: 1994ApJ...420..913O
Altcode:
Observation of solar Ly alpha radiation scattered by coronal neutral
hydrogen atoms can be used to investigate the acceleration region of the
solar wind. In this paper we focus on the use of these observations to
study Alfven waves, which can accelerate the solar wind plasma to flow
speeds observed in high-speed streams if their amplitude at the coronal
base is 20 km/s or larger. The wave amplitude is then larger than the
proton thermal speed in the outer corona, so that the mean proton speed
(averaged over a wave period) is significantly larger than the proton
thermal speed. For low-frequency wave the hydrogen atoms follow the
proton motion in the waves, while for higher frequencies the protons
move relative to the neutrals. Nevertheless, in the higher frequency
case, the rates for charge exchange and recombination are high enough
to broaden the velocity distribution function of neutral hydrogen. Both
the wave motion of the hydrogen atoms in low-frequency Alfven waves
and the 'heating' by higher frequency waves lead to a broadening of
the scattered solar Ly alpha line. For coronal base amplitudes of 20
km/s, the line broadening increases with heliocentric distance beyond
4-5 solar radii.
Title: The SPARTAN 201-1 White Light Coronagraph Experiment
Authors: Guhathakurta, M.; Fisher, R. R.; Holzer, T. E.; Sime, D. G.
Bibcode: 1993BAAS...25Q1213G
Altcode:
No abstract at ADS
Title: Diffusion Effects on the Helium Abundance of the Solar
Transition Region and Corona
Authors: Hansteen, Viggo H.; Holzer, Thomas E.; Leer, Egil
Bibcode: 1993ApJ...402..334H
Altcode:
The diffusion of helium in the solar transition region is
studied by solving the mass and momentum conservation equations
for a hydrogen-helium plasma given a representative temperature
profile. Steady state solutions show that two distinct atmospheres
may result. In cases where the thermal force on alpha-particles is
balanced by the partial pressure gradient force, helium is the dominant
coronal species. On the other hand, if it is the frictional force
between protons and alpha-particles which balances the thermal force on
alpha-particles then hydrogen is the major coronal component. In order
to explore which of these solutions are attainable within reasonable
time scales, the time-dependent equations are solved, starting from
an initial state with a uniform helium abundance of 10 percent. The
atmosphere as a whole is close to hydrostatic equilibrium, but due the
thermal forces the individual elements are not. This force inbalance
leads to a differential flow between species. It is found that this
differential flow leads to a significant enhancement of the coronal
helium abundance. Even for the relatively shallow temperature gradient
used the helium abundance in the lower corona increases to 30 percent
over a 24 hr period.
Title: Dynamical polar wind and its response to kinetic ion heating
Authors: Chen, Margaret W.; Ashour-Abdalla, Maha; Holzer, Thomas E.
Bibcode: 1992JGR....9719433C
Altcode:
The dynamic polar wind and its response to kinetic ion heating are
examined in this paper. We used a time-dependent hydrodynamic polar
wind code to study the dynamic flow characteristics of an H+
and O+ polar wind from 200 km to ~6-7 RE. We
found that the polar wind ion relaxation times are comparable to the
time required for the ions to propagate at the ion speed of sound over
the altitudinal range considered. Although there may be large transient
O+ fluxes lasting ~15 min during the early stage of expansion
of the unheated polar wind, these fluxes cannot be sustained because
of the large O+ gravitational potential. We subsequently
studied how polar wind ion heating affects the ion outflow. Our previous
work showed that O+ and H+ polar wind ions can
become heated use to ion beam instabilities in the polar cap region. We incorporate these kinetic effects into our hydrodynamic model by
specifying ion temperature profiles in the ion momentum equations. Two
limiting cases were considered, (1) preferential O+ and
(2) preferential H+ ion heating. We found that ion heating
does not have much effect on the escape of H+ ions because
of the limiting nature of the H+ escape fluxes. However,
O+ heating can sustantially increase the upward O+
pressure gradient in the heating region. This leads to increased
O+ ion escape from the polar ionosphere. Thus O+
heating is a viable explanation for the unexpectedly large O+
fluxes which are frequently observed in the polar magnetosphere.
Title: A Parameter Study of the Two-Fluid Solar Wind
Authors: Sandbaek, Ornulf; Leer, Egil; Holzer, Thomas E.
Bibcode: 1992ApJ...400..362S
Altcode:
A two-fluid model of the solar wind was introduced by Sturrock and
Hartle (1966) and Hartle and Sturrock (1968). In these studies the
proton energy equation was integrated neglecting the heat conductive
term. Later several authors solved the equations for the two-fluid
solar wind model keeping the proton heat conductive term. Methods
where the equations are integrated simultaneously outward and inward
from the critical point were used. The equations were also integrated
inward from a large heliocentric distance. These methods have been
applied to cases with low coronal base electron densities and high
base temperatures. In this paper we present a method of integrating
the two-fluid solar wind equations using an iteration procedure where
the equations are integrated separately and the proton flux is kept
constant during the integrations. The technique is applicable for a
wide range of coronal base densities and temperatures. The method is
used to carry out a parameter study of the two-fluid solar wind.
Title: Solar wind from a corona with a large helium abundance
Authors: Leer, Egil; Holzer, Thomas E.; Shoub, Edward C.
Bibcode: 1992JGR....97.8183L
Altcode:
Observations of quasi-steady high-speed solar wind streams show
that the proton mass flux density at 1 AU is remarkably constant,
varying by less than 10% over long time periods. The observations are
problematic, for simple theoretical models predict that the proton mass
flux density is a sensitive function of the coronal base temperature,
which is not expected to be unvarying to the degree required by the
observations. In this paper we investigate the possibility that the
presence of alpha particles in the coronal base region can reduce the
sensitivity of the proton mass flux to base temperature. The equations
of mass and momentum conservation are solved for electrons, protons,
and alpha particles using a variety of assumed temperature profiles
for each species. A wide range of base conditions are considered. We
find that for an alpha particle to proton density ratio at the base
as small as 10%, alpha particles can reduce the sensitivity of the
proton mass flux density to variations in the base temperature. We
also study the effects of enhanced collisional coupling and of Alfvén
waves on the flux of protons and alpha particles. As an aid to future
observational determination of the alpha particle density in the corona,
we present calculations of the intensities of the resonantly scattered
lines HeII λ304 and HI λ1216 for selected models.
Title: A Comparison of the Reduced and Approximate Systems for the
Time Dependent Computation of the Polar Wind and Multiconstituent
Stellar Winds
Authors: Browning, G. L.; Holzer, T. E.
Bibcode: 1992JGR....97.1289B
Altcode:
The ``reduced'' system of equations commonly used to describe
the time evolution of the polar wind and multiconstituent stellar
winds is derived from the equations for a multispecies plasma with
known temperature profiles by assuming that the electron thermal
speed approaches infinity. The reduced system is proved to have
unbounded growth near the sonic point of the protons for many of the
standard parameter cases. For the same parameter cases, however, the
unmodified system (from which the reduced system is derived) exhibits
growth in some of the Fourier modes, but this growth is bounded. (A
physical explanation is provided for the unbounded growth in the
reduced system and the bounded growth in the unmodified system.) An
alternate system (the ``approximate'' system) in which the electron
thermal speed is slowed down is introduced. The approximate system
retains the mathematical behavior of the unmodified system and can be
shown to accurately describe the smooth solutions of the unmodified
system. The approximate system has a number of other advantages over
the reduced system. For example, when the proton speed approaches the
electron sound speed, the reduced system becomes inaccurate. Also, for
three-dimensional flows the correct reduced system requires the solution
of an elliptic equation, while the approximate system is hyperbolic
and only requires a time step approximately 1 order of magnitude less
than the reduced system. Numerical solutions from models based on the
two systems are compared with each other to illustrate these points.
Title: A two-fluid model of the solar wind
Authors: Sandbaek, O.; Leer, E.; Holzer, T. E.
Bibcode: 1992sws..coll...95S
Altcode:
A method is presented for the integration of the two-fluid
solar-wind equations which is applicable to a wide variety of coronal
base densities and temperatures. The method involves proton heat
conduction, and may be applied to coronal base conditions for which
subsonic-supersonic solar wind solutions exist.
Title: The Interstellar Probe: A Frontier Mission to the Heliospheric
Boundary and Interstellar Space
Authors: Holzer, T. E.; Mewaldt, R. A.; Neugebauer, M.
Bibcode: 1991ICRC....2..535H
Altcode: 1991ICRC...22b.535H
No abstract at ADS
Title: The Effects of Mass Flow on the Temperature and Abundance
Structure of the Solar Transition Region
Authors: Woods, D. T.; Holzer, Thomas E.
Bibcode: 1991ApJ...375..800W
Altcode:
The density and temperature structure of a multicomponent plasma
consisting of electrons, protons, ionized helium, and a trace minor
ion species are computed. The equations of force and energy balance
for this model are developed and solved. It is found that in the case
of downflows the minor ion temperature can be significantly hotter
than the electron temperature, and significant abundance enhancements
are possible due to the slowdown of the minor species from the effect
of the thermal force. A simple physical picture of the source of the
thermal force is given.
Title: Report of the cosmic and heliospheric panel
Authors: Mewaldt, Richard A.; Mason, Glenn M.; Barnes, Aaron; Binns,
W. Robert; Burlaga, Leonard F.; Cherry, Michael L.; Holzer, Thomas E.;
Jokipii, J. R.; Jones, Vernon; Ling, James C.
Bibcode: 1991spsi....1...15M
Altcode:
The Cosmic and Heliospheric Branch proposes a bold new program for
the years 1995 to 2010 that is centered on the following two themes:
(1) the global heliosphere and interstellar space; and (2) cosmic
particle acceleration and the evolution of matter. Within these major
themes are more specific goals that have been studied and continue to be
examined for a better understanding of their processes. These include:
origin, structure, and evolution of the solar wind; interaction
of the heliosphere, the solar wind, and the interstellar medium;
fundamental microscopic and macroscopic plasma processes; acceleration
and transport of energetic particles; and the origin and evolution
of matter. Finally, the report summarizes a wide variety of proposed
small and large space missions.
Title: Some Theoretical Topics for RISE
Authors: Holzer, T.
Bibcode: 1991BAAS...23.1040H
Altcode:
No abstract at ADS
Title: The solar wind mass flux problem.
Authors: Leer, E.; Holzer, T. E.
Bibcode: 1991AnGeo...9..196L
Altcode: 1991AnG.....9..196L
The variation of the proton flux with coronal temperature and density
in thermally driven solar wind models is discussed. It is shown that
the rapid increase of the proton flux with increasing temperature can
be reduced by adiabatic cooling of the expanding plasma. A significant
coronal helium abundance can also act as a "regulator" for the solar
wind proton flux.
Title: Stellar wind acceleration.
Authors: Holzer, T. E.
Bibcode: 1991cwlt.conf....3H
Altcode:
A framework is developed for understanding several important aspects
of the acceleration of stellar winds by considering certain simple
implications of mass, momentum, and energy balance in a steady,
spherically symmetric flow. Using this framework, it is possible to
examine a number of physical mechanisms thought to play significant
roles in driving winds ranging from the solar wind to massive, low-speed
winds from cool stars to massive, high-speed winds from hot stars.
Title: Standing Shocks in the Inner Solar Wind
Authors: Leer, Egil; Holzer, Thomas E.
Bibcode: 1990ApJ...358..680L
Altcode:
It has been pointed out by several authors that the equations describing
rapidly diverging flow in the solar wind and in related astrophysical
systems allow for solutions with standing shocks in the acceleration
region of the flow. The range of plasma and flow-geometry parameters
that allow for such solutions are investigated. It is shown that, for
reasonable geometries, shocks can occur only for a very narrow range
of flow parameters in the case of the solar wind. Similar results can
be expected for related astrophysical systems.
Title: Lower Solar Chromosphere-Corona Transition Region. II. Wave
Pressure Effects for a Specific Form of the Heating Function
Authors: Woods, D. Tod; Holzer, Thomas E.; MacGregor, Keith B.
Bibcode: 1990ApJS...73..489W
Altcode:
Lower transition region models with a balance between mechanical heating
and radiative losses are expanded to include wave pressure effects. The
models are used to study the simple damping length form of the heating
function. The results are compared to the results obtained by Woods et
al. (1990) for solutions in the lower transition region. The results
suggest that a mixture of fast-mode and slow-mode waves may provide
the appropriate heating mechanism in the lower transition region, with
the decline in effective vertical wave speed caused by the refraction
and eventual total reflection of the fast-mode wave resulting from
the decreasing atmospheric density.
Title: Lower Solar Chromosphere-Corona Transition
Region. I. Theoretical Models with Small Temperature Gradients
Authors: Woods, D. Tod; Holzer, Thomas E.; MacGregor, Keith B.
Bibcode: 1990ApJ...355..295W
Altcode:
A study of transition region models including the effects of classical
thermal conduction, heating, and radiative cooling is carried out
with attention directed toward the problem of understanding the
observed emission in the lower transition region. It is found that the
observationally inferred emission measure curve implies a near-balance
between heating and radiative cooling in the lower transition region,
and that the presence of strong hydrogen Ly-alpha cooling leads to
the existence of singularities in the solutions of the force balance
and energy balance equations when such a near-balance between heating
and cooling is assumed. These singularities place strong constraints
on the nature of viable models of the lower transition region and must
be considered when Ly-alpha cooling is important. Previously suggested
explanations of the observed emission from the lower transition region
are considered in the context of the results of the present study,
and conditions for the applicability of these suggested explanations
are discussed.
Title: Lower Solar Chromosphere-Corona Transition
Region. III. Implications of the Observed Quiet-Sun Emission Measure
Including Wave Pressure Effects
Authors: Woods, D. Tod; Holzer, Thomas E.; MacGregor, Keith B.
Bibcode: 1990ApJ...355..309W
Altcode:
The observed form of the emission measure (EM) is used as a function
of temperature to infer the wave energy flux density and pressure
throughout the lower transition region (TR). This procedure eliminates
the need for specifying how the wave energy flux density is damped and
addresses the question of whether there is any form of the mechanical
heating associated with the degradation of an upward traveling wave
energy flux density which is consistent with the observed EM and other
observational constraints for the quiet sun. It is found that the
observed form of the EM curve is incompatible with waves traveling
vertically at the sound speed, regardless of any filling factor
arguments. The same conclusion also applies to waves traveling at
the Alfven speed, unless it is assumed that the emission in lower TR
lines originates solely from small, spatially unresolved regions of
large magnetic field strength (100 G), which cover a small fraction
(filling factors of 1 percent) of the solar surface.
Title: Multi-Species Treatment of Mass Flow Through the Solar
Transition Region
Authors: Woods, D. T.; Holzer, T. E.
Bibcode: 1990BAAS...22..795W
Altcode:
No abstract at ADS
Title: The solar probe mission
Authors: Feldman, W. C.; Anderson, J.; Bohlin, J. D.; Burlaga, L. F.;
Farquhar, R.; Gloeckler, G.; Goldstein, B. E.; Harvey, J. W.; Holzer,
T. E.; Jones, W. V.; Kellogg, P. J.; Krimigis, S. M.; Kundu, M. R.;
Lazarus, A. J.; Mellott, M. M.; Parker, E. N.; Rosner, R.; Rottman,
G. J.; Slavin, J. A.; Suess, S. T.; Tsurutani, B. T.; Woo, R. T.;
Zwickl, R. D.
Bibcode: 1990AIPC..203..101F
Altcode: 1990pacr.rept..101F
The Solar Probe will deliver a 133.5 kg science payload into a 4 Rs
perihelion solar polar orbit (with the first perihelion passage in 2004)
to explore in situ one of the last frontiers in the solar system-the
solar corona. This mission is both affordable and technologically
feasible. Using a payload of 12 (predominantly particles and
fields) scientific experiments, it will be possible to answer many
long-standing, fundamental problems concerning the structure and
dynamics of the outer solar atmosphere, including the acceleration,
storage, and transport of energetic particles near the Sun and in the
inner (<65 Rs) heliosphere.
Title: Slow shocks in an open magnetic field near the sun
Authors: Hu, You-Qiu; Zhu, Zhong-Wei; Hundhausen, A. J.; Holzer,
T. E.; Low, B. C.
Bibcode: 1990SCSMP..33..332H
Altcode:
A numerical study on the formation of the slow shock in an open
magnetic field due to the motion of a coronal mass ejection driven by
a magnetic flux eruption from below the corona is presented. The slow
shock obtained in the numerical model is characterized by a limited
latitudinal extent and a slightly flattened shape. It is determined
that a fast-mode wave always coexists and interacts with the medium
ahead of the slow shock and deflects the background magnetic field
to create a rarefaction ahead of the slow shock and a compression in
the flank. Thus, these effects have a significant influence on the
geometry and features of the slow shock.
Title: Line Broadening of MG X lambda lambda 609 and 625 Coronal
Emission Lines Observed above the Solar Limb
Authors: Hassler, Donald M.; Rottman, Gary J.; Shoub, Edward C.;
Holzer, Thomas E.
Bibcode: 1990ApJ...348L..77H
Altcode:
A University of Colorado sounding rocket experiment on March 17, 1988,
provided high-resolution EUV spectra along a solar diameter and out
to 1.2 solar radius with spatial resolution of 20 x 60 arcsec. Each
spectrum contains transition region and coronal emission lines in
the wavelength range 605-635 A and 1210-1270 A, including the emission
lines Mg X 609 and 625 A, Fe XII 1242 A, O V 629 A, N V 1238 and 1242 A,
corresponding to a wide range of temperatures of formation. Increased
line broadening is observed above the limb for all lines, and this
effect is illustrated by presenting observed line widths as a function
of height above the limb for the higher temperature lines Mg X 609
and 625 A. On the basis of calculations, the most likely cause of
the increased broadening above the limb appears to be the presence of
hydromagnetic waves in the corona.
Title: Interaction between the solar wind and the interstellar medium.
Authors: Holzer, Thomas E.
Bibcode: 1989ARA&A..27..199H
Altcode:
The basic dynamical interaction between the solar wind and the
interstellar medium involves the relaxation toward pressure equilibrium
between the solar and interstellar magnetized plasmas. This interaction
leads to the formation of a cavity in the interstellar medium carved
out by the solar plasma, which we refer to as the heliosphere. It
is not difficult to determine what heliospheric and interstellar
parameters are likely to be important in the interaction between the
solar wind and the interstellar medium, and the author provides an
overview of the observationally inferred values of these parameters,
including the uncertainties in the inferences. Then, he examines from a
theoretical point of view the basic physical processes that are likely
to be important in this interaction, and he concludes by combining
this theoretical information with the observational information in
an effort to develop the currently most likely overall picture of the
heliosphere that is shaped by the local interstellar medium.
Title: SWAN: A study of solar wind anisotropies
Authors: Bertaux, J. L.; Pellinen, R.; Chassefiere, E.; Dimarellis,
E.; Goutail, F.; Holzer, T. E.; Kelha, V.; Korpela, S.; Kyrola, E.;
Lallement, R.
Bibcode: 1988sohi.rept...63B
Altcode:
The SWAN (solar wind anisotropies) Lyman photometer project is
described. It will map the interplanetary hydrogen emission every
other day. From these sky maps, the latitude distribution of the solar
wind mass flux from equator to pole can be measured, as well as the
variation of this distribution. Solar wind mass flux at high latitude
is a key boundary condition to the dynamics of the expansion of the
solar wind, particularly in the coronal holes, and correlatives studies
conducted with other SOHO (solar and heliospheric observatory) coronal
instruments. Secondary objectives include the monitoring of known
comets, the possible discovery of new comets, and coronal observations.
Title: Line Broadening of Transition Region and Coronal Emission
Lines Observed Above the Solar Limb
Authors: Hassler, D. M.; Rottman, G. J.; Holzer, T. E.
Bibcode: 1988BAAS...20R1008H
Altcode:
No abstract at ADS
Title: The solar coronal mass ejection of 20 21 November, 1973
Authors: MacQueen, R. M.; Holzer, T. E.
Bibcode: 1988SoPh..116..349M
Altcode:
The coronal transient event of 20-21 November is unusual in that its
appearance is distinctly non-loop-like; rather, the transient resembles
a confined ray or fan-like volume. Studies of the distribution of the
coronal material with time indicate that this is a mass ejection event,
involving about 1 × 1015 g of material from the lower
corona. Analysis of the polarization signal of the event suggests that
the event is associated with chromospheric activity in a region near
longitude E68. The observed properties (distributions in brightness
and polarization) of the transient are compared with the properties
of a well-studied event of typical loop-like appearance, but rotated
to simulate an `edge-on' appearance; the differences suggest that
the 20-21 November event is not such an edge-on, loop-like transient,
but rather is most simply described as an axisymmetric-cylindrical or
conical volume, the boundaries of which remain constant over the events'
lifetime. On this basis, the variation of the transient spatial density
with height and the variation of density with time can be specified
rather more certainly than for previously-studied coronal mass ejection
events. Densities are found to range from 3 × 10−16
g cm−3 at 2.1 R⊙ heliocentric height early
in the event to 1 × 10−18 g cm−3 at 4.0
R⊙ late in the event. Typical temporal variations of the
ejected material (at a given heliocentric height) are found to be on the
order of 10−18 g cm−3 s−1. The
mass and momentum balance in the event have been estimated from the
observed parameters, employing a multiparameter approach. We find that a
model with modest mass flux typified by material speed u0 ≲
50 km s−1 and a near balance between the event's pressure
gradient force and gravity — with possibly a small hydromagnetic
wave contribution to the total pressure — is consistent with the
observations. The kinetic energy of the event, determined from the
motion of the center of mass of the ejected material, is only about
1026 ergs, and thus is the smallest for any solar mass
ejection studied to date.
Title: Interaction Between the Solar Wind and the Interstellar Medium
Authors: Holzer, T. E.
Bibcode: 1988BAAS...20..740H
Altcode:
No abstract at ADS
Title: Drawing inferences about solar wind acceleration from coronal
minor ion observations
Authors: Esser, Ruth; Holzer, Thomas E.; Leer, Egil
Bibcode: 1987JGR....9213377E
Altcode:
A parameter study is designed and carried out to illustrate the physical
effects that can be studied through analysis and interpretation of
coronal minor ion spectral line observations. It is shown that minor
ion line width, together with the coronal Lyα line width and coronal
white light observations, can yield important information concerning the
transport and dissipation of energy carried outward from the coronal
base by hydromagnetic waves. Although it is difficult to infer minor
ion velocities through the Doppler dimming technique, the application
of this technique using both radiatively and collisionally excited
lines can provide constraints on the acceleration of coronal minor
ions. It is concluded tha the observation of coronal minor ion spectral
lines represents an important component of a concerted observational
approach to the solar wind acceleration problem. It must be emphasized,
however, that the measurement of line widths is the most important
coronal minor ion observation to obtain.
Title: Do slow shocks precede some coronal mass ejections?
Authors: Hundhausen, A. J.; Holzer, T. E.; Low, B. C.
Bibcode: 1987JGR....9211173H
Altcode:
The observed speeds of coronal mass ejections are often below the
estimated Alfvén speed but above the sound speed for the background
solar corona. This suggets that slow magnetohydrodynamic shocks may form
as mass ejections sweep through the corona. We argue on the basis of
the Rankine-Hugoniot relations and the propagation of small-amplitude
slow mode waves that the shape of a slow shock front would be flattened
(with respect to a sun-centered sphere) or perhaps even concave outward
(from the sun) and thus present a very different appearance from the
fast coronal shock waves that have been commonly modeled as wrapping
around a mass ejection. The region behind a slow shock front standing
just off the top of a coronal mass ejection would extend well out
beyond the visible flanks of the ejection. The deflections of coronal
structures that are commonly observed well outside of these flanks
(and which are inconsistent with a fast shock wrapped around the mass
ejection) are consistent with the presence of the slow shock, whether
they lie in the enlarged postshock region or in a region still further
beyond. Although the flattering of the tops of some mass ejections
suggests our proposed slow shock configuration, a true test of its
existence awaits formulation of quantitative models and detailed
comparison with observations.
Title: Book Review - Physics of the Sun
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich,
R. K.; Carson, T. R.
Bibcode: 1987Obs...107..173S
Altcode:
No abstract at ADS
Title: Shallow Temperature Gradient Solutions and Wave Pressure
Effects in the Lower Transition Region
Authors: Woods, D. T.; MacGregor, K. B.; Holzer, T. E.
Bibcode: 1987BAAS...19Q.937W
Altcode:
No abstract at ADS
Title: Acceleration of Stellar Winds (R)
Authors: Holzer, T. E.
Bibcode: 1987sowi.conf....3H
Altcode:
No abstract at ADS
Title: Mathematical descriptions and physical effects of the classical
viscosity in the solar wind near the sector boundaries.
Authors: Zhao, X. -P.; Holzer, T. E.
Bibcode: 1987AcGSn..30..219Z
Altcode:
The questions existing in both the formulas of the radial viscous
force and heating and the formula of the corrected viscous stress by
the magnetic field in the solar wind viscous models are proposed. The
various viscous formulas for the radial and spherical-symmetric plasma
flow in the Parker's spiral configuration of the interplanetary magnetic
field have been derived.
Title: Theory of winds from cool stars.
Authors: Holzer, Thomas E.
Bibcode: 1987IAUS..122..289H
Altcode:
The goal of this paper is to provide a framework for thinking about the
various physical processes that may play significant roles in driving
the massive winds of cool, low-gravity stars. First, some general
theoretical considerations involving mass, momentum, and energy balance
are discussed. Next, the value of the solar wind as an analog for these
late-type stellar winds and for related astrophysical flows is briefly
examined. Finally, four specific mass-loss mechanisms are discussed,
and the possible importance of each of these mechanisms for massive
winds from cool, low-gravity stars is evaluated.
Title: Book-Review - Physics of the Sun - VOL.1 - the Solar
Interior - VOL.2 - the Solar Atmosphere - VOL.3 - Astrophysics and
Solar-Terrestrial Relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
Bibcode: 1987ApL....25..267S
Altcode:
No abstract at ADS
Title: Sixth International Solar Wind Conference
Authors: Pizzo, V. J.; Holzer, T.; Sime, D. G.
Bibcode: 1987sowi.conf.....P
Altcode:
No abstract at ADS
Title: Book-Review - Physics of the Sun - V.I - the Solar Interior
- V.II - the Solar Atmosphere - V.III - Astrophysics and Solar /
Terrestrial Relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich,
R. K.; Parker, E. N.
Bibcode: 1986Natur.323..210S
Altcode:
No abstract at ADS
Title: Solar wind expansion in a polar coronal hole: Inferences from
coronal white light and interplanetary Lyman alpha observations
Authors: Lallement, R.; Holzer, T. E.; Munro, R. H.
Bibcode: 1986JGR....91.6751L
Altcode:
Analysis of white light coronagraph observations of a polar
coronal hole led Munro and Jackson (1977) to infer large solar wind
speeds in the coronal hole and a consequent need for substantial
energy addition to the outflow well above the coronal base. Recent
interplanetary Lyman α observations by Kumar and Broadfoot (1979)
and Lallement et al. (1985) indicate that the solar wind mass flux from
well-developed polar coronal holes may be considerably less than that
typically observed in situ near the ecliptic plane. A reexamination
of the Munro and Jackson analysis, with attention given both to the
inferences drawn from the interplanetary Lyman α observations and to
the uncertainties inherent in the coronal white light observations,
leads to conclusions significantly different from those drawn by
Munro and Jackson. Specifically, the coronal observations are found
to be consistent not only with the high flow speeds and substantial
energy addition inferred by Munro and Jackson, but also with much lower
flow speeds and the absence of any significant energy addition in the
region observed. This removal of definite observational confirmation
of substantial energy addition to the coronal expansion between 1
RS and 5 RS has important implications for our
understanding of energy balance in the solar wind.
Title: Reexamination of the viscous effect in the solar wind.
Authors: Zhao, X. -F.; Holzer, T. E.
Bibcode: 1986ChJSS...6Q...1Z
Altcode:
The Helios observations of the plasma and magnetic field in the
high-speed solar wind streams between 1 AU and 0.3 AU are used to
examine the radial distribution of the various forces exerted on the
streams. It is shown that the classical expression of the viscosity
derived under the condition of collision-dominated plasma is not
suitable for describing the viscous effect in the high speed wind
streams, and the viscous force appears to exist in order to balance
the inertial force of the fluid element with a resulting force, which
approximates to the solar gravity between 0.3 AU and 1 AU. The radial
dependence of the real viscous force in the streams is deduced and the
corresponding viscosity is derived by assuming the trend of the real
viscosity to approach the classical viscosity at small heliocentric
distances. It is found that the ratio of the real to the classical
viscosity at 1 AU should be equal to or greater than one tenth.
Title: Re-examination of the viscous effect in the solar wind
Authors: Zhao, Xue-fu; Holzer, Thomas E.
Bibcode: 1986ChA&A..10..148Z
Altcode:
The Helios observations of the plasma and magnetic field in the
high-speed solar wind streams between 1 AU and 0.3 AU are used to
examine the radial distribution of the various forces exerted on the
streams. It is shown that the classical expression of the viscosity
derived under the condition of collision-dominated plasma is not
suitable for describing the viscous effect in the high speed wind
streams, and the viscous force appears to exist in order to balance
the inertial force of the fluid element with a resulting force, which
approximates to the solar gravity between 0.3 AU and 1 AU. The radial
dependence of the real viscous force in the streams is deduced and the
corresponding viscosity is derived by assuming the trend of the real
viscosity to approach the classical viscosity at small heliocentric
distances. It is found that the ratio of the real to the classical
viscosity at 1 AU should be equal to or greater than one tenth.
Title: Viscosity in the solar wind
Authors: Holzer, T. E.; Leer, E.; Zhao, X. -P.
Bibcode: 1986JGR....91.4126H
Altcode:
The effects of viscosity on a steady, radial, spherically
symmetric solar wind with an embedded, non-radial magnetic field are
reconsidered. The correct expression for the classical viscosity in
the presence of a non-radial magnetic field is shown to be different
from that used in the past, and a means of describing non-classical
viscosity is presented. A physical interpretation of the classical and
nonclassical description of viscosity is provided, and observational
inferences are used in discussing the nature and degree of viscous
effects in the solar wind.
Title: Physics of the Sun. Vol. I: The solar interior. Vol. II:
The solar atmosphere. Vol. III: Astrophysics and solar-terrestrial
relations.
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
Bibcode: 1986psvi.book.....S
Altcode:
No abstract at ADS
Title: Physics of the sun. Volume 3: Astrophysics and
solar-terrestrial relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
Bibcode: 1986psun....3.....S
Altcode:
No abstract at ADS
Title: Physics of the sun. Volume 2: The solar atmosphere
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
Bibcode: 1986psun....2.....S
Altcode:
Aspects related to the solar interior are discussed, taking into account
thermonuclear reactions in the solar interior, atomic and radiative
processes in the solar interior, hydrodynamic and hydromagnetic
phenomena in the deep solar interior, rotation and magnetic fields,
solar waves and oscillations, and observations and theories of solar
convection, global circulation, and magnetic fields. In a discussion
of the solar atmosphere, attention is given to the radiation output,
the chromospheric fine structure, physical processes in the solar
corona, magnetic energy storage and conversion in the solar atmosphere,
the acceleration and propagation of solar flare energetic particles,
solar radio emission, and structure, dynamics, and heating of the solar
atmosphere. Other subjects explored are concerned with astrophysics and
solar-terrestrial relations. The formation of the sun and its planets
is considered along with the solar neutrino problem, solar and stellar
magnetic activity, the effects of solar electromagnetic radiation on
the terrestrial environment, and the effect of the solar wind.
Title: Reexamination of the viscous effect in the solar wind
Authors: Zhao, Xue-Pu; Holzer, T. E.
Bibcode: 1986ChJSS...6R...1Z
Altcode:
The Helios observations of the plasma and magnetic field in the
high-speed solar wind streams between 1 AU and 0.3 AU are used to
examine the radial distribution of the various forces exerted on the
streams. It is shown that the classical expression of the viscosity
derived for the condition of collision-dominated plasma is not suitable
to be used to describe the viscous effect in high-speed wind streams,
and the viscous force appears to exist in order to balance the inertial
force of the fluid element with the resulting force, which approximates
to the solar gravity in value between 0.3 AU and 1 AU. The radial
dependence of the real viscous force in the streams is deduced in the
present work, and the corresponding viscosity is derived by assuming
the trend of the real viscosity approaching the classical viscosity
as the heliocentric distance decreases. It is found that the ratio of
the real viscosity to the classical one at 1 AU is equal to or greater
than one tenth.
Title: Physical processes in the solar corona.
Authors: Rosner, R.; Low, B. C.; Holzer, T. E.
Bibcode: 1986psun....2..135R
Altcode:
Contents: Transport theory (fundamental parameter regimes, the "ideal"
problem, viscosity, parallel thermal energy transport, perpendicular
transport, some comments on model building). Magnetohydrodynamic
processes in the corona (equilibrium magnetic fields, linear stability
and nonequilibrium, time-dependent phenomena). Energy and momentum
balance of open and closed coronal structures (coronal holes and
high-speed streams, Alfvén waves in the lower solar atmosphere,
energy supply to magnetically closed coronal regions).
Title: Physics of the sun
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
Bibcode: 1986psun....1.....S
Altcode: 1986QB521.P48......
Aspects related to the solar interior are discussed, taking into account
thermonuclear reactions in the solar interior, atomic and radiative
processes in the solar interior, hydrodynamic and hydromagnetic
phenomena in the deep solar interior, rotation and magnetic fields,
solar waves and oscillations, and observations and theories of solar
convection, global circulation, and magnetic fields. In a discussion
of the solar atmosphere, attention is given to the radiation output,
the chromospheric fine structure, physical processes in the solar
corona, magnetic energy storage and conversion in the solar atmosphere,
the acceleration and propagation of solar flare energetic particles,
solar radio emission, and structure, dynamics, and heating of the solar
atmosphere. Other subjects explored are concerned with astrophysics and
solar-terrestrial relations. The formation of the sun and its planets
is considered along with the solar neutrino problem, solar and stellar
magnetic activity, the effects of solar electromagnetic radiation on
the terrestrial environment, and the effect of the solar wind.
Title: Mass Loss Mechanisms for Cool, Low-Gravity Stars (Review)
Authors: Holzer, T. E.; MacGregor, K. B.
Bibcode: 1985ASSL..117..229H
Altcode: 1985mlrg.proc..229H
A number of physical effects relevant to mass loss from cool,
low-gravity stars is explored in order to provide a basis for
understanding the various mechanisms proposed to explain such
quasi-steady and non-steady mass loss. After considering a few general
implications of the requirements of mass, momentum, and energy balance,
four specific mass loss mechanisms are examined in some detail. Emphasis
is placed on the basic physical constraints imposed uniformly on all
these mechanisms by inferences drawn from observations of a broad
range of stars. It is suggested that these physical constraints,
rather than the techniques used to observe particular objects should
serve as the dominant factor in organizing thinking about massive,
low speed, late type stellar winds.
Title: Inferences Concerning Solar Wind Momentum and Energy Balance
Drawn From Coronal Density Observations
Authors: Lallement, R. L.; Holzer, T. E.; Munro, R. H.
Bibcode: 1985BAAS...17..638L
Altcode:
No abstract at ADS
Title: Solar Wind and Coronal Holes
Authors: Leer, E.; Holzer, T. E.
Bibcode: 1985ESASP.235....3L
Altcode: 1985fmsh.work....3L; 1985shpp.rept....3L
The authors discuss the basic physics of the solar wind emanating from
coronal holes, and show that thermally driven solar wind models cannot
explain the high flow speeds. The effect of MHD waves on both the solar
wind and wind from late-type giants and supergiants is also considered.
Title: Acceleration of the Solar Wind
Authors: Holzer, T. E.
Bibcode: 1985spit.conf..995H
Altcode:
No abstract at ADS
Title: Fast-mode magnetohydrodynamic waves in coronal holes and the
solar wind
Authors: Fla, T.; Habbal, S. R.; Holzer, T. E.; Leer, E.
Bibcode: 1984ApJ...280..382F
Altcode:
Fast-mode MHD waves in the solar corona can propagate in any direction
relative to the background magnetic field. In coronal holes, they
refract into regions of low Alfven speed and are relatively difficult
to damp. These characteristics lead to the possibility that fast-mode
waves transport energy from magnetically closed coronal regions into
coronal holes, that they are refracted into the central regions of
coronal holes, and that they deposit most of their energy in the
region of supersonic flow of high-speed solar wind streams emanating
from coronal holes. To investigate whether this possibility might be
realized and fast-mode waves might play a significant role in driving
high-speed streams, a parameter study is carried out to examine the
propagation and damping of fast-mode waves in various coronal hole
models. This study indicates a broad range of coronal hole parameters
for which fast-mode waves can play such a role and emphasizes the need
for an improved knowledge of large-scale coronal magnetic structure,
which is required before any firm conclusions can be drawn.
Title: Alfven waves in stellar winds
Authors: Holzer, T. E.; Fla, T.; Leer, E.
Bibcode: 1983ApJ...275..808H
Altcode:
An analytic description of a stellar wind with waves which are undamped
in the region of subsonic flow is developed for a range of stellar
conditions, and numerical models with wave damping are applied to the
massive winds from cool, low gravity stars, in an examination of the
propagation and damping of Alfven waves in stellar winds. Attention is
also given to the effects of these waves on the wind mass loss rate,
asymptotic flow speed, and radial temperature profile. No evidence is
found for the belief that winds driven by Alfven waves from cool, low
gravity stars can exhibit both a very large mass loss rate and a very
small asymptotic flow speed. It is noted that the radial temperature
profile produced by invoking a constant damping length for the waves
is different from that produced by self-consistent description of
frictional wave damping for a wave frequency which is presumably
consistent with the chosen constant damping length.
Title: The solar wind ionization state as a coronal temperature
diagnostic
Authors: Owocki, S. P.; Holzer, T. E.; Hundhausen, A. J.
Bibcode: 1983ApJ...275..354O
Altcode:
The 'frozen' solar wind ionization state within a few solar radii
of the photosphere suggests that ion measurements at 1 AU may yield
information on the electron temperature conditions at the base of
the coronal expansion. The freezing-in process is examined in light
of traditional assumptions as to coronal expansion, where electron
temperature decreases monotonically with height, the bulk flow of all
charge states of a given ion species are equal to the proton speed,
and the ion outflow is spherically symmetric. The consequences of
the relaxation of these assumptions include the underestimation of
the magnitude of a temperature maximum occurring near the freezing-in
radius. Because it is associated with high speed, low density flow,
an areal divergence that is faster than that in a spherical outflow
lowers the ionization state freezing-in level relative to that which
is typical in spherically symmetric expansion.
Title: Alfvén waves in stellar winds.
Authors: Holzer, T. E.
Bibcode: 1983NASCP2280..279H
Altcode:
No abstract at ADS
Title: The acceleration and propagation of solar flare energetic
particles
Authors: Forman, M. A.; Ramaty, R.; Zweibel, E. G.; Holzer, T. E.;
Mihalas, D.; Sturrock, P. A.; Ulrich, R. K.
Bibcode: 1982STIN...8329162F
Altcode:
Observations and theories of particle acceleration in solar flares
are reviewed. The most direct signatures of particle acceleration
in flares are gamma rays, X-rays and radio emissions produced by the
energetic particles in the solar atmosphere and energetic particles
detected in interplanetary space and in the Earth's atmosphere. The
implication of these observations are discussed. Stochastic and shock
acceleration as well as acceleration in direct electric fields are
considered. Interplanetary particle propagation is discussed and
an overview of the highlights of both current and promising future
research is presented.
Title: Intrinsic stellar mass flux and steady stellar winds
Authors: Wolfson, R. L. T.; Holzer, T. E.
Bibcode: 1982ApJ...255..610W
Altcode:
The suggestion that the rates of mass loss from sun-like stars are
determined by conditions imposed on the flow at or below photospheric
levels, and that the warm chromosphere and hot corona of the star
type in question are consequences of this imposed photospheric flow
and dissipation in the resultant stellar wind, is examined through
application of gas dynamic theories which include dissipation. Analytic
and numerical calculations for both polytropic and thermally-conductive
flows including viscosity indicate that arbitrary intrinsic mass flux
specification is not consistent with steady, radial, spherically
symmetric flow in the absence of energy addition. It is therefore
concluded that there is not theoretical support for the suggestion
stated.
Title: The role of spicules in heating the solar atmosphere
Authors: Athay, R. G.; Holzer, T. E.
Bibcode: 1982ApJ...255..743A
Altcode:
From observations of downflowing material at transition region
temperature, together with reasonable assumptions about the fate
of spicules after they disappear from view in the visual spectrum,
it is shown that the rise and fall of spicular material can supply
the thermal energy required by radiative losses from the transition
region and upper chromosphere in the network. If sufficient heat
is added to spicules, in conjunction with their acceleration, the
spicule phenomenon may also play a major role in the production and
maintenance of much of the solar corona. Thus, the processes whereby
spicules are generated and heated may be of central importance to the
energy balance of the outer solar atmosphere. This conclusion points
to the need for developing an understanding of the acceleration and
heating of spicules and to the need for observations of spicules after
they have disappeared in the visual spectrum.
Title: Acceleration of the solar wind.
Authors: Leer, E.; Holzer, T. E.; Fla, T.
Bibcode: 1982SSRv...33..161L
Altcode:
In this review, we discuss critically recent research on the
acceleration of the solar wind, giving emphasis to high-speed solar
wind streams emanating from solar coronal holes. We first explain why
thermally driven wind models constrained by solar and interplanetary
observations encounter substantial difficulties in explaining high speed
streams. Then, through a general discussion of energy addition to the
solar wind above the coronal base, we indicate a possible resolution of
these difficulties. Finally, we consider the question of what role MHD
waves might play in transporting energy through the solar atmosphere
and depositing it in the solar wind, and we conclude by examining,
in a simple way, the specific mechanism of solar wind acceleration by
Alfvén waves and the related problem of accelerating massive stellar
winds with Alfvén waves.
Title: Theory of Mass and Energy Flow in the Solar Wind
Authors: Holzer, T. E.; Leer, E.
Bibcode: 1981sowi.conf...28H
Altcode:
No abstract at ADS
Title: Stellar Winds with Excess Mass Flux
Authors: Wolfson, R. L. T.; Holzer, T. E.
Bibcode: 1980BAAS...12Q.864W
Altcode:
No abstract at ADS
Title: Conductive solar wind models in rapidly diverging flow
geometries
Authors: Holzer, T. E.; Leer, E.
Bibcode: 1980JGR....85.4665H
Altcode:
A detailed parameter study of conductive models of the solar wind has
been carried out, extending the previous similar studies of Durney
(1972) and Durney and Hundhausen (1974) by considering collisionless
inhibition of thermal conduction, rapidly diverging flow geometries, and
the structure of solutions for the entire n0-T0
plane (n0 and T0 are the coronal base density
and temperature). Primary emphasis is placed on understanding the
complex effects of the physical processes operative in conductive
solar wind models. There are five points of particular interest that
have arisen from the study: (1) neither collisionless inhibition
of thermal conduction nor rapidly diverging flow geometries can
significantly increase the solar wind speed at 1 AU; (2) there exists
a firm upper limit on the coronal base temperature consistent with
observed values of the coronal base pressure and solar wind mass
flux density; (3) the principal effect of rapidly diverging flow
geometries is a decrease in the solar wind mass flux density at 1 AU
and an increase in the mass flux density at the coronal base; (4)
collisionless inhibition of thermal conduction can lead to a solar
wind flow speed that either increases or decreases with increasing
coronal base density (n0) and temperature (T0,
depending on the region of the n0-T0 plane
considered; (5) there is a region of the n0-To
plane at high coronal base densities where low-speed, high-mass-flux,
transonic solar wind flows exist-a region not previously considered.
Title: Energy addition in the solar wind.
Authors: Leer, E.; Holzer, T. E.
Bibcode: 1980JGR....85.4681L
Altcode:
A general study of energy addition, energy loss, and energy
redistribution in the solar wind, for both spherically symmetric and
rapidly diverging flow geometries, is presented. It is found that
energy addition in the region of subsonic flow increases the solar
wind mass flux but either has little effect on (for heat addition) or
significantly reduces (for momentum addition) the solar wind flow speed
at 1 AU. In contrast, energy addition in the region of supersonic flow
has no effect on the solar wind mass flux but significantly increases
the flow speed at 1 AU. It is also found that both momentum loss in the
subsonic region and energy exchange (involving loss in the subsonic
region and gain in the supersonic region) can lead to an increase in
the asymptotic flow speed. This general study thus places certain
constraints on viable mechanisms for driving high-speed solar wind
streams and points to a number of specific, self-consistent studies
of such mechanisms that need to be carried out in the future.
Title: Large-Scale Solar Magnetic Fields, Coronal Holes and High-Speed
Solar Wind Streams
Authors: Hundhausen, A. J.; Holzer, T. E.
Bibcode: 1980RSPTA.297..521H
Altcode: 1980RSLPT.297..521H
The connection between geomagnetic disturbances recurring with
the 27 day synodic solar rotation period and streams of plasma
emitted from particular regions on the Sun (so-called M-regions)
has been one of the long-standing problems of solar-terrestrial
physics. The 'plasma streams' have been identified with long-lived
streams of fast solar wind, imbedded in unipolar magnetic 'sectors',
for more than a decade. The solar sources of these streams have been
identified unequivocally only within the past few years as large-scale
coronal regions of open, diverging magnetic fields and abnormally
low particle densities, observed as 'coronal holes'. The temporal
evolution of holes and streams seems to reflect the evolution of
the large-scale solar magnetic fields; the observed spatial pattern
of holes suggests a grand three-dimensional structure of solar wind
flow and interplanetary magnetic fields organized by a near-equatorial
neutral sheet. The conclusion that much of the solar wind comes from
coronal holes implies several important modifications of our ideas
regarding the physical origins of the solar wind and any theoretical
models of solar wind formation.
Title: Alfvén-wave acceleration of the solar wind.
Authors: Leer, E.; Fla, T.; Holzer, T. E.
Bibcode: 1980NCimC...3..114L
Altcode:
The increase in mass flux and energy flux from the sun is calculated
for an increasing Alfven-wave amplitude, in the lower corona and
fixed values for the coronal pressure, the coronal temperature and the
interplanetary magnetic field. The energy per mass and the flow speed
at the orbit of the earth increase with the wave amplitude and reach a
maximum for a wave amplitude of approximately 50 km/sec. For reasonable
values of the coronal pressure and temperature and of the magnetic
field, high-speed solar-wind streams can be driven by Alfven waves with
an amplitude approximately equal to 20-25 km/sec in the lower corona.
Title: The Corona and Heliosphere
Authors: Holzer, T.
Bibcode: 1980NASCP2098...13H
Altcode: 1980sscs.nasa...13H
The eleven-year solar cycle is an especially appropriate period
over which to study the solar output and its variation, because
during this cycle most of the important types of solar variability
(many characterized by periods shorter than eleven years) are
manifested. Studies of solar variability over a solar cycle will
improve understanding of solar structure and of the generation of
the solar wind, and this improved understanding can be useful in
the related studies of stellar structure and stellar winds, since
stellar observations are necessarily less detailed and sophisticated
than are solar observations. A particularly significant benefit that
will accrue from a thorough study of the solar atmosphere and its
variability over the next solar cycle is a great enhancement in the
usefulness of so-called 'proxy' data in studying longer term solar
variations and their terrestrial implication.
Title: Theory of the Solar Wind and Winds from Late-Type Stars
Authors: Holzer, T. E.
Bibcode: 1980SAOSR.389..153H
Altcode: 1980csss....1..153H
No abstract at ADS
Title: Heating of Coronal Loops by Fast-Mode Magnetohydrodynamic Waves
Authors: Habbal, Shadia Rifai; Leer, Egil; Holzer, Thomas E.
Bibcode: 1979SoPh...64..287H
Altcode:
A possible mechanism for the formation and heating of coronal loops
through the propagation and damping of fast mode waves is proposed
and studied in detail. Loop-like field structures are represented by
a dipole field with the point dipole at a given distance below the
solar surface. The density of the medium is determined by hydrostatic
equilibrium along the field lines in an isothermal atmosphere. The
fast mode waves propagating outward from the coronal base are refracted
into regions with a low Alfvén speed and suffer collisionless damping
when the gas pressure becomes comparable to the magnetic pressure. The
propagation and damping of these waves are studied for three different
cases: a uniform density at the coronal base, a density depletion
within a given flux tube, and a density enhancement within a given flux
tube. The fast mode waves are found to be important in the formation
and heating of the loops if the wave energy flux density is of the order
105 ergs cm-2 s-1 at the coronal base.
Title: Mass Flow and the Validity of Ionization Equilibrium on the Sun
Authors: Joselyn, J.; Munro, R. H.; Holzer, T. E.
Bibcode: 1979SoPh...64...57J
Altcode:
Ionization equilibrium is a useful assumption which allows
temperatures and other plasma properties to be deduced from spectral
observations. Inherent to this assumption is the premise that the ion
stage densities are determined solely by atomic processes which are
local functions of the plasma temperature and electron density. However,
if the time scale of plasma flow through a temperature gradient is
less than the characteristic time scale for an important atomic
process, deviations from the ionization stage densities expected
for equilibrium will occur which could introduce serious errors
into subsequent analyses. In the past few years, significant flow
velocities in the upper solar atmosphere have been inferred from
observations of emission lines originaing in the transition region
(about 104-106 K) and corona. In this paper,
three models of the solar atmosphere (quiet Sun, coronal hole, and
a network model) are examined to determine if the emission expected
from these model atmospheres could be produced from equilibrium
ion populations when steady flows of several kilometers per second
are assumed. If the flows are quasi-periodic instead of steady,
spatial and temporal averaging inherent in the observations may
allow for the construction of satisfactory models based on the
assumption of ionization equilibrium. Representative emission lines
are analysed for the following ions: C III, IV, O IV, V, VI, Ne VII,
VIII, Mg IX, X, Si XII, and Fe IV-XIV. Two principle conclusions
are drawn. First, only the iron ions are generally in equilibrium
for steady flows of 20 km s−1. For carbon and oxygen,
ionization equilibrium is not a valid assumption for steady flows as
small as 1 km s−1. Second, the three models representing
different solar conditions behave in a qualitatively similar manner,
implying that these results are not particularly model dependent over
the range of temperature gradients and electron densities thus far
inferred for the Sun. In view of the flow velocities which have been
reported for the Sun, our results strongly suggest caution in using
the assumption of ionization equilibrium for interpreting spectral
lines produced in the transition region.
Title: Constraints on the solar coronal temperature in regions of
open magnetic field.
Authors: Leer, E.; Holzer, T. E.
Bibcode: 1979SoPh...63..143L
Altcode:
It is shown that the simultaneous consideration of observed values
of the solar wind proton flux density at 1 AU and of the electron
pressure at the base of the solar corona leads to relatively strong
constraints on the coronal temperature in the region of subsonic solar
wind flow. The extreme upper limit on the mean coronal temperature
in the subsonic region is found to be about 2.6 × 106 K,
but this upper limit is reduced to about 2.0 × 106 K if
reasonable, rather than extreme, assumptions are made; the limit on
the maximum temperature is about 0.5 × 106 K greater than
the limit on the mean. It is also found that the same two observations
limit the rate of momentum addition possible in the region of subsonic
solar wind flow.
Title: The validity of ionization equilibrium in highly ionized
astrophysical plasmas.
Authors: Joselyn, J. A.; Munro, R. H.; Holzer, T. E.
Bibcode: 1979ApJS...40..793J
Altcode:
Conditions of steady flow through a temperature gradient are determined
for which the assumption of ionization equilibrium remains approximately
valid. A simplified solution for ionization stage densities is obtained
for the set of mass conservation equations under conditions of steady
flow through a temperature gradient for the following elements and
ionization stages: C II through C VII, N III through N VIII, O I through
O IX, Ne I through Ne XI, Mg II through Mg XII, Si I through Si XIV, S
I through S X, and Fe VI through Fe XVII. The results obtained show that
some ions may reflect conditions appropriate to ionization equilibrium,
but ionization equilibrium may be a very poor assumption for other ions.
Title: The solar wind and related astrophysical phenomena
Authors: Holzer, T. E.
Bibcode: 1979sswp.book..101H
Altcode:
In the present paper, the current status of understanding of
the large-scale dynamics of the solar wind are reviewed, in the
context of recent studies of coronal holes, on board Skylab. The
relationship between physical processes in the solar wind and in various
astrophysical plasmas is examined, with particular reference to the
study of stellar winds. The basic mathematical framework, including
both microscopic and macroscopic descriptions of the solar wind plasma,
is outlined. The discussion is limited mostly to the macroscopic MHD
description, as it applied to large-scale dynamic processes. Some
directions of future research are proposed.
Title: The Solar Wind and Related Astrophysical Phenomena
Authors: Holzer, T. E.
Bibcode: 1979spp2.conf....1H
Altcode:
No abstract at ADS
Title: Heating of Coronal Loops by Fast Mode Mhd-Waves
Authors: Habbal, S. R.; Holzer, T. E.; Leer, E.
Bibcode: 1979phsp.coll..228H
Altcode: 1979phsp.conf..228H; 1979IAUCo..44..228H
This paper discusses the formation and heating of solar coronal loops
by fast mode MHD waves which, unlike Alfven waves, have an acoustic
component. These fast mode waves can carry a substantial energy flux
along the wave normal only in coronal regions with a strong magnetic
field. The propagation and damping of these waves in a two dimensional
solar atmosphere is considered. It is noted that the damping occurs
mainly in the region where beta = 2nkT/(B-squared/8pi) is larger than
0.05, and that most of the energy is transferred to the plasma in the
region where beta approximately equals 0.2. In this case the plasma
in the flux tube with a height approximately equal to 0.2R is heated
most, and the wave energy flux from the base deposits more energy
in this tube than is lost by radiation and heat conduction at the
footpoints. Therefore, density and temperature perturbations across the
field lines will develop and 'loops' may be formed. Heating mechanisms
of the surrounding plasma in both large density and low density loops
are then described.
Title: A steady three-fluid coronal expansion for nonspherical
geometries
Authors: Joselyn, J.; Holzer, T. E.
Bibcode: 1978JGR....83.1019J
Altcode:
A steady three-fluid model of the solar coronal expansionk in which
4He++ ions (alphas) are treated as a nonminor
species, is developed for nonspherically symmetric flow geometries
of the general sort thought to be characteristic of coronal holes. It
is found that the very high mass fluxes in the low corona, which are
associated with rapidly diverging flow geometries, lead to a locally
enhanced frictional coupling between protons and alphas and consequently
to a significant reduction of the He/H abundance ratio in the lower
corona from that normally predicted by multifluid models. In the models
considered, the frictional drag on the protons by the alphas (a process
neglected in most studies) is found to play an important role near the
sun. Heavy ions, other than alphas, are treated as minor species and
are seen to exhibit varying responses to the rapidly diverging flow
geometries, depending on the ion mass and charge. As for the protons,
the frictional effect of the alphas on the heavier ions is found to
be significant in the models considered.
Title: Neutral hydrogen in interplanetary space.
Authors: Holzer, T. E.
Bibcode: 1977RvGSP..15..467H
Altcode: 1977RvGeo..15..467H
Several problems relating to interplanetary hydrogen are
discussed. Various possible interplanetary sources and sinks for H and
He atoms are considered, and their contributions to the distribution of
interplanetary neutral gas are compared. A theoretical description of
the penetration of interstellar H and He into interplanetary space is
presented with reference to observations of interplanetary neutral
gas. The implications of interplanetary H for the solar wind are
examined, and some qualitative aspects of the passage of the solar
system through an interstellar H cloud are discussed. Future research
goals are outlined.
Title: Neutral hydrogen in interplanetary space
Authors: Holzer, Thomas E.
Bibcode: 2021JPhCS2105a2001D
Altcode:
The theory and observations relevant to the problem of neutral hydrogen
in interplanetary space are reviewed. Emphasis is placed on those
theoretical problems whose treatment in the existing literature
is not entirely satisfactory, but discussion of all significant
observational and theoretical aspects of the interplanetary H problem
is provided. Attention is also given to other neutral constituents
(particularly He) that are relatively abundant in interplanetary space
and in the local interstellar medium, which is the primary source of
the interplanetary neutral gas. Some consequences of the passage of the
solar system through an interstellar cloud are also briefly considered.
Title: The Validity of Ionization Equilibrium in Steady-State Flows.
Authors: Joselyn, J. A.; Munro, R. H.; Holzer, T. E.
Bibcode: 1977BAAS....9..650J
Altcode:
No abstract at ADS
Title: INVITED PAPER - The Solar Wind and Stellar Winds.
Authors: Holzer, T. E.
Bibcode: 1977BAAS....9..344H
Altcode:
No abstract at ADS
Title: Effects of rapidly diverging flow, heat addition, and momentum
addition in the solar wind and stellar winds
Authors: Holzer, T. E.
Bibcode: 1977JGR....82...23H
Altcode:
The roles of rapid flow tube divergence and heat and momentum addition
in one-fluid models of the solar wind and stellar winds and the role of
heat addition in two-fluid models of the solar wind are explored. It
is found that under certain circumstances heat addition, momentum
addition, or the rapid divergence of a flow tube can produce more
than one critical point in the solution topologies of the solar and
stellar wind equations. For the solar wind, additional critical points
associated with rapid flow tube divergence (e.g., in coronal holes)
and/or with momentum addition can lead to high expansion speeds near the
coronal base, and these high speeds, in conjunction with a rapid flow
tube divergence, may in certain cases produce an increased conductive
energy supply to the solar wind. If such an increased conductive energy
supply is produced, the need for energy addition above the coronal base
is correspondingly reduced. In addition, the high flow speeds at low
altitudes make it possible for any required energy addition to occur
relatively near the coronal base, so that the need for extended heating
of the solar wind may be substantially less than has been suggested in
the past. For radiation-driven stellar winds the additional critical
points associated with rapid flow tube divergence can lead to supersonic
flow much deeper in the stellar atmosphere than is predicted by radial,
spherically symmetric flow models, and this might resolve the apparent
conflict between radiation-driven wind models and certain observations
of Of stars. In two-fluid solar wind models including proton heat
addition it is shown that the radial electron temperature profile
has a sufficiently important dynamical influence that the accurate
treatment of electron energy transport is a primary prerequisite to
obtaining quantitatively significant results.
Title: The Magnetosphere
Authors: Holzer, Thomas
Bibcode: 1977soiv.conf....5H
Altcode:
No abstract at ADS
Title: Dynamics of coronal hole regions. I. Steady polytropic flows
with multiple critical points.
Authors: Kopp, R. A.; Holzer, T. E.
Bibcode: 1976SoPh...49...43K
Altcode:
The hydrodynamic properties of a steadily expanding corona are explored
for situations in which departures from spherically symmetric outflow
are large, in the sense that the geometrical cross section of a given
flow tube increases outward from the Sun faster than r2
in some regions. Assuming polytropic flow, it is shown that in
certain cases the flow may contain more than one critical point. We
derive the criterion for determining which of these critical points is
actually crossed by the transonic solution which begins at the Sun and
extends continuously outward. Next, we apply the theory to geometries
which exhibit rapid spreading of the flow tubes in the inner corona,
followed by more-or-less radial divergence at large distances. This is
believed to be the type of geometry found in coronal hole regions. The
results show that, if this initial divergence is sufficiently large,
the outflow becomes supersonic at a critical point encountered low in
the corona in the region of high divergence, and it remains supersonic
at all greater heights in the corona. This feature strongly suggests
that coronal hole regions differ from other open-field regions of
the corona in that they are in a `fast', low density expansion state
over much of their extent. Such a dynamical configuration makes it
possible to reconcile the low values of electron density observed in
coronal holes with the large particle fluxes in the associated high
speed streams seen in the solar wind.
Title: Interaction between the Solar Wind and the Interstellar Medium
Authors: Holzer, Thomas E.
Bibcode: 1976PrAA...50...21H
Altcode:
No abstract at ADS
Title: Our quantitative understanding of the coronal expansion.
Authors: Holzer, T. E.
Bibcode: 1976pspe.proc..366H
Altcode: 1976pspe.conf..366H
A review of the current state of our quantitative understanding of
the coronal expansion is presented. Emphasis is placed on the problem
of supplying the mass and energy fluxes observed in high speed solar
wind streams from the low-density, rapidly diverging coronal hole
regions. Future directions for theoretical research on this problem
are indicated, but it is pointed out that at the present time our
quantitative understanding of the coronal expansion is severely limited
by the current state of coronal observations.
Title: Relationship between the interplanetary magnetic field and
‘isolated substorms’
Authors: Hirshberg, J.; Holzer, T. E.
Bibcode: 1975JGR....80.3553H
Altcode:
The study of 54 ‘isolated substorms’ by Foster et al. (1971)
is reexamined, and five different explanations of the results of
this study are found to be consistent with the data. For each of the
five explanations the decay time of the AE index is found not to be
characteristic of internal magnetospheric processes but to be due to
data selection. In four of the five explanations the time lag that
maximizes the correlation coefficient between Bz and AE
is found not to represent the time lag between an interplanetary
cause and a consequent magnetospheric effect. It is shown that by
simple extensions of the Foster et al. study, at least four of the
five explanations can be eliminated. The implications of the Foster
et al. study with regard to the ‘growth phase controversy’ are
considered, and proposed extensions of the study appear likely to
resolve the controversy.
Title: The response of the day side magnetosphere-ionosphere
system to time-varying field line reconnection at the magnetopause,
1. Theoretical model
Authors: Holzer, T. E.; Reid, G. C.
Bibcode: 1975JGR....80.2041H
Altcode:
The process whereby magnetic flux is removed from the day side region of
the magnetosphere and transferred to the magnetotail has been referred
to as ‘erosion’ of the day side magnetosphere. Observations have
suggested that the occurrence of this erosion process is related
to increases in the southward component of the interplanetary
magnetic field and hence by inference to increases in the rate of
field line reconnection at the day side magnetopause. Similarly, the
inverse of the erosion process (i.e., the net transfer of flux from
the magnetotail to the day side magnetosphere) is associated with
decreases in the southward component of the interplanetary magnetic
field and hence to decreases in the magnetopause reconnection rate. A
quantitative theory of the day side erosion process (and its inverse)
is developed here in terms of an electrical circuit analogy, in
which the ionosphere acts as a resistance with a voltage generator
connected in parallel and the closed magnetosphere acts as a set of
inductances and a capacitance. Changes in the rate of day side field
line reconnection lead directly to changes in the potential drop across
the magnetospheric capacitor and, after a characteristic time delay,
to changes in the voltage applied by the generator. The response
of the coupled ionosphere-magnetosphere circuit to such changes is
studied in some detail, and a quantitative estimate for the rate of
erosion is obtained. In addition to describing the mean motion of the
magnetopause associated with erosion the theory predicts oscillations of
the magnetopause about this mean with characteristic periods of several
minutes. Such oscillations have frequently been observed by spacecraft.
Title: The response of the day side magnetosphere-ionosphere system
to time-varying field line reconnection at the magnetopause 2. Erosion
event of March 27, 1968
Authors: Reid, G. C.; Holzer, T. E.
Bibcode: 1975JGR....80.2050R
Altcode:
The circuit analogy for the response of the coupled
magnetosphere-ionosphere system to changes in day side field line
reconnection rate is applied to real conditions and is used to calculate
the expected variation in magnetopause position during the erosion
event described by Aubry et al. (1970). Generally good agreement
between observation and theory is found. The role of the dawn-dusk
electric field responsible for magnetospheric convection is examined
in some detail and is treated in the circuit analogy as the field due
to an external generator connected across the circuit. It is found
that the erosion process requires two distinct time constants for a
proper description: (1) the time needed for magnetosheath plamsa to
travel down the freshly reconnected field lines to the ionosphere and
(2) roughly, the time required for the foot of a reconnected field
line to travel one quarter of the total noon-midnight dimension of
the polar cap. The second time constant is the dominant one and is
not related to the ionospheric conductivity, as has been suggested
previously. Examination of high-latitude magnetograms obtained during
the erosion event discussed shows that the electric field oscillations
predicted by the theory and observed by the spacecraft in terms
of oscillations in the magnetopause position are also reflected in
oscillations in ionospheric current flow.
Title: The effect of asymmetric solar wind on the Lyman α sky
background
Authors: Joselyn, J. A.; Holzer, T. E.
Bibcode: 1975JGR....80..903J
Altcode:
The Lyman α (Ly α) sky background arises from the scattering
of solar Ly α from a spatial distribution of neutral hydrogen in
interplanetary space. This distribution is partially determined by
the solar wind proton flux, which provides the principal mechanism
of loss by charge exchange of the neutral hydrogen. By generating
isophotal maps of scattered Ly α for several choices of interstellar
wind direction and solar wind proton flux distributions, the results
show that latitudinal variations of the solar wind proton flux can have
a significant effect on the observed location and shape of the Ly α
intensity maximum. This fact should aid in the interpretation of Ly
α maps and also indicates a possible method for inferring values for
the average solar wind proton flux out of the ecliptic plane.
Title: Solar Wind Heating Beyond 1 AU
Authors: Holzer, Thomas E.; Leer, Egil
Bibcode: 1973Ap&SS..24..335H
Altcode:
The effect of an interplanetary atomic hydrogen gas on solar
wind proton, electron and α-particle temperatures beyond 1 AU is
considered. It is shown that the proton temperature (and probably
also the α-particle temperature) reaches a minimum between 2 AU and
4 AU, depending on values chosen for solar wind and interstellar gas
parameters. Heating of the electron gas depends primarily on the thermal
coupling of the protons and electrons. For strong coupling (when T
p ≳T e ), the electron temperature reaches a
minimum between 4 AU and 8 AU, but for weak coupling (Coulomb collisions
only), the electron temperature continues to decrease throughout the
inner solar system. A spacecraft travelling to Jupiter should be able
to observe the heating effect of the solar wind-interplanetary hydrogen
interaction, and from such observations it may be possible of infer
some properties of the interstellar neutral gas.
Title: Quiet auroral arcs and electrodynamic coupling between the
ionosphere and the magnetosphere, 2
Authors: Holzer, Thomas E.; Sato, Tetsuya
Bibcode: 1973JGR....78.7330H
Altcode:
The auroral arc model of Sato and Holzer (1973) (this issue) is
extended and applied to the real auroral ionosphere-magnetosphere
system. A discussion is presented of the model's predictions regarding
electric fields in and near quiet arcs, the spacing of multiple arcs,
the latitudinal conjugacy of quiet arcs, the location of quiet arcs,
and the current system (field aligned and cross field) associated
with quiet arcs. These predictions are then compared with relevant
observations, and it is found that the model is reasonably consistent
with existing observational data.
Title: Quiet auroral arcs and electrodynamic coupling between the
ionosphere and the magnetosphere, 1
Authors: Sato, Tetsuya; Holzer, Thomas E.
Bibcode: 1973JGR....78.7314S
Altcode:
The magnetosphere-ionosphere system associated with the nighttime
auroral region is considered for quiet conditions, and it is shown
that in the presence of an electric field an ionospheric electron
density perturbation that is narrow in latitude and broad in local
time will grow exponentially in time, driving an ac current through
the magnetosphere-ionosphere system. Under favorable conditions a
field-aligned current-driven instability is excited in the lower
magnetosphere, and associated wave-particle interactions give rise
to pitch angle scattering of energetic magnetospheric particles and
an anomalous resistivity along field lines. In a region of upward
field-aligned current the pitch angle scattering and the field-aligned
electric field (arising from anomalous resistivity) lead to an enhanced
flux of precipitating magnetospheric electrons and an energization of
these electrons that in turn give rise to an enhanced auroral electrojet
current and a nearly coincident visible auroral arc.
Title: Book Review: Particles and fields in the magnetosphere. Edited
by B. M. MCCORMACK. D. Reidel, Dordrecht, Holland; Springer-Verlag,
New York, 1970. ix + 453 pp. Price $27.00
Authors: Holzer, Thomas E.
Bibcode: 1972Icar...16..408H
Altcode:
No abstract at ADS
Title: Neutral Hydrogen in Cometary Comas
Authors: Mendis, D. A.; Holzer, T. E.; Axford, W. I.
Bibcode: 1972Ap&SS..15..313M
Altcode:
The strong Lα radiation observed recently in comets Tago-Sato-Kosaka
and Bennett can be explained in terms of the resonant scattering of
solar Lα radiation on neutral hydrogen formed by the photo-dissociation
of H2O which is vaporized from a nucleus having an ice
core. A complete hydrodynamic description of an atmosphere composed of
H2O and its daughter products OH, H and O coupled through
frictional interaction as well as production and loss processes is
given. Numerical results are computed in a typical case, and it is
found that a temperature of about 3000 K for the cometary atmosphere
provides the best fit with observation.
Title: Interaction of the solar wind with the neutral component of
the interstellar gas
Authors: Holzer, Thomas E.
Bibcode: 1972JGR....77.5407H
Altcode:
A model is constructed to represent the interaction between the solar
wind and the neutral component of the interstellar gas. It is found
that the neutral gas has several important effects on the solar-wind
expansion beyond the orbit of the earth and that it should be possible
to infer the presence of the neutral gas from observations of the solar
wind made by a space probe traveling into the outer solar system. The
effects include a deceleration and heating of the supersonic solar
wind, a cooling of and pressure reduction in the subsonic solar wind,
and a tightening of the spiral magnetic field in the supersonic solar
wind. Although in principle the neutral gas can lead to a shock-free
transition from supersonic to subsonic flow, it appears that in practice
a shock is present. The minimum distance to the shock is estimated to
be less than 50 AU and probably more than 25 AU.
Title: Collisionless solar wind protons: A comparison of kinetic
and hydrodynamic descriptions
Authors: Leer, Egil; Holzer, Thomas E.
Bibcode: 1972JGR....77.4035L
Altcode:
Kinetic and hydrodynamic descriptions of a collisionless solar wind
proton gas are compared. Heat conduction and viscosity are neglected
in the hydrodynamic formulation but are automatically included in the
kinetic formulation. The fact that the results of the two models are
very nearly the same indicates that heat conduction and viscosity are
not important in the solar wind proton gas beyond approximately 0.1
AU. It is concluded that the hydrodynamic equations provide a valid
description of the collisionless solar wind protons and, hence, that
future models of the quiet solar wind should be based on a hydrodynamic
formulation.
Title: A comparison of kinetic and hydrodynamic models of an expanding
ion-exosphere
Authors: Holzer, Thomas E.; Fedder, Joel A.; Banks, Peter M.
Bibcode: 1971JGR....76.2453H
Altcode:
The results of calculations based on kinetic and hydrodynamic models of
a collisionless ion-exosphere are compared, and it is found that the
density and velocity of an ionic constituent flowing supersonically
throughout the exosphere can be adequately described by ordinary
hydrodynamic equations with isotropic pressure. This suggests that
the basic flow characteristics of the polar wind can be determined
by hydrodynamic equations throughout the polar ionosphere. We derive
a set of CGL-type hydrodynamic equations (for anisotropic pressure)
that include the effects of energy and momentum transfer processes
(e.g., collisions), and we show that such equations are applicable
to problems of polar wind and solar wind temperature anisotropies,
as well as to related flow problems.
Title: Interaction between interstellar helium and the solar wind
Authors: Holzer, T. E.; Axford, W. I.
Bibcode: 1971JGR....76.6965H
Altcode:
No abstract at ADS
Title: Solar Wind Ion Composition
Authors: Holzer, T. E.; Axford, W. I.
Bibcode: 1970JGR....75.6354H
Altcode:
No abstract at ADS
Title: The Theory of Stellar Winds and Related Flows
Authors: Holzer, T. E.; Axford, W. I.
Bibcode: 1970ARA&A...8...31H
Altcode:
No abstract at ADS
Title: Stellar Winds and Related Flows.
Authors: Holzer, Thomas Edward
Bibcode: 1970PhDT........78H
Altcode:
No abstract at ADS
Title: Accidentally resonant charge exchange and ion momentum transfer
Authors: Holzer, Thomas E.; Banks, Peter M.
Bibcode: 1969P&SS...17D....H
Altcode:
No abstract at ADS
Title: Accidentally resonant charge exchange and ion momentum transfer
Authors: Holzer, Thomas E.; Banks, Peter M.
Bibcode: 1969P&SS...17.1074H
Altcode:
No abstract at ADS
Title: Charge exchange and ion diffusion for thermal nonequilibrium
conditions
Authors: Banks, Peter M.; Holzer, Thomas E.
Bibcode: 1968P&SS...16.1019B
Altcode:
The ion-neutral diffusion coefficient for resonance charge exchange
has been obtained directly from Boltzmann's equation for conditions of
separate ion and neutral Maxwellian gas temperatures. With application
to the problems of O +-O and H +-H diffusion it is
found that there is little effect upon the F2-region maximum
since T i$∼T n. At higher altitudes, where
T > Tn to a significant degree, the present diffusion
coefficient becomes substantially larger than previous expressions based
upon a condition of thermal equilibrium between ion and neutral gases.