共查询到20条相似文献,搜索用时 31 毫秒
1.
D. J. McComas J. L. Phillips S. J. Bame J. T. Gosling B. E. Goldstein M. Neugebauer 《Space Science Reviews》1995,72(1-2):93-98
In the 25 months since Jupiter flyby, the Ulysses spacecraft has climbed southward to a heliolatitude of 56°. This transit has been marked by an evolution from slow, dense coronal streamer belt solar wind through two regions where the rotation of the Sun carried Ulysses back and forth between streamer belt and polar coronal hole flows, and finally into a region of essentially continuous fast, low density solar wind from the southern polar coronal hole. Throughout these large changes, the momentum flux normalized to 1 AU displays very little systematic variation. In addition, the bulk properties of the polar coronal hole solar wind are quite similar to those observed in high speed streams in the ecliptic plane at 1 AU. Coronal mass ejections and forward and reverse shocks associated with corotating interaction regions have also been observed at higher heliolatitudes, however they are seen less frequently with increasing southern heliolatitude. Ulysses has thus far collected data from 20° of nearly contiguous solar wind flows from the polar coronal hole. We examine these data for characteristic variations with heliolatitude and find that the bulk properties in general show very little systematic variation across the southern polar coronal hole so far. 相似文献
2.
H. Kunow M.A. Lee L.A. Fisk R.J. Forsyth B. Heber T.S. Horbury E. Keppler J. Kóta Y.-Q. Lou R.B. McKibben C. Paizis M.S. Potgieter E.C. Roelof T.R. Sanderson G.M. Simnett R. Von Steiger B.T. Tsurutani R.F. Wimmer-Schweingruber J.R. Jokipii 《Space Science Reviews》1999,89(1-2):221-268
Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After
the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere
as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational basis of the investigation
into the latitudinal structure of CIRs. The first CIR was caused by an extension of the northern coronal hole into the southern
hemisphere during declining solar activity, whereas the second CIR near solar minimum activity was caused by small warps in
the streamer belt. The latitudinal structure is described through the presentation of three 26-day periods during the southern
CIR. The first at ∼24°S shows the full plasma interaction region including fast and slow wind streams, the compressed shocked
flows with embedded stream interface and heliospheric current sheet (HCS), and the forward and reverse shocks with associated
accelerated ions and electrons. The second at 40°S exhibits only the reverse shock, accelerated particles, and the 26-day
modulation of cosmic rays. The third at 60°S shows only the accelerated particles and modulated cosmic rays. The possible
mechanisms for the access of the accelerated particles and the CIR-modulated cosmic rays to high latitudes above the plasma
interaction region are presented. They include direct magnetic field connection across latitude due to stochastic field line
weaving or to systematic weaving caused by solar differential rotation combined with non-radial expansion of the fast wind.
Another possible mechanism is particle diffusion across the average magnetic field, which includes stochastic field line weaving.
A constraint on connection to a distant portion of the CIR is energy loss in the solar wind, which is substantial for the
relatively slow-moving accelerated ions. Finally, the weaker northern CIR is compared with the southern CIR. It is weak because
the inclination of the streamer belt and HCS decreased as Ulysses traveled to lower latitudes so that the spacecraft remained
at about the maximum latitudinal extent of the HCS.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
E. Marsch 《Space Science Reviews》1999,87(1-2):1-24
There are three major types of solar wind: The steady fast wind originating on open magnetic field lines in coronal holes,
the unsteady slow wind coming probably from the temporarily open streamer belt and the transient wind in the form of large
coronal mass ejections. The majority of the models is concerned with the fast wind, which is, at least during solar minimum,
the normal mode of the wind and most easily modeled by multi-fluid equations involving waves. The in-situ constraints imposed
on the models, mainly by the Helios (in ecliptic) and Ulysses (high-latitude) interplanetary measurements, are extensively
discussed with respect to fluid and kinetic properties of the wind. The recent SOHO observations have brought a wealth of
new information about the boundary conditions for the wind in the inner solar corona and about the plasma conditions prevailing
in the transition region and chromospheric sources of the wind plasma. These results are presented, and then some key questions
and scientific issues are identified.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
Robert F. Wimmer-Schweingruber Rudolf Von Steiger Johannes Geiss George Gloeckler Fred M. Ipavich Berend Wilken 《Space Science Reviews》1998,85(1-2):387-396
Recent observations with UVCS on SOHO of high outflow velocities of O5+ at low coronal heights have spurred much discussion about the dynamics of solar wind acceleration. On the other hand, O6+ is the most abundant oxygen charge state in the solar wind, but is not observed by UVCS or by SUMER because this helium-like
ion has no emission lines falling in the wave lengths observable by these instruments. Therefore, there is considerable interest
in observing O5+ in situ in order to understand the relative importance of O5+ with respect to the much more abundant O6+. High speed streams are the prime candidates for the search for O5+ because all elements exhibit lower freezing-in temperatures in high speed streams than in the slow solar wind. The Ulysses
spacecraft was exposed to long time periods of high speed streams during its passage over the polar regions of the Sun. The
Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses is capable of resolving this rare oxygen charge state. We present
the first measurement of O5+ in the solar wind and compare these data with those of the more abundant oxygen species O6+ and O7+. We find that our observations of the oxygen charge states can be fitted with a single coronal electron temperature in the
range of 1.0 to 1.2 MK assuming collisional ionization/recombination equilibrium with an ambient Maxwellian electron gas.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
R. Esser 《Space Science Reviews》1999,87(1-2):93-104
Summarized below are the discussions of working group 3 on "Coronal hole boundaries and interactions with adjacent regions"
which took place at the 7th SOHO workshop in Northeast Harbor, Maine, USA, 28 September to 1 October 1998. A number of recent
observational and theoretical results were presented during the discussions to shed light on different aspects of coronal
hole boundaries. The working group also included presentations on streamers and coronal holes to emphasis the difference between
the plasma properties in these regions, and to serve as guidelines for the definition of the boundaries. Observations, particularly
white light observations, show that multiple streamers are present close to the solar limb at all times. At some distance
from the sun, typically below 2 R, these streamers merge into a relatively narrow sheet as seen, for example, in LASCO and
UVCS images. The presence of multiple current sheets in interplanetary space was also briefly addressed. Coronal hole boundaries
were defined as the abrupt transition from the bright appearing plasma sheet to the dark coronal hole regions. Observations
in the inner corona seem to indicate a transition of typically 10 to 20 degrees, whereas observations in interplanetary space,
carried out from Ulysses, show on one hand an even faster transition of less than 2 degrees which is in agreement with earlier
Helios results. On the other hand, these observations also show that the transition happens on different scales, some of which
are significantly larger.
The slow solar wind is connected to the streamer belt/plasma sheet, even though the discussions were still not conclusive
on the point where exactly the slow solar wind originates. Considered the high variability of plasma characteristics in slow
wind streams, it seems most likely that several types of coronal regions produce slow solar wind, such as streamer stalks,
streamer legs and open field regions between active regions, and maybe even regions just inside of the coronal holes. Observational
and theoretical studies presented during the discussions show evidence that each of these regions may indeed contribute to
the solar slow wind.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
W. Pryor I. Stewart K. Simmons M. Witte J. Ajello K. Toskiba D. McComas D. Hall 《Space Science Reviews》2001,97(1-4):393-399
We model interplanetary H Lyman-α (Lα) observations from Galileo UVS (Ultraviolet Spectrometer) and EUVS (Extreme Ultraviolet Spectrometer) (Hord et al., 1992) and the Ulysses interstellar neutral gas (GAS) instrument (Witte et al., 1992). EUVS measurements near solar maximum (max) in 1990–1992 have a peaked brightness maximum upwind due to a rather isotropic
solar wind charge-exchange ionization pattern (A=0–0.25). GAS measurements from solar minimum (min) in 1997 have a plateau in the upwind direction that we model using Ulysses
SWOOPS (solar wind plasma experiment) solar min data on solar wind density and velocity at different heliographic latitudes.
The isotropic ionization pattern deduced from EUVS at solar max may be consistent with recent SWOOPS results (McComas et al., 2000b, c) that high speed solar wind is absent at high latitudes during solar max. Galileo and Ulysses Lα data favor higher H temperatures (15 000–18 000 K) than previous models.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
B. Heber E. Keppler R.G. Marsden C. Tranquille B. Blake M. Fränz 《Space Science Reviews》2001,97(1-4):363-366
Moraal and Steenberg (1999), showed that the peak energy in the anomalous cosmic ray spectra is independent of the radial
distance up to a few AU away from the termination shock but dependent on the solar wind speed, the radius of the termination
shock and the scattering strength. In this paper we will discuss the variation of the cosmic ray oxygen energy spectrum as
measured by the Ulysses EPAC and the COSPIN/LET on board Ulysses. We found that the peak energy decreased from ∼5 MeV nucl−1, when Ulysses was at high northern heliographic latitudes embedded in the fast solar wind to ∼3.5 MeV n−1, in the streamer belt. The shift towards lower energy might also be caused by changing modulation although Voyager measurements
indicate no variation of the ACR Oxygen spectrum at ∼60 AU.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Ester Antonucci 《Space Science Reviews》2006,124(1-4):35-50
The dynamics of the solar corona as observed during solar minimum with the Ultraviolet Coronagraph Spectrometer, UVCS, on
SOHO is discussed. The large quiescent coronal streamers existing during this phase of the solar cycle are very likely composed
by sub-streamers, formed by closed loops and separated by open field lines that are channelling a slow plasma that flows close
to the heliospheric current sheet. The polar coronal holes, with magnetic topology significantly varying from their core to
their edges, emit fast wind in their central region and slow wind close to the streamer boundary. The transition from fast
to slow wind then appears to be gradual in the corona, in contrast with the sharp transition between the two wind regimes
observed in the heliosphere. It is suggested that speed, abundance and kinetic energy of the wind are modulated by the topology
of the coronal magnetic field. Energy deposition occurs both in the slow and fast wind but its effect on the kinetic temperature
and expansion rate is different for the slow and fast wind. 相似文献
9.
U. Feldman 《Space Science Reviews》1998,85(1-2):227-240
Recent spectroscopic measurements from instruments on the Solar and Heliospheric Observatory (SOHO) find that the coronal
composition above a polar coronal hole is nearly photospheric. However, similar SOHO observations show that in coronal plasmas
above quiet equatorial regions low-FIP elements are enhanced by a factor of ≈ 4. In addition, the process of elemental settling
in coronal plasmas high above the solar surface was shown to exist. Measurements by the Ulysses spacecraft, which are based
on non-spectroscopic particle counting techniques, show that, with the exception of He, the elemental composition of the fast
speed solar wind is similar to within a factor of 1.5 to the composition of the photosphere. In contrast, similar measurements
in the slow speed wind show that elements with low first ionization potential (FIP < 10 eV) are enhanced, relative to the
photosphere, by a factor of 4-5. By combining the SOHO and Ulysses results, ideas related to the origin of the slow speed
solar wind are presented. Using spectroscopic measurements by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER)
instrument on SOHO the photospheric abundance of He was determined as 8.5 ± 1.3% (Y = 0.248).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
We have developed a 2D semi-empirical model (Sittler and Guhathakurta 1999) of the corona and the interplanetary medium using
the time independent MHD equations and assuming azimuthal symmetry, utilizing the SOHO, Spartan and Ulysses observations.
The model uses as inputs (1) an empirically derived global electron density distribution using LASCO, Mark III and Spartan
white light observations and in situ observations of the Ulysses spacecraft, and (2) an empirical model of the coronal magnetic
field topology using SOHO/LASCO and EIT observations. The model requires an estimate of solar wind velocity as a function
of latitude at 1 AU and the radial component of the magnetic field at 1 AU, for which we use Ulysses plasma and magnetic field
data results respectively. The model makes estimates as a function of radial distance and latitude of various fluid parameters
of the plasma such as flow velocity V, temperature Teff, and heat flux Qeff which are derived from the equations of conservation of mass, momentum and energy, respectively, in the rotating frame of
the Sun. The term "effective" indicates possible wave contributions. The model can be used as a planning tool for such missions
as Solar Probe and provide an empirical framework for theoretical models of the solar corona and solar wind.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
We present results derived from the analysis of an equatorial streamer structure as observed by the UVCS instrument aboard
SOHO. From observations of the H I Lyα and Lyβ lines we infer the density and temperature of the plasma. We develop a preliminary
axisymmetric, magnetostatic model of the corona which includes the effects of gas pressure gradients on the magnetic structure.
We infer a coronal plasma β > 1 in the closed field regions and near the cusp of the streamer. We add to the model a parallel
velocity field assuming mass flux conservation along magnetic flux tubes. We then compute the Lyα emissivity and the line-of-sight
integrals to obtain images of Lyα intensity, taking into account projection effects and Doppler dimming. The images we obtain
from this preliminary model are in good general agreement with the UVCS observations, both qualitatively and quantitatively.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
12.
M. P. Miralles L. Strachan L. D. Gardner P. L. Smith J. L. Kohl M. Guhathakurta R. R. Fisher 《Space Science Reviews》1999,87(1-2):277-281
The Spartan 201 flights from 1993 to 1995 provided us with observations in H I Lyman-α of several coronal hole/streamer boundaries
and adjacent streamers during the declining phase of the current solar cycle: Analysis of the latitudinal dependence of the
line intensities clearly shows that there is a boundary region at the coronal hole/streamer interface where the H I Lyman-α
intensity reaches a minimum value. Similar results are also found in UVCS/SOHO observations. We also discuss differences in
the coronal hole/streamer boundaries for different types of streamers and their changes over the three year period of Spartan
201 observations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
Recent SOHO/UVCS observations indicate that the perpendicular proton and ion temperatures are much larger than electron temperatures.
In the present study we simulate numerically the solar wind flow in a coronal hole with the two-fluid approach. We investigate
the effects of electron and proton temperatures on the solar wind acceleration by nonlinear waves. In the model the nonlinear
waves are generated by Alfvén waves with frequencies in the 10-3 Hz range, driven at the base of the coronal hole. The resulting electron and proton flow profile exhibits density and velocity
fluctuations. The fluctuations may steepen into shocks as they propagate away from the sun. We calculate the effective proton
temperature by combining the thermal and wave velocity of the protons, and find qualitative agreement with the proton kinetic
temperature increase with height deduced from the UVCS Ly-α observations by Kohl et al. (1998).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The synodic recurrence of the Mt. Wilson plage index (MPSI) and the Calgary cosmic ray (CR) intensity is investigated, using
the wavelet power spectra in the range of 18–38 days, during the last three solar cycles. The unique temporal coincidence
between the quasi–synodic MPSI and the CR periods is detected in 1978–1982 (the 21st solar cycle). In the 22nd cycle there
is a very strong MPSI synodic recurrence, from 1989.5 to 1990.5, but it is absent in the CR data. In 1992.5–1993.5 the MPSI
and CR recurrence phenomenon is in good accordance with the solar wind speed and cosmic ray modulation as measured during
the first Ulysses passage around the Sun. The Gnevyshev gap is present in the 27-day recurrence of CR, in agreement with Kudela
et al. (1999).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
The spectroscopic observations of the Ultraviolet Coronagraph Spectrometer (UVCS), on board the SOHO observatory, allow the study and the full characterization of the expansion of the solar atmosphere by means of measurements of the outflow speeds and the physical properties of the wind, directly in the region where the solar plasma is heated and accelerated: the extended corona. During solar minimum, when the magnetic configuration of the corona is rather simple, the open magnetic fields emerging from the wide polar coronal holes channel toward the heliosphere both the fast and the slow wind. The fast wind flows along flux tubes with lower areal divergence than the slow wind which is guided by flux tubes characterized by non-monotonic areal expansion functions. Differences in the physical properties, such as kinetic temperature, electron density, composition and density fluctuations, of the fast and slow wind in the corona are discussed. 相似文献
16.
Guhathakurta Madhullika Sittler Ed Fisher Richard Kucera Theresa Gibson Sarah McComas Dave Skoug Ruth 《Space Science Reviews》2001,97(1-4):45-50
The large-scale coronal magnetic fields of the Sun are believed to play an important role in organizing the coronal plasma
and channeling the high and low speed solar wind along the open magnetic field lines of the polar coronal holes and the rapidly
diverging field lines close to the current sheet regions, as has been observed by the instruments aboard the Ulysses spacecraft from March 1992 to March 1997. We have performed a study of this phenomena within the framework of a semi-empirical
model of the coronal expansion and solar wind using Spartan, SOHO, and Ulysses observations during the quiescent phase of the solar cycle. Key to this understanding is the demonstration that the white
light coronagraph data can be used to trace out the topology of the coronal magnetic field and then using the Ulysses data to fix the strength of the surface magnetic field of the Sun. As a consequence, it is possible to utilize this semi-empirical
model with remote sensing observation of the shape and density of the solar corona and in situ data of magnetic field and
mass flux to predict values of the solar wind at all latitudes through out the solar system. We have applied this technique
to the observations of Spartan 201-05 on 1–2 November, 1998, SOHO and Ulysses during the rising phase of this solar cycle and speculate on what solar wind velocities Ulysses will observe during its polar passes over the south and the north poles during September of 2000 and 2001. In order to do
this the model has been generalized to include multiple streamer belts and co-located current sheets. The model shows some
interesting new results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
The goal of Working Group 1 was to discuss constraints on solar wind models. The topics for discussion, outlined by Eckart
Marsch in his introduction, were: (1) what heats the corona, (2) what is the role of waves, (3) what determines the solar
wind mass flux, (4) can stationary, multi-fluid models describe the fast and slow solar wind, or (5) do we need time dependent
fluid models, kinetic models, and/or MHD models to describe solar wind acceleration.
The discussion in the working group focused on observations of "temperatures" in the corona, mainly in coronal holes, and
whether the observations of line broadening should be interpreted as thermal broadening or wave broadening. Observations of
the coronal electron density and the flow speed in coronal holes were also discussed. There was only one contribution on observations
of the distant solar wind, but we can place firm constraints on the solar wind particle fluxes and asymptotic flow speeds
from observations with Ulysses and other spacecraft. Theoretical work on multi-fluid models, higher-order moment fluid models,
and MHD models of the solar wind were also presented.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
R. J. Macdowall M. D. Desch M. L. Kaiser R. G. Stone R. A. Hess A. Balogh S. J. Bame B. E. Goldstein 《Space Science Reviews》1995,72(1-2):125-128
A primary goal of the Ulysses mission is to study the 3-dimensional structures making up the interplanetary medium, and example of which is the high speed solar wind stream observedin situ by Ulysses beginning in July 1992. In order to study the longitudinal extent of this stream as a function of Ulysses' increasing heliographic latitude, a second point of reference is required to separate spatial and temporal variations. Such a reference point is provided at Jupiter by a class of Jovian radio bursts, whose occurrence rate varies in a predictable way with solar wind speed. Using thein situ and remote observations from Ulysses, the extent of the high speed stream at 5 AU is mapped and compared to the associated coronal hole boundary on the Sun. 相似文献
19.
R. G. Marsden 《Space Science Reviews》1996,78(1-2):67-72
The Ulysses mission has provided the first in-situ observations of the solar wind covering all solar latitudes from the equator to the poles in both hemispheres. The measurements from the first polar passes, made at near-minimum solar activity conditions, have confirmed the basic picture established on the basis of remote sensing techniques: the high-latitude wind is fast, and originates in the polar coronal holes. The detailed in-situ observations have, however, revealed a number of features related to the global solar wind structure that were not expected: the transition between slow and fast wind was relatively abrupt, followed by a slight increase in speed toward the poles; the mass flux is almost independent of latitude, with only a modest increase at the equator; the momentum flux is significantly higher over the poles than near the equator, suggesting a non-circular cross-section for the flanks of the heliosphere. 相似文献
20.
Solar Wind Electron Proton Alpha Monitor (SWEPAM) for the Advanced Composition Explorer 总被引:1,自引:0,他引:1
McComas D.J. Bame S.J. Barker P. Feldman W.C. Phillips J.L. Riley P. Griffee J.W. 《Space Science Reviews》1998,86(1-4):563-612
The Solar Wind Electron Proton Alpha Monitor (SWEPAM) experiment provides the bulk solar wind observations for the Advanced
Composition Explorer (ACE). These observations provide the context for elemental and isotopic composition measurements made
on ACE as well as allowing the direct examination of numerous solar wind phenomena such as coronal mass ejections, interplanetary
shocks, and solar wind fine structure, with advanced, 3-D plasma instrumentation. They also provide an ideal data set for
both heliospheric and magnetospheric multi-spacecraft studies where they can be used in conjunction with other, simultaneous
observations from spacecraft such as Ulysses. The SWEPAM observations are made simultaneously with independent electron and
ion instruments. In order to save costs for the ACE project, we recycled the flight spares from the joint NASA/ESA Ulysses
mission. Both instruments have undergone selective refurbishment as well as modernization and modifications required to meet
the ACE mission and spacecraft accommodation requirements. Both incorporate electrostatic analyzers whose fan-shaped fields
of view sweep out all pertinent look directions as the spacecraft spins. Enhancements in the SWEPAM instruments from their
original forms as Ulysses spare instruments include (1) a factor of 16 increase in the accumulation interval (and hence sensitivity)
for high energy, halo electrons; (2) halving of the effective ion-detecting CEM spacing from ∼5° on Ulysses to ∼2.5° for ACE;
and (3) the inclusion of a 20° conical swath of enhanced sensitivity coverage in order to measure suprathermal ions outside
of the solar wind beam. New control electronics and programming provide for 64-s resolution of the full electron and ion distribution
functions and cull out a subset of these observations for continuous real-time telemetry for space weather purposes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献