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1.
In this article we have discussed reasons both of solar and of interstellar origin giving rise to a pronounced three-dimensional structure of the expanding solar wind and thus of the global configuration of the heliosphere. Our present observational knowledge on these structurings is reviewed, and all attempts to theoretically model these solar wind structures are critically analysed with respect to their virtues and flaws. It is especially studied here by what mechanisms interstellar imprints on the actual type of solar wind expansion can be envisaged. With concern to this aspect it hereby appears to be of eminent importance that the solar system maintains a relative motion with a submagnetosonic velocity of about 23km/sec with respect to the ambient magnetized interstellar medium corresponding to a magnetosonic Mach number of about 0.5.A heliopause closing the distant heliospheric cavity within a solar distance of about 100AU on the upwind side and opening it into an largely extended tail on the downwind side results as a first consequence from this relative motion. As a second consequence an asymmetric heliospheric shockfront with upwind distances smaller than downwind distances by ratios between 1/3 and 2/3 is most likely provoked which gives rise to at least two important upwind-downwind asymmetric processes influencing the supersonic solar wind expansion downstream from the shock: the anomalous cosmic ray diffusion into the solar wind, and high energetic jet electrons originating at the shock and moving inwards up to an inner critical point at around 20AU. As we shall demonstrate both processes are influencing the solar wind expansion beyond 20AU, however, more efficiently in the upwind hemisphere as compared to the downwind hemisphere. In the region inside 20AU other mechanisms are operating to propagate the interstellar imprint on the solar wind expansion further downstream into the inner heliosphere because here even the original solar wind electrons, in view of the solar wind bulk velocities, behave as a subsonic plasma constituent which can modify the solar wind solutions by means of an appropriate detuning of the circumsolar electric polarisation field. We give quantitative estimates for these effects.What concerns the theory of a solar wind expansion into a counterflowing ambient interstellar medium, some flaws of the present theoretical attempts are identified impeding that the interstellar influence on the actual solar wind solutions can become visible. We thus conclude that there is a clear need for three-dimensional and time-dependent solar wind models with a free outflow geometry taking into account the multisonicity of the solar wind plasma with different eigenmodes for a perturbation propagation. 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.
By the time of the 34th ESLAB symposium, dedicated to the memory of John Simpson, Ulysses had nearly reached its peak southerly latitude in its second polar orbit. The global solar wind structure observed thus far
in Ulysses' second orbit is remarkably different from that observed over its first orbit. In particular, Ulysses observed highly irregular solar wind with less periodic stream interaction regions, much more frequent coronal mass ejections,
and only a single, short interval of fast solar wind. Ulysses also observed the slowest solar wind seen thus far in its ten-year
journey (∼270 km s−1). The complicated solar wind structure undoubtedly arises from the more complex coronal structure found around solar activity
maximum, when the large polar coronal holes have disappeared and coronal streamers, small-scale coronal holes, and frequent
CMEs are found at all heliolatitudes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
During the past few years, significant progress has been made in identifying the coronal sources of structures observed in
the solar wind. This recent work has been facilitated by the relative simplicity and stability of structures during solar
minimum. The challenge now is to continue to use coordinated coronal/solar wind observations to study the far more complicated
and time-evolving structures of solar maximum. In this paper I will review analyses that use a wide range of observations
to map out the global heliosphere and connect the corona to the solar wind. In particular, I will review some of the solar
minimum studies done for the first Whole Sun Month campaign (WSM1), and briefly consider work in progress modeling the ascending
phase time period of the second Whole Sun Fortnight campaign (WSF) and SPARTAN 201-05 observations, and the solar maximum
third Whole Sun Month campaign (WSM3). In so doing I hope to demonstrate the increase in complexity of the connections between
corona and heliosphere with solar cycle, and highlight the issues that need to be addressed in modeling solar maximum connections.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Observations of ion acoustic waves in the solar wind during the first and second orbit of the Ulysses spacecraft are presented. The observations show variations of the wave activity with the heliolatitude and with the phase
of the solar cycle. The interrelationships between the wave intensity and the electron heat flux and the ratio of electron
to proton temperature, T
e/T
p, are examined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Formation and Evolution of Corotating Interaction Regions and their Three Dimensional Structure 总被引:1,自引:0,他引:1
Corotating interaction regions are a consequence of spatial variability in the coronal expansion and solar rotation, which
cause solar wind flows of different speeds to become radially aligned. Compressive interaction regions are produced where
high-speed wind runs into slower plasma ahead. When the flow pattern emanating from the Sun is roughly time-stationary these
compression regions form spirals in the solar equatorial plane that corotate with the Sun, hence the name corotating interaction
regions, or CIRs. The leading edge of a CIR is a forward pressure wave that propagates into the slower plasma ahead, while
the trailing edge is a reverse pressure wave that propagates back into the trailing high-speed flow. At large heliocentric
distances the pressure waves bounding a CIR commonly steepen into forward and reverse shocks. Spatial variation in the solar
wind outflow from the Sun is a consequence of the solar magnetic field, which modulates the coronal expansion. Because the
magnetic equator of the Sun is commonly both warped and tilted with respect to the heliographic equator, CIRs commonly have
substantial north-south tilts that are opposed in the northern and southern hemispheres. Thus, with increasing heliocentric
distance the forward waves in both hemispheres propagate toward and eventually across the solar equatorial plane, while the
reverse shocks propagate poleward to higher latitudes. This paper provides an overview of observations and numerical models
that describe the physical origin and radial evolution of these complex three-dimensional (3-D) heliospheric structures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Planar magnetic structures are regions of the solar wind where the magnetic field is oriented parallel to a fixed plane for
several hours or more. Discontinuities in the field direction may be encountered during these periods, their surfaces also
being parallel to the plane containing the field. A survey of Ulysses magnetic field data returned during 1990–1998 revealed that the solar wind's magnetic field was planar in nature for at least
9% of the time. A survey is presented of planar magnetic structures encountered by Ulysses during two periods when the spacecraft was travelling south from the ecliptic to high southern heliographic latitudes, in
1992–1994 and 1998–2000. The characteristics of the planar magnetic structures encountered during these times of declining
and near-maximum solar activity are described, as well as their apparent relationships with interplanetary shocks and heliospheric
current sheet crossings. Planar magnetic structures are more common near solar maximum. However, the proportion of structures
coinciding with HCS crossings and shocks seems relatively constant.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
We examine the occurrence and intensity of Langmuir wave activity (electrostatic waves at the electron plasma frequency) during
the solar minimum and solar maximum orbits of Ulysses. At high latitudes during the solar minimum orbit, occurrences of Langmuir waves in magnetic holes were frequent; in the
second orbit, they were less common. This difference, in comparison with observations from the first Ulysses fast heliolatitude scan, suggests that Langmuir wave activity in magnetic holes is enhanced in solar wind from polar coronal
holes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Understanding properties of solar energetic particle (SEP) events associated with coronal mass ejections has been identified
as a key problem in solar-terrestrial physics. Although recent CME shock acceleration models are highly promising, detailed
agreement between theoretical predictions and observations has remained elusive. Recent observations from ACE have shown substantial
enrichments in the abundances of 3He and He+ ions which are extremely rare in the thermal solar wind plasma. Consequently, these ions act as tracers of their source material,
i.e.,
3He ions are flare suprathermals and He+ ions are interstellar pickup ions. The average heavy ion composition also exhibits unsystematic differences when compared
with the solar wind values, but correlates significantly with the ambient suprathermal material abundances. Taken together
these results provide compelling evidence that CME-driven shocks draw their source material from the ubiquitous but largely
unexplored suprathermal tail rather than from the more abundant solar wind peak. However, the suprathermal energy regime has
many more contributors and exhibits much larger variability than the solar wind, and as such needs to be investigated more
thoroughly. Answers to fundamental new questions regarding the preferred injection of the suprathermal ions, the spatial and
temporal dependence of the various sources, and the causes of their variability and their effects on the SEP properties are
needed to improve agreement between the simulations and observations. 相似文献
10.
A. Balogh J. A. Gonzalez-Esparza R. J. Forsyth M. E. Burton B. E. Goldstein E. J. Smith S. J. Bame 《Space Science Reviews》1995,72(1-2):171-180
Between its launch in October 1990 and the end of 1993, approximately 160 fast collisionless shock waves were observed in the solar wind by the Ulysses space probe. During the in-ecliptic part of the mission, to February 1992, the observed shock waves were first caused mainly by solar transient events following the solar maximum and the reorganisation of the large scale coronal fields. With the decay in solar activity, relatively stable Corotating Interaction Regions (CIRs) were observed betwen 3 and 5.4 AU, each associated with at least one forwardreverse shock pair. During the out-of-ecliptic phase of the orbit, from February 1992 onwards, CIRs and shock pairs associated with them continued to dominate the observations. From July 1992, Ulysses encountered the fast solar wind flow from the newly developed southern polar coronal hole, and from May 1993 remained in the unipolar magnetic region associated with this coronal hole. At latitudes beyond 30°, CIRs were associated almost exclusively with reverse shocks only. A comprehensive list of shock waves identified in the magnetic field and solar wind plasma data from Ulysses is given in Table 1. The principal characteristics were determined mainly from the magnetic field data. General considerations concerning the determination of shock characteristics are outlined in the Introduction. 相似文献
11.
R. Schwenn 《Space Science Reviews》2006,124(1-4):51-76
In this paper I will briefly summarize the present status of our knowledge on the four different sorts of solar wind, their
sources and their short- and long-term variations. First: the fast solar wind in high-speed streams that emerges from coronal
hole regions. Second: the slow solar wind emerging from the non-active Sun near the global heliospheric current sheet above
helmet streamers and underlying active regions. Third: the slow solar wind filling most of the heliosphere during high solar
activity, emerging above active regions in a highly turbulent state, and fourth: the plasma expelled from the Sun during coronal
mass ejections. The coronal sources of these different flows vary dramatically with the solar activity cycle. 相似文献
12.
We studied solar wind observations of five different spacecraft: Helios 1, Helios 2, IMP-8, Voyager 1 and Voyager 2, from November 1977 to February 1978. In this period the large-scale dynamics of the solar wind near of the ecliptic plane
was characterized by transient forward shocks (TFSs), ejecta, unstable corotating interaction regions (CIRs), and complex
and variable magnetic sector structures. We identified 12 forward shock events of different origin. We did not find any clear
tendency of the shock parameters with heliocentric distance nor longitudinal angle, but comparing the observations of each
shock event we found local variations in the shock strength and the mean propagation velocities from one spacecraft to another.
These unsystematic variations indicate that there were local deformations of the shock fronts, which we attribute to the inhomogenuos
solar wind structure that affects the shock propagation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
Microstreams and pressure balance structures in fast solar wind were more easily detected at Ulysses at 2.2 AU over the poles than at Helios at 0.3 AU. This is because solar rotation leads to dynamic interactions between different speed regimes at a rate that depends
on latitude for the same size features. Dynamic interactions make structures more difficult to detect with increasing distance
from the Sun. At solar maximum, Ulysses will sample high latitude solar wind coming from streamers, providing information on fine structure at the tops of streamers
and on the source of slow solar wind. Examples are given here of the detectability of various sized structures at Ulysses when it is over the polar regions of the Sun.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
We discuss the underlying direction of the heliospheric magnetic field measured by Ulysses in the latitude range 6° S-65° S by examining distributions of the magnetic field azimuthal angle with respect to the simple
Parker spiral model. During the first Ulysses traversal of this latitude range in 1992–1994, while solar activity was declining, the shape of the distributions obtained
at high latitudes in the fast solar wind differed from that at lower latitudes. In the present data set, obtained during rising
solar activity, both field polarities are present at all latitudes and the peaks of the distributions agree with the predicted
spiral direction to first approximation. However, compared to the first orbit, a significantly greater percentage of the observed
field vectors have large deviations from the spiral direction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
The modulation of galactic cosmic rays in the heliosphere seems to be dominated by four major mechanisms: convection, diffusion,
drifts (gradient, curvature and current sheet), and adiabatic energy losses. In this regard the global structure of the solar
wind, the heliospheric magnetic field (HMF), the current sheet (HCS), and that of the heliosphere itself play major roles.
Individually, the four mechanisms are well understood, but in combination, the complexity increases significantly especially
their evolvement with time - as a function of solar activity. The Ulysses observations contributed significantly during the past solar minimum modulation period to establish the relative importance
of these major mechanisms, leading to renewed interest in developing more sophisticated numerical models, and in the underlying
physics, e.g., what determines the diffusion tensor. With increased solar activity, the relative contributions of the mentioned
mechanisms change, but how they change and what causes these changes over an 11-year solar cycle is not well understood. It
can therefore be expected that present and forthcoming observations during solar maximum activity will again produce very
important insights into the causes of long-term modulation. In this paper the basic theory of solar modulation is reviewed
for galactic cosmic rays. The influence of the Ulysses observations on the development of the basic theory and numerical models are discussed, especially those that have challenged
the theory and models. Model-based predictions are shown for what might be encountered during the next solar minimum. Lastly,
modulation theory and modelling are discussed for periods of maximum solar activity when a global reorganization of the HMF,
and the HCS, occurs.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
The ISEE-1 and 2 spacecraft contain two complementary experiments to measure the ambient electron density by radio techniques: a propagation experiment which measures the integrated electron density between ISEE-1 and 2, and a resonance sounder which measures the electron density in the vicinity of ISEE-1, and also provides AC electric field data. These experiments have been described elsewhere (Harvey et al., 1978). Results from these two experiments are presented here for the first time. The propagation experiment permits high time resolution studies of density fluctuations in the solar wind and magnetospheric frontier regions. The sounder experiment has detected for the first time plasma resonances in the solar wind and in the Earth's magnetosheath, as well as in the regions of the magnetosphere where resonances have already been observed by the spacecraft GEOS-1. We present here a preliminary review of the different types of electric field noise observed in the solar wind and magnetosheath, and discuss their relationship to the measured plasma density.CRPE/CNET, 92131 Issy-les-Moulineaux, France. 相似文献
17.
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
18.
Ulysses observed well-defined stream interaction regions, SIRs, associated with solar wind stream structure up to a latitude of S65°
and shocks to at least a latitude of S71° during the second polar orbit. These SIRs and shocks produced a substantial heliospheric
processing of the solar wind. Only a subset of the SIRs recurred on successive solar rotations and only about half of the
well-defined SIRs observed poleward of S9.8° were bounded by forward-reverse shock pairs. The majority of the SIRs had local
magnetic topologies and azimuthal orientations similar to, but meridional tilts different from, those observed in the first
polar orbit when most SIRs corotated with the Sun. The irregular meridional tilts presumably were a consequence of a complex
coronal geometry and the temporally evolving nature of the solar wind flow at this time. A lack of reverse shocks poleward
of S54° (with one exception) and a lack of well defined SIRs poleward of S65° is evidence that SIRs develop more slowly with
distance at high latitudes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
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
20.
The Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were launched in 1972, 1974, and 1977, respectively. While these three spacecraft are all at compartively low heliographic latitudes compared with Ulysses, their observation span almost two solar cycles, a range of heliocentric distances from 1 to 57 AU, and provide a unique insight into the long-term variability of the global structure of the solar wind. We examine the spatial and temporal variation of average solar wind parameters and fluxes. Our obsevations suggest that the global structure of the outer heliosphere during the declining phase of the solar cycle at heliographic latitudes up to 17.5°N was charaterized by two competing phenomena: 1) a large-scale increase of solar wind density, temperature, mass flux, dynamic pressure, kinetic energy flux, and thermal enery flux with heliographic latitude, similar to the large-scale latitudinal gradient of velocity seen in IPS observations, 2) a small-scale decrease in velocity and temperature, and increase in density near the heliospheric current sheet, which is associated with a band of low speed, low temperature, and high density solar wind similar to that observed in the inner heliosphere. 相似文献