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1.
Statistical Comparison of Magnetic Clouds with Interplanetary Coronal Mass Ejections for Solar Cycle 23 总被引：1，自引：0，他引：1
We compare the number and characteristics of interplanetary coronal mass ejections (ICMEs) to those of magnetic clouds (MCs)
by using in-situ solar wind plasma and magnetic field observations made at 1 AU during solar cycle 23. We found that ≈ 28% of ICMEs appear
to contain MCs, since 103 magnetic clouds (MCs) occurred during 1995 – 2006, and 307 ICMEs occurred during 1996 – 2006. For
the period between 1996 and 2006, 85 MCs are identified as part of ICMEs, and six MCs are not associated with ICMEs, which
conflicts with the idea that MCs are usually a subset of ICMEs. It was also found that solar wind conditions inside MCs and
ICMEs are usually similar, but the linear correlation between geomagnetic storm intensity (Dst
min ) and relevant solar wind parameters is better for MCs than for ICMEs. The differences between average event duration (Δt) and average proton plasma β (〈β〉) are two of the major differences between MCs and ICMEs: i) the average duration of ICMEs (29.6 h) is 44% longer than for MCs (20.6 hours), and ii) the average of 〈β〉 is 0.01 for MCs and 0.24 for ICMEs. The difference between the definition of a MC and that for an ICME is one of the major
reasons for these average characteristics being different (i.e., listed above as items i) and ii)), and it is the reason for the frequency of their occurrences being different. 相似文献
2.
W. B. Song 《Solar physics》2010,261(2):311-320
Referring to the aerodynamic drag force, we present an analytical model to predict the arrival time of coronal mass ejections
(CMEs). All related calculations are based on the expression for the deceleration of fast CMEs in the interplanetary medium
(ICMEs),
[(v)\dot]=-\frac115 700(v-VSW)2\dot{v}=-\frac{1}{15\,700}(v-V_{\mathrm{SW}})^{2}
, where V
SW is the solar wind speed. The results can reproduce well the observations of three typical parameters: the initial speed of
the CME, the speed of the ICME at 1 AU and the transit time. Our simple model reveals that the drag acceleration should be
really the essential feature of the interplanetary motion of CMEs, as suggested by Vršnak and Gopalswamy (J. Geophys. Res.
107, 1019, 2002). 相似文献
3.
We report kinematic properties of slow interplanetary coronal mass ejections (ICMEs) identified by SOHO/LASCO, interplanetary scintillation, and in situ observations and propose a modified equation for the ICME motion. We identified seven ICMEs between 2010 and 2011 and compared them with 39 events reported in our previous work. We examined 15 fast (V SOHO?V bg>500 km?s?1), 25 moderate (0 km?s?1≤V SOHO?V bg≤500 km?s?1), and 6 slow (V SOHO?V bg<0 km?s?1) ICMEs, where V SOHO and V bg are the initial speed of ICMEs and the speed of the background solar wind. For slow ICMEs, we found the following results: i) They accelerate toward the speed of the background solar wind during their propagation and reach their final speed by 0.34±0.03 AU. ii) The acceleration ends when they reach 479±126 km?s?1; this is close to the typical speed of the solar wind during the period of this study. iii) When γ 1 and γ 2 are assumed to be constants, a quadratic equation for the acceleration a=?γ 2(V?V bg)|V?V bg| is more appropriate than a linear one a=?γ 1(V?V bg), where V is the propagation speed of ICMEs, while the latter gives a smaller χ 2 value than the former. For the motion of the fast and moderate ICMEs, we found a modified drag equation a=?2.07×10?12(V?V bg)|V?V bg|?4.84×10?6(V?V bg). From the viewpoint of fluid dynamics, we interpret this equation as indicating that ICMEs with 0 km?s?1≤V?V bg≤2300 km?s?1 are controlled mainly by the hydrodynamic Stokes drag force, while the aerodynamic drag force is a predominant factor for the propagation of ICME with V?V bg>2300 km?s?1. 相似文献
4.
An extended Ulysses interplanetary coronal mass ejections (ICMEs) list is used to statistically study the occurrence rate of ICMEs, the interaction
of ICMEs with solar wind, and the magnetic field properties in ICMEs. About 43% of the ICMEs are identified as magnetic clouds
(MCs). It is found that the occurrence rate of ICMEs approximately follows the solar activity level, except for the second
solar orbit; the rate is higher in the southern heliolatitude than in the northern heliolatitude; and it roughly decreases
with the increase of ICME speeds. Our results show that the speed difference between the ICME and the solar wind in front
of it shows a slight decrease with increasing heliocentric distance for ICMEs preceded by a shock, whereas no such dependence
is found for the ICMEs without shock association. It is also found that approximately 23% of the ICMEs are associated with
radial field events, in which the interplanetary magnetic field with near-radial direction lasts for many hours, in the Ulysses detected range, and these associated events are not necessarily confined to fast ICMEs or the trailing portions of ICMEs.
Nearly all these associated events occur during the period of declining solar wind speed and most of them occur at low heliolatitudes. 相似文献
5.
We report radial-speed evolution of interplanetary coronal mass ejections (ICMEs) detected by the Large Angle and Spectrometric Coronagraph onboard the Solar and Heliospheric Observatory (SOHO/LASCO), interplanetary scintillation (IPS) at 327 MHz, and in-situ observations. We analyze solar-wind disturbance factor (g-value) data derived from IPS observations during 1997?–?2009 covering nearly the whole period of Solar Cycle 23. By comparing observations from SOHO/LASCO, IPS, and in situ, we identify 39 ICMEs that could be analyzed carefully. Here, we define two speeds [V SOHO and V bg], which are the initial speed of the ICME and the speed of the background solar wind, respectively. Examinations of these speeds yield the following results: i) Fast ICMEs (with V SOHO?V bg>500 km?s?1) rapidly decelerate, moderate ICMEs (with 0 km?s?1≤V SOHO?V bg≤500 km?s?1) show either gradually decelerating or uniform motion, and slow ICMEs (with V SOHO?V bg<0 km?s?1) accelerate. The radial speeds converge on the speed of the background solar wind during their outward propagation. We subsequently find; ii) both the acceleration and the deceleration are nearly complete by 0.79±0.04 AU, and those are ended when the ICMEs reach a 480±21 km?s?1. iii) For ICMEs with (V SOHO?V bg)≥0 km?s?1, i.e. fast and moderate ICMEs, a linear equation a=?γ 1(V?V bg) with γ 1=6.58±0.23×10?6 s?1 is more appropriate than a quadratic equation a=?γ 2(V?V bg)|V?V bg| to describe their kinematics, where γ 1 and γ 2 are coefficients, and a and V are the acceleration and speed of ICMEs, respectively, because the χ 2 for the linear equation satisfies the statistical significance level of 0.05, while the quadratic one does not. These results support the assumption that the radial motion of ICMEs is governed by a drag force due to interaction with the background solar wind. These findings also suggest that ICMEs propagating faster than the background solar wind are controlled mainly by the hydrodynamic Stokes drag. 相似文献
6.
L. K. Jian C. T. Russell J. G. Luhmann R. M. Skoug J. T. Steinberg 《Solar physics》2008,250(2):375-402
We have performed a survey of the characteristics of two types of large spatial-scale solar-wind structures, stream interaction
regions (SIRs), and interplanetary coronal mass ejections (ICMEs), near 5.3 AU, using solar-wind observations from Ulysses. Our study is confined to the three aphelion passes of Ulysses, and also within ± 10° of the solar ecliptic plane, covering a part of 1992, 1997 – 1998, and 2003 – 2005, representing three
slices of different phases of the solar activity cycle. Overall, there are 54 SIRs and 60 ICMEs in the survey. Many are merged
in hybrid events, suggesting that they have undergone multiple interactions prior to reaching Jovian orbit. About 91% of SIRs
occur with shocks, with 47% of such shocks being forward – reverse shock pairs. The solar-wind velocity sometimes stays constant
or even decreases within the interaction region near 5.3 AU, in contrast with the gradual velocity increase during SIRs at
1 AU. Shocks are driven by 58% of ICMEs, with 94% of them being forward shocks. Some ICMEs seem to have multiple small flux
ropes with different scales and properties. We quantitatively compare various properties of SIRs and ICMEs at 5.3 AU, and
study their statistical distributions and variations with solar activity. The width, maximum dynamic pressure, and peak perpendicular
pressure of SIRs all become larger than ICMEs. Dynamic pressure (P
dyn) is expected to be important for Jovian magnetospheric activity. We have examined the distributions of P
dyn of SIRs, ICMEs, and general solar wind, but these cannot explain the observed bimodal distribution of the location of the
Jovian magnetopause. By comparing the properties of SIRs and ICMEs at 0.72, 1, and 5.3 AU, we find that the ICME expansion
slows down significantly between 1 and 5.3 AU. Some transient and small streams in the inner heliosphere have merged into
a single interaction region.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
7.
In a previous study (Cane and Richardson, J. Geophys. Res.
108(A4), SSH6-1, 2003), we investigated the occurrence of interplanetary coronal mass ejections in the near-Earth solar wind during 1996 – 2002,
corresponding to the increasing and maximum phases of solar cycle 23, and provided a “comprehensive” catalog of these events.
In this paper, we present a revised and updated catalog of the ≈300 near-Earth ICMEs in 1996 – 2009, encompassing the complete
cycle 23, and summarize their basic properties and geomagnetic effects. In particular, solar wind composition and charge state
observations are now considered when identifying the ICMEs. In general, these additional data confirm the earlier identifications
based predominantly on other solar wind plasma and magnetic field parameters. However, the boundaries of ICME-like plasma
based on charge state/composition data may deviate significantly from those based on conventional plasma/magnetic field parameters.
Furthermore, the much studied “magnetic clouds”, with flux-rope-like magnetic field configurations, may form just a substructure
of the total ICME interval. 相似文献
8.
M. J. Owens 《Solar physics》2018,293(8):122
Magnetic field and plasma properties of the solar wind measured in near-Earth space are a convolution of coronal source conditions and in-transit processes which take place between the corona and near-Earth space. Elemental composition and heavy ion charge states, however, are not significantly altered during transit to Earth and thus such properties can be used to diagnose the coronal source conditions of the solar wind observed in situ. We use data from the Advanced Composition Explorer (ACE) spacecraft to statistically quantify differences in the coronal source properties of interplanetary coronal mass ejections (ICMEs). Magnetic clouds, ICMEs which contain a magnetic flux-rope signature, display heavy ion properties consistent with significantly hotter coronal source regions than non-cloud ICMEs. Specifically, magnetic clouds display significantly elevated ion charge states, suggesting they receive greater heating in the low corona. Further dividing ICMEs by speed, however, shows this effect is primarily limited to fast magnetic clouds and that in terms of heavy ion properties, slow magnetic clouds are far more similar to non-cloud ICMEs. As such, fast magnetic clouds appear distinct from other ICME types in terms of both ion charge states and elemental composition. ICME speed, rather ICME type, correlates with helium abundance and iron charge state, consistent with fast ICMEs being heated through the more extended corona. Fast ICMEs also tend to be embedded within faster ambient solar wind than slow ICMEs, though this could be partly the result of in-transit drag effects. These signatures are discussed in terms of spatial sampling of ICMEs and from fundamentally different coronal formation and release processes. 相似文献
9.
Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12
Lorenzo Iorio 《Journal of Astrophysics and Astronomy》2010,31(3):147-153
We investigate on the relative inclination of the planets B and C orbiting the pulsar PSR B1257+12. First, we show that the
third Kepler’s law does represent an adequate model for the orbital periods P of the planets, because other Newtonian and Einsteinian corrections are orders of magnitude smaller than the accuracy in
measuring P
B/C. Then, on the basis of available timing data, we determine the ratio sin i
C/ sin i
B = 0.92±0.05 of the orbital inclinations i
B and i
C independently of the pulsar’s mass M. It turns out that coplanarity of the orbits of B and C would imply a violation of the equivalence principle. Adopting a
pulsar mass range 1 ≲ M ≲ 3, in solar masses (supported by present-day theoretical and observational bounds for pulsar’s masses), both face-on and
edge-on orbital configurations for the orbits of the two planets are ruled out; the acceptable inclinations for B span the
range 36 deg ≲ i
B ≲ 66 deg, with a corresponding relative inclination range 6 deg ≲ (i
C − i
B) ≲ 13 deg. 相似文献
10.
The Grad–Shafranov reconstruction is a method of estimating the orientation (invariant axis) and cross section of magnetic
flux ropes using the data from a single spacecraft. It can be applied to various magnetic structures such as magnetic clouds
(MCs) and flux ropes embedded in the magnetopause and in the solar wind. We develop a number of improvements of this technique
and show some examples of the reconstruction procedure of interplanetary coronal mass ejections (ICMEs) observed at 1 AU by
the STEREO, Wind, and ACE spacecraft during the minimum following Solar Cycle 23. The analysis is conducted not only for ideal localized ICME
events but also for non-trivial cases of magnetic clouds in fast solar wind. The Grad–Shafranov reconstruction gives reasonable
results for the sample events, although it possesses certain limitations, which need to be taken into account during the interpretation
of the model results. 相似文献
11.
T.R. McEnulty J.G. Luhmann I. de Pater D.A. Brain A. Fedorov T.L. Zhang E. Dubinin 《Planetary and Space Science》2010,58(14-15):1784-1791
We have used the ion mass analyzer (IMA) and magnetometer (MAG) on Venus Express (VEX) to study escaping O+ during interplanetary coronal mass ejections (ICMEs). Data from 389 VEX orbits during 2006 and 2007 revealed 265 samples of high energy pick-up ion features in 197 separate orbits. Magnetometer data during the same time period showed 17 ICMEs. The interplanetary conditions associated with the ICMEs clearly accelerate the pick-up ions to higher energies at lower altitudes compared to undisturbed solar wind. However, there is no clear dependence of the pick-up ion flux on ICMEs which may be attributed to the fact that this study used data from a period of low solar activity, when ICMEs are slow and weak relative to solar maximum. Alternatively, atmospheric escape rates may not be significantly changed during ICME events. 相似文献
12.
We present a comprehensive survey of 230 interplanetary CMEs (ICMEs) during 1995 – 2004 using Wind and ACE in situ observations near one AU, and examine the solar-cycle variation of the occurrence rate, shock association rate, scale size,
velocity change, and other properties of ICMEs. The ICME occurrence rate increases (from 5 in 1996 to 40 in 2001) with solar
activity; and 66% of all ICMEs occurred with shock(s). A compound parameter, the total pressure perpendicular to the magnetic
field (Pt), i.e., the sum of magnetic and perpendicular plasma thermal pressures, assists us in effectively distinguishing ICMEs from other
solar-wind structures such as stream interactions, and in quantifying the interaction strength. We interpret the characteristic
signatures of the Pt temporal variation in terms of the inferred distance perpendicular to the flow to the center of the obstacle. Group 1 includes
events that appear to be traversed near the ICME center, showing an apparent enhanced central Pt; Group 3 represents ICMEs passed far away from the center, displaying a rapid rise and then gradual decay in Pt; and Group 2 includes events with intermediate signatures. About 36% of 198 classifiable ICMEs are Group 1 events, consistent
with the conventional wisdom that at one AU a magnetic cloud is found during crossings of only ~1/3 of ICMEs. Our set of Group
1 ICMEs and the set of magnetic clouds from other researchers have significant overlap and a similar solar-cycle dependence.
The rough decline of the Group 1 fraction as solar activity increases, is consistent with rough increases of scale size, shock
percentage, and peak Pt. These results call into question the need to have different mechanisms to create differently appearing ICMEs. Rather it
is possible that all ICMEs have a central flux rope that is traversed about 33% of the time, but in the majority of cases
is missed by the spacecraft.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
13.
The transfer of wave energy to plasma energy is a very crucial issue in coronal holes and helmet streamer regions. Mixed mode
Alfvén waves, also known as kinetic Alfvén wave (KAW) can play an important role in the energization of the plasma particles
because of their potential ability to heat and accelerate the plasma particles via Landau damping. This paper presents an
investigation of the growth of a Gaussian perturbation on a non-uniform kinetic Alfvén wave having Gaussian wave front. The
effect of the nonlinear coupling between the main KAW and the perturbation has been studied. The dynamical equations for the
field of the main KAW and the perturbation have been established and their semi-analytical solution has been obtained in the
low (β≪ me/mi≪ 1) and the high (β≫ me/mi≪ 1) β cases. The critical field of the main KAW and the perturbation has been evaluated. Nonlinear evolution of the main
KAW and the perturbation into the filamentary structures and its dependence on various parameters of the solar wind and the
solar corona have been investigated in detail. These filamentary structures can act as a source for the particle acceleration
by wave particle interaction because the KAWs are mixed modes and Landau damping is possible. Especially, in the solar corona,
the low β and the high β cases could correspond to the coronal holes and the helmet streamer. The presence of the primary
and the secondary filaments of the perturbation may change the spectrum of the Alfvénic turbulence in the solar wind. 相似文献
14.
Measurement of the floor in the interplanetary magnetic field and estimation of the time-invariant open magnetic flux of the
Sun require knowledge of closed magnetic flux carried away by coronal mass ejections (CMEs). In contrast with previous papers,
we do not use global solar parameters to estimate such values: instead we identify different large-scale types of solar wind
for the 1976 – 2000 interval to obtain the fraction of interplanetary CMEs (ICMEs). By calculating the magnitude of the interplanetary
magnetic field B averaged over two Carrington rotations, the floor of the magnetic field can be estimated from the B value at a solar cycle minimum when the number of ICMEs is minimal. We find a value of 4.65±0.6 nT, in good agreement with
previous results. 相似文献
15.
Jae-Ok Lee Kyung-Suk Cho Rok-Soon Kim Soojeong Jang Katsuhide Marubashi 《Solar physics》2018,293(9):129
To better understand geomagnetic storm generations by ICMEs, we consider the effect of substructures (magnetic cloud, MC, and sheath) and geometries (impact location of flux-rope at the Earth) of the ICMEs. We apply the toroidal magnetic flux-rope model to 59 CDAW CME–ICME pairs to identify their substructures and geometries, and select 20 MC-associated and five sheath-associated storm events. We investigate the relationship between the storm strength indicated by minimum Dst index \((\mathrm{Dst}_{\mathrm{min}})\) and solar wind conditions related to a southward magnetic field. We find that all slopes of linear regression lines for sheath-storm events are steeper (\({\geq}\,1.4\)) than those of the MC-storm events in the relationship between \(\mathrm{Dst}_{\mathrm{min}}\) and solar wind conditions, implying that the efficiency of sheath for the process of geomagnetic storm generations is higher than that of MC. These results suggest that different general solar wind conditions (sheaths have a higher density, dynamic and thermal pressures with a higher fluctuation of the parameters and higher magnetic fields than MCs) have different impact on storm generation. Regarding the geometric encounter of ICMEs, 100% (2/2) of major storms (\(\mathrm{Dst}_{\mathrm{min}} \leq -100~\mbox{nT}\)) occur in the regions at negative \(P_{Y}\) (relative position of the Earth trajectory from the ICME axis in the \(Y\) component of the GSE coordinate) when the eastern flanks of ICMEs encounter the Earth. We find similar statistical trends in solar wind conditions, suggesting that the dependence of geomagnetic storms on 3D ICME–Earth impact geometries is caused by asymmetric distributions of the geoeffective solar wind conditions. For western flank events, 80% (4/5) of the major storms occur in positive \(P_{Y}\) regions, while intense geoeffective solar wind conditions are not located in the positive \(P_{Y}\). These results suggest that the strength of geomagnetic storms depends on ICME–Earth impact geometries as they determine the solar wind conditions at Earth. 相似文献
16.
M. Youssef 《Earth, Moon, and Planets》2012,109(1-4):13-27
We studied the relation between the near-Earth signatures of the interplanetary coronal mass ejections (ICMEs) shocks such as sudden storms commencement (SSC), and their counterparts of coronal mass ejections (CMEs) observed near-Sun by solar and heliospheric observatory (SOHO)/large angle and spectrometric coronagraph (LASCO) coronagraph during 1996?C2008. Our result showed that there is a good correlation between the travel time of the ICMEs shocks and their associated radial speeds. Also we have separated the ICME shocks into two groups according to their effective acceleration and deceleration. The results showed that the faster ICME shocks (with negative accelerations which decelerated by solar wind plasma) are more correlated to their associated travel time than those with positive accelerations. 相似文献
17.
High-latitude interplanetary mass ejections (ICMEs) observed beyond 1 AU are not studied very often. They are useful for improving
our understanding of the 3D heliosphere. As there are only few such events registered by the Ulysses spacecraft, the task of detecting their solar counterparts is a challenge, especially during high solar activity periods,
because there are dozens coronal mass ejections (CMEs) registered by SOHO that might be chosen as candidates. We analyzed
a high-latitude ICME registered by the Ulysses spacecraft on 18 January 2002. Our investigation focused on the correlation between various plasma parameters that allow
the identification to be made of the ICME and its components such as the forward shock, the magnetic cloud and the reverse
shock. 相似文献
18.
The features of a homogeneous scalar field ϕ with classical Lagrangian L = ϕ;i
ϕ;i
/2 − V(ϕ) and tachyon field Lagrangian L = −V(ϕ)√1 − ϕ;i
ϕ;i
causing the observable accelerated expansion of the Universe are analyzed. The models with constant equation-of-state parameter
w
de = p
de/ρde < −1/3 are studied. For both cases the fields ϕ(a) and potentials V(a) are reconstructed for the parameters of cosmological model of the Universe derived from the observations. The effect of
rolling down of the potential V(ϕ) to minimum is shown.
Published in Ukrainian in Kinematika i Fizika Nebesnykh Tel, 2008, Vol. 24, No. 5, pp. 345–359.
The article was translated by the authors. 相似文献
19.
The ionizing star BD+60°2522 is known as the central star of Bubble Nebulae NGC 7635—wind-blown bubble created by the interaction
of the stellar wind of BD+60°2522 (O6.5 IIIef, V=8.7 mag, mass loss rate 10−5.76
M
⊙/year) with the ambient interstellar medium. From the evolutionary calculations for the star with mass loss and overshooting,
we find that the initial mass of the star is 60M
⊙, its present age is 2.5×106 years, and the present mass is 45M
⊙. 相似文献
20.
This is a study of the stability of strange dwarfs, superdense stars with a small quark core (M
0core
/M
⨀ < 0.017) and an extended crust consisting of atomic nuclei and a degenerate electron gas where the density may be two orders
of magnitude greater than the maximum density for white dwarfs. For a given equation of state, the mass, total number of baryons,
and radius of strange dwarfs are uniquely determined by the central energy density ρ
c
and the energy density ρ
tr
of the crust at the surface of the quark core. Thus, the entire range of variation of ρ
c
and ρ
tr
must be taken into account in studying the stability of these configurations. This can be done by examining a series of configurations
with a fixed rest mass M
0 (total baryon number) of the quark core and different masses of the crust. In each series, ρ
tr
ranges from the value for white dwarfs to ρ
drip
= 4.3∙1011 g/cm3, at which free neutrons are created in the crust. According to the static criterion for stability, stability is lost in an
individual series when the mass of the strange dwarf reaches a maximum as a function of ρ
tr
.
Translated from Astrofizika, Vol. 52, No. 2, pp. 325–332 (May 2009). 相似文献