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1.
The anisotropy of 35–1000 keV ions in two corotating particle events associated with high-speed solar wind streams at 1 AU is examined in terms of the diffusion-convection propagation model using data from the Energetic Proton Anisotropy Spectrometer on ISEE-3. The calculated diffusive anisotropy in the solar wind frame is found to be sunward and closely field-aligned, with a nearly energy-independent magnitude of ～ 40%. For one stream, using the Voyager 2 data of Decker et al. (1981), a positive gradient of ～ 100%/AU is found for ? 50 keV ions between 1 and 4 AU. The observations do not appear to support the scatter-free propagation model and indicate that ions with energies as low as a few tens of keV may be in diffusive equilibrium with the solar wind in this class of events.  相似文献   

2.
The possibility of the statistical acceleration of solar wind ions to energies above 10 keV in the vicinity of co-rotating high speed solar wind streams by scattering from hydromagnetic waves is considered. We find that this process may occur only in the compressed fast stream plasma within the interaction region between the stream interface and the trailing edge, and may account for the energetic ion enhancements observed in this region by Richardson and Zwickl (Planet. Space Sci. 32, 1179, 1984). When statistical acceleration occurs in the outer heliosphere, the accelerated ions may provide a source population for acceleration at the co-rotating reverse shock.  相似文献   

3.
We combined simultaneous solar wind observations from five different spacecraft: Helios 1, Helios 2, IMP-8, Voyager 1 and Voyager 2, from November 1977 to February 1978 (Carrington rotations 1661?–?1664, ascending phase of Solar Cycle 21). The concurrence of the five trajectories makes this interval unique for the purpose of studying solar wind dynamics during this phase of the cycle. We analyzed the observations identifying five corotating interaction regions (CIRs) and produced maps of interplanetary large-scale features, unifying and summarizing the data. The maps show the compressive events and the magnetic sectors associated with the solar wind streams causing the CIRs. We analyzed the relative position of the stream interfaces immersed within the CIRs. About 70 % of the stream interfaces in this study were located closer to the forward edge of the CIR. From the analysis of the geometry of the stream interfaces, we found that all the CIRs presented latitudinal tilts, having their fronts pointing towards the ecliptic plane and their tails northwards or southwards. These results are in agreement with the origin of the fast streams coming from mid-latitude coronal holes and the predominance of forward shocks over reverse shocks bounding the CIRs, which characterize this phase of the cycle. From the analysis of the ratio of dynamic pressures between fast and slow solar wind streams associated with the CIRs, we found that in about 60 % of the cases the fast stream was transferring momentum to the slow one ahead, but in the rest of the cases the momentum was flowing sunward. This result indicates significant inhomogeneities in the solar wind streams during the ascending phase of the cycle that affect the local form and evolution of CIR events. We did a limited comparison between a global magneto-hydrodynamic (MHD) model of SW flows and the orientation of the SI from in-situ observations, we found, in general, a qualitative agreement between the pressure profiles at 1 AU predicted by the model and the inclinations of the stream interfaces deduced from the data analysis.  相似文献   

4.
Fine time resolution observations of the angular distributions of the intensities of energetic electrons (220 ≤ E e ≤ 500 keV) by the IMP-7 and 8 spacecraft during the onsets of solar electron events and the technique of mapping the solar wind to the solar corona have been incorporated in this work in order to obtain the large-angle scattering distance of these particles under different configurations of the large scale structure of the interplanetary medium. It is found that in the presence of stream-stream interaction regions with compressed magnetic fields beyong 1 AU, the large-angle scattering is determined by the distance along the streamlines from the spacecraft to their intersection by a faster solar wind stream. In cases of diverging magnetic fields the estimated large-angle scattering distance exceeds 1 AU.  相似文献   

5.
A forward-reverse interplanetary shock was observed on 25 March 1969 by the magnetometer and plasma detector on the HEOS-1 satellite. This relatively rare event was described by Chao et al (1972) who concluded that the shock pair was formed at a distance 0.10–0.13 A.U. upstream of the Earth as a result of the interaction between a fast and a slow solar wind streams. Simultaneous observations of 1 MeV solar proton fluxes were also performed on HEOS-1. A characteristic intensity peak was observed as the forward shock passed by the spacecraft. The evolution of the proton intensity, together with a detailed analysis of anisotropies and pitch angle distributions show a complex dynamic picture of the effect of the forward shock on the ambient proton population. Significant changes in particle fluxes are seen to be correlated with fluctuations in the magnetic field. It is suggested that simple geometrical models of shock-associated acceleration should be expanded to include the effect of magnetic fluctuations on particle fluxes. The interaction region limited by the forward and reverse shocks contained a large variety of magnetic fluctuations. Following the tangential discontinuity separating the fast solar wind stream from the preceding slow stream, a sunward flow was observed in the proton data, followed by a small but significant drop in intensity prior to the reverse shock.  相似文献   

6.
Interplanetary scintillation (IPS) measurements of the solar wind speed for the distance range between 13 and 37 R S were carried out during the solar conjunction of the Nozomi spacecraft in 2000?–?2001 using the X-band radio signal. Two large-aperture antennas were employed in this study, and the baseline between the two antennas was several times longer than the Fresnel scale for the X-band. We successfully detected a positive correlation of IPS from the cross-correlation analysis of received signal data during ingress, and estimated the solar wind speed from the time lag corresponding to the maximum correlation by assuming that the solar wind flows radially. The speed estimates range between 200 and 540?km?s?1 with the majority below 400?km?s?1. We examined the radial variation in the solar wind speed along the same streamline by comparing the Nozomi data with data obtained at larger distances. Here, we used solar wind speed data taken from 327 MHz IPS observations of the Solar-Terrestrial Environment Laboratory (STEL), Nagoya University, and in?situ measurements by the Advanced Composition Explorer (ACE) for the comparison, and we considered the effect of the line-of-sight integration inherent to IPS observations for the comparison. As a result, Nozomi speed data were proven to belong to the slow component of the solar wind. Speed estimates within 30 R S were found to be systematically slower by 10?–?15 % than the terminal speeds, suggesting that the slow solar wind is accelerated between 13 and 30 R S.  相似文献   

7.
Whang  Y.C.  Burlaga  L.F.  Ness  N.F.  Smith  C.W. 《Solar physics》2001,204(1-2):253-263
Near 1 AU the solar wind structure associated with the solar flare of 14 July 2000 (Bastille Day) consisted of a large high-speed stream of 15 July and five nearby small streams during a 10-day period. At the leading edge of the large high-speed stream, in less than 6 hours, the flow speed increased from 600 km s−1 to 1100 km s−1, the magnetic field intensity increased from 10 nT to 60 nT, and an interaction region was identified. The interaction region was bounded between the pair of a forward shock F and a reverse shock R. Additional forward shocks were also identified at the leading edge of each of the five smaller streams. This paper presents a magnetohydrodynamics (MHD) simulation using ACE plasma and magnetic field data near 1 AU as input to study the radial evolution of the Bastille Day solar wind event. The two shocks, F and R, propagated in opposite directions away from each other in the solar wind frame and interacted with neighboring shocks and streams; the spatial and temporal extent of the interaction region continued to increase with the heliocentric distance. The solar wind was restructured from a series of streams at 1 AU to a huge merged interaction region (MIR) extending over a period of 12 days at 5.5 AU. Throughout the interior of the MIR bounded by the shock pair F and R the magnetic field intensity was a few times stronger than that outside the MIR. The simulation shows how merging of shocks, collision of shocks, and formation of new shocks contributed to the evolution process.  相似文献   

8.
Proton heating at stream interaction regions in the solar wind is investigated based on the solar wind data obtained by Suisei spacecraft between 0.68 and 1.01 AU from the Sun. The deflection angle of the solar wind flow in the ecliptic plane is used to identify the interaction region. In the solar wind flows coming from east of the Sun in low-speed streams and coming from west in high-speed streams, the radial gradient of proton temperature is flattened owing to heating in the interaction region. From comparison of the best-fitted power law dependence of proton temperature on the radial distance in the deflected flow with that in the non-deflected flow, it is suggested that heating in the interaction regions starts around 0.6–0.7 AU from the Sun.  相似文献   

9.
Opitz  A.  Karrer  R.  Wurz  P.  Galvin  A. B.  Bochsler  P.  Blush  L. M.  Daoudi  H.  Ellis  L.  Farrugia  C. J.  Giammanco  C.  Kistler  L. M.  Klecker  B.  Kucharek  H.  Lee  M. A.  Möbius  E.  Popecki  M.  Sigrist  M.  Simunac  K.  Singer  K.  Thompson  B.  Wimmer-Schweingruber  R. F. 《Solar physics》2009,256(1-2):365-377

The two STEREO spacecraft with nearly identical instrumentation were launched near solar activity minimum and they separate by about 45° per year, providing a unique tool to study the temporal evolution of the solar wind. We analyze the solar wind bulk velocity measured by the two PLASTIC plasma instruments onboard the two STEREO spacecraft. During the first half year of our measurements (March?–?August 2007) we find the typical alternating slow and fast solar wind stream pattern expected at solar minimum. To evaluate the temporal evolution of the solar wind bulk velocity we exclude the spatial variations and calculate the correlation between the solar wind bulk velocity measured by the two spacecraft. We account for the different spacecraft positions in radial distance and longitude by calculating the corresponding time lag. After adjusting for this time lag we compare the solar wind bulk velocity measurements at the two spacecraft and calculate the correlation between the two time-shifted datasets. We show how this correlation decreases as the time difference between two corresponding measurements increases. As a result, the characteristic temporal changes in the solar wind bulk velocity can be inferred. The obtained correlation is 0.95 for a time lag of 0.5 days and 0.85 for 2 days.

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10.
We analyze in situ measurements of the solar wind velocity obtained by the Advanced Composition Explorer (ACE) and the Helios spacecraft during the years 1998?–?2012 and 1975?–?1983, respectively. The data mainly belong to solar cycles 23 (1996?–?2008) and 21 (1976?–?1986). We used the directed horizontal-visibility-graph (DHVg) algorithm and estimated a graph functional, namely, the degree distance (D), which is defined using the Kullback–Leibler divergence (KLD) to understand the time irreversibility of solar wind time-series. We estimated this degree-distance irreversibility parameter for these time-series at different phases of the solar activity cycle. The irreversibility parameter was first established for known dynamical data and was then applied to solar wind velocity time-series. It is observed that irreversibility in solar wind velocity fluctuations show a similar behavior at 0.3 AU (Helios data) and 1 AU (ACE data). Moreover, the fluctuations change over the phases of the activity cycle.  相似文献   

11.
Mason  G. M.  Desai  M. I.  Mall  U.  Korth  A.  Bucik  R.  von Rosenvinge  T. T.  Simunac  K. D. 《Solar physics》2009,256(1-2):393-408

During the 2007 and 2008 solar minimum period, STEREO, Wind, and ACE observed numerous Corotating Interaction Regions (CIRs) over spatial separations that began with all the spacecraft close to Earth, through STEREO separation angles of ～?80 degrees in the fall of 2008. Over 35 CIR events were of sufficient intensity to allow measurement of He and heavy ion spectra using the IMPACT/SIT, EPACT/STEP and ACE/ULEIS instruments on STEREO, Wind, and ACE, respectively. In addition to differences between the spacecraft expected on the basis of simple corotation, we observed several events where there were markedly different time-intensity profiles from one spacecraft to the next. By comparing the energetic particle intensities and spectral shapes along with solar wind speed we examine the extent to which these differences are due to temporal evolution of the CIR or due to variations in connection to a relatively stable interaction region. Comparing CIRs in the 1996?–?1997 solar minimum period vs. 2007?–?2008, we find that the 2007?–?2008 period had many more CIRs, reflecting the presence of more high-speed solar wind streams, whereas 1997 had almost no CIR activity.

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12.
Interplanetary magnetic field data obtained from near-Earth spacecraft are used to compile a catalogue of high-velocity solar wind streams for the period June 1978 through October 1982 (Bartels rotations 1980–2039). The compilation of high-velocity streams is a continuation of two previous lists which covered the periods 1964–1975 and 1975–1978, respectively. The total number of high-speed solar wind streams listed in the catalogues is 637 of which 520 are corotating streams and 117 are classified as flare-associated streams.  相似文献   

13.
To propel a spacecraft in the direction leaving the Sun, a magnetic sail (MagSail) blocks the hypersonic solar wind plasma flow by an artificial magnetic field. In order to simulate the interaction between the solar wind and the artificially deployed magnetic field produced around a magnetic sail spacecraft, a laboratory simulator was designed and constructed inside a space chamber. As a solar wind simulator, a high-power magnetoplasmadynamic arcjet is operated in a quasisteady mode of 0.8 ms duration. It can generate a simulated solar wind that is a high-speed (above 20 km/s), high-density (1018 m−3) hydrogen plasma plume of ∼0.7 m in diameter. A small coil (2 cm in diameter), which is to simulate a magnetic sail spacecraft and can obtain 1.9-T magnetic field strength at its center, was immersed inside the simulated solar wind. Using these devices, the formation of a magnetic cavity (∼8 cm in radius) was observed around the coil, which indicates successful simulation of the plasma flow of a MagSail in the laboratory.  相似文献   

14.
The declining phases of solar cycles are known for their high speed solar wind streams that dominate the geomagnetic responses during this period. Outstanding questions about these streams, which can provide the fastest winds of the solar cycle, concern their solar origins, persistence, and predictability. The declining phase of cycle 23 has lasted significantly longer than the corresponding phases of the previous two cycles. Solar magnetograph observations suggest that the solar polar magnetic field is also ～?2?–?3 times weaker. The launch of STEREO in late 2006 provided additional incentive to examine the origins of what is observed at 1 AU in the recent cycle, with the OMNI data base at the NSSDC available as an Earth/L1 baseline for comparisons. Here we focus on the year 2007 when the solar corona exhibited large, long-lived mid-to-low latitude coronal holes and polar hole extensions observed by both SOHO and STEREO imagers. STEREO provides in situ measurements consistent with rigidly corotating solar wind stream structure at up to ～?45° heliolongitude separation by late 2007. This stability justifies the use of magnetogram-based steady 3D solar wind models to map the observed high speed winds back to their coronal sources. We apply the WSA solar wind model currently running at the NOAA Space Weather Prediction Center with the expectation that it should perform its best at this quiet time. The model comparisons confirm the origins of the observed high speed streams expected from the solar images, but also reveal uncertainties in the solar wind source mapping associated with this cycle’s weaker solar polar fields. Overall, the results illustrate the importance of having accurate polar fields in synoptic maps used in solar wind forecast models. At the most fundamental level, they demonstrate the control of the solar polar fields over the high speed wind sources, and thus one specific connection between the solar dynamo and the solar wind character.  相似文献   

15.
Corotating solar wind streams emanating from stable coronal structures provide an unique opportunity to compare the response of planetary ionospheres to the energy conveyed in the streams. For recurrent solar conditions the signal propagating outward along spiral paths in interplanetary space can at times exhibit rather similar content at quite different downstream locations in the ecliptic plane. Using solar wind measurements from plasma detectors on ISEE-3, Pioneer Venus Orbiter (PVO) and Helios-A, as well as in-situ ion composition measurements from Bennett Ion Mass Spectrometers on the Atmosphere Explorer-E and PVO spacecraft, corotating stream interactions are examined at Earth and Venus. During May–July 1979 a sequence of distinct, recurrent coronal regions developed at the Sun. Analysis of these regions and the associated solar wind characteristics indicates a corrresponding sequence of corotating streams, identifiable over wide distances. The time series of solar wind velocity variations observed at Earth, Venus, and the Helios-A positions during June–July attests to intervals of corotating stream propagation. The characteristics of the stream which passed Earth on July 3, are observed at Helios-A and at Venus (PVO) about 8 days later, consistent with the spiral path propagation delay times between the locations in the ecliptic plane. On July 3, Earth and Venus have a wide azimuthal separation of about 142 . Although the planetary environments are distinctly different, pronounced and somewhat analagous ionospheric responses to the stream passage are observed at both Earth and Venus. The response to the intercepted stream is consistent with independent investigations which have shown that the variability of the solar wind momentum flux is an important factor in the solar wind-ionosphere interaction at both planets.  相似文献   

16.
We study the abundances of the elements He through Pb in Fe-rich impulsive solar energetic-particle (SEP) events with measurable abundances of ions with atomic number Z>2 observed on the Wind spacecraft, and their relationship with coronal mass ejections (CMEs) observed by the Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). On an average the element abundances in these events are similar to coronal abundances at low Z but, for heavier elements, enhancements rise as a power law in the mass-to-charge ratio A/Q of the ions (at coronal temperatures of 2.5?–?3 MK) to a factor of 3 at Ne, 9 at Fe, and 900 for 76≤Z≤82. Energy dependences of abundances are minimal in the 2?–?15 MeV amu?1 range. The 111 of these Fe-rich impulsive SEP events we found, between November 1994 and August 2013 using the Wind spacecraft, have a 69 % association rate with CMEs. The CMEs are narrow with a median width of 75°, are characteristically from western longitudes on the Sun, and have a median speed of ≈?600 km?s?1. Nearly all SEP onsets occur within 1.5?–?5 h of the CME onset. The faster (>?700 km?s?1), wider CMEs in our sample are related to SEPs with coronal abundances indicating hot coronal plasma with fully ionized He, C, N and O and moderate enhancements of heavier elements, relative to He, but slower (<?700 km?s?1), narrower CMEs emerge from cooler plasma where higher SEP mass-to-charge ratios, A/Q, yield much greater abundance enhancements, even for C/He and O/He. Apparently, the open magnetic-reconnection region where the impulsive SEPs are accelerated also provides the energy to drive out CME plasma, accounting for a strong, probably universal, impulsive SEP-CME association.  相似文献   

17.
A correlative study is made between inferred solar sources of high-speed solar wind streams and extended white-light coronal features. The solar wind data used in the study consists of 110 co-rotating high-speed plasma streams observed from spacecraft at 1 AU in the period February 1971-December 1974; the coronal data consists of 144 equatorward extensions of polar coronal holes and 15 equatorial coronal holes, derived fromK-coronometer maps of the white-light corona during the same period. Of 110 observed solar wind streams 88 could directly be associated with an equatorward extension of a polar-cap coronal hole and 14 could be associated with a low-latitude equatorial coronal hole. In 8 cases no visible coronal feature was identified. Of 144 identified polar-cap extensions 102 were associated with a high-speed stream observed at 1 AU; 19 coronal features were related in time to data gaps in the solar wind measurements, while 38 features did not give rise to solar wind streams observed at Earth orbit. The probability of an association depended on the heliographic co-latitude of a polar hole extension, being 50% for a polar lobe extending down to 45° co-latitude and 100% for a polar coronal hole extending to 80° co-latitude or more.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Univese, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.  相似文献   

18.

The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100?keV/n and 10?MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU?1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res. 83, 4723, 1978) of ～?350% AU?1 using Helios and Pioneer data.

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19.
A consistent study of the solar wind has been extended to a wide region of interplanetary space, up to distances from the Sun R ? 90 R s . Experiments are carried out with the radio telescopes of the Pushchino Radio Astronomy Observatory (Astrospace Center, Lebedev physical Institute, Russian Academy of Sciences): DKR-1000 (λ ≈ 2.7–2.9 m) and RT-22 (λ ≈ 1.35 cm), respectively. The radio-wave scattering characteristics, the scattering angle θ(R) and the scintillation index m(R), are studied. The formation of a steady supersonic solar wind is associated with a sequence of four stages whose scale in different solar wind streams changes within the range 10–23 R s , depending on the initial stream speed. These circumstances should be taken into account when predicting the state of the near space using data on the solar wind in regions of the interplanetary medium close to the Sun.  相似文献   

20.
In this paper we use the observations of solar wind helium ions made by the Ion Composition Instrument (ICI) on the ISEE-3/ICE spacecraft to study the variation of helium abundance in the solar wind and to arrive at an average value of that quantity for the period August 1978 to December 1982. The abundance varies in a similar way to that observed in the previous solar cycle, but more detailed dependence on velocity and solar cycle epoch is observed. The long-term average helium abundance is used in conjunction with long term abundances of 3He, O, Ne, Si, and Fe, measured with respect to helium using the same instrument, to compile abundances with respect to hydrogen which can be reliably compared with solar system abundances. With the extended data set we are able to show Si and Fe to be overabundant by a factor of three with respect to solar system abundances and He underabundant by a factor of two.  相似文献   

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