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1.
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   

2.
We consider a stationary model of the propagation of galactic cosmic rays (GCR) in the heliosphere and adjacent interstellar space. The heliosphere is assumed to be a two-layer medium consisting of two adjacent regions that are spherically symmetric relative to the sun. The solar wind velocity is supersonic in the inner heliosphere bounded by the standing termination shock, and this velocity is subsonic in the outer heliosphere bounded by the heliosheath. The GCR scattering in these regions is due to different factors characterized by relevant diffusion coefficients. The solar wind velocity is assumed to be zero in the interstellar medium, where the scattering becomes weaker. No particle sources are presumed to exist at the boundaries between the layers. An exact analytical solution of the corresponding mathematical problem can be obtained without essential difficulties, although it is extremely cumbersome. Analytical expressions for the GCR spectra of particles with very high energies (>2500 MeV) and very low energies (<1400 MeV) are obtained for each region of particle propagation. The low-energy particle distribution corresponds to the data obtained by the Voyager spacecraft. It is shown that the low-energy particle density continuously increases from the sun toward the heliospheric boundary, regardless of the scattering mode in the inner and outer parts of the heliosphere.  相似文献   

3.
We present the analysis of a large solar near-relativistic electron event observed by the Ulysses and the ACE spacecraft on 8 November 2000, when Ulysses was located at a heliocentric distance of 2.4 AU and at a heliographic latitude of ??80° S. We use a particle propagation model to infer the local interplanetary transport conditions and the injection histories of the near-relativistic electrons observed by both spacecraft. We find different local transport conditions for each set of observations. The inferred injection profiles for both spacecraft extend for several hours; but the injection at Ulysses was smaller and started later. The association with type II radio emission suggests that the heliospheric electrons were provided by coronal shock acceleration. An analysis of the in situ magnetic field and plasma measurements indicates that the global configuration of the heliosphere (disturbed by transient structures) could play a role in shaping the characteristics of solar energetic particle events observed from different locations.  相似文献   

4.
《Planetary and Space Science》1987,35(10):1323-1345
Observations of energetic water-group pick-up ions made by the EPAS instrument during the ICE fly-by of comet P/Giacobini-Zinner are investigated for evidence concerning the processes which accelerate the ions from initial pick-up energies of around 10 keV up to energies of a few hundred kilo-electronvolts. The form of the ion spectrum in the ion rest frame is first investigated and compared with theoretical suggestions that exponential energy distributions might be produced by either first or second order Fermi acceleration in the cometary environment. It is shown that such distributions do not fit the data at all well, but that rather (over the EPAS ion bulk rest frame energy range of ∼30 to <300 keV) the observed distribution functions closely approximate an exponential in ion speed. The higher energy (> 50 keV) data also fit a power law distribution very well, but at lower energies the data tend to show a flattening below the power law form. It is also shown that the observed spectra are much softer than those calculated by Ip and Axford (1986, Planet. Space Sci. 34, 1061) for the G-Z ion pick-up region upstream of the bow shock, indicating that if these distributions are indeed due to second order Fermi acceleration as they propose, then the ion mean free path must be rather larger than used in their calculations (i.e. rather larger than 5 water-group ion gyroradii). Overall, it is concluded that at the present stage of theoretical development it is premature to draw firm conclusions about acceleration mechanisms from studies of the ion spectrum alone. However, from the general spectral analysis it is also possible to investigate the variations of ion intensity and spectral hardness which take place during the comet encounter, and to gain an indication of the degree of isotropy of the ion distribution in the rest frame of the flow. We find that a ∼.5 × 104km-wide region (∼ 35 min along the spacecraft trajectory) of rapid ion intensification and spectral hardening occurs immediately upstream from the turbulent mass-loaded region, suggestive of a first order Fermi process in which ions are successively reflected between the outer layer of the slowed, turbulent region and waves in the faster upstream flow. It is shown that within the turbulent region the ion distribution becomes rapidly isotropized in its own bulk rest frame, indicative of a sudden reduction in ion mean free path. Additional processes (possibly second order Fermi acceleration) must also occur in order to account for the further modest intensifications of the energetic ion fluxes observed within the turbulent mass-loaded region, as well as the presence of ions in the outer pick-up region which have energies well in excess of the local pick-up energy.  相似文献   

5.
This contribution to the 100th commemoration of the discovery of cosmic rays (6–8 August, 2012 in Bad Saarow, Germany) is about observations of those cosmic rays that are sensitive to the structure and the dynamics of the heliosphere. This places them in the energy range of 107–1010 eV. For higher energies the heliosphere becomes transparent; below this energy range the particles become strictly locked into the solar wind. Rather than give a strict chronological development, the paper is divided into distinct topics. It starts with the Pioneer/Voyager missions to the outer edges of the heliosphere, because the most recent observations indicate that a distinct boundary of the heliosphere might have been reached at the time of the meeting. Thereafter, the Ulysses mission is described as a unique one because it is still the only spacecraft that has explored the heliosphere at very high latitudes. Next, anomalous cosmic rays, discovered in 1972–1974, constitute a separate component that is ideally suited to study the acceleration and transport of energetic particles in the heliosphere. At this point the history and development of ground-based observations is discussed, with its unique contribution to supply a stable, long-term record. The last topic is about solar energetic particles with energies up to ∼1010 eV.  相似文献   

6.
The spacecraft ISEE-3 was launched in August 1978 and subsequently placed in orbit about the Sun-Earth L1 libration point where it continuously monitored the particles and fields in interplanetary space until mid-1982. The ISEE-3 Energetic Proton Anisotropy Spectrometer makes 3-dimensional intensity measurements of 35–1600 keV, Z ? 1 ions. This data is used in conjunction with simultaneous solar wind plasma and magnetic field data from the same spacecraft to study the properties of ions in interaction regions lying at the leading edges of nine corotating high speed solar wind streams observed during October 1978–July 1979. Seven streams have an enhancement of ? 300 keV ions in the compressed fast stream plasma between the stream interface and interaction region trailing edge. These enhancements are associated with plasma heating to above 3 × 105 K, have soft spectra (spectral index ～ 4.5?6.0) and in five cases show anti-solar streaming in the solar wind frame.  相似文献   

7.
Measurements of the composition and spatial distribution of pick-up ions inside the heliosphere are reviewed. The first interstellar 4He+pick-up ions were detected with the SULEICA instrument on the AMPTE spacecraft near Earth's orbit. Most data on pick-up ions were taken in the solar-wind and suprathermal energy range of SWICS on Ulysses while the spacecraft cruised from 1.4 to 5.4 AU and explored the high-latitude heliosphere and solar wind from the ecliptic to ± 80° heliolatitude. This includes the discovery of H+, 4He++, 3He+, N+,O+, and Ne+ pick-up ions that originate from the interstellar neutralgas penetrating the heliosphere. From their fluxes properties of the interaction region between the heliosphere and the Local Interstellar Cloud such as the limits on filtration and the strength of the interstellar magnetic field have been revealed. Detailed analysis of the velocity distributions of pick-up ions led to 1) the discovery of a new distinct source, the so-called Inner Source, consisting of atoms released from interstellar and interplanetary dust inside the heliosphere, 2) the determination of pick-up ion transport parameters such as the long mean free path for pitch-angle scattering of order1 AU, and 3) detailed knowledge on the very preferential injection and acceleration of pick-up ions during interplanetary energetic particle events such as Co-rotating Interaction Regions and Coronal Mass Ejections. SWICS measurements have fully confirmed the theory of Fisk, Koslovsky, and Ramaty that pick-up ions derived from the interstellar gas are the dominant source of the Anomalous Cosmic Rays; they are pre-accelerated inside the heliosphere and re-accelerated at the solar-wind Termination Shock according to Pesses, Eichler, and Jokipii. The data indicate that the Inner Source of pick-up ionsis largely responsible for the occurence of C+ in the Anomalous Cosmic Rays. The abundances of recently discovered Inner-Source Mg+ and Si+ are solar-wind like and consistent with their abundances in the energetic particles associated with Co-rotating Interaction Regions. Knowledge on the injection and acceleration processes in Co-rotating Interaction Regions is applied to discuss the current observational evidence for the Interplanetary Focusing Cone of the interstellar neutral gas due to the Sun's gravitational force. The 25–150 keV/amu suprathermal 4He+ pick-up ion fluxes measured by CELIAS/STOF on board SOHO over 360° of ecliptic longitude represent a `local' ionization and acceleration of interstellar atoms at 1 AU or smaller heliocentric distances. Completing the first limited data set of SULEICA/AMPTE on 4He+ pick-up ions they indicate a density enhancement in the Interplanetary Focusing Cone which is confirmed by recent SWICS/ACE data. Clear evidence for signatures in ecliptic longitude are found in the data on energetic neutral H fluxes observed with the CELIAS/HSTOF sensor on board SOHO. These fluxes are enhanced in the upstream and downstream directions of the interstellar wind. Detection of energetic H atoms, which propagate unaffected by the Heliospheric Magnetic Field, provided for the first time a diagnostic tool for observations near Earth to analyze the structure in ecliptic longitude of the interface region between the heliosphere and the Local Interstellar Cloud. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
The twin STEREO and the Wind spacecraft make remote multipoint measurements of interplanetary radio sources of solar origin from widely separated vantage points. One year after launch, the angular separation between the STEREO spacecraft reached 45°, which was ideal for locating solar type III radio sources in the heliosphere by three-spacecraft triangulation measurements from STEREO and Wind. These triangulated source locations enable intrinsic properties of the radio source, such as its beaming characteristics, to be deduced. We present the first three-point measurements of the beaming characteristics for two solar type III radio bursts that were simultaneously observed by the three spacecraft in December of 2007 and in January of 2008. These analyses suggest that individual type III bursts exhibit a wide beaming pattern that is approximately beamed along the direction tangent to the Parker spiral magnetic field line at the source location.  相似文献   

9.
Quite an unusual behavior of the low-energy ion fluxes measured with the LECP and CRS instruments onboard Voyager 1, which is located in the outer heliosphere at a distance of about 90 AU, has been observed since July 2002 until recently (February 2003). This behavior can be interpreted as a possible manifestation of a combination of the global heliospheric disturbance produced by solar activity and the precursor of the outer heliosphere with its termination shock. The extremely large variability of the enhanced ion fluxes since the second half of 2002 in several energy channels from 0.5 to several MeV/nucleon is presumed to be associated with the sources of their acceleration near the termination shock. The simultaneous increase in the flux of protons with energies above 70 MeV may result from the easier penetration of Galactic cosmic rays because of the reduction in modulation at the declining phase in the current solar cycle 23 after the maximum in 2000 and from an admixture of the anomalous component accelerated at the termination shock.  相似文献   

10.
We present initial 3D tomographic reconstructions of the inner heliosphere during the Whole Heliosphere Interval (WHI) – Carrington Rotation 2068 (CR2068) – using Solar-Terrestrial Environment Laboratory (STELab) Interplanetary Scintillation (IPS) observations. Such observations have been used for over a decade to visualise and investigate the structure of the solar wind and to study in detail its various features. These features include co-rotating structures as well as transient structures moving out from the Sun. We present global reconstructions of the structure of the inner heliosphere during this time, and compare density and radial velocity with multi-point in situ spacecraft measurements in the ecliptic; namely STEREO and Wind data, as the interplanetary medium passes over the spacecraft locations.  相似文献   

11.
The European Incoherent SCATter (EISCAT) radar has been used for remote-sensing observations of interplanetary scintillation (IPS) for a quarter of a century. During the April/May 2007 observing campaign, a large number of observations of IPS using EISCAT took place to give a reasonable spatial and temporal coverage of solar wind velocity structure throughout this time during the declining phase of Solar Cycle 23. Many co-rotating and transient features were observed during this period. Using the University of California, San Diego three-dimensional (3-D) time-dependent computer assisted tomography (C.A.T.) solar-wind reconstruction analysis, we show the velocity structure of the inner heliosphere in three dimensions throughout the time interval of 20 April through 20 May 2007. We also compare to white-light remote-sensing observations of an interplanetary coronal mass ejection (ICME) seen by the STEREO Ahead spacecraft inner Heliospheric Imager on 16 May 2007, as well as to in-situ solar-wind measurements taken with near-Earth spacebourne instrumentation throughout this interval. The reconstructions show clear co-rotating regions during this period, and the time-series extraction at spacecraft locations compares well with measurements made by the STEREO, Wind, and ACE spacecraft. This is the first time such clear structures have been revealed using this 3-D technique with EISCAT IPS data as input.  相似文献   

12.
The magnetic field in the outer corona and in interplanetary space has been calculated from the photospheric magnetic fields measured around the time of the 7 March, 1970 eclipse. The field-line maps are compared with eclipse photographs showing coronal structures out to about 12 r . The projected field lines as well as the observed streamers appear straight. This is caused by the rapid expansion of the outer corona and is not an indication of corotation. The calculations show that the angular velocity of the coronal plasma decreases rapidly with distance.The relation between magnetic fields and density enhancements is discussed. The field strength in the photosphere seems to determine the amount of mechanical heating of the lower corona. The density structure higher up in the corona will, however, depend decisively on the topology of the field, particularly on whether we are on open or closed field lines, and not simply on field strength.The calculations show a sector structure of the interplanetary field, which agrees well with spacecraft observations. Also the magnitudes of the observed and calculated interplanetary field agree after the Mt. Wilson magnetograph data have been corrected to account for the temperature and saturation effects in the spectral line Fei 5250 Å.On leave from the Astronomical Observatory, Lund, Sweden.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

13.
It is usually difficult to gain a consistent global understanding of a coronal mass ejection (CME) eruption and its propagation when only near-Sun imagery and the local measurements derived from single-spacecraft observations are available. Three-dimensional (3D) density reconstructions based on heliospheric imaging allow us to “fill in” the temporal and spatial gaps between the near-Sun and in situ data to provide a truly global picture of the propagation and interactions of the CME as it moves through the inner heliosphere. In recent years the heliospheric propagation of dense structures has been observed and measured by the heliospheric imagers of the Solar Mass Ejection Imager (SMEI) and on the twin Solar TErrestrial RElations Observatory (STEREO) spacecraft. We describe the use of several 3D reconstruction techniques based on these heliospheric imaging data sets to distinguish and track the propagation of multiple CMEs in the inner heliosphere during the very active period of solar activity in late July?–?early August 2010. We employ 3D reconstruction techniques used at the University of California, San Diego (UCSD) based on a kinematic solar wind model, and also the empirical Tappin–Howard model. We compare our results with those from other studies of this active period, in particular the heliospheric simulations made with the ENLIL model by Odstrcil et al. (J. Geophys. Res., 2013) and the in situ results from multiple spacecraft provided by Möstl et al. (Astrophys. J. 758, 10?–?28, 2012). We find that the SMEI results in particular provide an overall context for the multiple-density flows associated with these CMEs. For the first time we are able to intercompare the 3D reconstructed densities with the timing and magnitude of in situ density structures at five spacecraft spread over 150° in ecliptic longitude and from 0.4 to 1 AU in radial distance. We also model the magnetic flux-rope structures at three spacecraft using both force-free and non-force-free modelling, and compare their timing and spatial structure with the reconstructed density flows.  相似文献   

14.
I. G. Richardson 《Solar physics》2014,289(10):3843-3894
Previous studies have discussed the identification of interplanetary coronal mass ejections (ICMEs) near the Earth based on various solar wind signatures. In particular, methods have been developed of identifying regions of anomalously low solar wind proton temperatures (T p) and plasma compositional anomalies relative to the composition of the ambient solar wind that are frequently indicative of ICMEs. In this study, similar methods are applied to observations from the Ulysses spacecraft that was launched in 1990 and placed in a heliocentric orbit over the poles of the Sun. Some 279 probable ICMEs are identified during the spacecraft mission, which ended in 2009. The identifications complement those found independently in other studies of the Ulysses data, but a number of additional events are identified. The properties of the ICMEs detected at Ulysses and those observed near the Earth and in the inner heliosphere are compared.  相似文献   

15.
The Suprathermal Plasma Analysers on GEOS-2 are able to make differential energy measurements of plasma particles down to sub-eV energies because the entire sensor package can be biased relative to the spacecraft. When the package is biased negatively with respect to space potential, low energy positive ions are sucked in and are more easily detected against the background. Large fluxes of ions with temperatures of the order of 1 eV or less were consistently detected at space potential when the spacecraft was in the magnetosheath though not when it was in the nearby magnetosphere. This apparent geophysical correlation, suggesting that the ions were part of the magnetosheath ion population, was contradicted by the fact that the ions showed no signs of the large drift velocity associated with the electric field in the magnetosheath. We conclude, after further investigation, that the observed ions were probably sputtered as neutrals from the spacecraft surface by the impact of solar wind ions and subsequently ionized by sunlight or electron impact. The effect of sputtering by solar wind ions has not been previously observed, although it could have consequences for the long-term stability of spacecraft surfaces.  相似文献   

16.
The asymmetry of fluxes of solar wind and planetary ions is studied by using the ASPERA-3 observations onboard the Mars Express spacecraft in February 2004 to March 2006. Due to the small scale of the Martian magnetosphere and its induced origin, the flow pattern near Mars is sensitive to the directions of the interplanetary magnetic and electric (-V×B) fields. Asymmetry of the magnetic field draping produces an asymmetry in plasma flows in the plane containing the IMF. The crustal magnetic fields on Mars also influence the flow pattern. Scavenging of planetary ions is less efficient in the regions of strong crustal magnetization and therefore the escape fluxes of planetary ions in the southern hemisphere are smaller. The results of the observations are compared to simulations based on a 3D hybrid model with several ion species.  相似文献   

17.
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18.
Observations of energetic-ion intensity enhancements (E 290 keV) associated with solar flare generated shock waves (solar flare ESP events), obtained during nearly a decade by the APL/JHU instruments on board the Earth orbiters IMP-7 and 8, are incorporated in this work in order to examine the role of the heliolongitude depended large scale shock morphology with relation to the upstream interplanetary magnetic field in the formation of these ESP events. It is shown that a clear east-west solar hemisphere asymmetry is present in the distribution of the ESP relative intensity enhancements with respect to the heliolongitudes of the shock wave source-flare sites. The large ion-intensity enhancements superimposed on the ambient solar flare ion population are preferentially associated with solar flare sites located to the east of the spacecraft meridian, whereas on the average only weak ESP events are associated with solar flare sites to the west of the spacecraft meridian. The observed asymmetry and its implications on the dominant processes for the generation of the solar flare ESP events are discussed on the basis of the presented extensive survey.  相似文献   

19.
Observations are presented of long-lived global Pc5 ULF wave activity observed at a wide range of local times. The event was monitored in the high latitude ionosphere (∼60–80° magnetic latitude) by several SuperDARN HF radars and 5 magnetometer chains in Scandinavia, Greenland, Canada, Alaska and Russia. The event coincided with a protracted period (∼36 h) of northward interplanetary magnetic field (IMF). The study focuses on 4 h during which distinct dawn/dusk asymmetries in the wave characteristics were observed with multiple field line resonance (FLR) structures observed in the dawn flank at 1.7, 2.6, 3.3, 4.2 and 5.4 mHz and compressional oscillations in the dusk flank at 1.7 and 2.3 mHz. The data indicated an anti-sunward propagation in both the dawn and dusk flanks and a low azimuthal m number (∣m∣∼6) suggesting a generation mechanism external to the Earth's magnetosphere. A sudden increase in the solar wind dynamic pressure followed by a period of strongly northward, Bz dominated IMF, coincides with the observations and also a large increase in Pc5 wave power observed in the dawn flank. The observed enhancements in the wave activity and FLR structures are thought to be due to a Kelvin–Helmholtz driven waveguide mode. Additionally, there is no evidence that the frequencies of the FLRs are intrinsic to the solar wind. It thus seems that the frequencies were determined by the dimensions of the magnetospheric cavity.  相似文献   

20.
We report observations of MeV heavy ions made with Explorer 45 in the earth's radiation belts during the 7-month period June–December 1972 when four major magnetic storms occurred. Significant fluxes of ions heavier than fluorine (i.e. with nuclear charge Z ? 9) were observed stably trapped in the interior of the radiation belts at L ～ 2–4. These energetic very heavy ions, were found to appear suddenly during the August 1972 magnetic storm period and their fluxes decayed during the following months on time scales typically several tens of days. Simultaneously, strong increases in the geomagnetically trapped MeV helium and CNO ion fluxes were observed, and the post-injection flux decay of these ions was found to be slower than that of the Z ? 9 ions. The relative enhancements in trapped fluxes during the storm increased with increasing ion mass and/or increasing ion energy.  相似文献   

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