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1.
Solar wind plasma and magnetic field observations from multiple spacecraft can be used to separate temporal and spatial variations and to determine the accuracy of predictions of solar wind conditions near Earth based on distant-spacecraft measurements. The study of correlations between the ion fluxes measured by three spatially separated spacecraft (IMP 8, WIND and INTERBALL-1) was one of the first steps in this direction. This paper describes a complex multifactor analysis of different physical, geometrical, and statistical parameters that control such correlations (considered separately and in combination). A linear-regression and an artificial neural network techniques are used for this analysis. The analysis is applied to an extensive array of correlation coefficients for the ion flux in the solar wind and provides estimates of the relative significance of the factors that control these correlation coefficients. The study shows that the most influential parameters are the solar wind density and the standard deviations of solar wind density, solar wind velocity and interplanetary magnetic field. This set of parameters permits us to develop a sufficiently accurate (with a relative error of less than a few per cent) quantitative model for the correlation between the ion fluxes measured on two spatially separated spacecraft.  相似文献   

2.
Compressible fluctuations in solar wind plasma are analyzed on the basis of the 1995–2010 WIND and Advanced Composition Explorer (ACE) spacecraft data. In the low-speed solar wind (V 0 < 430 km/s), correlations between fluctuations in the magnetic field direction and plasma density, as well as between velocity fluctuations and plasma density, are found. The covariance functions of these parameters calculated as functions of the local magnetic field direction are axially symmetric relative to the axis, which is oriented nearly along the regular magnetic field of the heliosphere (the Parker spiral). Fluctuations in the magnetic field and velocity are polarized in the plane that is orthogonal to the axis of symmetry. Plasma oscillations of these properties can be caused by fast magnetosonic waves propagating from the Sun along the Parker spiral.  相似文献   

3.
The two-position radio sounding of the solar wind by the Galileo and Cassini spacecraft has been first performed. These spacecraft followed the Sun from east to west from May 12 to 24, 2000 and sounded the regions spaced in radial directions by several millions of kilometers. Stable correlation has been revealed between fluctuation effects detected in spatially spaced radio-sounding paths of disturbed plasma structures of the coronal mass ejection (CME) type. The radio effects have been found to correlate also with the data on the solar wind density near the Earth orbit. It has been shown that the two-position radio-sounding method together with the data on solar radiation in the X-ray and optic ranges and with the results of local plasma measurements provides information on the structure and velocity of the propagation of CMEs from the photosphere to the Earth orbit. In the most powerful event recorded on May 13, 2000, the CME velocity at the heliocentric distances of about 15R ⊙ (R ⊙ is the solar radius) reached 1200 km/s. At (15–25) R ⊙, the velocity was about 1300 km/s. At distances larger than 25R ⊙, disturbance was decelerated from 1300 to 450 km/s near the Earth orbit.  相似文献   

4.
We present here a statistical study quantifying the errors associated with the most commonly used methods for propagating discontinuities in the interplanetary magnetic field (IMF) from an upstream monitor to the magnetosphere by the magnetospheric and ionospheric communities. The purpose of this paper is to show the quantified errors in the different techniques. Step changes in the IMF orientation were first identified at the WIND satellite. A total of 363 events were identified. Ninety percent of the events measured at WIND (330) were clearly observed in the IMP 8 data. Of those events, the time delay between the satellites could be determined to within 2 min in 288 events. Four propagation methods were used to estimate the time delay between WIND and IMP 8: (1) using only the X distance between the satellites; (2) assuming that the propagation front plane is in the plane of the Parker spiral; (3) using the IMF in the X–Y plane to estimate the propagation front plane; and (4) using the total IMF to determine the Z component of the propagation front plane. The average (Ē) and maximum (Emax) propagation error (in minutes) as a function of Y–Z distance (in Re) were determined for each method. It is concluded that the average uncertainty in propagation is 7.5–8.5 min for off-axis distances of 30 Re (which is the average WIND off-axis distance, and approximately the largest off-axis distance of IMP 8). For off-axis distances of 100 Re (the largest off-axis distance of WIND), the uncertainties are 17.5–25 min, depending on the propagation method.  相似文献   

5.
Observations of a flux transfer event (FTE) have been made simultaneously by the Equator-S spacecraft near the dayside magnetopause whilst corresponding transient plasma flows were seen in the near-conjugate polar ionosphere by the CUTLASS Finland HF radar. Prior to the occurrence of the FTE, the magnetometer on the WIND spacecraft ≈226 RE upstream of the Earth in the solar wind detected a southward turning of the interplanetary magnetic field (IMF) which is estimated to have reached the subsolar magnetopause ≈77 min later. Shortly afterwards the Equator-S magnetometer observed a typical bipolar FTE signature in the magnetic field component normal to the magnetopause, just inside the magnetosphere. Almost simultaneously the CUTLASS Finland radar observed a strong transient flow in the F region plasma between 78° and 83° magnetic latitude, near the ionospheric region predicted to map along geomagnetic field lines to the spacecraft. The flow signature (and the data set as a whole) is found to be fully consistent with the view that the FTE was formed by a burst of magnetopause reconnection.  相似文献   

6.
White corona images are analyzed based on the calibrated data of the LASCO-C2/SOHO instrument (processing level 1) and the solar wind (SW) parameters with hourly and minute resolutions on the Wind spacecraft. The quasistationary events, excluding coronal mass ejections and their manifestations in SW are studied. It has been indicated that the angular dimensions and relative variations in the density of the streamer belt segments remain almost unchanged over the entire distance from the Sun to the Earth’s orbit. In the Earth’s orbit, the ray structure of the belt streamer manifests itself as sharp (with steep fronts lasting several minutes and less) peaks (of several hours in duration) of the solar wind plasma density with maximal values N max > 10 cm?3.  相似文献   

7.
Using Time History of Events and Macroscale Interactions during Substorms(THEMIS) observations from 2007 to 2011 tail seasons, we study the plasma properties of high speed flows(HSFs) and background plasma sheet events(BPSs) in Earth's magnetotail(|Y_(GSM)|13R_E, |Z_(GSM)|5R_E, –30R_EX_(GSM)–6R_E), and their correlations with solar wind parameters. Statistical results show that the closer the HSFs and BPSs are to the Earth, the hotter they become, and the temperature increase of HSFs is larger than that of BPSs. The density and temperature ratios between HSFs and BPSs are also larger when events are closer to Earth. We also find that the best correlations between the HSFs(BPSs) density and the solar wind density occur when the solar wind density is averaged 2(3.5) hours prior to the onset of HSFs(BPSs). The normalized densities of both HSFs and BPSs are correlated with the interplanetary magnetic field(IMF) θ angles(θ=arctan(B_Z/((B_x~2)+(B_y~2))~(1/2) which are averaged 3 hours before the observation time. Further analysis indicates that both HSFs and BPSs become denser during the northward IMF period.  相似文献   

8.
Based on the DMSP F6 and F7 satellite observations, the characteristics of precipitating particles in different auroral precipitation regions of the dayside sector have been studied depending on the solar wind plasma density. Under quiet geomagnetic conditions (|AL| < 100 nT and B z > 0), a considerable increase in the fluxes of precipitating ions is observed in the zones of structured auroral oval precipitation (AOP) and soft diffuse precipitation (SDP). A decrease in the mean energy of precipitating ions is observed simultaneously with the flux growth in these regions. The global pattern of variations in the fluxes of precipitating ions, which shows the regions of effective penetration of solar wind particles into the magnetosphere at a change in the solar wind density from 2 to 20 cm?3, has been constructed. The maximal flux variation (ΔJ i = 1.8 · 107 cm?2 s?1, i.e., 3.5% of an increase in the solar wind particle flux) is observed in the SDP region on the dayside of the Earth. The dependence of precipitating ion fluxes in the low-latitude boundary layer (LLBL), dayside polar cusp, and mantle on the solar wind density at positive and negative values of the IMF B z component has been studied. In the cusp region, an increase in the precipitating ion flux is approximately 17% of an increase in the solar wind density. The IMF southward turning does not result in an appreciable increase in the ion precipitation fluxes either in the cusp or in the mantle. This fact can indicate that the reconnection of the geomagnetic field with southward IMF is not the most effective mechanism for penetration of solar wind particles into these regions.  相似文献   

9.
We report here preliminary results of a mission analysis for a space weather monitoring system that provides continuous transmission of solar wind conditions 0.10 A.U. upstream from Earth. The system is based on four platforms that are phased into eccentric heliocentric orbits but, from the perspective of a fixed Sun–Earth line, the spacecraft appear to orbit Earth. This system offers a 10× improvement in reporting solar wind plasma and magnetic field characteristics beyond similar platforms located at the Lagrangian L-1 point. We describe launch and energy considerations, along with a preliminary analysis of communication requirements. The Space Weather Diamond offers significant potential for scientific insight into problems requiring coordinated observations from multiple vantage points by providing the ability to separate spatial from temporal variations. We discuss examples for payloads including both in situ and remote sensing instrumentation.  相似文献   

10.
The magnetotail lobes are two vast regions between the plasma sheet (PS) and the magnetotail boundary layers at the magnetopause, where the plasma has very low temperature and densities. The open magnetic field lines of the lobes directly couple the ionospheric polar caps with the solar wind (SW) through the magnetosheath. The survey of 576 h INTERBALL-1 measurements in the near (XGSM>−27RE) lobes in October–November 1997 shows that they are populated with plasmas of various origin and properties. Presented and discussed in details are four cases of lobe measurements under different geomagnetic conditions. Discrete plasma structures encountered in the lobes could originate from the PS, from the magnetosheath or the mantle. A ubiquitous picture in the lobes is the registration of ‘clouds’ of anisotropic electrons with energies up to 300–500 eV, with no accompanying ions. The electron distributions are highly variable and complex, with different degree of anisotropy. The earthward flowing electrons originate in the SW, the anisotropy of the electron fluxes reflects the anisotropy of the SW electrons. In some cases the tailward electrons are not only mirrored earthward fluxes but an additional source earthward of the observations is present. The positive spacecraft potential plays a substantial role in modifying the observed electron distributions.  相似文献   

11.
WIND observations of coherent electrostatic waves in the solar wind   总被引：4，自引：0，他引：4  
The time domain sampler (TDS) experiment on WIND measures electric and magnetic wave forms with a sampling rate which reaches 120 000 points per second. We analyse here observations made in the solar wind near the Lagrange point L1. In the range of frequencies above the proton plasma frequency fpi and smaller than or of the order of the electron plasma frequency fpe, TDS observed three kinds of electrostatic (e.s.) waves: coherent wave packets of Langmuir waves with frequencies f ≃ fpe, coherent wave packets with frequencies in the ion acoustic range fpi ≥ f ≥ fpe, and more or less isolated non-sinusoidal spikes lasting less than 1 ms. We confirm that the observed frequency of the low frequency (LF) ion acoustic wave packets is dominated by the Doppler effect: the wavelengths are short, 10 to 50 electron Debye lengths λD. The electric field in the isolated electrostatic structures (IES) and in the LF wave packets is more or less aligned with the solar wind magnetic field. Across the IES, which have a spatial width of the order of ≃25D, there is a small but finite electric potential drop, implying an average electric field generally directed away from the Sun. The IES wave forms, which have not been previously reported in the solar wind, are similar, although with a smaller amplitude, to the weak double layers observed in the auroral regions, and to the electrostatic solitary waves observed in other regions in the magnetosphere. We have also studied the solar wind conditions which favour the occurrence of the three kinds of waves: all these e.s. waves are observed more or less continuously in the whole solar wind (except in the densest regions where a parasite prevents the TDS observations). The type (wave packet or IES) of the observed LF waves is mainly determined by the proton temperature and by the direction of the magnetic field, which themselves depend on the latitude of WIND with respect to the heliospheric current sheet.  相似文献   

12.
The studies are based on the experimental mass sounding of the interplanetary plasma near the Sun at radial distances of R = 4−70 R S, performed at Pushchino RAO, Russian Academy of Sciences, and on the calculated magnetic fields in the solar corona based on the magnetic field strength and structure measured on the Sun’s surface at J. Wilcox Solar Observatory, United States. The experimental data make it possible to localize the position of the boundary closest to the Sun of the transition transonic region of the solar wind in the near-solar space (R ≈ 10−20 R S) and to perform an interrelated study of the solar wind structure and its sources, namely, the magnetic field components in the solar corona based on these data. An analysis of the evolution of the flow types in 2000–2007 makes it possible to formulate the physically justified criterion responsible for the time boundaries of different epochs in the solar activity cycle.  相似文献   

13.
Electron and ion temperature (Te and Ti) data observed using RPA on board SROSS C2 satellite are investigated for the variation with local time, season, latitude (0–30°N geographic) over a half of a solar cycle (1995–2000). The nighttime Te (∼1000 K) is independent of the season and the solar flux whereas Ti exhibits positive correlation with the solar activity during all three seasons. In the early morning hours during summer, Te is higher by ∼500 K than other seasons in all three levels of solar activity. During winter and equinox in the early morning hours, Te and Ti are higher during low solar activity, showing a negative correlation with solar flux. During daytime, the Ti increases with the solar flux in winter and summer solstice, but is independent in equinox. IRI underestimates Te and Ti during the morning period by 50–75% in the equatorial and near-equatorial stations during all levels of solar activities.  相似文献   

14.
The satellite INTERBALL-2 has an orbit with high inclination (62.8°), covering the altitude range between a few hundred and about 20000 km. The ambient plasma conditions along this orbit are highly variable, and the interactions of this plasma with the spacecraft body as well as the photo-electron sheath around it are considered to be interesting topics for detailed studies. The electric potential of the spacecraft with respect to the ambient plasma that develops as a result of the current equilibrium reacts sensitively to variations of the boundary conditions. The measurement and eventual control of this potential is a prerequisite for accurate measurements of the thermal plasma. We describe the purpose and technical implementation of an ion emitter instrument on-board INTERBALL-2 utilising ion beams at energies of several thousand electron volts in order to reduce and stabilise the positive spacecraft potential. First results of the active ion beam experiments, and other measures taken on INTERBALL-2 to reduce charging are presented. Furthermore, the approach and initial steps of modelling efforts of the sheath in the vicinity of the INTERBALL-2 spacecraft are described together with some estimates on the resulting spacecraft potential, and effects on thermal ion measurements. It is concluded that even moderate spacecraft potentials as are commonly observed on-board INTERBALL-2 can significantly distort the measurements of ion distribution functions, especially in the presence of strongly aniso-tropic distributions.  相似文献   

15.
The solar magnetic field B s at the Earth’s projection onto the solar-wind source surface has been calculated for each day over a long time interval (1976–2004). These data have been compared with the daily mean solar wind (SW) velocities and various components of the interplanetary magnetic field (IMF) near the Earth. The statistical analysis has revealed a rather close relationship between the solar-wind parameters near the Sun and near the Earth in the periods without significant sporadic solar and interplanetary disturbances. Empirical numerical models have been proposed for calculating the solar-wind velocity, IMF intensity, and IMF longitudinal and B z components from the solar magnetic data. In all these models, the B s value plays the main role. It is shown that, under quiet or weakly disturbed conditions, the variations in the geomagnetic activity index Ap can be forecasted for 3–5 days ahead on the basis of solar magnetic observations. Such a forecast proves to be more reliable than the forecasts based on the traditional methods.  相似文献   

16.
We assess the contributions of various types of solar wind structures (transients, coronal hole high-speed streams (HSS), and slow-speed wind) to hourly average auroral electron power (Pe). The time variation of the solar wind velocity (Vsw) and Pe are determined by HSS, which contribute ～47% to Pe and Vsw. Transients contribute ～42% of Pe in solar maxima, and ～6% in solar minimum. Cross-correlations of Pe with Vsw|B| for negative Bz are significant. Pe exhibits solar rotational periodicities similar to those for Vsw, with strong 7- and 9-day periodicities in 2005–2008 and equinox semiannual periodicities in 1995–1999.  相似文献   

17.
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18.
The artificial neural network technique is applied to dividing discontinuities in space plasma and magnetic field parameters into classes corresponding to known types of magnetohydrodynamic discontinuities. Parameter discontinuities registered on the WIND spacecraft between 1996 and 1999 are classified using a network of the Kohonen Layer type. An algorithm for determining the orientation of discontinuity surfaces on the basis of one-dimensional observations of solar wind parameter discontinuities on board spacecraft is proposed.  相似文献   

19.
Plasma and magnetic field data from the Helios 1/2 spacecraft have been used to investigate the structure of magnetic clouds (MCs) in the inner heliosphere. 46 MCs were identified in the Helios data for the period 1974–1981 between 0.3 and 1 AU. 85% of the MCs were associated with fast-forward interplanetary shock waves, supporting the close association between MCs and SMEs (solar mass ejections). Seven MCs were identified as direct consequences of Helios-directed SMEs, and the passage of MCs agreed with that of interplanetary plasma clouds (IPCs) identified as white-light brightness enhancements in the Helios photometer data. The total (plasma and magnetic field) pressure in MCs was higher and the plasma- lower than in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large-scale quasi-cylindrical magnetic flux tubes. The axes of the flux tubes usually had a small inclination to the ecliptic plane, with their azimuthal direction close to the east-west direction. The large-scale flux tube model for MCs was validated by the analysis of multi-spacecraft observations. MCs were observed over a range of up to 60° in solar longitude in the ecliptic having the same magnetic configuration. The Helios observations further showed that over-expansion is a common feature of MCs. From a combined study of Helios, Voyager and IMP data we found that the radial diameter of MCs increases between 0.3 and 4.2 AU proportional to the distance, R, from the Sun as R0.8 (R in AU). The density decrease inside MCs was found to be proportional to R–2.4, thus being stronger compared to the average solar wind. Four different magnetic configurations, as expected from the flux-tube concept, for MCs have been observed in situ by the Helios probes. MCs with left-and right-handed magnetic helicity occurred with about equal frequencies during 1974–1981, but surprisingly, the majority (74%) of the MCs had a south to north (SN) rotation of the magnetic field vector relative to the ecliptic. In contrast, an investigation of solar wind data obtained near Earths orbit during 1984–1991 showed a preference for NS-clouds. A direct correlation was found between MCs and large quiescent filament disappearances (disparition brusques, DBs). The magnetic configurations of the filaments, as inferred from the orientation of the prominence axis, the polarity of the overlying field lines and the hemispheric helicity pattern observed for filaments, agreed well with the in situ observed magnetic structure of the associated MCs. The results support the model of MCs as large-scale expanding quasi-cylindrical magnetic flux tubes in the solar wind, most likely caused by SMEs associated with eruptions of large quiescent filaments. We suggest that the hemispheric dependence of the magnetic helicity structure observed for solar filaments can explain the preferred orientation of MCs in interplanetary space as well as their solar cycle behavior. However, the white-light features of SMEs and the measured volumes of their interplanetary counterparts suggest that MCs may not simply be just H-prominences, but that SMEs likely convect large-scale coronal loops overlying the prominence axis out of the solar atmosphere.  相似文献   

20.
Using calculations of the magnetic field in the solar atmosphere in the potential approximation, it is shown that, (1) as distance R from the Sun’s center grows, the area of the positive magnetic field (S +field) in 10-deg latitude zones tends to 100% (0%) in the neighborhood of the solar minimum. At the distance R = 2.5R ⊙(R ⊙ is the solar radius), these values of the positive field are observed during ≈(12–55) Carrington rotations (CRs) for solar minima between neighboring cycles; (2) polar magnetic field reversals can occur repeatedly. Note that a polar reversal at large heights ends by 6–16 Carrington rotations earlier than on the Sun’s surface. On the Sun’s surface, a field polar reversal begins earlier at lower latitudes than at high ones; (3) for each longitude at different Rs and separately for each solar hemisphere the radial component of the field was averaged on synoptic maps in the 0°–40° latitude range. It is established that the T R rotation periods of the boundaries between the sectors (areas of longitudes with the same sign of the averaged field) can be shorter than, longer than, and equal to Carrington solar rotation period T CR. It turned out that boundaries with T R < T CR are observed at all heights, while boundaries with T R > T CR are observed at relatively small heights.  相似文献   

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