CN111605727B

CN111605727B - Method for observing and authenticating interplanetary slow shock waves

Info

Publication number: CN111605727B
Application number: CN202010365036.5A
Authority: CN
Inventors: 冯恒强; 赵岩
Original assignee: Luoyang Normal University
Current assignee: Luoyang Normal University
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2023-07-18
Anticipated expiration: 2040-04-30
Also published as: CN111605727A

Abstract

The invention relates to the technical field of space technology and plasma, in particular to a method for observing and authenticating an interplanetary slow shock wave. The method comprises the following steps: firstly, determining constraint conditions; secondly, judging whether the physical quantity at two sides of the discontinuities meet constraint conditions or not; thirdly, judging whether the discontinuities meet the basic characteristics of slow shock waves; fourth, determine if it is a slow shock wave by the time difference observed by two or more satellites; by the method, misjudgment of TD (tangential discontinuity) as slow shock waves can be avoided; eliminating the uncertainty that exists in authenticating the type of discontinuity; the accuracy of the authentication of the slow shock wave is improved.

Description

Method for observing and authenticating interplanetary slow shock waves

Technical Field

The invention relates to the technical field of space technology and plasma, in particular to a method for observing and authenticating an interplanetary slow shock wave.

Background

A number of observations indicate that magnetic fields are important sources of energy during celestial activities. To address how quickly magnetic energy is converted into plasma kinetic and thermal energy during, for example, flare bursts, magnetic layer sub-bursts, and other cosmic bursts, astronomists are looking for a possible mechanism for rapid annihilation of magnetic fields.

In 1946 Giovanelli first proposed the concept of magnetic field reconnection, which considers that discharge phenomenon occurs at or near the neutral point where the magnetic field strength is zero, and may have an important influence on the occurrence of solar flare. In 1958, sweet and Parker proposed the first steady state magnetic field reconnection model, the Sweet-Parker reconnection model, based on observations of solar flare activity. The Sweet-Parker model considers that a macro-scale diffusion region plasma exists in the middle region of the antiparallel magnetic lines, carries a magnetic field to continuously enter the diffusion region from the upper side and the lower side of the diffusion region, and in the region, magnetic energy is converted into plasma kinetic energy and heat energy through joule dissipation. The plasma flows out of the diffusion region along both sides of the current plate. However, according to the Sweet-Parker model, the rate of energy conversion is too slow to be well interpreted by many bursts in celestial and spatial physics, and is quite different from actual observations. In order to solve the problem of the reconnection rate, a new magnetic field reconnection model was proposed by Petschek in 1964 based on the Sweet-Parker model. In the Petscheck model, the reconnection diffusion region exists only in a small region near the neutral line, and two pairs of slow standing shock waves are associated with both sides of the diffusion region. In the Petschek model, two sets of slow shock waves play a critical role in the energy release and current sheet formation process, and most of the plasma can be accelerated by the slow shock waves without flowing through the diffusion region. The conversion of magnetic energy is accomplished mainly by slow shock waves. So far, solar wind is the only natural laboratory which can directly detect the heavy magnetic field by a satellite, so that the identification of the slow shock wave by correct authentication in the interplanetary space has very important significance.

According to the magnetic fluid (MHD) theory, there are typically various magnetic field discontinuities, abbreviated discontinuities, in the solar wind. Since the observation of the first inter-planetary magnetic field discontinuity in the 60 s of the last century, it has been increasingly recognized that a discontinuity is a fundamental feature of solar wind with an average occurrence of 1-2 events, whereas of so many observed discontinuities, most are tangential discontinuities, and only a few inter-planetary discontinuities events are identified as slow shock waves. Although there are few reported slow shock events, it is very important to study slow shock waves, because slow shock waves play an important role in the magnetic field reconnection process, and correctly recognizing the magnetic field reconnection process is a key to solving a series of problems existing in solar physics, spatial physics, magnetic layer physics, and even plasma physics. At present, no related effective method is available for effectively authenticating the interstellar slow shock wave.

Disclosure of Invention

The invention aims to solve the problem that an effective authentication method for the interplanetary slow shock wave is lacking at present, and provides a method for observing and authenticating the interplanetary slow shock wave.

Determination of magnetic cloud boundaries and configurations has been an important topic in magnetic cloud related research, and almost all magnetic cloud researches are independent of determining magnetic cloud boundaries and configurations.

Coronal Mass Ejection (CME) interacts with other different flows during interplanetary space propagation to create various magnetic discontinuities, typically the boundaries of the interplanetary magnetic flux ropes. Authentication of different types of discontinuities is a fundamental problem in related studies on discontinuities due to the large uncertainty that exists between the different discontinuities. In past studies on discontinuities, tangential Discontinuities (TDs) were often misidentified as Rotational Discontinuities (RDs), and even shock waves were misidentified as RDs.

The technical scheme adopted for solving the technical problems is as follows: a method of observing authenticated interplanetary slow shock waves, the steps comprising:

firstly, determining constraint conditions;

secondly, judging whether the physical quantity at two sides of the discontinuities meet constraint conditions or not;

thirdly, judging whether the discontinuities meet the basic characteristics of slow shock waves;

fourth, determine if it is a slow shock wave by the time difference observed by two or more satellites;

time difference Δt=Δr·n/V observed for each satellite _DD ；

Δr is the displacement between two satellites,

V _DD is the propagation velocity of discontinuities in a stationary coordinate system,

V _DD and the normal direction n of the discontinuity may be calculated from observations local to the discontinuity, the result of which depends on the type of the discontinuity.

Preferably: the constraint condition is a compatibility condition of discontinuities, namely R-H relation:

[B _n ]＝0，

[ρV _n ]＝0，

[V _t B _n -V _n B _t ]＝0，

[V _n B _q -V _q B _n ]＝0，

wherein subscripts n and t denote normal He Qie directions, respectively, and q denotes a direction perpendicular to n-t directions;

brackets indicate differences in physical quantities on either side of the discontinuity;

p is the thermal pressure, and can be expressed as:

P _|| and P _⊥ Thermal pressure parallel and perpendicular to the magnetic field, respectively; ζ is an anisotropic parameter, defined as:

preferably, when determining whether the physical quantities on both sides of the discontinuity meet the constraint condition, the magnetic field discontinuity based on the interplanetary space is not a perfectly ideal magnetic fluid discontinuity, and the physical quantities on both sides of the discontinuity are not required to strictly meet the R-H relationship.

Preferably, when determining whether or not the physical quantities on both sides of the discontinuities satisfy the constraint condition, R-H relationship fitting is performed on the observed values by a least square method, and differences between the observed values and the theoretical values are considered to satisfy the R-H relationship within the error allowable range.

Preferably, the slow shock fundamental features include:

(1) The upstream and downstream intermediate Mach numbers are all less than 1;

(2) The upstream slow Mach number is greater than 1 and the downstream slow Mach number is less than 1;

(3) From upstream to downstream, the magnetic field strength decreases and the proton density and temperature rise.

The beneficial effects of the invention are as follows: by the method, misjudgment of TD (tangential discontinuity) as slow shock waves can be avoided; eliminating the uncertainty that exists in authenticating the type of discontinuity; the accuracy of the authentication of the slow shock wave is improved.

Drawings

Fig. 1 shows the shock coordinate system of the present invention.

FIG. 2 is a graph showing the magnetic field and plasma parameters over time for the 9 month 18 day break event of 1997 observed for the wing airship of example 1 of the present invention.

Fig. 3 shows a comparison of the magnetic fields of the moment events of the moment of 1997, 9 months and 18 days observed by the airship Wind and ACE according to example 1 of the present invention, wherein the dotted line is observed by ACE and the time sequence thereof is shifted back by 34.2 minutes.

FIG. 4 shows the magnetic field and plasma parameters over time for the 8 day break event of month 10 2001 observed for the Wind craft of example 2 of the present invention and the best fit of the upstream and downstream parameters from the R-H relationship.

Fig. 5 shows the change curve of the observed magnetic field in the shock coordinate system for the break event of 10/8/2001 in example 2 of the present invention.

Fig. 6 shows a comparison of the magnetic fields of the 8-day break event of 10-month 2001 observed by the airship winds and ACE in example 2 of the present invention, wherein the dotted line is observed by geoail and its time sequence is shifted 14.6 minutes later.

FIG. 7 is a schematic view showing the normal direction of the discontinuities and the satellite positions according to embodiment 2 of the present invention.

Detailed Description

The implementation will now be further refined. It should be understood that the following description is not intended to limit the embodiments to one preferred embodiment. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the embodiments as defined by the appended claims.

In the following detailed description, while these embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, it is to be understood that these examples are not limiting so that other examples may be used and that corresponding modifications may be made without departing from the spirit and scope of the embodiments.

A method of observing an authenticated interplanetary slow shock, comprising:

firstly, determining constraint conditions;

secondly, judging whether the physical quantity at two sides of the magnetic field discontinuity surface meets constraint conditions or not;

thirdly, judging whether the magnetic field discontinuities meet the basic characteristics of slow shock waves;

whether or not the slow shock wave is determined by the time difference observed by two or more satellites.

The constraint conditions are that from the MHD theory, the physical quantities on both sides of the discontinuities must satisfy basic physical laws such as mass conservation, momentum conservation, energy conservation, maxwell equations, and the like, that is, the magnetic field and plasma parameters are constrained by these conditions. The constraint is the compatibility of discontinuities, i.e., the R-H relationship:

[B _n ]＝0，

[ρV _n ]＝0，

[V _t B _n -V _n B _t ]＝0，

[V _n B _q -V _q B _n ]＝0，

p is the thermal pressure, and can be expressed as:

through the above constraints, four discontinuities that satisfy the principle of entropy increase can be derived: contact discontinuities (ContactDiscontinuity, RD), rotational discontinuities (Rotational Discontinuity, RD), tangential discontinuities (TangentialDiscontinuity, TD), and Shock waves (Shock).

When judging whether a discontinuity is a slow shock wave, firstly, whether the physical quantity at two sides of the discontinuity meets the R-H relation or not is judged, and whether the physical quantity at two sides of the discontinuity meets the constraint condition or not is judged, the magnetic field discontinuity based on the inter-satellite space is not a completely ideal magnetic fluid discontinuity, and the physical quantity at two sides of the discontinuity is not required to strictly meet the R-H relation. In addition, the detecting instrument on the satellite has systematic errors and measurement errors in the measurement process, and the measured value cannot completely meet the R-H relationship.

When determining whether or not the physical quantities on both sides of the discontinuities satisfy the constraint condition, it is common practice to fit the R-H relationship to the observed values by the least squares method, and the difference between the observed values and the theoretical values is considered to satisfy the R-H relationship within the error allowable range.

The R-H relationship is required to be satisfied for all magnetic fluid discontinuities, so that the satisfaction of the R-H relationship is only a basic condition and cannot tell the type of the discontinuities therebetween.

It is also a commonly used criterion for judging slow shock to judge that a discontinuity is a slow shock, and that the discontinuity satisfies both the R-H relationship and the observed characteristics of the slow shock. The basic characteristics of slow shock waves include:

(1) The upstream and downstream intermediate Mach numbers are all less than 1;

As shown in fig. 1, fig. 1 is a shock coordinate system; in the figure, n _s In the normal direction of the shock wave, the upper and lower magnetic fields are all in the plane n _s Within t, the s-t plane is the wavefront of the shock wave; if considered as TD, the s-direction is the normal direction, n _s The t-plane is a discontinuity.

For magnetic fluid shock waves, the coplanarity principle requires a magnetic field B upstream and downstream of the discontinuities ₁ 、B ₂ And normal direction n of shock wave _s In the same plane. Thus, as shown in fig. 1, the shock coordinate system can be defined, the s direction is perpendicular to the surface where the upstream and downstream magnetic fields and the normal line are located, and the direction of the other coordinate axis t is as follows: t=n _s X s. Thus the t-s plane is the wave front of the shock wave, and the upstream and downstream magnetic fields are all in n _s -in the t-plane. For TD, the magnetic field is in the TD plane due to the absence of normal magnetic field components. Thus, the shock coordinate system can also be used to describe TD: t-n _s The plane is TD plane, and the normal direction (n _TD ) Pointing to s.

According to the R-H relationship, TD only requires two basic conditions:

(1) The upstream and downstream velocities and magnetic fields are perpendicular to the TD plane,

(2) The total pressure of the upstream and downstream is balanced.

For a slow shock wave, the magnetic fields at the upper and lower stream in the shock wave coordinate system are all t-n _s If both the upstream and downstream flow rates are in this plane, then the slow shock wave satisfies the first condition of TD. In addition, for slow shock waves, the upstream magnetic pressure is greater than the downstream, while the thermal pressure across the shock plane increases, and the total pressure across the shock may reach equilibrium or near equilibrium, i.e., the second condition of TD is met. Therefore, whether a discontinuity is a slow shock wave or a TD has great uncertainty can be determined by the R-H relationship based on the observation of only one satellite, and one TD may be misjudged to be a slow shock wave.

Thus, the present application adds to the limitations. Two or more satellite observation method regions are employed to overcome this uncertainty.

Because each discontinuity may be considered a large, wireless plane in the interplanetary space, the discontinuities in the earth relative to the sun's wind may be considered points, and thus the same discontinuity is always observed by multiple scientific satellites in the vicinity of the earth. It is assumed that the same discontinuity (slow shock or tangential) is observed by two different satellites at different locations and at different times.

The time difference Δt=Δr·n/V observed by two satellites _DD ；

Δr is the displacement between two satellites,

As mentioned above, n for the same discontinuity as TD or slow shock will be 90 degrees apart (see fig. 1), i.e., the discontinuities can be seen as infinitely large planes at 90 degrees apart. The time difference t estimated through the two satellites based on the TD model and the slow shock model may also be quite different. How much the specific time difference t will be related to the satellite's position for specific event analysis. The time difference between the actual observation of discontinuities by two satellites can be easily obtained if one of the time difference and the time difference estimated by two different models is substantially the same and the other one is significantly different, beyond the allowable range of the observation error. Then the type of the discontinuity may be determined relatively accurately. Therefore, the slow shock wave can be intermittently and effectively authenticated by combining the R-H relation, and TD can not be misjudged as the slow shock wave. Of course, it is also possible that two satellites are closely spaced to observe the same discontinuity, but still cannot accurately authenticate their type of discontinuity, which requires more (more than three) satellite observations, and the same approach is taken to eliminate the possibility of misjudging the TD as a slow shock.

Example 1: a 9 month 18 day section event in 1997.

Slow shock characteristics of discontinuities: determining parameters of the shock wave by fitting is important to study the interplanetary shock wave, most importantly to establish a relatively accurate shock coordinate system. Such as the coplanar principle and the MVA method, are relatively common methods for determining the shock coordinate system. A new shock fitting procedure recently proposed by Lin et al [2006] was used here to analyze the shock characteristics of this discontinuity, and they used a complete set of R-H relationships (or modified R-H relationships) to give a solution to the fit of the R-H relationships within the observed data error range by Monte Carlo simulation in combination with least squares. Lin et al split their methods into method A, which uses a common R-H relationship, and method B, which uses a modified R-H relationship. For details on the fitting method reference may be made to the relevant literature [ Lin et al, 2006].

This discontinuity was observed by the wing airship near day 0255:15UT, 9, 1997, month 18, when the airship was located at (83.51, -13.58, -1.45) RE of the GSE coordinate system, RE being the earth radius. Fig. 2 shows the magnetic field and plasma parameters of this event as a function of time. Wherein the magnetic field is data recorded by a MFI (MagneticField Investigation) magnetometer on the fly with a time resolution of 3 seconds; the speed and density of protons are data detected by a 3DP (3-Dimension Plasma) onboard the airship, with a time resolution of 3 seconds. In addition, table 1 shows the magnetic fields, densities and velocities upstream and downstream of this discontinuity, the directions of the three coordinate axes of the shock coordinate system obtained by fitting, and the estimated shock propagation velocity. The propagation velocity of the shock wave in the interplanetary space according to the conservation relation can be calculated by:

the observations and shock fit results in fig. 2 and table 1 show that this discontinuity event fully meets the requirements of slow shock:

(1) From upstream to downstream, the magnetic field strength is reduced, and the proton density is increased;

(2) All observed values can well meet the R-H relationship;

(3) In the shock coordinate system, the upstream normal flow velocity is greater than the local slow magneto-acoustic velocity, and the downstream normal flow velocity is less than the local slow magneto-acoustic velocity.

It can be authenticated that this event is a slow shock based on the slow shock criteria commonly used.

TD characteristics of discontinuities: based on magnetic fluid theory, if this discontinuity is considered to be TD, the magnetic field conditions are satisfied, only that no flow passes through the discontinuity in the discontinuity coordinate system and the total pressure on both sides is balanced. If this discontinuity is considered as TD, then the normal direction nTD (-0.43,0.88,0.17) should be pointing in the s-axis direction of the shock coordinate system (see FIG. 1). Table 2 gives estimates of the thermal, magnetic and total pressures on both sides of this discontinuity. As can be seen from Table 2, the total pressure on both sides of the discontinuity is very close, and the upstream-downstream pressure difference is only 3% of the upstream pressure. If the systematic error of the scope and the standard deviation of the observed values are taken into account, the total pressure balance across the discontinuity can be considered, i.e. the second basic condition of TD is fulfilled. In addition, the result of multiplying the upstream-downstream velocity difference (w=v2-V1) by the normal vector nTD of the discontinuity was 0.66km/s. This indicates that little flow passes through the discontinuities, i.e., the first condition of TD is satisfied. This discontinuity thus also meets all the requirements of TD.

Observations of multiple satellites: this discontinuity was also observed by the ACE satellite at 0221:01UT when the ACE was located at (193.31, -24.78,20.78) RE. Fig. 3 shows the magnetic field curves around this discontinuity observed by both Wind and ACE, where the solid line is observed by Wind and the dotted line is observed by ACE, with the time series of ACE being delayed by 34.2 minutes. As can be seen from fig. 3, the changing profiles of the two sets of magnetic field curves are relatively identical, with only a few differences in some detailed structures. Since the two satellites observe not the same location of the discontinuities, some difference in detail is quite normal. It can be determined that the two satellites observe the same discontinuity.

The slow shock model and the TD model are used to estimate the time difference (Δt) between two satellite observations. Assuming this discontinuity as a slow shock, Δt _s ＝ΔR·n _s /v _sh Δt _s ＝ΔR·n _s /v _sh The calculated time difference was 15.3 minutes, which is quite different from the time difference of 34.2 minutes actually observed by the two satellites. If using TD model, Δt _TD ＝ΔR·n _TD /V _TD . Wherein V is _TD Is the propagation velocity of TD in a stationary coordinate system, and the upstream velocity (V) can be multiplied by the normal unit vector point of TD _TD ＝n _TD ·V ₁ = 160.22 km/s) or downstream speed (V ₂ ) Obtained. Since there is little flow through the TD plane, there is little difference in the results from estimating the propagation speed of the TD with either the upstream or downstream speed. The estimated time difference between two satellite observations is 35.6 minutes, which is very close to the actual time difference of 34.2 minutes. Taking into account systematic errors in observations, it can be determined that this discontinuity is TD over a large scale structure rather than a slow shock.

Assuming that the discontinuities can be approximately represented as an infinite thin surface and the propagation velocity does not change with time and space, four satellites of the Cluster are used to determine the normal direction of the discontinuities. Four satellites may give three independent analogs of Δt=Δr·n/V _DD Adding the discontinuities normal direction as unit vectors yields a set of closed equations:

where Vn is the propagation velocity of the discontinuities ΔR _1i Is the position vector between Cluster 1 and Cluster i satellites, Δt _i Representing the time difference in which they observed discontinuities, respectively. Four equations, four unknowns, can solve for the propagation velocity and normal direction of discontinuities. The method does not need an observed magnetic field and speed, and the calculated result is relatively accurate.

The 18 day section of 9.1997 was also around 0312UT by Geotail satellite, (24.85, -11.57, -1.52)) Observed at RE. Thus, three satellites may be used to calculate the normal direction of the discontinuities. Typically, the magnetic field values observed by satellites are much more accurate than the velocity values. The equation is used here: n.B ₁ ＝n·B ₂ Substitution equationi=2to 4, a closed set of equations can be obtained:

wherein DeltaR _WG (Δt _WG ) Representing the displacement (time difference) between Wind and geoail satellites, Δr _WA (Δt _WA ) Then representing the displacement (time difference) between the windd and ACE satellites, B1 and B2 are the magnetic fields upstream and downstream of the discontinuities observed with windd satellites. The normal direction n of the discontinuity and the propagation velocity Vn of the discontinuity can be solved by the above four equations. Solved n= (-0.42,0.89,0.15) and deriving n from magnetic field above _TD (-0.43,0.88,0.17) are nearly identical, solving for the velocity V of discontinuities _n Also sum calculated v= 164.99km/s _TD (160.22 km/s) are very close. This again demonstrates that this discontinuity should be TD as a large-scale planar structure, rather than a slow shock. However, TD as an interface between two different fluids may interact near the boundary during propagation, possibly forming a localized, local slow shock structure, which is almost impossibleCan be observed by two satellites. So that the observation of Wind is also likely to be a local slow shock, and when the shock analysis is performed on the discontinuities, if the upstream and downstream time intervals are selected to be slightly longer, the observation value cannot well meet the R-H relationship, which may be the evidence of a small-scale local shock. In addition, some substructures may appear in the middle during the three-dimensional simulation with respect to TD, which also likely corresponds to such local shock waves.

Example 2: a 10 month 8 day section event in 2000.

Intermediate shock characteristics of discontinuities: this discontinuity is observed by the wing satellite at RW= (37.20, -59.72,4.91) RE near 0117:30UT. The second column of fig. 4 shows the magnetic field and plasma profile for this event. In addition, table 3 shows observations upstream and downstream of this discontinuity and shock parameters derived directly using these observations. These parameters include the normal direction ns of the shock wave, the direction of the other two axes t and s of the shock wave coordinate system,

upstream and downstream plasma beta values, upstream and downstream normal allphen Mach number (M _AN ＝V _n /V _An ) Upstream and downstream magneto-acoustic Mach number (M _F ＝V _n /V _f ) And slow magneto acoustic Mach number (M) _SL ＝V _n /V _sl ) The ratio of the magnetic field intensities upstream and downstream (m=b ₂ /B ₁ ) The density ratio of the upstream and downstream (y=n ₁ /N ₂ ) Upstream-downstream tangential component ratio (u=b _t2 /B _t1 ) Included angle theta between shock normal and upstream magnetic field _BN ＝cos ^-1 (B ₁ ·n _s /B ₁ ). In the above expression, V _An Alfin velocity (V) using normal magnetic field component _An ＝B _n /(μ ₀ ρ) ^1/2 )，V _n Is the normal component of the flow velocity in the shock coordinate system, V _f And V _sl The magnetic sound wave speeds are respectively fast and slow. We use Lin et al 2006]The method of (a) fits this discontinuity and results obtained with methods a and B are substantially identical. Table 3 also shows the fitting results obtained with method A and the corresponding parameter values, and FIG. 5.4 also shows the fitting upstream and downstreamResults (horizontal dotted line). It can be seen in combination with fig. 4 and table 3 that the observations and the fitting results are quite consistent.

According to the theory of magnetic fluid, an intermediate shock wave has the following characteristics:

(1) Upstream normal alfin mach number is greater than 1 and downstream normal alfin mach number is less than 1;

(2) The tangential components of the magnetic fields at the upstream and downstream are in opposite directions;

(3) Increasing density from upstream to downstream;

(4) Of all the 4 intermediate shocks, type 2-4 has a greater density modulation than the other 3.

Fig. 5 shows the variation of the magnetic field in the shock coordinate system. As can be seen from fig. 5, tangential component B _t Through the reverse sign of the back direction of the laser surface, the normal component B _n Remain unchanged, B _s The component is approximately zero. In combination with the fitting parameters given in table 3, this discontinuity is well able to meet the requirements of the intermediate shock. In addition, the fast Mach number of the shock wave upstream and downstream is smaller than 1, and the slow Mach number is larger than 1. Therefore, based on these characteristics, it can be generally authenticated that this discontinuity is a type 2→3 intermediate shock.

TD characteristics of discontinuities: table 4 gives the thermal, magnetic and total pressures on both sides of this discontinuity. As can be seen from Table 4, the total pressure across the discontinuities is substantially uniform. In addition, if this discontinuity is considered as TD, the velocity difference between the upstream and downstream is multiplied by the unit vector n of the normal to TD _TD The product of (-0.689, -0.694, -0.210) is also small (-1.58 km/s). I.e. this discontinuity meets two basic requirements of TD, i.e. it may also be considered to be TD.

Observations of multiple satellites: this discontinuity is also observed by the Geotail satellite at around 0102:50UT, when the satellite position is R _G ＝(29.91,-7.11,4.13)R _E . Fig. 6 shows a comparison of the magnetic fields observed by two satellites, wing and geoail, where the solid line is observed by wing and the dotted line is observed by geoail and its time sequence is delayed by 14.6 minutes. As can be seen in FIG. 6, the two sets of curves are relatively consistent in profile, which makes it clear that they are the same discontinuities observed by different satellites.

We treat this discontinuity as an intermediate shock and TD, respectively, to calculate the time difference between two satellite observations. If this discontinuity is considered as an intermediate shock, the normal direction (n _s ) And displacement between two satellites (Δr=r _G –R _W ) Fig. 7a presents a schematic view of the orientation between them. As can be seen from FIG. 7a, the shock normal vector n _s The result of the point-to-0.58,0.36,0.73-multiplied displacement between two satellites is positive. This means that the Wind satellite should observe this shock first, but the fact is that geoail observes this shock first. If this discontinuity is considered to be TD, FIG. 7b shows the TD normal direction (n _TD ) And a schematic of two satellite displacements. As can be seen from the figure, n _TD ·ΔR<0, and the estimated time difference (Δt _TD ＝ΔR·n _TD /v _TD ) This is in agreement with the fact that Wind observed this discontinuity 14.6 minutes later than geoail for minus 13.9 minutes. This discontinuity may be a TD rather than an intermediate shock.

In addition, when the shock wave analysis is performed on the intermittent event, the time interval of the upstream and downstream of the selected shock wave is also relatively short, and if the time interval is selected to be slightly longer, the observed value cannot well meet the R-H relationship. This discontinuity may also be a special structure: a local, intermediate shock structure is formed between a large TD structure. This intermediate shock is a localized structure formed by the interaction of two different fluids near the interface.

To eliminate uncertainty, the observation time difference of any two satellites can be calculated through the observation of a plurality of satellites. This uncertainty is eliminated because the time differences calculated using the TD model and the slow (or intermediate) shock model tend to be quite different and then compared to the actual observed time differences. Such as the 8 th day of 1997, the 18 th day of 9 and the 8 th day of 2000, which satisfy all conditions of slow shock waves and intermediate shock waves, respectively; on the other hand, they all meet the TD condition. Through multiple satellite analyses, it can be confirmed that they are TD rather than shock waves on a large scale. We propose that care should be taken in validating the slow (or intermediate) shock wave, preferably with multiple satellites.

While it is possible to confirm with multiple satellites that the two discontinuities above are TD on a large scale, the interaction of TD as an interface of two different streams may occur near the boundary during propagation, possibly forming a local, slow (or intermediate) shock structure that is almost impossible to observe by the two satellites. This may be similar to the structure of the top of the magnetic layer, which may be considered a TD on a large scale, whereas RD structures are often present on a small scale. The two discontinuities events observed by winter on month 9, 18 and 8 of 1997 and 10, 2000, respectively, may also be localized slow and intermediate shocks.

Table 1: observed parameters of upstream and downstream of 18-day section of 9-month 1997, and fitted to each axis of the obtained shock coordinate system

And an estimated shock velocity.

Table 2 pressure across the 18 day section of 9 months 1997.

Table 3. Observations upstream and downstream of 8 day section at 10 month 2001, and fitting parameters for intermediate shock waves.

Table 4: pressure on both sides of the section between 10 and 8 days in 2001.

For ease of explanation, specific nomenclature is used in the above description to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that these specific details are not required in order to practice the embodiments described above. Thus, the foregoing descriptions of specific embodiments described herein are presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. It will be apparent to those skilled in the art that certain modifications, combinations and variations are possible in light of the above teachings.

Claims

1. A method for observing and authenticating an interplanetary slow shock wave is characterized by comprising the following steps: comprising the following steps:

firstly, determining constraint conditions;

fourth, determining whether the magnetic field discontinuities are slow shock waves by observing time differences observed by two or more satellites;

time difference Δt=Δr·n/V observed for each satellite _DD ；

Δr is the displacement between two satellites,

V _DD and the normal direction n of the discontinuity may be calculated from observations local to the discontinuity, the result of which depends on the type of the discontinuity;

the constraint condition is a compatibility condition of discontinuities, namely R-H relation:

[B _n ]＝0，

[ρV _n ]＝0，

[V _t B _n -V _n B _t ]＝0，

[V _n B _q -V _q B _n ]＝0，

wherein subscripts n and t denote normal and tangential directions, respectively, and q denotes a direction perpendicular to the n-t plane;

p is the thermal pressure, and can be expressed as:

when judging whether the physical quantity at two sides of the discontinuities meet the constraint condition, the magnetic field discontinuities based on the inter-satellite space are not completely ideal magnetic fluid discontinuities, and the physical quantity at two sides of the discontinuities are not required to strictly meet the R-H relationship;

when judging whether the physical quantity at two sides of the discontinuities meets constraint conditions or not, carrying out R-H relation fitting on the observed values by using a least square method, and considering that the difference between the observed values and theoretical values meets the R-H relation within an error allowable range;

the basic characteristics of slow shock waves include:

(1) The upstream and downstream intermediate Mach numbers are all less than 1;

(3) From upstream to downstream, the magnetic field strength decreases and the proton density and temperature rise;

assuming that the discontinuities can be approximately represented as an infinite thin surface and propagation speed does not change with time and space, four satellites of the Cluster are used to determine the normal direction of the discontinuities; four satellites may give three independent analogs of Δt=Δr·n/V _DD Adding the discontinuities normal direction as unit vectors yields a set of closed equations:

where Vn is the propagation velocity of the discontinuities ΔR _1i Is the position vector between Cluster 1 and Cluster i satellites, Δt _i Representing the time difference in which they observed discontinuities, respectively.