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1.
The magnetoconvection problem under the magnetostrophic approximation is investigated as the nonlinear regime is entered. The model consists of a fluid filled sphere, internally heated, and rapidly rotating in the presence of a prescribed, axisymmetric, toroidal magnetic field. For simplicity only a dipole parity and a single azimuthal wavenumber (m = 2) is considered here. The leading order nonlinearity at small amplitude is the geostrophic flow U
g
which is introduced to the previously linear model (Walker and Barenghi, 1997a, b). Walker and Barenghi (1997c) considered parameter space above critical and found that U
g
acts as an equilibration mechanism for moderately supercritical solutions. However, for solutions well above critical a Taylor state is approached and the system can no longer equilibrate. More importantly though, in the context of this paper, is that subcritical solutions were found.
Here subcritical solutions are considered in more detail. It was found that, at
is strongly dependent on . (
is the critical value of the modified Rayleigh number
is a measure of the maximum amplitude of the generated geostrophic flow while , the Elsasser number, defines the strength of the prescribed toroidal field.) Rm at
proves to be the key measure in determining how far into the subcritical regime the system can advance. 相似文献
2.
Andrzej Kijko 《Pure and Applied Geophysics》1977,115(4):1011-1021
Summary Seven optimal networks consisting of 4 to 10 stations are compared for a given region, where velocity-depth profiles and the distribution of seismic intensity are known. Assuming that the standard error of arrival time is
t
=0.05 s and the standard errors of the parameters of velocity-depth profiles are equal to 5% of their values, the average standard errors of the origin time
and focus coordinates
are estimated. The application of optimum methods to the planning of seismic networks in the Lublin Coal Basin is presented, and maps of standard errors of origin time
, depth
and epicenter (
xy
) for the case of an optimum network of 6 seismic stations are given. 相似文献
3.
Synthesis of empirical natural materials and thermodynamic computer modeling of geochemical processes in water–rock systems at different boundary conditions (solid-to-liquid ratio,
, T) were used to determine the genetic causes of the inverse geochemical zonality that forms in deep horizons of oil-and-gas bearing structures. The geochemical pattern of inversion water was found to form chiefly because of changes in the Eh–pH-conditions of the original groundwater under the effect of organic components of rocks and because of an increase in temperature to 100°C at low values of solid-to-liquid ratios and at
no higher than 10–2 bar. 相似文献
4.
Types of focal mechanism solutions and parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces 总被引：1，自引：0，他引：1
Based on P- and S-wave amplitudes and some clear initial P-wave motion data, we calculated focal mechanism solutions of 928 M≥2.5 earthquakes （1994-2005） in four sub-blocks of Sichuan and Yunnan Provinces, namely Sichuan-Qinghai, Yajiang, Central Sichuan and Central Yunnan blocks. Combining these calculation results with those of the focal mechanism solutions of moderately strong earthquakes, we analyzed the stress field characteristics and dislocation types of seismogenic faults that are distributed in the four sub-blocks. The orientation of principal compressive stress for each block is： EW in Sichuan-Qinghai, ESE or SE in Yajiang, Central Sichuan and Central Yunnan blocks. Based on a great deal of focal mechanism data, we designed a program and calculated the directions of the principal stress tensors, σ1, σ2 and σ3, for the four blocks. Meanwhile, we estimated the difference （also referred to as consistency parameter θ^- ） between the force axis direction of focal mechanism solution and the direction of the mean stress tensor of each block. Then we further analyzed the variation of θ^- versus time and the dislocation types of seismogenic faults. Through determination of focal mechanism solutions for each block, we present information on the variation in θ^- value and dislocation types of seismogenic faults. 相似文献
5.
Summary The object of the present paper is to investigate the propagation of surface waves on a non-homogeneous aeolotropic cylindrical shell surrounded by vacuum. The elastic constantsc
ij
(i, j=1,2...) and density of the material of the shell are assumed to be of the form
and
respectively, where ij, 0 are constants andk
1,k
2 are any integers. 相似文献
6.
Distribution of empirical recurrence intervals for segment-rupturing earthquakes on active faults of the Chinese mainland 总被引：2，自引：0，他引：2
闻学泽 《地震学报(英文版)》1999,12(6):667-675
IntroductionInassessingtheprobabilitiesoftime-dependentandlong-termseismichazardsforsegmentsofactivefaults,itisnecessarytohavetheprobabilitydensity,f(O,fordescribingtherecurrenceintervaldistributionforsegment-rupturingearthquakes.Fromf(nandthefollowingequation,theconditionalprobability,pc,whichincreaseswiththetime,Te,elapsedsincethelatestearthquake,isabletobecalculated(Nishenko,Buland,1987,WorkingGrouponCaliforniaEarthquakeProbabilities,1995;Wen,1995,1998)fwhereATisthetimeintervalforthefor… 相似文献
7.
葛焕称 《地震学报(英文版)》1995,8(1):57-63
ＯｎｓｏｍｅｐｒｏｂｌｅｍｓｏｆｓｅｉｓｍｉｃｃｒｕｓｔａｌｐｈａｓｅＨｕａｎ－ＣｈｅｎｇＧＥ（葛焕称）（ＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕｏｆＪｉａｎｇｓｕＰｒｏｖｉｎｃｅ,Ｎａｎｊｉｎｇ２１００１４,Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｉｎｔｈｉｓ... 相似文献
8.
Lubomír Kubáček Lea Bartalošová Ján Pecár Reviewer F. Charamza 《Studia Geophysica et Geodaetica》1977,21(3-4):227-235
Summary If the condition R(A)=k(n), whereA is the design matrix of the type n × k and k the number of parameters to be determined, is not satisfied, or if the covariance matrixH is singular, it is possible to determine the adjusted value of the unbiased estimable function of the parameters f(), its dispersion D(
(x)) and
2
as the unbiased estimate of the value of
2
by means of an arbitrary g-inversion of the matrix
. The matrix
, because of its remarkable properties, is called the Pandora Box matrix. The paper gives the proofs of these properties and the manner in which they can be employed in the calculus of observations. 相似文献
9.
The conditions under which two magmas can become mixed within a rising magma batch are investigated by scaling analyses and fluid-dynamical experiments. The results of scaling analyses show that the fluid behaviours in a squeezed conduit are determined mainly by the dimensionless number
where
1 is the viscosity of the fluid, U is the velocity, g is the acceleration due to gravity, is the density difference between the two fluids, and R is the radius of the tube. The parameter I represents a balance between the viscous effects in the uppermost magma which prevent it from being moved off the conduit walls, and the buoyancy forces which tend to keep the interface horizontal. The experiments are carried out using fluid pairs of various density and viscosity contrasts in a squeezed vinyl tube. They show that overturning of the initial density stratification and mixing occur when I>order 10-1; the two fluids remain stratified when I 10-3. Transitional states are observed when 10-3<I<10-1. These results are nearly independent of Reynolds number
and viscosity ratio
in the range of
and Re
1<300. Applying these results to magmas shows that silicic to intermediate magmas overlying mafic magma will be prone to mixing in a rising magma batch. This mechanism can explain some occurrences of small-volume mixed lava flows. 相似文献
10.
Zusammenfassung Als Zusammenhang zwischen der kennzeichnenden Wellenperiode
und der durchschnittlichen Periode
im Seegang wird die Formel
angesetzt. Mit Hilfe empirischer Unterlagen wird nachgewiesen, daßc eine Funktion des von D. E. Cartwright und M. S. Longuet-Higgins [1956] eingeführten Spektralparameters ist. Es wird eine vorläufige quantitative Beziehung zwischenc und abgeleitet.
相似文献
Empirical investigations of the relation between the mean and the significant wave period in the sea
Summary It is supposed that the formula represents the relation between the significant wave period and the mean period in the sea. With the aid of empirical data it is demonstrated thatc is a function of the spectral parameter introduced by D. E. Cartwright and M. S. Longuet-Higgins [1956]. A preliminary quantitative relation betweenc and is derived.
Etudes empiriques de la relation entre la période moyenne et la période significative des vagues dans la houle
Résumé On suppose que la formule représente la relation entre la période significative des vagues et la période moyenne dans la houle. A l'aide des données empiriques on montre quec est une fonction du paramètre spectral , introduit par D. E. Cartwright et M. S. Longuet-Higgins [1956]. Une relation quantitative préliminaire entrec et est dérivée.
相似文献
11.
Fermat's variational principle states that the signal propagates from point S to R along a curve which renders Fermat's functional
(l) stationary. Fermat's functional
(l) depends on curves l which connect points S and R, and represents the travel times from S to R along l. In seismology, it is mostly expressed by the integral
(l) =
(x
k,x
k
')du, taken along curve l, where (x
k,x
k
') is the relevant Lagrangian, x
k are coordinates, u is a parameter used to specify the position of points along l, and x
k
' = dx
k÷du. If Lagrangian (x
k,x
k
') is a homogeneous function of the first degree in x
k
', Fermat's principle is valid for arbitrary monotonic parameter u. We than speak of the first-degree Lagrangian (1)(x
k,x
k
'). It is shown that the conventional Legendre transform cannot be applied to the first-degree Lagrangian (1)(x
k,x
k
') to derive the relevant Hamiltonian (1)(x
k,p
k), and Hamiltonian ray equations. The reason is that the Hessian determinant of the transform vanishes identically for first-degree Lagrangians (1)(x
k,x
k
'). The Lagrangians must be modified so that the Hessian determinant is different from zero. A modification to overcome this difficulty is proposed in this article, and is based on second-degree Lagrangians (2). Parameter u along the curves is taken to correspond to travel time , and the second-degree Lagrangian (2)(x
k,
k
) is then introduced by the relation (2)(x
k,
k
) = [(1)(x
k,
k
)]2, with
k
= dx
k÷d. The second-degree Lagrangian (2)(x
k,
k
) yields the same Euler/Lagrange equations for rays as the first-degree Lagrangian (1)(x
k,
k
). The relevant Hessian determinant, however, does not vanish identically. Consequently, the Legendre transform can then be used to compute Hamiltonian (2)(x
k,p
k) from Lagrangian (2)(x
k,
k
), and vice versa, and the Hamiltonian canonical equations can be derived from the Euler-Lagrange equations. Both (2)(x
k,
k
) and (2)(x
k,p
k) can be expressed in terms of the wave propagation metric tensor g
ij(x
k,
k
), which depends not only on position x
k, but also on the direction of vector
k
. It is defined in a Finsler space, in which the distance is measured by the travel time. It is shown that the standard form of the Hamiltonian, derived from the elastodynamic equation and representing the eikonal equation, which has been broadly used in the seismic ray method, corresponds to the second-degree Lagrangian (2)(x
k,
k
), not to the first-degree Lagrangian (1)(x
k,
k
). It is also shown that relations (2)(x
k,
k
) =
; and (2)(x
k,p
k) =
are valid at any point of the ray and that they represent the group velocity surface and the slowness surface, respectively. All procedures and derived equations are valid for general anisotropic inhomogeneous media, and for general curvilinear coordinates x
i. To make certain procedures and equations more transparent and objective, the simpler cases of isotropic and ellipsoidally anisotropic media are briefly discussed as special cases. 相似文献
12.
Résumé La formule de base, traduisant une propriété analytique d'une classe très générale de fonctions, est un corollaire du théorème fondamental démontré dans un mémoire précédent, d'après lequel, étant donnés une fonction continue,p(, ,t) des points (, ) d'une surface régulière fermée et du temps et le champ
d'un vecteur vitesse de transfert ou d'advection tangent à et ayant des lignes de flux fermées et régulières, il existe un opérateur spatial, linéaire, non singulierA tel que la fonctionA(p+Const.) soit purement advective par rapport a
(sans creusement ni comblement). Ce théorème peut être exprimé par l'équation
, où
est un opérateur spatial, linéaire et non singulier, fonction deA.La détermination de
peut être faite, soit en comparant deux formes différentes de la solution générale de l'équation en
, soit en utilisant un raisonnement a priori très simple. On arrive ainsi au résultat
pour un certain scalaireu(, ).Dans le cas oùp(, ,t) est la perturbation de la pression sur la surface du géoïde l'équation
résulte aussi, comme nous l'avons montré dans le mémoire précédent, de notre théorie hydrodynamique des perturbations. On montre ici que la même équation peut encore être déduite de l'équation de continuité associée à la condition d'équilibre quasi statique selon la verticale.Comme applications de la formule de base (solution générale de l'équation enM), on étudie les problèmes suivants: 1o creusement et comblement en général; 2o creusement et comblement des centres et des cols; 3o mouvement des centres et des cols; 4o instabilité d'un champ moyen; 5o propriétés spatiales des champsp(, ,t) et des vecteurs d'advection
analytiques.Après une discussion des erreurs de la prévision d'un champp(, ,t) par la formule de base, du fait des erreurs des observations et du fonctionnement du calculateur, on examine quelques particularités du transfert ou advection d'un champf
0(, ) par le vecteur
. Enfin, le dernier chapitre du mémoire donne des éclaircissements complémentaires sur la structure du calculateur électronique «Temp» (qui effectue automatiquement les opérations mathématiques de la formule de base) et expose l'état actuel de sa construction.
Summary The basic formula, expressing an analytical property of a very general class of functions, is a corollary of the fundamental theorem, proved in a previous paper, according to which, given a functionp(, ,t) of the points (, ) of a closed regular surface and of the time, and a transfer or advection velocity vector tangent to and having regular closed streamlines, there is a spatial, linear, non singular operatorA such thatA(p+const.) is a purely advective function in respect to (no deepening). This theorem can be expressed by the equation where is a spatial, linear, non singular operator depending onA.The determination of can be attained, either by the comparison of two different forms of the general solution of the -equation, or by a simple a priori reasonning. The conclusion is thus reached that for a certain scalaru(, ).Whenp(, ,t) is the pressure perturbation at sea level, it was shown, in the preceding paper, that the equation can also be derived from our hydrodynamical perturbation theory. We now show that for this particular case, the same equation is also a consequence of the equation of continuity together with the condition of quasi statical vertical equilibrium.The following problems are then analysed by means of the basic formula: 1o deepening and filling in general; 2o deepening and filling of the centres and cols; 3o motion of the centres and cols; 4o instability of a mean field; 5o spatial properties of the analytical fields and advection vectors .The errors in the forecast of a field,p(, ,t) by means of the basic formula, due to the observational and computational errors, are discussed, and some peculiarities of the transfer or advection of a fieldf 0(, ) by are examined. Finally, complementary points are disclosed on the structure of the electronic computer «Temp» which performs automatically the mathematical operations of the basic formula, and a brief report is given of the present state of its construction.相似文献
13.
A maximum likelihood method is used to estimate the earthquake hazard parameters maximum magnitudeM
max, annual activity rate , and theb value of the Gutenberg-Richter equation in the Vrancea (Romania) region. The applied procedure permits the use of mixed catalogs with incomplete historical as well as complete instrumental parts, the consideration of variable detection thresholds, and the incorporation of earthquake magnitude uncertainty.Our imput data, comprises 105 historical earthquakes which occurred between 984 and 1934, and a complete data file containing 1067 earthquakes which occurred during the period 1935–30 August, 1986. The complete part was divided into four subcatalogs according to different thresholds of completeness. Only subcrustal events were considered, and dependent events were removed.The obtained
value (=0.65) is at the lower range of the previously reported results, but it appears concurrent with conceptual and observational facts. The same concerns inferred value of
max = 7.8 and activity rate
4.0 = 5.34. 相似文献
14.
15.
J. Kjensmo 《Aquatic Sciences - Research Across Boundaries》1967,29(2):361-365
Summary A water sampler for investigation of detailed stratification of different factors in lake waters is described. The working
mechanism of the sampler is illustrated in Fig. 1 and 2, and in greater detail in Fig. 3 and 4. The present sampler consists
in six smaller samplers which are placed in pairs in three different vertical planes around a central tube which latter slides
on a central rod.
Two examples of stratifications found by means of the sampler are given. Table 1 shows the stratification of O2, H2S and
in the chemocline region of a small meromictic lake. Table 2 illustrates the redox potential just above the mud surface of
a small holomictic lake.
Zusammenfassung Ein Sch?pfger?t, das der Untersuchung der genauen Schichtung von verschiedenen Faktoren in Binnengew?ssern dient, wird beschrieben. Die Abb. 1, 2, 3 und 4—die beiden letzteren ausführlicher—veranschaulichen den Arbeitsmechanismus des Ger?ts. Das vorliegende Sch?pfger?t besteht aus sechs kleineren Ger?ten, die in drei verschiedenen Ebenen paarweise um ein zentrales Rohr angeordnet sind, welches sich auf einer zentralen Stange bewegt. Es werden zwei Beispiele von Schichtungen angeführt, welche mit diesem Sch?pfger?t gefunden wurden. Tab. 1 zeigt die Schichtung von O2, H2S und in der chemoklinen Region eines kleinen meromiktischen Sees. Tab. 2 zeigt das Redoxpotential unmittelbar über der Schlammoberfl?che eines kleinen holomiktischen Sees.相似文献
16.
Generating ground motion by two new techniques of adding harmonic wave in the time domain and approximating to response spectrum as a whole 总被引：2，自引：0，他引：2
ＧｅｎｅｒａｔｉｎｇｇｒｏｕｎｄｍｏｔｉｏｎｂｙｔｗｏｎｅｗｔｅｃｈｎｉｑｕｅｓｏｆａｄｄｉｎｇｈａｒｍｏｎｉｃｗａｖｅｉｎｔｈｅｔｉｍｅｄｏｍａｉｎａｎｄａｐｐｒｏｘｉｍａｔｉｎｇｔｏｒｅｓｐｏｎｓｅｓｐｅｃｔｒｕｍａｓａｗｈｏｌｅＣＨＡＮＧ... 相似文献
17.
Résumé On commence par définir le creusement et le comblement d'une fonctionp(, t) du tempst et des points (, ) d'une surface régulière fermée en se donnant, sur cette surface, un vecteur vitesse d'advection ou de transfert
tangent à . Le creusement (ou le comblement) est la variation dep sur les particules fictives se déplaçant constamment et partout à la vitesse
, A chaque vecteur
et pour un mêmep(, ,t) correspond naturellement une fonction creusementC (, ,t) admissible a priori; mais une condition analytique très générale (l'intégrale du creusement sur toute la surface fermée du champ est nulle à chaque instant), à laquelle satisfont les fonctions de perturbation sur les surfaces géopotentielles, permet de restreindre beaucoup la généralité des vecteurs d'advection admissibles a priori et conduit à des vecteurs de la forme:
, oùT
est un scalaire régulier, () une fonction régulière de la latitude ,
le vecteur unitaire des verticales ascendantes etR/2 une constante. Ces vecteurs sont donc une généralisation naturelle des vitesses géostrophiques attachées à tout scalaire régulier. Dans le cas oùp(, ,t) est la perturbation de la pression sur la surface du géoïde, le vecteur d'advection par rapport auquel on doit définir le creusement est précisément une vitesse géostrophique: on a alors ()=sin etT
un certain champ bien défini de température moyenne.On déduit ensuite une formule générale de géométrie et de cinématique différentielles reliant la vitesse de déplacement d'un centre ou d'un col d'un champp(, ,t) à son champ de creusementC (, ,t) et au vecteur d'advection
correspondant. Cette formule peut être transformée et prend la forme d'une relation générale entre le creusement (ou le comblement) d'un centre ou d'un col et la vitesse de son déplacement, sans que le vecteur d'advection
intervienne explicitement. On analyse alors les conséquences de ces formules dans les cas suivants: 1o) perturbations circulaires dans le voisinage du centre; 2o) perturbations ayant, dans le voisinage du centre, un axe de symétrie normal ou tangent à la vitesse du centre; 3o) évolution normale des cyclones tropicaux.Finalement, on examine les relations qui existent entre le creusement ou le comblement d'un champ, le vecteur d'advection et la configuration des iso-lignes du champ dans le voisinage d'un centre.Ces considérations permettent d'expliquer plusieurs propriétés bien connues du comportement des perturbations dans différentes régions.
Communication à la 2ème Assemblée de la «Società Italiana di Geofisica e Meteorologia» (Gênes, 23–25 Avril 1954). 相似文献
Summary The deepening and filling (development) of a functionp(, ,t) of the timet and the points (, ) of a regular closed surface is first of all defined, in respect to a given advection or transfer velocity field tangent to , as the variation ofp on any fictitious particle moving constantly and everywhere with the velocity . For a givenp(, ,t) and to any there corresponds a well defined development fieldC (, ,t). All theseC fields are a priori admissible, but a very general analytical condition of the perturbation fields in synoptic meteorology (the integral of the development fieldC (, ,t) on any geopotential surface vanishes at any moment), leads to an important restriction to advection vectors of the form: , whereT is any regular scalar, () any regular function of latitude, the unit vector of the ascending verticals andR/2 a constant. These vectors are a natural generalisation of the geostrophic velocities attached to any regular scalar. Whenp(, ,t) is the pressure perturbation at sea level, its development must be defined in respect to a geostrophic advection vector belonging to the above defined class of vectors with ()=sin andT a well defined mean temperature field.A general formula of the differential geometry and kinematics ofp(, ,t) is then derived, giving the velocity of any centre and col of ap(, ,t) as a function of the advection vector and the corresponding development fieldC (, ,t). This formula can be transformed and takes the form of a general relation between the deepening (and filling) of a centre (or a col) of ap(, ,t) and its displament velocity, the advection vector appearing no more explicitly. A detailed analysis of the consequences of these formulae is then given for the following cases: 1o) circular perturbations in the vicinity of a centre; 2o) perturbations having, in the vicinity of a centre, an axis of symmetry normal or tangent to the velocity of the centre; 3o) normal evolution of the tropical cyclones.Finally, the relations between the developmentC (, ,t) of a fieldp(, ,t), the advection velocity vector and the configuration of the iso-lines in the vicinity of a centre are analysed.These theoretical results give a rational explanation of several well known properties of the behaviour of the perturbations in different geographical regions.
Communication à la 2ème Assemblée de la «Società Italiana di Geofisica e Meteorologia» (Gênes, 23–25 Avril 1954). 相似文献
18.
Ferdinand Hesek 《Studia Geophysica et Geodaetica》1970,14(4):414-420
Zusammenfassung Der Artikel hatte zur Aufgabe den Einfluss von Ver?nderung Beobachtungs-Intervalls auf die Konzentration der passiven, von
erh?hter und steitiger Punktquelle ausgelassenen Substanz auszudrücken. Zu diesem Zwecke wurde ein Modell der sog, nichtstation?ren
Rauchspur—einer durchschnittlichen Rauchspur im Messintervall T—konstruiert. Man setzt voraus, dass die Verteilung von Teilchen
in der nichtstation?ren Rauchspur eine Gauss'sche ist mit der Dispersion
in den Richtungen y, z. Für die Dispersion
wurde die Beziehung (15) abgeleitet. Analoge Beziehung gilt auch in der Richtung z. Wenn uns die Auslenkung der Achse der
nichtstation?ren Rauchspur von der Achse der station?ren Rauchspur, der Geraden (t,O, H), bekannt ist, so k?nnen wir die Konzentration qT(t,y,z) explizit ausdrücken.
Address: Dúbravská cesta 4, Bratislava-Patr?nka. 相似文献
Address: Dúbravská cesta 4, Bratislava-Patr?nka. 相似文献
19.
A seismic refraction investigation across the southern part of the Oslo Rift has been made, based on quarry blasts at three localities. The study shows a three-layered crust with the followingP-wave velocities:
.
the upper mantleP-wave celocity, is 8.07 km/s. The velocity-depth relationship for the uppermost crust, obtained by solving the Wiechert-Herglotz integral equation numerically, shows a continuously decreasing velocity gradient in the region of the Oslo Rift which approaches zero at a depth of 9 km, the corresponding increase in theP-wave velocity being from 5.55 km/s to 6.34 km/s. The interface separating the subsurface layer (
=6.60 km/s) from the uppermost layer
, interpreted as the Conrad discontinuity, is essentially horizontal in the investigated part of the Oslo Rift at a depth of approximately 15 km. A deep crustal layer with aP-wave velocity of 7.10 km/s appears to be related to the rift, though the top of this layer extends somewhat eastwards beneath the Precambrian rocks from the southern part of the rift at a depth of approximately 20 km. The Moho discontinuity is elevated beneath the Oslo Region compared with the surrounding area. A broad regional gravity high of about 45 mgal is observed along the entire rift zone. It is suggested that this anomaly is caused by the elevation of the sub-Conrad and Moho discontinuities during the rifting processes. 相似文献
20.
A new technique for the treatment of the kinematic dynamo problem is presented. The method is applicable when the dynamo is surrounded by a medium of finite conductivity and is based on a reformulation of the induction equation and boundary conditions at infinity into an integral equation.
We show that the integral operator
involved here is compact in the case of homogeneous conductivity, which is important for both mathematical and numerical treatment. A lower bound for the norm of
then yields a necessary condition for the generation of magnetic fields by kinematic dynamos.
Numerical results are presented for some simple 2-dynamo models.
The far-field asymptotics for stationary and time-dependent field modes are discussed. 相似文献