Calculation of the Initial Magnetic Field for Mercury’s Magnetosphere Hybrid Model

Abstract. Magnetic holes (MHs) are depressions of the magnetic field magnitude. Turner et al. (1977) identified the first MHs in the solar wind and determined an occurrence rate of 1.5 MHs/d. Winterhalter et al. (1994) developed an automatic identification criterion to search for MHs in Ulysses data in the solar wind between 1 AU and 5.4 AU. We adopt their criterion to expand the search to the heliocentric distances down to 0.3 AU using data from Helios 1 and 2 and up to 17 AU using data from Voyager 2. We relate our observations to two theoretical approaches which describe the so-called linear MHs in which the magnetic vector varies in magnitude rather than direction. Therefore we focus on such linear MHs with a directional change less than 10º. With our observations of about 850 MHs we present the following results: Approximately 30% of all the identified MHs are linear. The maximum angle between the initial magnetic field vector and any vector inside the MH is 20º in average and shows a weak relation to the depth of the MHs. The angle between the initial magnetic field and the minimum variance direction of those structures is large and very probably close to 90º. The MHs are placed in a high β environment even though the average solar wind shows a smaller β. The widths decrease from about 50 proton inertial length in a region between 0.3 AU and 0.4 AU heliocentric distance to about 15 proton inertial length at distances larger than 10 AU. This quantity is correlated with the β of the MH environments with respect to the heliocentric distance. There is a clear preference for the occurrence of depressions instead of compressions. We discuss these results with regard to the main theories of MHs, the mirror instability and the alternative soliton approach. Although our observational results are more consistent with the soliton theory we favour a combination of both. MHs might be the remnants of initial mirror mode structures which can be described as solitons during the main part of their lifetime.

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A note on disturbances in a layered medium containing a magnetic field

Bulletin of the Seismological Society of America ◽

10.1785/bssa05406a1771 ◽

1964 ◽

Vol 54 (6A) ◽

pp. 1771-1777

Author(s):

D. K. Sinha

Keyword(s):

Magnetic Field ◽

Free Surface ◽

Layered Medium ◽

Present Note ◽

Infinite Medium ◽

The Other ◽

Time Dependent ◽

The Earth ◽

Propagation Of Waves ◽

Initial Magnetic Field

abstract In recent years, Kaliski has contributed a series of papers on the interaction of elastic and magnetic fields and some of them, [1], [2], [3] are concerned with the propagation of waves in a semi-infinite medium either loaded or conditioned otherwise, at its free surface. Such problems, as Kaliski [1] has remarked, may have relevance in the practical seismic problem of detecting the mechanical explosions inside the earth. Moreover, their geophysical implications have also been examined by Knopoff [4[, Cagniard [5], Banos [6], and Rikitake [7]. The present note seeks to investigate disturbances in a medium consisting of two layers (one finite and the other infinite) of elastic medium intervened by a thin layer of vacuum. The vacuum is traversed by an initial magnetic field. The disturbances in the medium are assumed to have been produced by a time-dependent load on the free surface of the medium. The method of Laplace transform has been used to facilitate the solution of the problem.

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HYBRID MODEL STUDIES OF MAGNETIC FIELD DIFFUSION IN HIGH-β PINCHES

Pulsed High Beta Plasmas ◽

10.1016/b978-0-08-020941-8.50053-6 ◽

1976 ◽

pp. 329-334 ◽

Cited By ~ 1

Author(s):

A.G. SGRO ◽

C.W. NIELSON

Keyword(s):

Magnetic Field ◽

Hybrid Model ◽

Model Studies ◽

Field Diffusion

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On the Loss of Angular Momentum from Stars in the Pre-Main Sequence Phase

International Astronomical Union Colloquium ◽

10.1017/s025292110002707x ◽

1970 ◽

Vol 4 ◽

pp. 73-81

Author(s):

Isao Okamoto

Keyword(s):

Magnetic Field ◽

Angular Momentum ◽

Main Sequence ◽

Magnetic Energy ◽

Rotational Velocity ◽

The State ◽

Rotational Instability ◽

Stellar Rotation ◽

Initial State ◽

Initial Magnetic Field

AbstractThe braking of stellar rotation in the wholly convective phase in the pre-main sequence is numerically discussed. The structure of stars in that phase is expressed by a rotating polytrope with an index of 1.5 and the Schatzman-type mechanism is used as the means of loss of angular momentum. The magnetic energy is assumed to change with evolution as H02/8π(R/R0)s, where H0 and R0 are initial magnetic field and radius, and s is a free parameter. The changes of angular momentum, rotational velocity, etc. with contraction are calculated from the initial state, which is taken to be the state when the stars flared up to the Helmholtz-Kelvin contraction. It is shown that the exponent s must be in the range from – 1 to – 3 so that the stars with adequate strength of the initial magnetic field may lose almost all of their angular momenta in a suitable rate if they are initially in the state of rotational instability.Stellar rotation from the time of star formation to the main sequence stage is discussed. Also, the formation of the solar system and other planetary systems is discussed, with respect to the braking.

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On the Possibility of Local Magnetic Field Intensification in Evaporating Chromospheric Solar Flare Plasma

International Astronomical Union Colloquium ◽

10.1017/s0252921100154491 ◽

1989 ◽

Vol 104 (2) ◽

pp. 341-344

Author(s):

V. N. Dermendjiev ◽

G. T. Buyukliev ◽

I. Ph. Panayotova

Keyword(s):

Magnetic Field ◽

Solar Flare ◽

Solar Flares ◽

Local Magnetic Field ◽

Plume Structure ◽

The Subject ◽

Convective Plume ◽

Flare Plasma ◽

Initial Magnetic Field ◽

Moving Vortex

The investigations of plasma motions at the initial phases of solar flares (Antonucci and Dennis, 1983; Doschek, 1983; Watanabe, 1987) suggest evaporation from the chromospheric flaring area. According to de Jager (1983) when seen at the limb the evaporated plasma will look like a “convective plume” and it can be seen separated from heated footpoint areas.The subject of this work is the study of the possibility of forming hydrodynamic structures o-f thermal and starting plume's kind at the time of evaporation of the upper chromosphere in a flaring area. Also the possibility of increasing an initial magnetic field by a periodically moving vortex in a plume structure is investigated.

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A Self-Similar Flow behind a Magnetogasdynamic Shock Wave Generated by a Moving Piston in a Gravitating Gas with Variable Density: Isothermal Flow

Physics Research International ◽

10.1155/2011/782172 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 7

Author(s):

G. Nath ◽

A. K. Sinha

Keyword(s):

Magnetic Field ◽

Shock Wave ◽

Ambient Medium ◽

Initial Density ◽

Power Laws ◽

Variable Density ◽

Ideal Gas ◽

Piston Velocity ◽

Azimuthal Magnetic Field ◽

Initial Magnetic Field

The propagation of a cylindrical (or spherical) shock wave in an ideal gas with azimuthal magnetic field and with or without self-gravitational effects is investigated. The shock wave is driven out by a piston moving with time according to power law. The initial density and the initial magnetic field of the ambient medium are assumed to be varying and obeying power laws. Solutions are obtained, when the flow between the shock and the piston is isothermal. The gas is assumed to have infinite electrical conductivity. The shock wave moves with variable velocity, and the total energy of the wave is nonconstant. The effects of variation of the piston velocity exponent (i.e., variation of the initial density exponent), the initial magnetic field exponent, the gravitational parameter, and the Alfven-Mach number on the flow field are obtained. It is investigated that the self-gravitation reduces the effects of the magnetic field. A comparison is also made between gravitating and nongravitating cases.

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