scholarly journals Chemical and Temperature Inhomogeneities on Stellar Surfaces as a Result of an Instability

1986 ◽  
Vol 90 ◽  
pp. 395-396
Author(s):  
A.Z. Dolginov
Keyword(s):  
Hydrogen Plasma ◽  
Heavy Ion ◽  
Space Distribution ◽  
Magnetic Traps ◽  
Rare Elements ◽  
A Value ◽  
Long Time ◽  
Chemical Anomalies ◽  
Ion Species ◽  
The Magnetic Field

Observations show that chemical anomalies are distributed inhomogeneously on Ap star surfaces. The most elaborated explanation of the observations is based on the fact that different ions and atoms are affected by radiative forces of different strengths and, hence, have different diffusion velocities. The diffusion across the magnetic field is a factor of (l + νH2/νC2)−1 slower than along the field (νH is the gyrofrequency and νC is the collision frequency of the ions). It leads to the increasing of the heavy ion number density in regions occupied by magnetic traps.However, such an explanation meets a number of difficulties: a) the conditions holds for the most of ion species only in regions where the optical depth is less than 10−2 if the field H exceeds 105 gs. Although little is known on the depth of the region occupied by the chemical anomalies, there are some indirect indications that it is larger than 10−2; b) The observed dipole field has a value 103−104 gs and does not form traps corresponding to the observed chemical spots which have very complicated configurations; c) the magnetic trap is imperfect. The separation process in the field is assumed to be produced by the diffusion which needs a long time. However, ions can escape from the trap together with the surrounding hydrogen plasma because of various plasma instablished which take much shorter time; d) observed space distribution of rare elements and also of Fe, Cr, Ti contradicts the predictions of the magnetic separation hypothesis (cf. V. Khohlova IAU Coll. No. 90, this volume).

scholarly journals Nonlinear 1-D stationary flows in multi-ion plasmas – sonic and critical loci – solitary and "oscillatory" waves

2006 ◽  
Vol 24 (11) ◽  
pp. 3041-3057 ◽  
Author(s):  
E. M. Dubinin ◽  
K. Sauer ◽  
J. F. McKenzie
Keyword(s):  
Magnetic Field ◽  
Critical Points ◽  
Heavy Ion ◽  
Energy Functions ◽  
Ion Motion ◽  
Stationary Flows ◽  
Energy Integrals ◽  
Ion Cloud ◽  
Ion Species ◽  
The Magnetic Field

Abstract. One-dimensional stationary flows of a plasma consisting of two ion populations and electrons streaming against a heavy ion cloud are studied. The flow structure is critically governed by the position of sonic and critical points, at which the flow is shocked or choked. The concept of sonic and critical points is suitably generalized to the case of multi-ion plasmas to include a differential ion streaming. For magnetic field free flows, the sonic and critical loci in the (upx, uhx) space coincide. Amongst the different flow patterns for the protons and heavy ions, there is a possible configuration composed of a "heavy ion shock" accompanied by a proton rarefaction. The magnetic field introduces a "stiffness" for the differential ion streaming transverse to the magnetic field. In general, both ion fluids respond similarly in the presence of "ion obstacle"; the superfast (subfast) flows are decelerated (accelerated). The collective flow is choked when the dynamic trajectory (upx, uhx) crosses the critical loci. In specific regimes the flow contains a sequence of solitary structures and as a result, the flow is strongly bunched. In each such substructure the protons are almost completely replaced by the heavies. A differential ion streaming is more accessible in the collective flows oblique to the magnetic field. Such a flexibility of the ion motion is determined by the properties of energy integrals and the Bernoulli energy functions of each ion species. The structure of flows, oblique to the magnetic field, depends critically on the velocity regime and demonstrates a rich variety of solitary and oscillatory nonlinear wave structures. The results of the paper are relevant to the plasma and field environments at comets and planets through the interaction with the solar wind.

scholarly journals Phase space growth during RF capture in the GSI heavy ion synchrotron SIS-18

2003 ◽  
Vol 21 (1) ◽  
pp. 85-89
Author(s):  
M. KIRK ◽  
H. DAMERAU ◽  
I. HOFMANN ◽  
O. BOINE-FRANKENHEIM ◽  
P. SPILLER ◽  
...  
Keyword(s):  
Phase Space ◽  
Nuclear Research ◽  
Heavy Ion ◽  
Beam Current ◽  
Current Profile ◽  
Momentum Spread ◽  
European Organization ◽  
Frequency Capture ◽  
A Value ◽  
Ion Species

This study reports on the optimization of the radio frequency capture phase during the operational cycle of the SIS-18 synchrotron at Gesellschaft für Schwerionenforschung, Darmstadt, Germany. The ion species studied were 238U+28 and 238U73+ at an injection energy of 11.4 MeV/u. The longitudinal relative momentum spread derived from Schottky spectra of the coasting beam at injection provides a value of |Δp/p0|full-width ∼ 5 × 10−3. Simulation results from the synchrotron tracking code ESME (FermiLab) were compared with beam-current profile measurements obtained from a pickup. To gain further insight, the Tomography program (European Organization for Nuclear Research) has been used to derive the longitudinal phase space development from waterfall plots of the measured beam current profile, which may then be compared against simulation. Possible causes of this nonadiabaticity are discussed and solutions are proposed.

scholarly journals Broadband Linear Polarization in Ap Stars

1993 ◽  
Vol 138 ◽  
pp. 305-309
Author(s):  
Marco Landolfi ◽  
Egidio Landi Degl’Innocenti ◽  
Maurizio Landi Degl’Innocenti ◽  
Jean-Louis Leroy ◽  
Stefano Bagnulo
Keyword(s):  
Magnetic Field ◽  
Circular Polarization ◽  
Linear Polarization ◽  
Rotation Axis ◽  
Spectral Lines ◽  
Line Of Sight ◽  
Long Time ◽  
Rotating Star ◽  
Ap Stars ◽  
The Magnetic Field

AbstractBroadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.

Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

2002 ◽  
Author(s):  
Masahiro Ishibashi
Keyword(s):  
Fine Structure ◽  
Steady State ◽  
Discharge Coefficient ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Time Intervals ◽  
Critical Flow Rate ◽  
A Value ◽  
Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

Value Configurations

2010 ◽  
pp. 75-97
Author(s):  
Hans Solli-Sæther ◽  
Petter Gottschalk
Keyword(s):  
Value Chain ◽  
Theory And Practice ◽  
Professional Service ◽  
Insurance Companies ◽  
Service Firms ◽  
Professional Service Firms ◽  
Value Network ◽  
A Value ◽  
Long Time ◽  
Contingent Approach

Understanding how firms differ is a central challenge for both theory and practice of management. For a long time, Porter’s (1985) value chain was the only value configuration known to managers. Stabell and Fjeldstad (1998) identified two alternative value configurations. First, a value shop schedules activities and applies resources in a fashion that is dimensioned and appropriate to the needs of client problems, while a value chain performs a fixed set of activities that enables it to produce a standard product in large numbers. Examples of value shops are professional service firms, as found in medicine, law, architecture and engineering. Next, a value network links clients or customers who are or wish to be interdependent. Examples of value networks are logistic companies, telephone companies, retail banks and insurance companies. In this chapter, we apply the contingent approach to systems outsourcing by making the outsourcing decision dependent on the value configuration of the enterprise. We present the three different value configurations – the value chain, the value shop, and the value network. Next, the three different value configurations are compared according to key characteristics, e.g. use of information systems. Then, we take a look at interfirm relations to be able to identify areas for outsourcing, and value configuration as a determinant and predictor for the extent of outsourcing. Finally, we discuss levels of strategy and we introduce the Y-model for IS/IT strategy work.

Wellenabsorption in einem Plasma mit zwei Ionensorten/ Wave Absorption in a Plasma with Two Ion Species

1975 ◽  
Vol 30 (12) ◽  
pp. 1600-1605 ◽  
Author(s):  
H. Schlüter ◽  
G. Schürger
Keyword(s):  
Magnetic Field ◽  
Theoretical Study ◽  
Hydrogen Plasma ◽  
Power Source ◽  
Rf Power ◽  
Neutral Species ◽  
Plasma Cylinder ◽  
Inductively Coupled ◽  
Resistive Loading ◽  
Ion Species

Abstract A theoretical study is carried out for the resistive loading of an rf power source inductively coupled to a plasma cylinder which is immersed in a magnetic field. The plasma is assumed to consist of electrons, two ion and two neutral species. The results are compared with measurements in a hydrogen plasma.

scholarly journals Alinement of Solid Interstellar Particles by a Magnetic Field

1965 ◽  
Vol 7 ◽  
pp. 73-76
Author(s):  
Lyman Spitzer ◽  
R. V. Jones
Keyword(s):  
Magnetic Field ◽  
Basic Mechanism ◽  
Thermal Fluctuations ◽  
Solid Particles ◽  
Large Field ◽  
Interstellar Space ◽  
Interstellar Grains ◽  
Long Time ◽  
Satisfactory State ◽  
The Magnetic Field

For a Long Time the Davis-Greenstein Theory (ref. 1) has been generally considered an adequate explanation of the mechanism responsible for the alinement of interstellar grains and thus for the observed interstellar polarization. The magnetic field required to orient paramagnetic grains is apparently somewhat greater than 10-5 gauss, a relatively large field, but according to reference 2 ferromagnetic grains, proposed by the authors of reference 3, can be oriented by a field of only 10-7 gauss. These results indicate that orientation of interstellar grains is easily explained, even if the magnetic field in interstellar space is relatively weak.Unfortunately, this relatively satisfactory state of affairs has been upset by two developments. Firstly, the basic mechanism of magnetic relaxation proposed by Davis and Greenstein has been questioned by Dr. C. Kittel of the University of California, who has pointed out that the disorienting effect associated with thermal fluctuations of magnetization within the solid particles is ignored in the formulation of this mechanism.

Three-Dimensional Lithography for Rutile TiO2 Single Crystals using Swift Heavy Ions

2003 ◽  
Vol 797 ◽  
Author(s):  
Koichi Awazu ◽  
Makoto Fujimaki ◽  
Yoshimichi Ohki ◽  
Tetsuro Komatsubara
Keyword(s):  
Single Crystal ◽  
Hydrofluoric Acid ◽  
Ion Irradiation ◽  
Three Dimensional ◽  
Heavy Ion ◽  
High Energy ◽  
Stopping Power ◽  
A Value ◽  
Microscopy Measurement ◽  
Electronic Stopping Power

ABSTRACTWe have developed a nano-micro structure fabrication method in rutile TiO2 single crystal by use of swift heavy-ion irradiation. The area where ions heavier than Cl ion accelerated with MeV-order high energy were irradiated was well etched by hydrofluoric acid, by comparison etching was not observed in the pristine TiO2 single crystal. Noticed that the irradiated area could be etched to a depth at which the electronic stopping power of the ion decayed to a value of 6.2keV/nm. We also found that the value of the electronic stopping power was increased, eventually decreased against depth in TiO2 single crystal with, e.g. 84.5MeV Ca ion. Using such a beam, inside of TiO2 single crystal was selectively etched with 20% hydrofluoric acid, while the top surface of TiO2 single crystal subjected to irradiation was not etched. Roughness of the new surface created in the single crystal was within 7nm with the atomic forth microscopy measurement.

Conduction electron diamagnetism in alloys and magnetic-field-dependent dielectric constant of a Fermi gas

1964 ◽  
Vol 280 (1380) ◽  
pp. 85-96 ◽  
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Free Electrons ◽  
Impurity Potential ◽  
First Order ◽  
Dilute Alloys ◽  
A Value ◽  
Field Dependent ◽  
Self Consistency ◽  
The Magnetic Field

The diamagnetism of free electrons in the presence of charged impurity centres which are sufficiently dilute to be non-interacting is calculated to first order in the strength of the potential of the impurity centre. This is done by combining the density-matrix treatment of Landau diamagnetism with the impurity-screening theory o f March & Murray. The susceptibility involves the integrated value of the impurity potential through the crystal, and its first derivative with respect to the magnetic field, B. If the impurity potential is assumed to have a value appropriate to B — 0, then the result for the change in diamagnetic susceptibility on alloying agrees with that of Kohn & Luming (1963). It is shown, however, that the impurity potential is modified in the presence of the magnetic field, and in particular it has angular dependence. The correction to the dia­magnetic susceptibility due to this self-consistency is shown to be significant (25% ). The relevance of the theory to experimental results on dilute alloys is briefly discussed. Finally, as a by-product of the investigation, we have obtained interesting results about the form of the field-dependent dielectric constant.

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