Jupiter's Interior as Revealed by Juno

2020 ◽  
Vol 48 (1) ◽  
pp. 465-489 ◽  
Author(s):  
David J. Stevenson
Keyword(s):  
Magnetic Field ◽  
Local Structure ◽  
Gravity Data ◽  
Heavy Elements ◽  
Blue Spot ◽  
Helium Gas ◽  
Strong Winds ◽  
Gravitational Compression ◽  
Even Harmonics ◽  
Central Concentration

Jupiter is in the class of planets that we call gas giants, not because they consist of gas but because they were primarily made from hydrogen-helium gas, which upon gravitational compression becomes a metallic fluid. Juno, in orbit about Jupiter since 2016, has changed our view: The gravity data are much improved, and the simplest interpretation of the higher order even harmonics implies that the planet may have a diluted central concentration of heavy elements. Jupiter has strong winds extending to perhaps ∼3,000-km depth that are evident in the odd zonal harmonics of the gravity field. Jupiter's distinctive magnetic field displays some limited local structure, most notably the Great Blue Spot (a region of downward flux near the equator), and some evidence for secular variation, possibly arising from the winds. However, Juno is ongoing; it has not answered all questions and has posed new ones. ▪  Juno's mission reveals Jupiter's interior. ▪  A core exists but is diluted by hydrogen. ▪  The mission revealed wind depth and magnetic field.

DESIGN OF A 300 000-Oe TWO-REGION SOLENOID FOR INTERMITTENT OPERATION

1964 ◽  
Vol 42 (7) ◽  
pp. 1343-1357 ◽  
Author(s):  
Richard Stevenson
Keyword(s):  
Magnetic Field ◽  
Cooling System ◽  
Operating Time ◽  
Maximum Power ◽  
Magnet System ◽  
Total Operating Time ◽  
Helium Gas ◽  
Intermittent Operation ◽  
The Magnetic Field ◽  
Capital Expense

This paper contains a design of an aluminum solenoid magnet system capable of producing a field of 300 000 Oe over a bore of 5.8 cm. The magnetic field is produced by a two-region solenoid operated at 15 °K and cooled by compressed helium gas. Details of the structure are described, and calculations are given for all important parts of the cooling system. The magnet is designed for a total operating time at maximum power of at least 40 minutes in a week. The low capital expense of the system makes it suitable for installation in small laboratories.

Observations of the Sun

1997 ◽  
Author(s):  
Douglas V. Hoyt ◽  
Kenneth H. Shatten
Keyword(s):  
Nuclear Physics ◽  
Nuclear Reactions ◽  
Stellar Structure ◽  
Heavy Elements ◽  
Helium Nucleus ◽  
The Sun ◽  
Helium Gas ◽  
A Chain ◽  
The One ◽  
The Universe

Our sun is a typical “second generation,” or G2, star nearly 4.5 billion years old. The sun is composed of 92.1% hydrogen and 7.8% helium gas, as well as 0.1% of such all-important heavy elements as oxygen, carbon, nitrogen, silicon, magnesium, neon, iron, sulfur, and so forth in decreasing amounts (see Appendix 3). The heavy elements are generated from nucleosynthetic processes in stars, novae, and supernovae after the original formation of the Universe. This has led to the popular statement that we are, literally, the “children of the stars” because our bodies are composed of the elements formed inside stars. From astronomical studies of stellar structure, we know that, since its beginnings, the sun’s luminosity has gradually increased by about 30%. This startling conclusion has raised the so-called faint young sun climate problem: if the sun were even a few percent fainter in the past, then Earth could have been covered by ice. In this frozen state, it might not have warmed because the ice would reflect most of the incoming solar radiation back into space. Although volcanic aerosols covering the ice, early oceans moderating the climate, and other theories have been suggested to circumvent the “faint young sun” problem, how Earth escaped the ice catastrophe remains uncertain. How can the sun generate vast amounts of energy for billions of years and still keep shining? Before nuclear physics, scientists believed the sun generated energy by means of slow gravitational collapse. Still, this process would only let the sun shine about 30 million years before its energy was depleted. To shine longer, the sun requires another energy source. We now believe that a chain of nuclear reactions occurs inside the sun, with four hydrogen nuclei fusing into one helium nucleus at the sun’s center. Because the four hydrogen nuclei have more mass than the one helium nucleus, the resulting mass deficit is converted into energy according to Einstein’s famous formula E = mc2. The energy, produced near the sun’s center, creates a central temperature of about 15 million degrees Kelvin (°K).

Numerical Investigation of Laser Oscillation in a Recombining Hydrogen Plasma Interacting with Helium Gas in TPD-I

1985 ◽  
Vol 40 (5) ◽  
pp. 485-489 ◽  
Author(s):  
Toshiatsu Oda ◽  
Utaro Furukane
Keyword(s):  
Magnetic Field ◽  
Numerical Investigation ◽  
Axial Magnetic Field ◽  
Hydrogen Plasma ◽  
Plasma Source ◽  
Threshold Level ◽  
Laser Oscillation ◽  
Quantum Numbers ◽  
Magnetically Confined ◽  
Helium Gas

A numerical investigation on the basis of a collisional-radiative (CR) model has shown that laser oscillation between the levels with the principal quantum numbers i = 2 and 3 can be generated in a recombining hydrogen plasma interacting with a dense helium gas as a cooling medium in TPD-I, which is a magnetically confined quiescent high-density plasma source consisting basically of two parts, namely, the discharge region with the cathode at the center of the cusped magnetic field and the plasma column region with the axial magnetic field. The population inversion is found to exceed significantly a threshold level for the laser oscillation even in the quasi-steady state when the hydrogen plasma with ne = 1013 ~ 1014 cm−3 interacts with the helium gas with a pressure of about 50 Torr.

Evidence for a Universal Relationship Between Magnetization and Changes in the Local Structure

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3726-3728 ◽  
Author(s):  
L. Downward ◽  
F. Bridges ◽  
D. Cao ◽  
J. Neumeier ◽  
L. Zhou
Keyword(s):  
Magnetic Field ◽  
Distribution Function ◽  
Local Structure ◽  
Pair Distribution Function ◽  
Colossal Magnetoresistance ◽  
X Ray ◽  
Polaron State ◽  
Universal Relationship ◽  
High Fields ◽  
X Ray Absorption

X-ray Absorption Fine Structure (XAFS) measurements of the colossal magnetoresistance (CMR) sample La 0.79 Ca 0.21 MnO 3 at high fields indicate a decrease in the width parameter of the pair distribution function, σ, as the applied magnetic field is increased for T near Tc. The change in σ2 from the disordered polaron state varies approximately exponentially with magnetization irrespective of whether the sample magnetization was achieved through a change in temperature or the application of an external magnetic field. This suggests a more universal relationship between local structure and the sample magnetization than was previously indicated.

Helium gas bubble trapped in liquid helium in high magnetic field

2014 ◽  
Vol 104 (13) ◽  
pp. 133511 ◽  
Author(s):  
H. Bai ◽  
S. T. Hannahs ◽  
W. D. Markiewicz ◽  
H. W. Weijers
Keyword(s):  
Magnetic Field ◽  
Liquid Helium ◽  
High Magnetic Field ◽  
Gas Bubble ◽  
Helium Gas

Amplification of even Harmonics in Nonlinear Magnetoimpedance Response of Amorphous Wires in Presence of Longitudinal Alternating Magnetic Field

2012 ◽  
Vol 190 ◽  
pp. 573-576
Author(s):  
N.A. Buznikov ◽  
A.S. Antonov ◽  
A.A. Rakhmanov
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Magnetization Reversal ◽  
Field Amplitude ◽  
Alternating Magnetic Field ◽  
Voltage Response ◽  
Amorphous Wires ◽  
Reversal Process ◽  
Even Harmonics ◽  
Magnetization Reversal Process

A model to describe the influence of longitudinal alternating magnetic field on the nonli-near magnetoimpedance in amorphous wires is proposed. The appearance of even harmonics in the voltage response is shown to arise from the asymmetry in the magnetization reversal process in the wire due to the presence of the longitudinal alternating field. The behavior of even harmonics is analyzed as a function of the external field, alternating field amplitude and current amplitude.

scholarly journals Local Structure of the Galactic Magnetic Field

1967 ◽  
Vol 136 (4) ◽  
pp. 347-363 ◽  
Author(s):  
R. G. Bingham ◽  
J. R. Shakeshaft
Keyword(s):  
Magnetic Field ◽  
Local Structure ◽  
Galactic Magnetic Field

REDUCTION OF MAGNETIC AND GRAVITY DATA ON AN ARBITRARY SURFACE ACQUIRED IN A REGION OF HIGH TOPOGRAPHIC RELIEF

Geophysics ◽  
1977 ◽  
Vol 42 (7) ◽  
pp. 1411-1430 ◽  
Author(s):  
B. K. Bhattacharyya ◽  
K. C. Chan
Keyword(s):  
Magnetic Field ◽  
Integral Equation ◽  
Gravity Data ◽  
Analytical Relationship ◽  
Surface Distribution ◽  
Anomalous Field ◽  
Terrain Effect ◽  
Gravity Map ◽  
Finite Extent ◽  
Topographic Relief

The problem of reduction of magnetic and gravity data, when observed on an arbitrary surface in a region of high topographic relief, is studied with equivalent source representation at the points of observation. It is shown that the analytical relationship between the total magnetic field or the gravity effect and equivalent magnetization or density on an arbitrary observational surface is given by a Fredholm integral equation of the second kind. A rapidly convergent iterative scheme is described for the solution of the integral equation, yielding the surface distribution of magnetization or density. With this distribution, the field at any other surface can be easily computed. Then it has been demonstrated with model examples that the gravity or magnetic field observed on a rough terrain can be accurately reduced to a horizontal plane for processing and interpretation. A new method has been suggested for minimization of terrain‐induced anomalies on a magnetic or gravity map. This method is based on the concept that when the anomalous field observed on an arbitrary surface is continued to a surface parallel to the topography, the terrain effect in the continued field is sharply reduced relative to the field created by bodies of finite extent in the crust. Model examples are presented to show the accuracy and reliability of the method.

scholarly journals Two-dipole model of the asymmetric Sun

2020 ◽  
Vol 10 ◽  
pp. 40
Author(s):  
Bertalan Zieger ◽  
Kalevi Mursula
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Dipole Moments ◽  
Active Regions ◽  
Opposite Polarity ◽  
Heliospheric Current Sheet ◽  
Dipole Model ◽  
Photospheric Magnetic Field ◽  
Photospheric Field ◽  
Even Harmonics

The large-scale photospheric magnetic field is commonly thought to be mainly dipolar during sunspot minima, when magnetic fields of opposite polarity cover the solar poles. However, recent studies show that the octupole harmonics contribute comparably to the spatial power of the photospheric field at these times. Also, the even harmonics are non-zero, indicating that the Sun is hemispherically asymmetric with systematically stronger fields in the south during solar minima. We present here an analytical model of two eccentric axial dipoles of different strength, which is physically motivated by the dipole moments produced by decaying active regions. With only four parameters, this model closely reproduces the observed large-scale photospheric field and all significant coefficients of its spherical harmonics expansion, including the even harmonics responsible for the solar hemispheric asymmetry. This two-dipole model of the photospheric magnetic field also explains the southward shift of the heliospheric current sheet observed during recent solar minima.

scholarly journals Problems of modelization of circumstellar matter out of equilibrium

1994 ◽  
Vol 162 ◽  
pp. 431-433
Author(s):  
J-P. J. Lafon ◽  
E. Huguet
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
Interstellar Medium ◽  
Circumstellar Matter ◽  
Solid Particles ◽  
Heavy Elements ◽  
Circumstellar Envelopes ◽  
Interstellar Gas ◽  
The Core ◽  
Evolved Stars

Circumstellar envelopes of young and evolved stars are responsible for many important phenomena concerning the exchange of matter, angular momentum, energy and maybe magnetic field between the core structure of stars and the interstellar medium. In particular, it is through them that matter enriched in heavy elements flows from evolved stars towards the interstellar gas, submitted to complex ordinary chemistry or photochemistry and condensation into solid particles.

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