scholarly journals Inside the Sun: Unsolved Problems

1990 ◽  
Vol 121 ◽  
pp. 5-17 ◽  
Author(s):  
E. Schatzman
Keyword(s):  
Solar Wind ◽  
Planetary System ◽  
Solar Radius ◽  
Accretion Disc ◽  
The Sun ◽  
T Tauri ◽  
History Of ◽  
Strong Gradient ◽  
Rotating Star ◽  
Fast Rotating

AbstractAs it is impossible to approach all the problems concerning the inside of the Sun, a number of questions will not be taken into consideration during the meeting. In this brief overview of the presently unsolved questions I shall insist on some special aspects of the solar properties: the variations of the solar radius, the generation of the solar wind, some interesting effects due to the presence of a strong gradient of 3He, the history of the rotating Sun. The presence of the planetary system suggests that the Sun might have been a T Tauri star, with an accretion disc and may have started on the mains sequence as a fast rotating star. A sketch is given of the possible consequences.

scholarly journals The Principle of Least Interaction Action

1974 ◽  
Vol 3 ◽  
pp. 489-489
Author(s):  
M. W. Ovenden
Keyword(s):  
Solar System ◽  
Planetary System ◽  
Satellite System ◽  
Asteroid Belt ◽  
Correct Prediction ◽  
The Sun ◽  
Approximate Methods ◽  
Satellites Of Jupiter ◽  
History Of ◽  
Minimum Interaction

AbstractThe intuitive notion that a satellite system will change its configuration rapidly when the satellites come close together, and slowly when they are far apart, is generalized to ‘The Principle of Least Interaction Action’, viz. that such a system will most often be found in a configuration for which the time-mean of the action associated with the mutual interaction of the satellites is a minimum. The principle has been confirmed by numerical integration of simulated systems with large relative masses. The principle lead to the correct prediction of the preference, in the solar system, for nearly-commensurable periods. Approximate methods for calculating the evolution of an actual satellite system over periods ˜ 109 yr show that the satellite system of Uranus, the five major satellites of Jupiter, and the five planets of Barnard’s star recently discovered, are all found very close to their respective minimum interaction distributions. Applied to the planetary system of the Sun, the principle requires that there was once a planet of mass ˜ 90 Mθ in the asteroid belt, which ‘disappeared’ relatively recently in the history of the solar system.

scholarly journals Generation and evolution of interplanetary slow shocks

1996 ◽  
Vol 14 (4) ◽  
pp. 375-382 ◽  
Author(s):  
C.-C. Wu ◽  
S. T. Wu ◽  
M. Dryer
Keyword(s):  
Solar Wind ◽  
Mach Number ◽  
Solar Radius ◽  
Time Dependent ◽  
The Sun ◽  
Wave Perturbation ◽  
One Dimensional ◽  
Slow Shock ◽  
Square Wave ◽  
Pass Through

Abstract. It is well known that most MHD shocks observed within 1 AU are MHD fast shocks. Only a very limited number of MHD slow shocks are observed within 1 AU. In order to understand why there are only a few MHD slow shocks observed within 1 AU, we use a one-dimensional, time-dependent MHD code with an adaptive grid to study the generation and evolution of interplanetary slow shocks (ISS) in the solar wind. Results show that a negative, nearly square-wave perturbation will generate a pair of slow shocks (a forward and a reverse slow shock). In addition, the forward and the reverse slow shocks can pass through each other without destroying their characteristics, but the propagating speeds for both shocks are decreased. A positive, square-wave perturbation will generate both slow and fast shocks. When a forward slow shock (FSS) propagates behind a forward fast shock (FFS), the former experiences a decreasing Mach number. In addition, the FSS always disappears within a distance of 150R⊙ (where R⊙ is one solar radius) from the Sun when there is a forward fast shock (with Mach number ≥1.7) propagating in front of the FSS. In all tests that we have performed, we have not discovered that the FSS (or reverse slow shock) evolves into a FFS (or reverse fast shock). Thus, we do not confirm the FSS-FFS evolution as suggested by Whang (1987).

RETHINKING THE HISTORY OF SOLAR WIND STUDIES: EDDINGTON'S ANALYSIS OF COMET MOREHOUSE

2006 ◽  
Vol 60 (3) ◽  
pp. 261-270 ◽  
Author(s):  
Ian T Durham
Keyword(s):  
Solar Wind ◽  
Mathematical Analysis ◽  
Two Dimensions ◽  
Early Career ◽  
First Person ◽  
The Sun ◽  
Royal Observatory ◽  
History Of ◽  
The Creation ◽  
Periodic Comet

Arthur Eddington's very early career is often overshadowed by his later accomplishments. For many years the work he performed at the Royal Observatory, Greenwich, was little studied. In some cases, citations to his work in major journals did not appear for more than three decades. One of his earliest works was a mathematical analysis of the shapes of the envelopes of Comet Morehouse, a non-periodic comet discovered in 1908. Eddington's description of the envelopes, in mathematical terms, as paraboloids projected in two dimensions as parabolas, was not studied in earnest until after his death. Although the primary conclusion of his work has recently been modified, there are several other statements he makes about the source of the creation of these envelopes that suggest he should be acknowledged as the first person to suggest that there is a continuous outflow of ions from the Sun.

scholarly journals The Origin and Early History of the Sun and the Planetary System in the Context of Stellar Evolution

1983 ◽  
Vol 6 ◽  
pp. 15-28 ◽  
Author(s):  
G. H. Herbig
Keyword(s):  
Planetary System ◽  
Axial Rotation ◽  
Early History ◽  
The Sun ◽  
Primitive Earth ◽  
Stellar Astronomy ◽  
History Of ◽  
Solar Type ◽  
Fu Ori ◽  
Orion Trapezium

AbstractA plausible scenario for the early history of the sun can be constructed by combining the results of stellar astronomy with lunar and meteoritic chronologies. The meteorites apparently contain material exposed to two nucleosynthetic events, one about 108 yr and another a few 106 yr before solidification. Following II. Reeves, these are associated with supernovae occurring in star clusters in molecular clouds that formed during passage through successive galactic arm shocks. The Orion Trapezium Cluster may be a modern example; its density is such that encounters between members would have been close enough and frequent enough to have had major effects upon their circumstellar ‘solar nebulae,’ as would recurrent FU Ori-like eruptions of the stars themselves. The lunar bombardment continued for 7 × 108 yr following formation of our sun. If this represented disk cleanup, disks must persist for that long, and hence circumstellar activity may still be in progress around some young stars in the solar vicinity. The observed time decay of axial rotation and surface activity in solar-type stars can be extended backwards, and indicates that the ultraviolet radiation of the young sun would have had major photochemical consequences upon the primitive earth.

1. The Sun, our star

2020 ◽  
pp. 1-41
Author(s):  
Philip Judge
Keyword(s):  
Solar Wind ◽  
Magnetic Fields ◽  
Electric Fields ◽  
Coronal Mass Ejections ◽  
The Sun ◽  
Short History ◽  
Plasma State ◽  
History Of

‘The Sun, our star’ presents a short history of the Sun and its relationship with Earth. While our ancestors worshipped the Sun, we may now take it for granted. Alpha Centauri A, the nearest other Sun-like star, is four light years away, compared to the Sun’s eight light minutes. The Sun and stars are neither solid nor liquid but composed of ionized particles in a plasma state. This plasma can sustain magnetic fields but not electric fields. The Sun exhibits remarkable phenomena such as sunspots, the corona, flares, the solar wind, and coronal mass ejections. Its atmosphere is layered into photosphere, chromosphere, and corona.

The evolution of rotation in the early history of the Solar System

1984 ◽  
Vol 313 (1524) ◽  
pp. 5-18 ◽  
Keyword(s):  
Dipole Moment ◽  
Angular Momentum ◽  
Solar System ◽  
Giant Planets ◽  
Slow Rotation ◽  
The Sun ◽  
Early Solar System ◽  
Slowing Down ◽  
T Tauri ◽  
History Of

Theories that require the co-genetic formation of the Sun and planets have difficulty in explaining the slow rotation of the Sun. An analysis is made of various mechanisms for slowing down the core of an evolving nebula. Two of these involve a high magnetic dipole moment for the early Sun. The first envisages magnetic linkage to an external plasma but requires a dipole moment 10 6 times that of the present Sun. The other is based on the co-rotation of m atter leaving the Sun during a T Tauri stage, and requires a dipole moment 10 4 times the present value. A mechanical process for transferring angular momentum outward involving dissipation in a solar-nebula disc is incapable of giving what is required. Two processes of star formation in a turbulent cloud are discussed. Both are capable of giving a slowly rotating Sun. Various models for producing planets are examined in relation to the spin they would produce. Planets formed from floccules would be spinning quickly but could evolve in such a way as to give observed spins for giant planets and also satellite families. Accretion models are very sensitive to assumptions, and parameters and can be adjusted to explain almost any observation. Protoplanets formed in elliptical orbits would acquire spin angular momentum through solar tidal action and would evolve to give reasonable spin rates and regular satellite families. The various tilts of their spin axes could be explained by interactions between protoplanets in the early Solar System.

scholarly journals Internal dynamics and magnetism of the Sun

1995 ◽  
Vol 10 ◽  
pp. 327-329
Author(s):  
L. Paternò
Keyword(s):  
Angular Momentum ◽  
Angular Velocity ◽  
Initial Conditions ◽  
Sharp Decrease ◽  
The Sun ◽  
Internal Dynamics ◽  
Radial Gradient ◽  
T Tauri ◽  
Angular Momentum Loss ◽  
History Of

The present internal dynamics and magnetism of the Sun have been determined by the initial conditions in the pre-main sequence age, by the angular momentum loss and its redistribution in the interior, and the interaction of motion with magnetic field.The history of the Sun rotation is traced back by observing the present rotation of stars with the same mass as the Sun at earlier evolutionary stages. The present angular momentum of the Sun, as deduced from its internal rotational behavior derived from helioseismological data, appears to be a small percentage of the original one contained in similar mass stars (T Tauri and α Persei). It is not easy to reconcile the sharp decrease in the surface angular velocity, which follows the α Persei phase, with the subsequent soft decrease, taking place after Pleiades phase, unless some very effective mechanism transfers angular momentum from inner to outer regions, where is lost in the solar wind. Such a mechanism is probably magnetic in origin, since purely hydrodynamic instabilities fail to transfer angular momentum at a rate sufficient to determine the presently observed flat radial gradient of the internal angular velocity.

Nanoscale Dust Production at 1 Au; Identification and Tracking with 12 Spacecraft

2020 ◽  
Author(s):  
Hairong Lai ◽  
Yingdong Jia ◽  
Martin Connors ◽  
Christopher Russell
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Enhancement ◽  
Solar Radius ◽  
The Sun ◽  
The Earth ◽  
Complete Test ◽  
Spacecraft Data ◽  
The Magnetic Field ◽  
Field Enhancements

<p>Interplanetary Field Enhancements are phenomena in the interplanetary magnetic field, first discovered near Venus, during an extremely long duration (12 hours) and large size (about 0.1 AU) passage across the Pioneer Venus spacecraft. Three and a half hours later and 21 x 10<sup>6</sup> km farther from the Sun, this structure, somewhat weaker and off to the side of the expected radial path of any solar initiated disturbance, was seen by first Venera 13 and then Venera 14, trailing behind V13. Since this discovery, many smaller such disturbances have been observed and attributed to collisions of small rocks in space at speeds of about 20 km/s at 1 AU and faster, closer to the Sun. All sightings with magnetometers and other space plasma instruments give very precise measurements of the radial structure (of usually the magnetic field), but the scale transverse to the solar radius is poorly defined, as is the temporal evolution of the structure from single spacecraft data.</p><p>On January 16, 2018, near Earth, 12 spacecraft equipped with plasma spectrometers and magnetometers observed the passage of a single Interplanetary Field Enhancement. The magnetic field profiles at the four 1 AU spacecraft were very similar. The profiles were obtained at different times appropriate to their locations. The 4 Cluster spacecraft were closer to the Earth and in a region in which the solar wind had slowed down because of the Earth’s bow wave (shock) in the solar wind. The disturbance in the shocked solar wind occurred at the time expected if the IFE structure had not been slowed by the plasma, but rather had proceeded with the momentum it had prior to the shock crossing. If the disturbance causing particles are small bits of rock (not protons), then they should have kept most of their momentum in crossing the bow shock. We view this as a complete test of the dust producing collisional origin of these Interplanetary Field Enhancements, and a clear demonstration of how the solar wind clears out the dust in the inner solar system produced by the continuing destructive collisional process.</p>

scholarly journals The Secret of the Titius-Bode Law: A New Theory on How Our Planetary System Came Into Existence

2020 ◽  
Vol 11 (4) ◽  
pp. 58
Author(s):  
Hans Merkl
Keyword(s):  
Physical Mechanism ◽  
Planetary System ◽  
Young Stars ◽  
Asteroid Belt ◽  
Slow Rotation ◽  
The Sun ◽  
The Moon ◽  
High Iron Content ◽  
T Tauri ◽  
Dust Disk

Our planetary system still has several unsolved riddles. One of them is the Titius-Bode law. With the aid of this law, it is easy to find the distances of planets from the sun. For many astronomers, this is coincidence. They argue that there is no known physical mechanism that generates a particular sequence of planets’ distances. However, if one investigates the structure of the law, it quickly becomes clear that the Titius-Bode law is directly connected with the formation of planets. Our planets did not come into existence through so-called accretion. At the beginning of its existence, the sun was presumably a T-Tauri star. These are young stars in the process of their formation. They pulsate irregularly, thereby accelerating clouds of plasma in the surrounding dust disk. Each of these eruptions thus generated a planet. This of course goes much more quickly than if they had to be formed from the dust of planetary disks. This new theory not only describes how the planets and the distances of the planets came into existence. It also gives a new description of how the moon came into existence, the cause for large moon craters, the slow rotation of Venus, the formation of the asteroid belt, the high iron content of the planet Mercury, and the sun’s loss of rotational impulse, among other things.

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