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The sun, our star – Part 1

27 Jan

“When pain brings you down, don’t be silly, don’t close your eyes and cry, you just might be in the best position to see the sun shine.”  – Alanis Morisetti

“If I had to choose a religion, the sun as the universal giver of life would be my god.”  
―   Napoleon Bonaparte

Without our star, the Sun, we were not here on this planet, or any form of life we know, it is common knowledge. Its importance is clear in the myths of the sun and of the cycles of nature. Osiris, Adonis, Dionysus, Mithras, Buda, Bachus, Jesus Christ, they all were born on the 25th December, since it is …and they all die around Easter, when nature reborn from the cold winter (in north hemisphere).

Below it is shown the decorative theme in the tomb of Ramesses IX showing the king’s adoration of the sun disk, accompanied by Isis and Nephthys on the lintel over the entrance.

PLASMA: THE FOURTH STATE OF MATTER

To understand our sun we need to recall what is a plasma. The plasma is considered to be the fourth state of matter, after the gas, liquid and solid states. At ambient pressure and temperature, a gas is a good electrical insulator. For example, if we connect two electrodes separated by a few millimeters to an electric generator (let us say, feeding the circuit with 220 Volts), apparently there is no net current crossing the space between them. However, if you do the same experiment, with the electrodes immersed in a gas at a lower pressure, you will notice na electric current across the gas, and at the same time, the gas start to glow with a color that depends on the spectral composition of the gas and the current value and gas pressure (VIDEO 1). The current is mainly transported by free electrons that succeed to cross the gas from one electrode (cathode) to the other (anode) by taking energy from the electric field acting between the two electrodes. We say that the gas become a plasma, a phenomena that currently can be seen almost everywhere (VIDEO 2).

Another type of plasma discharge occurs around high-tension distribution lines that fed sub-stations and cities with electric energy. The electric field near electrodes (the role of electrodes being in this case played by two cables, or by a cable and electrical connection to earth). Electrons are created by several processes and are strongly transported by the field, producing streamers of electrons that originate from the ionization process of molecules and atoms. This type of discharge is called corona discharges, and are accompanied by a characteristic noise, and it is shown in Fig.2. Artificial sunlight can be obtained using small bulbs (for example, with a small drop of Mercury inside a quartz tube filled with a rare gas at a low pressure, typically a few millimeters of Mercury or one hundred pascal, see pressure units here). Seasonal affective disorder can be treated with sun lamp light therapy {1}.

enseignes lumineuses

Fig.1 – Tokyo is full of illuminated advertisements. Image credit: http://whisky.centerblog

When the voltage applied to the electrodes inside the bulb increases, a small current cross the gas, ionizing molecules and atoms (neutral particles) and a feeble luminosity appears – that’s what is called a glow discharge (see VIDEO). The word plasma was coined by Irving Langmuir (1881-1957), a term that ensued from his observations of the separation of the plasma into cell-like regions with boundaries formed by charged particles sheathes, whenever regions with different densities, temperatures, or electromagnetic fields inhomogeneity are present. [1]. In general terms, plasma is a state of matter composed by ions (positive and negative) and free electrons subject to collective Coulonbian forces in a médium composed by neutral particles (atomes and/or molecules).

If the electrons and ions densities are much lower than the desnity of neutral particles, the plasma is said to be weakly ionized (glow discharges, lightning); if, by the contrary, the density of neutral particles is much lower than thecharged particles density, the plasma is said to be strongly ionized (stars, thermonuclear reactors). If ñe    represents the average number density of electrons (average number of electrons per unit of volume) and ñZ is the average number density of ions with ionic positive charge , then the global condition is satisfied:

Globally, the plasma state is characterized by equal number of positive and negative charges.

Eq1

The electromagnetic field is well described by the set of Maxwell’s equations:

Eq2Eq3Eq4Eq5

This set of equations are defined when the Lorentz force is given by:

Eq6

and the constitutive equations are defined by D=εE  and B=μH, relating the electric field vector E and the displacement vector D, and as well the magnetic flux density vector B and magnetic field vector H, while ε and μ are the permittivity and permeability of the medium, and ρ and J are the electric charge and current densities, respectively. m and q are the mass and charge of the particle.

The sun magnetic field gives rise to sunspots, coronal loops, faculae, solar flares, solar wind and prominences, solar cycle, irradiance variability. Usually the magnetic field near the solar surface is measured using the Zeeman effect. Until now, the vast majority of all recordings of the magnetic field still refer to measurements of the Zeeman effect of the photosphere.

Image credit: http://www.daviddarling.info/

Coronal loops. Image credit: http://www.daviddarling.info/

The sun’s magnetic field is responsible for generating self-excited dynamos [2], magnetoconvection phenomena, interaction of radiation with magnetized gas, magnetic reconnection.

The sun rotates around its axis in 26 days (28 days when viewed from the Earth) in the equatorial region, while in the polar regions it takes 37 days (40,5 days when seen from Earth). The spacecraft Mariner II in 1962 detected the solar wind. the speed distribution, direction, temperature, composition, and spatial structure of the solar wind were mapped from a number of spacecraft, mostly sampling at low solar latitudes (few degrees from the plane of the ecliptic). It is the solar wind that stretches the interplanetary magnetic field. The source of the interplanetary sector structure is invariant with time. This means that the same boundary might be observed anew after 27 days. This is just na average value, since the solar wind velocity can modify the time of arrival of a sector boundary in 1 or 2 days.

Faculae, the birghtest region around a sunspot. Image credit: earthobservatory.nasa.gov

Faculae, the brightest region around a sunspot. Image credit: earthobservatory.nasa.gov

What is amazing is the Archimedes spiral that the magnetic field lines of force of the solar wind depict in space, and shown in the document shown below [4].

What scientists found is na Archimedean spiral like figure of the Interplanetary Magnetic Field that reminds the swastika (卐) (Sanskrit: स्वस्तिक), i.e., an equilateral cross with four arms bent at 90 degrees, sacred symbol in Hinduism, Buddhism, and Jainism, which literally means “to be good”, or “being with higher self”.Sun001

fig3-pdf

The Interplanetary magnetic field lines of force separated in sectors, as seen by Mariner II.

lord-ganesha-on-swastika-HG75_l

Swastika, means “to be good”

The resemblance between the IMF and the swastika suggest the following question: Did the ancients had knowledge that have been lost to time?…

Below it is shown the solar structure.

structure

The structure of the sun, our star. Image credit: astro-observer.com

SUN OBSERVATORY

You can check out in real-time the current status of our Sun here:
http://sohowww.nascom.nasa.gov/

To be continued…
REFERENCES:

[1] Mario J. Pinheiro, Plasma: the origin of the word, in Philica.com article 363

[2] Dynamo effect, page of the university of Oregon

[3] Geodynamo theory and simulations, Paul H. roberts and Gary A. Glatzmaier, Rev. Mod. Phys. vol. 72, Nº4, October 2000

[4] Large scale properties of the Interplanetary magnetic field, Kennett H. Schatten, NASA Report

SITES:

{1} Sun lamps.

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Field Physics

23 Jan

When a distinguished but elderly scientist states that something is possible he is almost certainly right. When he states that something is impossible he is very probably wrong – Arthur C. Clarke’s First Law.
Natural science, does not simply describe and explain nature; it is part of the interplay between nature and ourselves. – Werner Heisenberg

PART 1.

In the period 1820-30, Oersted, Ampère and Faraday have shown that electricity and magnetism are two faces of the same coin, they are interrelated phenomena. Their experiments showed that an electric current produced a magnetic field, and that a magnet in motion generates a current flow in a coil of wire.

The science of electromagnetism probably begins when Hoang-ti, the mythical founder of Chinese Empire, construct in 2634 B.C. the first magnetic compass.

Emperor Huang-ti, or the Yellow Emperor. Image credit: wikipedia

Although this invention is often credited to the Chinese, it may be well invented by Northern Europe sailors,

Chinese compass. Image credit: smith.edu

since this device is first described in 1180 by Alexander Neckham, an English monk (1157,1227) [1]. Neckham was born at St. Albans, studied in Paris, and spent the rest of his life at the Augustinain Canos at Cirencester. During his life he compilled a lot of knowledge through the readings of Pliny, Solinus and Cassiodorus. He was a good observer of natural phenomena and wrote numerous books, showing the results of his own observations and moralizing thoughts, one of them is named “Of the Natures of Things”. Neckham was the kind of man that «had no use for war and intrigue» at the second half of the twelfth century, times of development of our intellectual maturity and literature, times when the romance form was born. While the wars rage in Languedoc and Frederick Barbarossa was strugling to unite a patchwork of more than 1600 individual states, each rules by its won prince, others, like Neckham, led their quiet lives, sheltered in some monastery.

Magnesia. Image credit: ne.jp

Lodestone. Image credit: crystal-cure.com

The word magnet is due to the accidental discovery made by a shepherd that lodestones found near the city of Magnesia, in Asia Minor, had the property to attract metals.

Also, the history tells that Thales of Miletus who lives in 600 B.C., considered one of the Seven Wise Men of Greece, observed that when amber is rubbed with a nonconducting fabric it produced an electrical effect. The golden amber was named electron by the Greeks for its sunlight luminosity and was used for jewelery from the earliest times. In 300 B.C., Theophrastus make the following note: “Amber is a stone. It is dug out of the earth in Liguria and has a power of attraction. It is said to attract not only straws and small peces of sticks, but even copper and iron, if they are beaten into thin pieces”. These experimental findings led to distinguish between two kinds of electric charges, the positive (or, in outdated terminology, vitreous, because resulting from electrical phenomena excited by friction on glass), and the negative charges (or resineous, due to friction on sealing-wax). The former explanation of electrical phenomena was based on the hypothesis of the existence of an electrical fluid. Benjamin Franklin (1706,1790), one of the founding fathers of the United States of America, proposed the single fluid theory, that supposes electricity to be a subtle imponderable fluid, existing in all bodies in definite quantities. In order to evaluate the fragility of this explanation, we may add that, according to this view, if a body remains undisturbed, it remains neutral; if by friction or any other process, this quantity is increased, the body is said to be positively electrified, or negatively electrified if, instead, this quantity is diminished. Another outdated theory was the double fluid theory, proposed by Charles Du Fay (1698,1739), a French chemist.

Ambar. Image credit: purajoia.blogspot.

But these theories are referred to as action at a distance theories, because these theories do not speculate about how forces are transmitted thorough space. In addition, as there is any hypothesis about the mass these electric and magnetic fluids might have, they are referred as imponderable fluids. They are similar to the caloric fluid, supposedly responsable by thermal phenomena and the working of thermal machines.For a large number of centuries this knowledge remained without practical consequences, mostly because of the strong authority that Aristotle had on the intellect of the Western world until new ways of thought start to recognize that need to go beyond the metaphysical speculation and entering the realm of the physical investigation.Surprisingly, the contributions of physicians was decisive, with Galen and others using the electric shock provided by the torpedo fish for therapeutic purposes, in particular curing of gout and headaches; William Gilbert (Elizabeth’s physician) is currently considered the founder of electrical science; and we may also add the discovery of Galvani of Bologna.

Michael Faraday, the most extraordinary experimentalist of all times. Im. credit: wikipedia

Michael Faraday, the most extraordinary experimentalist of all times. Im. credit: wikipedia

Action at a distance theories do not provide us with a clear picture of electromagnetic phenomena, but Michell Faraday (1791, 1867) introduced the idea of electric and magnetic fields of force, which improved our ability to understand.

Michael Faraday representation of lines of force in one of his experiments. Image credit: http://www.unizar.es

When James Clerk Maxwell’s theory gained worldwide approval after the experiments made by Heinrich Hertz, the idea of these fields become one of the most fruitful in theoretical physics.

THE STANDARD MODEL

Circa 460 B.C., the Greek philosopher Democritus, asked himself: if I break any piece of matter in half, and keep doing this operation, it will end at some point when we cann’t go no further. This last bit of matter, Democritus called atoms. We should not blame Aristotles because he considered worthless the idea of atom, until John Dalton (1766-1844) in the 1800’s showed through a series of chemical experiments that matter was made of elementary bricks [2].

Elementary particles are organized in groups according to one of their fundamental properties, the spin, which represents an internal rotation and we may figure it as reminescence of the spinning of a billiard ball.

From atoms to quarks...Image credit: hadron.physics.fsu.edu

Particles associated with matter all have spin 1/2. For example, electrons, quarks (which constitute protons and neutrons, the elements of the atomic nuclei) all have spin 1/2. We call them fermions.

Particles associated with forces (electromagnetic, weak, strong forces) have spin 1, the exception is the graviton which has spin 2. They are called bosons.

But how do particles interact to each other? Classical electromagnetism describes this process in terms of a potential or field with source on charges, and this field permeates all the space around the source. Our modern view is that what happens is an exchange interaction, that is, particles interact because they exchange a certain kind of object which carries momentum from one charge to the other; the rate of exchange of momentum is what Newton defined to be the force:

An image of this process that we may give to the layman is the one of two ice-skatters sliding initially in parallel trajectories; when they start to exchange a ball (here, the analog of a boson) to each other, their trajectory starts to diverge, as if a repulsive force was acting on them (see Fig.).

Pictorial explanation for the "repulsive" force between two ice-skaters.

Table 1 shows the four fundamental forces together with their coupling strengths, type of gauge boson, its mass, ranges, and typical interaction time [3].

Properties of Fundamental Interactions.

We may notice that the stonger is the force the bigger is the coupling strength.

PART 2- To be continued…

REF:

[1] Alexander Neckam, De Naturis Rerum, Libri Duo, with the Poem De Laudibus Divinae Sapientiae (Longman, London, 1868)

[2] John Dalton and The Rise of Modern Chemistry, by Sir Henry E. Roscoe (Cassel and Company, Paris, 1901)

[3] Quang Ho-Kim and Xuan-Yem Pham, Elementary Particles and their Interactions (Springer, New York, 1998)

[4] Karl Friedrich Gauss, General Investigations of Curved Surfaces of 1827 and 1825 , Translated with notes and bibliography by Morehaead and Hiltebeitel (Princeton University Press, 1902)

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