Heliosphere – the region of the solar space in which the plasma of the solar wind from the Sun is moving from a non-zero velocity. From outside the heliosphere conditionally limited collisionless shock wave is determined by the balance the solar wind pressure on the one hand, on the other – the pressure of the magnetic field and the interstellar medium.
The first 10 billion kilometers solar wind speed is about a million miles an hour. As he encounters the interstellar medium, it is braking and mixing with it. The boundary at which the solar wind slowdown is called the boundary shock wave boundary along which balanced pressure of the solar wind and the interstellar medium, is called the heliopause, the boundary at which the collision of the interstellar medium with the incident solar wind – the bow shock.
The concept of “heliosphere,” is a particular example of a more general phenomenon – Astrosfery (and soon only available for research from the inside). Applied to arbitrary stars in English literature can also be used synonymous with the term “bubble stellar wind.” In this physics of formation and existence of bubbles is essentially the same [citation needed 451 days] physics of the heliosphere.
The solar wind is a stream of particles (atoms ionized solar corona) and fields, in particular, magnetic. As the Sun rotates, making the turn in 27 days, the magnetic field carried by the solar wind, takes the form of a spiral. Earth passing the spiral coils interacts with it its magnetic field, which can lead to magnetic storms.
In March 2005, published the results of measurements made by SOHO. They showed that a region of space filled by the solar wind, has no precise axial symmetry, and has a slightly distorted form, most likely under the influence of the local area obschegalakticheskogo
The heliospheric current sheet
The heliospheric current sheet is a “ripple” in the heliosphere, which is created by the magnetic field of the Sun, rotating and changing its polarity. Current sheet is outside the heliosphere, and is the scale structure of the solar system. Its form it resembles a multilayered skirt ballerina.
The heliospheric current sheet is a surface in the solar system, the intersection of which changes the polarity of the solar magnetic field. This surface extends along the equatorial plane of the Sun and reaches the limits of the heliosphere. The shape of the current sheet is determined by the influence of the rotating magnetic field of the sun on the plasma, which is in the interplanetary space. The thickness of the current sheet is about 10,000 km. In the current sheet there is a weak electrical current (hence the name) – about 10.10 -10 A / m ². Forms part of a current heliospheric current circuit. Sometimes called the heliospheric current sheet interplanetary current sheet
During the rotation of the Sun that its magnetic field coils in a special form of a spiral of Parker, which is a kind of Archimedean spiral and is named after its discoverer Eugene Parker. The magnetic field coil is divided into two parts, the current sheet, a mathematical model which was first developed in the early 70’s. Scrolling spiral magnetic field reverses its polarity and acquires a complex form of wavy spiral folds, more and more resembles a multilayered skirt ballerina.
The cause of the formation of such a complex shape is sometimes called the “effect of a garden hose.” That describes a surface water jet, if you move the hose up and down while turning on its axis. In the case of the role the sun plays a water jet solar wind.
The heliospheric current sheet rotates with the sun, making one revolution in 27 days. During this period, the Earth, along with its magnetosphere, passes through the humps and hollows of the current sheet, interacting with them. Magnetic induction on the surface of the Sun is approximately 10.10 -4 tesla. If the magnetic field was dipolar form, his strength would decrease in proportion to the cube of the distance and near the Earth’s orbit would have been 10.10 -11 tesla. The existence of the heliospheric current sheet leads to the fact that the actual figures in the Earth 100 times.
In accordance with the laws of electrodynamics, the electric current in the current sheet is perpendicular to the magnetic field, ie the current moves almost in a circle near the sun and directed almost radially at large distances. Closes the “circuit” current from the Sun, which is in the direction perpendicular to the equator of the Sun’s poles, then heliopause down to the equator, the heliospheric current layer. The total current in this circuit is approximately 3.109 amps. For comparison, currents, leading to the occurrence of auroras on Earth, about a thousand times weaker and the order one million amperes. The maximum current density in the sheet is about 10.10 -10 A / m ² (10.10 -4 A / km ²).
External structure of the heliosphere
External structure of the heliosphere is determined by the interaction of the solar wind with the flow of particles in interstellar space. Solar wind streams are moving in all directions from the sun around the earth at a speed of several hundred kilometers per second. At a certain distance from the Sun, beyond the orbit of Neptune, this supersonic flow begins to reduce speed. This inhibition occurs in several stages:
The solar wind is a supersonic speed of the solar system. On the so-called boundary shock is a falling velocity of the solar wind to the sound values.
Losing supersonic speed, the solar wind begins to interact with the surrounding interstellar matter. This interaction between the galactic material and moving it to the sun causes the heliosphere that takes the form of drop-shaped, elongated tail in the direction opposite to the movement of the sun. This region of space called the Heliospheric mantle (mantle solar system)
The surface, which limits the heliospheric robe and on which there is a final deceleration of solar wind and mixing it with the oncoming interstellar matter is called the heliopause. It is the boundary of the entire heliosphere.
Movement of the sun in the interstellar medium leads to the fact that in the surrounding interstellar disturbances occur. Similarly, the solar wind at the boundary of the shock wave loses its speed, interstellar wind, moving opposite to the motion of the sun changes its speed in a similar border, called the arc of a shock wave. It is outside the heliosphere, and there is no inhibition of solar and interstellar wind.
The boundary of the shock wave
The boundary of the shock – is the surface inside the heliosphere, which is a sharp slowdown in the solar wind to the sound velocity (relative to the speed of the sun). This is due to the fact that the matter of the solar wind “bumps” on the interstellar matter. Believe that in our solar system the shock boundary is at a distance of 75-90 astronomical units (about 11-13,5 billion km). In 2007, Voyager 2 crossed the shock wave . (In fact, he crossed it five times, because the border is not constant and changes its distance from the Sun as a result of fluctuations in solar activity and substance emitted by the Sun.)
The shock wave arises because solar wind particles travel at the speed of about 400 km / s, while the speed of sound in the interstellar space is about 100 km / s (the exact value depends on the density, and therefore may vary.) Although the interstellar matter has a very low density, it still creates a constant, though slight pressure, which at a certain distance from the sun is enough to slow down the solar wind to the sound velocity. In this place, and a shock wave.
Such boundaries of shock waves can be observed on Earth. The simplest example can be seen by watching the flow of water in the sink. Striking the sink, water jet spreads out in all directions at speeds exceeding the speed of propagation of mechanical waves in the water. Shaped disk of rapidly spreading water is very thin, which is a supersonic flow of the solar wind. At the edges of the disc formed water bank at which the water flows at a rate less than the velocity propagation of mechanical waves.
For more information: the shock wave
The evidence provided by Ed Stone at the meeting of the American Geophysical Union in May 2005, argued that the spacecraft Voyager 1 crossed the shock in December 2004, when he was at a distance of 94 AU from the Sun. This conclusion was made to change the parameters of the magnetic field derived from the unit. Apparatus Voyager 2, in turn, recorded the reverse movement of the particles at a distance of 76 AU in May 2006. this suggests some form of asymmetric heliosphere, the northern half of which is more south.
Interstellar Boundary Explorer satellite attempts to collect additional data on the boundary of the shock wave.
Abroad, the shock wave is the heliopause, where the solar wind, the final braking and blending it with interstellar matter, and beyond – bow shock, the passage of which the particles of the interstellar wind is decelerated, a similar inhibition of the solar wind.
In June 2011, it was announced that due to the research, “Voyager”, it became known that the magnetic field at the edge of the solar system has a structure similar to the foam. This occurs because the magnetized matter and small space objects form local magnetic fields, which can be compared with the bubbles.
Heliospheric mantle – the region heliosphere beyond the shock. It slowed the solar wind is compressed and its motion becomes turbulent. Heliospheric mantle begins at a distance of 80-100 AU from the Sun. However, in contrast to the interior of the heliosphere, the mantle has a spherical shape. Its shape is more like an extended cometary coma, extending in a direction opposite to the movement of the sun. The thickness of the mantle of the incoming interstellar wind is much smaller than the other. The current mission of the Voyager is to collect data on the Heliospheric mantle.
Heliopause – the theoretical boundary at which the solar wind finally braking. His pressure is already unable to squeeze interstellar matter of the solar system and the mixing agent of solar wind with the interstellar.
One hypothesis , between the bow shock and heliopause there is an area filled with hot hydrogen, called hydrogen wall. This wall contains interstellar matter, compressed interaction with the heliosphere. When the particles emitted by the Sun collide with particles of interstellar matter, they lose their speed by converting the kinetic energy into heat, which leads to the formation of the heated gas.
An alternative definition is that the heliopause – is the magnetopause, the boundary that limits the solar magnetosphere, beyond which begins obschegalakticheskoe magnetic field.
The hypothesis states that the sun also creates a shock wave moving through the interstellar matter, as well as a star on the right picture. This shock wave is an arc drawn bow, because of which it gets its second name – arc. It is like a wave appearing on the water surface before the prow of a ship, and there for the same reasons. Bow wave occurs when interstellar matter moves towards the Sun at supersonic speed. “Impact” of the heliosphere, the interstellar wind is slowed down and forms a shock wave similar to a wave that is formed within the heliosphere, the solar wind during braking. NASA experts Robert Nemiroff (born Robert Nemiroff) & Jerry Bonnell (born Jerry Bonnell) believe that the solar bow wave can exist at a distance of 230 AU from the Sun.
Shock, however, may not exist at all. In a study published in the data analysis of the probe IBEX, states that the velocity of the heliosphere through the interstellar matter is not large enough (84,000 kilometers per hour instead of the previously anticipated 95 000) for this. These findings are confirmed by the Voyager data sets.
GALEX space telescope observations showed that the star constellations World China is like a comet’s tail of whom erupted stellar matter, and clearly distinguishable bow shock (English) Russian., Located in the direction of motion of the star through space (at 130 km / s).