Our solar system has a star at the center, known as the Sun. This star emanates a rigorous stream of charged particles, forming an interplanetary space.
A heliosphere is nothing more than an interplanetary space (region of space) created by the Sun and vastly surrounds the same.
Belonging to the astronomical category, the noun Heliosphere (pronounced as hee-lee-uh-sfeer) is a region neighbouring the Sun, over which the effect of solar wind is significantly high.
History and Formation
The word heliosphere is derived from the Greek word helios, meaning the Sun.
The formation process of the sun heliosphere is not complex but definitely takes over a millennia.
Initial speculations about the existence and nature of the solar system heliosphere, begin in and around 1955 by a physicist, Leverett Davis.
Early credit for the existence of the heliosphere was attributed to the origin of cosmic rays. Back in 1955, 'solar wind' was called the solar corpuscular radiation and it was known to be an essential element in the mere presence of the sun's heliosphere.
An explanation was given, which if translated in simpler terms would mean that the solar corpuscular radiation whisks a spherical bubble that continues to expand over the years, circumferencing the solar system. Apparently, that 'spherical bubble' is the heliosphere.
Conditions regarding the exception of this solar process are also stated, the most acceptable of them being: the continuous expansion of the solar system heliosphere must stop if there is a pressure created in the interstellar medium.
NASA, also explains the formation of the heliosphere as the result of the magnetic flux created by the solar wind, but it adds a few more reasons as to why this must be so. After the sun sends out the solar wind (in the form of constant flow of charged particles), it (supposedly) travels past all the 8 planets of our solar system to some three times the distance to Pluto, after which it eventually gets obstructed by an interstellar medium, a process scientifically known as the termination shock.
Structure of Heliosphere
Heliospheric research has been in action for the past few decades. Attempts to provide information about the exact structure of the solar system heliosphere is made by numerous researchers, physicists, and scientific organizations.
Not surprisingly, the heliosphere is not actually a perfect sphere in its perception. The shape and size of the sun heliosphere are fluid, mainly because of the equally fluid composition and nature of the solar wind and the interstellar medium (ISM).
Broadly, the shape and size of the heliosphere are dependent upon 3 individual and interdependent solar phenomena, i.e, the comprehensive motion of the heliosphere and the Sun, the solar wind, and the interstellar medium (ISM), the last two being fluid, as mentioned earlier.
If you’re familiar with the shape of a comet, then assuming the shape of a heliosphere will not be as tough. The motion of the heliosphere through the fluxional medium of the ISM results in the same.
Some Components that Complete the Structure of a Heliosphere are:
Heliospheric Current Sheet: The rotating magnetic field of the Sun produces a ripple in the heliosphere, known as the heliospheric current sheet. Said to resemble a Ballerina’s skirt, the heliospheric current sheet is by far the largest structure in the solar system.
Heliosheath: Afar the termination shock, there lies a region of the heliosphere, known as the heliosheath. Lying approximately 80 to 100 AU from the Sun, the heliosheath is shaped like a coma.
Heliopause: This is the region, where the strength of the solar wind declines dramatically, making it difficult for the wind to fight and push back the winds of the surrounding stars (stellar winds). It is a theoretical boundary where the ISM meets the solar wind to hamper its speed.
Heliotail: As the name suggests, heliotail is the tail of the heliosphere, and can be understood as a region where the solar wind marks its exit from the heliosphere, attributing to the charge exchange. NASA’s IBEX recently found the shape of heliotail similar to that of a four-leaf clover.
The boundaries of the heliosphere are thought to extend about 9-10 billion miles from the Sun afar the orbit of Pluto. In this giant spherical bubble, the solar wind is the main component within the mixture of electrically neutral gas, ionized gas, and interstellar dust that are widely known to form our solar system’s local galactic environment.
The Heliosphere is a beautiful creation of nature and observing it might be one of the greatest gifts for space-lovers. In doing so, interplanetary spacecraft such as Pioneer 10, Pioneer 11, and New Horizons have been successful in getting a step closer to observe the phenomena and are eventually hoping to pass through the heliopause.
Importance of Heliosphere
Known as the ‘protective bubble’ of the earth, the heliosphere is primarily important because of its role in minimizing the harmful effects of external radiations such as high-intensity gamma rays, which are thought to deplete the integral composition of our solar system.
Distance: The solar system heliosphere is at a distance of about 123 AU (11 billion miles) from the Sun.
Location: In the Milky Way Galaxy, a region known as the Orion Arm comprises the sun heliosphere.
Edge: The outermost edge, heliopause, separates the hot solar plasma from the cooler interstellar plasma.
Given the significance and major properties of the heliosphere, more research in the concerned area is demanded to stir up the contemporary knowledge of this universal phenomenon.