Interplanetary Medium

From ages together, humans had always wondered about the space we live in and the planet in which we thrive on and other celestial objects in the sky. So what do we call the empty space that fills in between our planets, stars, asteroids, and other objects in our Solar System? This medium is called the Interplanetary Medium.

The Interplanetary Medium

The interplanetary medium is basically the material that surrounds all the celestial bodies in the Solar System. This medium’s state is described to be a ‘plasma’ which is a superheated form of matter – so hot that the atoms start to turn into ionised gases due to the elimination of electrons at a rapid rate. This plasma is ejected by the Sun’s atmosphere in the form of solar winds, and its concentration is around 5 plasma particles per cubic centimetre near Earth.

Range Of The Interplanetary Medium

The interplanetary medium is said to fill the volume of the Solar System up to the “Heliopause” which is the outermost boundary of the Solar System, almost at a distance of 110 to 160 AU from the sun. The Heliopause is theoretically said to stop the solar wind from entering the interstellar space i.e., it is the boundary between the solar and the stellar winds beyond the Solar System.

Composition Of The Interplanetary Medium

The interplanetary medium mainly consists of these components – 

• Interplanetary dust

• Cosmic rays

• Solar wind

Interplanetary Dust: 

• Being present in relatively small amounts, these dust particles are supposed to have originated from collisions between asteroids, comets, meteoroids, and Kuiper belt objects.

• The size of particles vary and can even be 10,000 times smaller than a millimetre

• On average in a year, 30,000 tons of interplanetary dust particles are estimated to enter Earth’s upper atmosphere

Cosmic Rays:

• The cosmic rays which have been previously detected around the Earth’s atmosphere are found to contain atomic nuclei and electrons of high speed and energy.

• They contain Hydrogen nuclei in major followed by Helium nuclei

• These either originate from the Sun during its elevated activity or from interstellar occurrences like novas and are called galactic cosmic rays.

Solar Wind:

• This is basically a flow of ionised gases containing free electrons and protons that is, plasma

• Its density at the distance of Earth’s orbit is about 5 particles per cubic cm and decreases with distance from the Sun

• The plasma helps in transporting the magnetic fields of force at the Sun’s surface radiating away from it and is also responsible for deflecting the tails of the Earth’s and other planetary magnetospheres and the tails of comets away from the Sun.

Interaction With Planets

The interplanetary medium has different interactions depending on whether a planet holds its own magnetic field or not. 

• Planets with the presence of magnetic field:

• These planets have their own magnetospheres, making them more dominant than that of the Sun. 

• This will either disrupt the flow of solar wind leading it elsewhere or experience small leaks due to solar wind,  causing phenomena such as aurorae and populating the Van Allen Belts with ionised material

• Planets with the absence of magnetic field:

• The solar wind directly impacts the surfaces of these planets due to the absence of magnetic fields

• Hence they tend to accumulate solar wind particles on their surfaces and due to the presence of high energy particles in these, tend to emit radiations faintly at X-ray wavelengths

Observable Phenomena Of The Interplanetary Medium

Various optical phenomena like those mentioned below are caused due to the planetary and interstellar space interactions-

• Zodiacal light: zodiacal light is a band of light in the night sky, is said to be sunlight reflected from the dense comet dust present in the plane of the zodiac or ecliptic in the interplanetary medium

Gegenschein: this is similar to zodiacal light is visible in a dark, moonless night sky and is said to have been caused by dust particles present beyond the Earth’s orbit backscattering the sunlight.

Conclusion

Thus, we can call the interplanetary medium the space which contains the mass and energy which fills the Solar System and is responsible for the various phenomena in the Solar system. Through this article, you will learn a lot of details about the interplanetary medium, its composition and its range. You will also get a brief detail about how planets interact with each other in the interplanetary medium.