interplanetary medium


interplanetary medium

      thinly scattered matter that exists between the planets and other bodies of the solar system, as well as the forces (e.g., magnetic and electric) that pervade this region of space. The material components of the interplanetary medium consist of neutral hydrogen, plasma gas comprising electrically charged particles from the Sun, cosmic rays (cosmic ray), and dust particles (interplanetary dust particle).

      Extremely small amounts of neutral (non-ionized) hydrogen have been detected throughout much of interplanetary space. At the distance of Earth's orbit from the Sun, for example, the concentration of neutral hydrogen is about one atom per 100 cubic cm (6 cubic inches). Some of the neutral hydrogen that enters the solar system from interstellar space is ionized by sunlight and by charge exchange with the plasma emanating from the Sun, called the solar wind.

      The solar wind is a flow of completely ionized gas—ions (chiefly protons (proton)) and electrons (electron)—that continuously expands outward through the solar system from the Sun's corona. Its density decreases with distance from the Sun; at the distance of Earth's orbit, it has a density of about 5 particles per cubic cm (0.06 cubic inch). This outflow of plasma transports the magnetic fields of force present at the surface of the Sun radially away from it. It also is responsible for deflecting the tails of the Earth's and other planetary magnetospheres (magnetosphere) and the tails of comets (comet) away from the Sun.

      Those cosmic rays (cosmic ray) detected in the vicinity of Earth comprise high-speed, high-energy atomic nuclei and electrons. Among the nuclei, the most abundant are hydrogen nuclei (protons; 90 percent) and helium nuclei (alpha particles; 9 percent). Nuclei outnumber electrons about 50 to 1. A minority of cosmic rays are produced in the Sun, especially at times of increased solar activity. The origin of those coming from outside the solar system—called galactic cosmic rays—remains to be conclusively identified, but they are thought to be produced in stellar processes such as supernova explosions.

      Relatively small amounts of dust particles (interplanetary dust particle)—often called micrometeroids—exist in the solar system, most of which appear to be orbiting the Sun in or near the plane of the solar system. Much of the dust is thought to have been produced in collisions between asteroids (asteroid) and in the shedding of material from comets while passing near the Sun. About 30,000 tons of interplanetary dust particles are estimated to enter Earth's upper atmosphere annually.

      The magnetic field lines that are carried outward from the Sun by the solar wind remain attached to the Sun's surface. Because of the Sun's rotation, the lines are drawn into a spiral structure. Closely associated with the interplanetary magnetic field are electric forces (electric charge) that act to attract or repel charged particles.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Interplanetary medium — [ heliospheric current sheet results from the influence of the Sun s rotating magnetic field on the plasma in the interplanetary medium. [http://quake.stanford.edu/ wso/gifs/HCS.html] ] The interplanetary medium is the material which fills the… …   Wikipedia

  • interplanetary medium — noun interplanetary space including forms of energy and gas and dust • Hypernyms: ↑interplanetary space • Part Holonyms: ↑solar system • Part Meronyms: ↑interplanetary dust, ↑interplanetary gas, ↑solar magnetic fiel …   Useful english dictionary

  • Medium — may refer to: Contents 1 Communication 2 Natural science 3 Entertainment …   Wikipedia

  • Interplanetary Magnetic Field — The Interplanetary Magnetic Field (IMF) is the term for the Sun’s magnetic field carried by the solar wind among the planets of the Solar System. [ heliospheric current sheet is a three dimensional form of a Parker spiral that results from the… …   Wikipedia

  • interplanetary dust — noun microscopic particles in the interplanetary medium • Hypernyms: ↑dust • Part Holonyms: ↑interplanetary medium …   Useful english dictionary

  • interplanetary gas — noun a rarefied flow of gas and charged particles (plasma) that stream from the sun and form the solar wind • Hypernyms: ↑plasma • Substance Holonyms: ↑solar wind • Part Holonyms: ↑interplanetary medium …   Useful english dictionary

  • interplanetary space — noun the part of outer space within the solar system (Freq. 3) • Hypernyms: ↑region, ↑part • Hyponyms: ↑interplanetary medium • Part Holonyms: ↑outer space, ↑space …   Useful english dictionary

  • Interplanetary spaceflight — or interplanetary travel is travel between planets within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System. Current achievements in interplanetary travel Remotely… …   Wikipedia

  • Interplanetary dust cloud — The interplanetary dust cloud is cosmic dust (small particles floating in space) which pervade the space between planets in the Solar System and in other planetary systems. It has been studied for many years in order to understand its nature,… …   Wikipedia

  • interplanetary dust particle — ▪ astronomy also called  micrometeoroid,  micrometeorite , or  cosmic dust particle   a small grain, generally less than a few hundred micrometres in size and composed of silicate minerals and glassy nodules but sometimes including sulfides,… …   Universalium


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.