Composition and Physical Characteristics
The interplanetary medium includes interplanetary dust, cosmic rays and hot plasma from the solar wind. The temperature of the interplanetary medium is approximately 100K, and its density is very low at about 5 particles per cubic centimeter in the vicinity of the Earth; it decreases with increasing distance from the sun, in inverse proportion to the square of the distance.
The density is variable, and may be affected by magnetic fields and events such as coronal mass ejections. It may rise to as high as 100 particles/cm³.
Since the interplanetary medium is a plasma, it has the characteristics of a plasma, rather than a simple gas; for example, it carries with it the Sun's magnetic field, is highly electrically conductive (resulting in the Heliospheric current sheet), forms plasma double layers where it comes into contact with a planetary magnetosphere or at the heliopause, and exhibits filamentation (such as in aurora).
The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. If space were a vacuum, then the Sun's 10−4 tesla magnetic dipole field would reduce with the cube of the distance to about 10−11 tesla. But satellite observations show that it is about 100 times greater at around 10−9 tesla. Magnetohydrodynamic (MHD) theory predicts that the motion of a conducting fluid (e.g., the interplanetary medium) in a magnetic field, induces electric currents which in turn generates magnetic fields, and in this respect it behaves like a MHD dynamo.
Read more about this topic: Interplanetary Medium
Famous quotes containing the words composition and, composition and/or physical:
“The naive notion that a mother naturally acquires the complex skills of childrearing simply because she has given birth now seems as absurd to me as enrolling in a nine-month class in composition and imagining that at the end of the course you are now prepared to begin writing War and Peace.”
—Mary Kay Blakely (20th century)
“Modern Western thought will pass into history and be incorporated in it, will have its influence and its place, just as our body will pass into the composition of grass, of sheep, of cutlets, and of men. We do not like that kind of immortality, but what is to be done about it?”
—Alexander Herzen (1812–1870)
“... life is moral responsibility. Life is several other things, we do not deny. It is beauty, it is joy, it is tragedy, it is comedy, it is psychical and physical pleasure, it is the interplay of a thousand rude or delicate motions and emotions, it is the grimmest and the merriest motley of phantasmagoria that could appeal to the gravest or the maddest brush ever put to palette; but it is steadily and sturdily and always moral responsibility.”
—Elizabeth Stuart Phelps (1844–1911)