The interplanetary material is filled insolar systemOf the solar systemcelestial bodies, such as planets, asteroids and comets all run in between.Interplanetary spaceAlthough it is empty, it is not a vacuum, in which extremely thin gas and a small amount of dust are distributed.In the interplanetary space near the Earth's orbit, each cubic centimeter contains an average of about fivePositive ion(mostly protons) and five electrons.In addition, it is also full of electromagnetic waves from the sun, planets and beyond the solar system.
The ground observation shows that the existence of interplanetary matter is based on: ①Zodiacal light, ② acceleration in comet tail gas.The former is caused by the scattering of sunlight by particles with mass less than 10 grams in interplanetary matter;The latter can be explained by the effect of solar wind.It is clear that the solar wind is the main source of interplanetary matter.The solar wind is a plasma stream emitted from the corona.The corona has a high temperature of one or two million degrees, and even the strong gravity of the sun cannot sustain this hot gas forever.Therefore, in a sense, interplanetary matter can be seen as a thin extension of the corona.
Discovery history
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At the end of the 19th century and the beginning of the 20th century, scientists believed that interplanetary matter came from so-called solar particle radiation, that is, high-energy electrons from the active region of the sun's surface.Later, German scholar Linderman realized that the so-called particle radiation was actually a gas plasma composed of electrons and positive ions.Alvin et al.'s research on the interaction between the sun's high-speed plasma and the earth's magnetic field makes people realize that "particle flow" originates from the solar active region.Due to the rotation of the sun, this charged particle flow frozen in the magnetic field line from the sun hasArchimedes spiralThe shape of.In 1958, Fan Ellen designed the Earth's satellite photogrammetry?NoInterplanetary spaceIt was detected in 1959Earth radiation zone。In 1962, Sailor 2, during its flight to Venus, proved that the solar wind was mainly composed of ionized hydrogen (i.e. electrons and protons), flowing from the sun towards the outer diameter, with a speed range of 350~800 km/s, an average density of 5.4 ions per cubic centimeter, an ion temperature of about 160000 degrees, and a magnetic field strength of 6 × 10 Gauss.During their flight, Pioneers 10 and 11 sent back information about interplanetary space and found that the average speed of the solar wind did not change much within 1-5 astronomical units from the sun, but the range of change was significantly reduced; the average ion temperature was reduced by half; and the average ion density was approximately reduced according to the inverse distance square law.The foil collector used in the Apollo moon landing project and variousSpace probeIt has been found that the interplanetary particles are mainly electrons, protons and nuclei of helium, carbon, nitrogen, oxygen and heavy elements.All these substances are inherent in the solar atmosphere, of which protons and electrons are the most. This is because hydrogen is the most abundant element in the solar atmosphere, while electrons are all substances.These particles are accelerated in the "shining" phase of the solar flare, leaving the sun and spreading outward through the interplanetary magnetic field.The solar wind flows outward at high speed and stops when it meets the interstellar gas.
The direct measurement range of the solar wind is only limited to the interplanetary space within 9 ° near the equator of the sun, and the measurement range of Pioneer 11 can only reach the interplanetary space at 20 ° latitude of the sun.Therefore, the study of the nature of interplanetary space at higher latitudes must rely on comet tail observation and analysis of the interplanetary spaceInterstellar plasmaThe irregularity caused by the "flicker" of radio signals from stars.This high latitude study will provide information on the three-dimensional distribution and physical properties of interplanetary matter.
In addition to the solar wind, the fragmentation of comets, the disintegration of asteroids, meteoroids and cosmic dust all constitute complementary sources of interplanetary material (see meteors).The study of ecliptic light is helpful to understand the distribution of interplanetary matter in the solar system.
