New concept of space weather

The traditional physical definition of "weather" is: the atmospheric state comprehensively displayed by meteorological elements such as wind, clouds, precipitation, temperature and pressure in an instant or in a short time. Daily weather refers to neutral atmospheric physical images and physical states that occur in the troposphere and affect human life and production, such as cloudy, sunny, rainy, snowy, cold, warm, dry and wet.

Space weather is a concept of near-earth space environment change. It is completely different from the weather in the planetary atmosphere, involving space plasma, magnetic field and radiation. Space weather is usually closely related to the magnetosphere in near-earth space, but it also studies the changes in interplanetary space. In our solar system, space weather is mainly influenced by the wind speed and density of solar wind and the interplanetary magnetic field brought by solar plasma. All kinds of physical phenomena are related to space weather, including geomagnetic storms and substorms, current in the Van Allen radiation belt, ionospheric disturbance and flicker, aurora and current induced by changes in the magnetic field on the earth's surface, etc.

Coronal mass ejections and related shock waves are also important driving forces of space weather, because they can compress the magnetosphere and cause geomagnetic storms. Solar high-energy particles, coronal mass ejections or solar flares are also important driving forces of space weather, because they will destroy spacecraft electronic equipment and threaten the lives of astronauts. Space weather has a far-reaching impact on space exploration and development. The change of geomagnetic field can cause the change of atmospheric density, which leads to the rapid decrease of the altitude of spacecraft in near-earth orbit. Geomagnetic storms caused by solar activities will blind the sensors on spacecraft and interfere with airborne electronic equipment. Understanding the space environment is very important for the design of artificial spacecraft protection system. Magnetic storms will also increase the radiation of flight attendants at high altitude.

Space weather refers to the state change of space environment in near-earth space or from solar atmosphere to earth atmosphere. Different from the concept of weather in the earth's atmosphere (troposphere and stratosphere), space weather describes the changes of background plasma, magnetic field and radiation in space. Most space weather events are driven by the energy carried by the solar wind originating from the near surface of the sun and the solar atmosphere (chromosphere and the surface of the sun). Space weather sometimes refers to the change of environmental state in interplanetary space (in rare cases, interstellar space).

Space weather has two emphases: scientific research and application. The term space weather didn't come into use until the 1990s. Prior to this, the current space weather activities were considered as a part of physics or upper atmospheric physics and space exploration.