The Solar WindThe Sun makes itself known throughout much of the Solar System by the influence the solar wind of high-speed charged particles constantly blowing off the Sun. The solar wind may be viewed as an extension of the outer atmosphere of the Sun (the corona) into interplanetary space. Components of the Solar WindThe solar wind contains roughly equal number of electrons and protons, along with a few heavier ions, and blows continously from the surface of the Sun at an average velocity of about 400 km/second. This is a remarkable velocity: particles in the solar wind from the Sun's surface travel at a speed that would allow them to go from Knoxville to Memphis in less than 2 seconds! This wind leads to a mass loss of more than 1 million tons of material per second, which may seem like a large number, but is insignificant relative to the total mass of the Sun.The Role of the Coronal Magnetic Field
The adjacent image shows an enhanced image of the solar corona. In
this image the magnetic field lines of the corona correspond
approximately to the boundaries between regions of different color (more
info). Notice that in the equatorial regions the field lines traced
by these color boundaries tend to form closed loops, indicating the
trapping of coronal gas. Influence of the Solar Wind on the EarthAs we have already discussed in the section on the Earth, the solar wind can have a large influence on our planet, particularly in times of the active Sun (near sunspot maximum) when the wind is strong and can contain bursts corresponding to flares and coronal mass ejections from the Sun. The solar wind has a significant influence on our ionosphere, the Earth's magnetic field, on Earth's auroras, and on telecommunication systems. For example, there is reason to believe that a burst of particles from a coronal mass ejection detected 5 days earlier by SOHO may have killed the Telstar 401 communications satellite on January 11, 1997 (News Story).Earth's Ionosphere and the SunThe level of activity on the Sun can have a large influence on the Earth's ionosphere, as illustrated in the following animations.
The level of solar activity has similar effects on related phenomena such as Earth's auroras. The "Space Weather" ReportOne can monitor solar data for the last 30 days. This data gives information on solar flares, sunspots, X-ray and radio-frequency fluxes. One can even tune into Today's Space Weather, which gives a "weather report" of current and predicted conditions in space with respect to the solar wind, solar activity, X-ray activity, and related phenomena. For example, here is the space weather outlook that was reported on January 27, 1998:
In this report, the region numbers refer to active areas on the Sun, C and M are classifications of solar flares, and CME stands for a coronal mass ejection. As noted above in conjuction with the ill-fated Telstar 401 satellite, "space weather" may have non-trivial practical consequences.
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