The solar wind is a stream of charged particles (i.e., a plasma) which are ejected from the upper atmosphere of the sun. It consists mostly of high-energy electrons and protons (about 1 keV) that are able to escape the sun's gravity in part because of the high temperature of the corona and the high kinetic energy particles gain through a process that is not well understood at this time.
Many phenomena are directly related to the solar wind, including geomagnetic storms that can knock out power grids on Earth, auroras (e.g., Northern Lights) and the plasma tail of a comet always pointing away from the sun. While early models of the solar wind used primarily thermal energy to accelerate the material, by the 1960s it was clear that thermal acceleration alone cannot account for the high speed solar wind. Some additional acceleration mechanism is required, but is not currently known, but most likely relates to magnetic fields in the solar atmosphere.

Properties
In the heliosphere, the composition of the solar wind is identical to the sun's corona: These components are present as a plasma, consisting of about 95% singly ionized hydrogen, 4% doubly ionized helium, and less than 0.5% other ions (often called minor ions). Carbon, nitrogen, oxygen, neon, magnesium, silicon and iron are the dominant minor ions. The exact composition has been routinely measured on Ulysses and ACE, two spacecraft carrying a Solar Wind Ion Composition Spectrometer. Unexpectedly, the solar wind composition shows substantial variation, likely directly reflecting the physics of the underlying corona. The first detailed composition measurements were performed by Geiss on the moon, which was part of the first Moon-landing. Solar wind was collected using a specially prepared metal-foil and then brought back for analysis. A similar technique was recently pursued using a robotic approach: A sample return mission, Genesis, returned to Earth in 2004 and is undergoing analysis, but it was damaged by crash-landing when its parachute failed to deploy on re-entry to Earth's atmosphere, possibly contaminating the solar samples.

Composition
Near Earth, the velocity of the solar wind varies from 200 to 889 km/s. The average is 450 km/s. Approximately 1×10) years. However, our current understanding of star formation implies that the Sun's solar wind may have been about 1000 times more massive in the distant past, which would seriously affect the history of planetary atmospheres and that of the martian atmosphere in particular.

Velocity and Mass Loss Rate
Since the solar wind is a plasma, it has the characteristics of a plasma, rather than a simple gas. For example, it is highly electrically conductive so that magnetic field lines from the sun are carried along with the wind. The dynamic pressure of the wind dominates over the magnetic pressure through most of the solar system (or heliosphere), so that the magnetic field is pulled into an Archimedean spiral pattern (the Parker spiral) by the combination of the outward motion and the Sun's rotation. Depending on the hemisphere and phase of the solar cycle, the magnetic field spirals inward or outward; the magnetic field follows the same shape of spiral in the northern and southern parts of the heliosphere, but with opposite field direction. These two magnetic domains are separated by a two current sheet (an electric current that is confined to a curved plane). This heliospheric current sheet has a similar shape to a twirled ballerina skirt, and changes in shape through the solar cycle as the Sun's magnetic field reverses about every 11 years.
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 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.

Interplanetary Magnetic Field
Outside the plane of the ecliptic the solar wind is steady and rapid, at speeds between 600 and 800 km/s; this is called the fast solar wind and it is known to emanate from solar coronal holes. In the plane of the ecliptic, near the heliospheric current sheet, the wind is slower, denser, and more variable, with typical speeds between 200 and 600 km/s and daily fluctuations by a factor of two or more. This is called the slow solar wind and its location of origin on the sun is less well known. This dichotomy is particularly true during or near solar minimum. During solar maximum, slow and fast winds are more mixed and can emanate from any latitude.

Fast and slow solar wind

Effects on the planets

Main article: Mercury (planet)#Atmosphere Mercury

Main article: Atmosphere of Venus Venus

Main article: Magnetosphere Earth

Main article: Atmosphere of Mars Mars

Main article: Space weather Outer limits

Magnetopause
Magnetosphere
Ionosphere
Geosphere
Heliosphere
Helium Focusing Cone
Plasmasphere
Shock wave
Solar sail (Note: solar sails are propelled almost entirely due to the force of the sun's EM radiation, not the solar wind)
Parker spiral
Interplanetary Magnetic Field
Stellar wind