This is a cropped portion of a data plot showing the solar wind speed and density from December 1999 - December 2000. Please click on image for full view. In that full view, you can see that wind speeds remain between 200-800 km/s. It's possible, but rare, for solar wind to reach speeds above 800 km/s. All data was collected by the SWOOPS instrument. Click on image for full size (75K JPEG) Courtesy of NASA, ESA and LANL (the principal investigator of SWOOPS)

The solar wind is approximately 95% protons or H+ ions (a Hydrogen atom which has lost one electron), 4% alpha particles or He+2 ions (a Helium atom which has lost two electrons) and 1% minor ions (Carbon, Nitrogen, Oxygen, Neon, Magnesium, Silicon and Iron are the most abundant). You can see that solar wind makeup basically mirrors the Sun's makeup which is mostly Hydrogen, then Helium, then Carbon, then Nitrogen, then Oxygen, then Neon, and so on...Scientists assume that on the broad scale, there are no neutral particles or negative ions in the solar wind. The plasma that makes up the solar wind is either a positive ion or a free electron. Also, the solar wind is electrically neutral - it contains an equal numbers of positive and negative charges.

At the orbit of the Earth, the solar wind has an average density of about 6 ions/cm3, compared to 2.5 10^19 molecules/cm3 in the Earth's sea-level atmosphere. That means that solar wind plasma is more rarefied than the best laboratory vacuum on Earth! The density of the solar wind decreases farther out from the Sun, because the particles are spreading out into space. Density is in fact inversely proportional to the square of the distance from the Sun.

Solar wind velocity is normally in the range from 300 to 600 km/s, but some impulsive events like solar flares or CME's can produce speeds over 1000 km/s! Past the Earth's orbit, the solar wind continues with undiminished speed well past the orbit of Pluto. The particles do not slow down until they reach the termination shock within the heliosphere, where the solar wind slows from supersonic to subsonic speeds. Scientists are hoping that the Voyager spacecraft will give more insight into the solar wind's realm of influence as Voyager I & II near the termination shock and the heliopause.

The temperature of solar wind plasma around the Earth is about 150,000°K.

This is a cropped portion of a data plot showing the solar wind speed and density from December 1999 - December 2000. Please click on image for full view. In that full view, you can see that wind speeds remain between 200-800 km/s. It's possible, but rare, for solar wind to reach speeds above 800 km/s. All data was collected by the SWOOPS instrument. Click on image for full size (75K JPEG) Courtesy of NASA, ESA and LANL (the principal investigator of SWOOPS)

The solar wind is made of Hydrogen (95%) and Helium (4%) and Carbon, Nitrogen, Oxygen, Neon, Magnesium, Silicon and Iron (~1%). These atoms are all in the form of positive ions which means they have lost electrons because the temperature is so hot. So really, solar wind is positive ions and the electrons these ions have lost. We call this plasma.

At the orbit of the Earth, the solar wind has an average density of about 6 ions/cm3. This is not very dense at all! Take a look at this picture for comparison with Earth's atmosphere. So even though the solar wind moves incredibly fast (normally in the range from 300 to 600 km/s), it wouldn't even ruffle your hair if you were to stand directly in the midst of a solar wind breeze! But, some explosive events like solar flares or CME's on the Sun can produce speeds over 1000 km/s!

The solar wind goes all the way past Pluto. Scientists hope the Voyager spacecraft will reach the end of the solar wind, the heliopause. Scientists sure are interested to see what the solar wind is like that far out!

The temperature of solar wind plasma around the Earth is about 150,000°K.

This is a cropped portion of a data plot showing the solar wind speed and density from December 1999 - December 2000. Please click on image for full view. In that full view, you can see that wind speeds remain between 200-800 km/s. It's possible, but rare, for solar wind to reach speeds above 800 km/s. All data was collected by the SWOOPS instrument. Click on image for full size (75K JPEG) Courtesy of NASA, ESA and LANL (the principal investigator of SWOOPS)

The solar wind is very hot, 150,000°K! Because it is so hot, it is not a solid or a liquid or even a gas. Solar wind is plasma.

The solar wind is not very dense at all! Take a look at this picture for comparison with Earth's atmosphere. So even though the solar wind moves SUPER fast (normally in the range from 300 to 600 km/s), it wouldn't even ruffle your hair if you were to stand in a solar wind breeze!

The solar wind goes all the way past Pluto. Scientists hope the Voyager spacecraft will reach the end of the solar wind, the heliopause. Scientists sure are interested to see what the solar wind is like that far out!