View Full Version : Questions About the Solar Wind

2011-May-01, 08:29 PM
I have some questions about the Solar Wind.

What is the trajectory of the solar wind - is it ballistic, shooting out of the Sun uniformly in all directions radially? Or is it somehow "flowing", like a current or jetstream? I've read that its speed is supersonic, implying that it is largely ballistic, but I'd like to confirm.

What is the Solar Wind composed of? Is it purely protons and electrons, or are there other significant constituents, such as helium nuclei or some such?

I assume that Solar Wind pressure falls off with the square of distance, as does gravitational pull. So, for a solar sail, does that mean at any given radius there should be a characteristic equilibrium value of mass per unit area that allows the sailing force to exactly counter the Sun's gravitational pull? Does anybody know where I can look this up?

2011-May-02, 12:01 AM
Wikipedia likely will help some. Yes falls off approximately as the square of the distance, mostly protons and electrons, but a few protons with one or two electrons and a few helium nuclei with zero, 1, 2 or 3 electrons, plus some rare more massive nuclei, some neutrons and lots of neutrinos. Neil

2011-May-02, 01:11 AM
Solar sails primarily use radiation pressure caused by photons. This pressure also falls off with the square of the distance, so your question is still interesting :). Gravity develops force based on the mass of the sun and that of whatever object you want to suspend (and the distance as you say). The solar sail pressure will be a function of the area of the object that faces perpendicular to the Sun. So there will be no set distance for equilibrium. But for any object and desired distance it should be possible to design a sail with the appropriate area. Ignoring that both the solar wind and photon pressures do vary in cycles and spontaneously.

Perhaps self adjusting sails would be the go.