Is solar wind positively charged? Many times I heared that the solar wind consists of protons and alpha particles. The both are positively charged, but are there electrons in solar wind?
 A: Generally plasma may be charged in regions smaller than the Debye length. Normally it happens at boundaries. For example, fast electrons tend to fly away and are deposited on a metallic wall first. (It is like electron emission from a hot cathode.) Thus a positive charge is created within some region. The Debye length depends on plasma density and temperature.
A: This is a citation about solar wind properties from:
Hargreaves, J. K. (1995). The solar-terrestrial environment. Cambridge University press

Although most ions are protons ($\mathrm{H}^+$) there is an $\alpha$-particle ($\mathrm{He}^{++}$) component typically amounting to 5% thought exceptionally up to 20% of the total. Heavier atoms total perhaps 0.5%, and, in contrast to the light ions, these are not fully ionized. The number density of positive ions varies between 3 and 10 $\mathrm{cm}^{-3} (3 \times 10^6\;\mathrm{to}\;10^7 \mathrm{m}^{-3})$, the most typical value being 5 $\mathrm{cm}^{-3}$, and there is a similar number of electrons for bulk neutrality.

So the answer (as it was posted before) is NO, the solar wind is overall neutral and YES there are enough electrons to make it so.
A: The lighter electrons are thermally accelerated more than the ions which, being ~ 1800 times heavier, feel the Sun's gravity more than electrons. As Ernesto said, this causes a charge separation which is addressed by the plasma by the setting up of an ambipolar electric field, which acts to retard the electrons and accelerate the ions. This ensures that ~ as many electrons as ions leave the corona, and that an equal amount remain. It must be so, otherwise we would end up with a huge space charge in the solar wind, and the Sun would charge up to the point where it would explode due to Coulomb repulsion.
A: Solar wind is neutral overall else the Sun will become globally very strongly charged and we don't see that happening.
It comprises Electrons/Protons and other particles.
A: The electrons in the solar atmosphere have a lower escape velocity because of their mass. The flux of electrons creates a positive charge in the solar atmosphere that in time creates an ambipolar electric field that then accelerate protons to space. This caused the solar wind to be essentially neutral.
A: Solar wind contains equal amounts of positive and negative charge per unit volume in any given region, but the energies and momenta of the particles do not have to agree. If they all have similar kinetic energy (which seems a good guess but I don't know) then the ones with higher mass will have higher momentum and therefore may have more noticeable effects on whatever they hit.
