APOD Robot wrote:
A Particle Beam Jet forms HH 24
Explanation: If you visit HH 24, don't go near the particle beam jet.
This potential future travel advisory might be issued because the powerful jet
likely contains
electrons and
protons moving hundreds of kilometers per second.
The potential
danger of a particle beam jet of electrons & protons
moving
hundreds of kilometers per second 
seems a little overblown considering that the Earth, itself, sits in
a solar wind of electrons & protons moving hundreds of kilometers per second.
So how does
the density of Herbig-Haro jets compare to the Solar Wind?
A 200 km/s Herbig-Haro jet of density 20,000 cm
-3 produces a dynamic pressure of ~1,300 nPa
versus a solar wind pressure at 1 AU typically in the range of 1–6 nPa (nano Pascals).
(Note:
Solar sails near Earth rely on photon reflection pressures of ~9,000 nPa.)
A Herbig-Haro jet thus would probably present a problem to both
the atmospheres and the dynamics of Oort cloud like objects.
However, a Herbig-Haro jet would present no more harm
to a well clad astronaut than non-relativistic alpha particles would:
http://en.wikipedia.org/wiki/Alpha_particle#Energy_and_absorption wrote:
<<Alpha particles have a lower speed (with a typical kinetic energy of 5 MeV;
the speed is 15,000 km/s, which is 5% of the speed of light) than any other common type of radiation (β particles, neutrons, etc.) [Such
non-relativistic] alpha particles are easily absorbed by materials, and they can travel only a few centimetres in air.
They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometres, equivalent to a few cells deep).>>
http://adsabs.harvard.edu/abs/1999A%26A...342..717B wrote:
Ionization and density along the beams of Herbig-Haro jets
Bacciotti, Francesca; Eislöffel, Jochen
Astronomy and Astrophysics, v.342, p.717-735 (1999)
Abstract:
Physical properties of several well-known Herbig-Haro jets are investigated using an improved version of the spectroscopic diagnostic technique originally developed by Bacciotti et al. The procedure allows one to derive in a model-independent way the hydrogen ionization fraction in regions of low excitation. The ionization fraction, the electron and gas density, and the average excitation temperature are derived for various positions along the flows. We find that the hydrogen ionization fraction, with typical initial values of 20-30%, generally decreases along the whole jet or along parts of the flow, following well-defined recombination laws. These results are consistent with the idea that the gas is initially ionized in the jet acceleration region, and then slowly recombines while traveling away from the source. If shocks along the jet beam are present, they can at most have a minor contribution to the ionization of the gas, as apparent in HH 34 and in the first 45\arcsec of the HH 46/47 jet, where the ionization fraction decreases almost monotonically. In the jets in which re-ionization episodes occur (i.e. HH 24C/E and HH 24G), the ionization fraction suddenly increases and then gently decays downstream of the re-ionization event. Both findings apparently disfavour a mini-bow shock interpretation for the production of the ionization of the beam. The total densities derived from the ratio between the electron density and the ionization fraction range from about 103 to a few 104 cm-3 . Without applying a correction for shock compression, the average mass loss rate varies from 3.8 10-8 (in the HL Tau jet) to 1.2 10-6 Msun yr-1 (in HH24 G), while momentum supply rates vary between 1.6 10-5 (in the HL Tau jet) and 3.1 10-4 Msun yr-1 km s-1 (in HH 24G). Taking shock compression into account, these values may be reduced by a factor 3-5.
http://en.wikipedia.org/wiki/Solar_wind wrote:
<<The solar wind is divided into two components, respectively termed the slow solar wind and the fast solar wind. The slow solar wind has a velocity of about 400 km/s, a temperature of 1.4–1.6×10
6 K and a composition that is a close match to the corona. By contrast, the fast solar wind has a typical velocity of 750 km/s, a temperature of 8×10
5 K and it nearly matches the composition of the Sun's photosphere. The slow solar wind is twice as dense and more variable in intensity than the fast solar wind. The slow wind also has a more complex structure, with turbulent regions and large-scale structures.
The slow solar wind appears to originate from a region around the Sun's equatorial belt that is known as the "streamer belt". Coronal streamers extend outward from this region, carrying plasma from the interior along closed magnetic loops. Observations of the Sun between 1996 and 2001 showed that emission of the slow solar wind occurred between latitudes of 30–35° around the equator during the solar minimum (the period of lowest solar activity), then expanded toward the poles as the minimum waned. By the time of the solar maximum, the poles were also emitting a slow solar wind.
The fast solar wind is thought to originate from coronal holes, which are funnel-like regions of open field lines in the Sun's magnetic field. Such open lines are particularly prevalent around the Sun's magnetic poles. The plasma source is small magnetic fields created by convection cells in the solar atmosphere. These fields confine the plasma and transport it into the narrow necks of the coronal funnels, which are located only 20,000 kilometers above the photosphere. The plasma is released into the funnel when these magnetic field lines reconnect.
The solar wind exerts a pressure at 1 AU typically in the range of 1–6 nPa, although it can readily vary outside that range.
The dynamic pressure is a function of wind speed and density. The formula is: P = 1.6726×10
−6 * n * V
2
where pressure P is in nPa (nano Pascals), n is the density in particles/cm3 and V is the speed in km/s of the solar wind.>>
