AboutJames Gort Expertise Questions on observational astronomy, optics, and astrophysics. Specializing in the evolution of stars, variable stars, supernovae, neuton stars/pulsars, black holes, quasars, and cosmology.
Experience I was a professional astronomer (University of Texas, McDonald Observatory), lecturer at the Adler Planetarium, professor of astrophysics, and amateur astronomer for 42 years. I have made numerous telescopes, and I am currently building one of the largest private observatories in Canada.
Publications StarDate, University of Texas, numerous Journal Publications
i have two questions if you will, (not very easy ones, i fear)
1. how long have we known about the heliosheath?
2. can you hazard a guess as to the effect on the earth if the heliosheath did not exist?
thanks
feivel
Answer Hi Feivel.
We've "known" about the heliosheath (theoretically) at least from the late 1950's. In 1957, S. Chapman developed a model of the corona which showed high temperatures and appreciable densities very far from the photosphere. This helped Eugene Parker in 1958 to develop his hydrodynamical model of a continuously expanding coronal plasma (the solar wind). Mariner 2 (in 1962) confirmed the solar wind's speed and particle density. The Parker model indicated the existence of a heliosphere, one part of which is the heliosheath. In 1992, indirect evidence of the heliosheath came from both Voyagers 1 and 2, when radio noise (at 1.8 to 3.5 kHz) was detected, and interpreted as the solar wind particles colliding with interstellar medium. But there was no direct evidence of the heliosheath until December 2004 (and early 2005), when Voyager 1 encountered a significant increase in the strength of the magnetic field carried by the solar wind. This is a direct consequence of the slowing down of solar wind particles when they collide with the interstellar medium.
The heliosheath does protect earth from some galactic cosmic rays, some of which are very energetic. If it did not exist, I would guess that our upper atmosphere could be disturbed (including the ionosphere and ozone layer), and radio communications on earth could be more frequently interrupted. Auroras would be more common. Occasionally, we could experience a cosmic ray storm which would more directly affect terrestrial life, including an increase in cancers.
