Question

The heliopause is now estimated to be something around 100 AU (1 AU = Astronomical unit = about the earth sun distance). See the wikipedia article:

http://en.wikipedia.org/wiki/Heliosphere

From reading a book on NASA's Voyager mission, I learned that before the launch of these spacecraft, the expectation was that the heliopause was at around Jupiter or Saturn's orbit which is about 5 to 10 AU. The book says that as the spacecraft continued to move away from the sun, the space physicists kept increasing their estimate of the position of the heliopause. If it's about an energy or flux balance, then the estimate would be defined by a certain area of the sphere where the heliopause occurs, and since areas are proportional to the square of the radius they got the number wrong by as much as (100/5)2=400. That's a huge underestimate of the sun's output or a huge overestimate of what goes on in interstellar space.

The book doesn't explain why it is that early estimates were wrong and I didn't see an explanation. Perhaps someone knows and will give a nice intuitive explanation for the estimates.

Answer 1

A brief history of the misapplication of magnetohydrodynamics to the analysis of the solar wind:

1959: Soviet satellite Luna 1 directly observed the solar wind for the first time and measured its strength.
http://en.wikipedia.org/wiki/Luna_1

So as of 1959, by direct experimental observation, it was known that the heliopause was at least the radius of the earth or R?.

Pneuman and Kopp 1971 Model: According to a more complex but still simplified MHD [MagnetoHydroDynamics] model of the coronal structure (ISP p. 114-117 etc., the model of Pneuman and Kopp 1971), the dipolar magnetic field lines form closed loops if they originate at solar latitudes of less than about 45