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By Edwin Bidwell Wilson

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Extra resources for A Statistical Discussion of Sets of Precise Astronomical Measurements III; Masses of the Stars

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This latter current must ftow down through the ionosphere, and a rough estimate, as will be shown shortly, suggests that this induced current dies out in aminute or two. After that, the raw solar wind ion currentjy remains, passing through the lower part of the 100 km magnetopause. This currentjy is not the current that terminates the magnetic field ofthe earth; the termination is effected by currents across the field lines as in Figure 14. The currentjy generates a new field not considered before.

2. Pancake Distribution A somewhat more artificial problem is to take a distribution of particles confined to the equatorial plane. The particles drift around the earth in the equatorial plane with 90° pitch angles. The easiest way to calculate the inflation of the field is to obtain the currentin the distribution by multiplying the velocity (58) by qN. In this model there is no term wrr. , the same as (63). This result mayaiso be calculated in a different way which will seem to be a bit trickier at first.

With some simple calculations, these considerations can be used to pi ace limits upon the density of the solar wind during active times. For a quiet-day wind, taking a density N = 5/cm 3 and a velocity V = 316 km/sec as representative, the impact pressure lS NMV 2 = 8 X 10- 9 dynes/cm 2 (49) and this just balances the pressure of the field at the stagnation or subsolar point of the magnetopause. The quiet-day balance is achieved at about 10 RE' Now take an extreme case and imagine that the compression ofthe geomagnetic field increases from its quiet-day value to about 100 y.

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A Statistical Discussion of Sets of Precise Astronomical Measurements III; Masses of the Stars by Edwin Bidwell Wilson


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