A new theory of magnetic storms

10.1—The distortion of the front surface of the stream produced by the magnetic field as the stream advances towards the Earth has been described briefly in §§6.6 and 7.7; as was there mentioned, we have not discussed in detail the shape of the hollow formed, or the subsequent phenomena occurring therein. We defer this consideration until we have a clearer understanding of the mode in which the ions near the surface of the stream are able to advance into the Earth's field. But certain general features can be deduced, as has been pointed out already in §1.8; the hollow gradually shrinks at a diminishing rate, but we cannot say at present whether it ultimately closes in upon the earth. The preceding analysis suggests that once the velocity of the particles is diminished to, say, 1/10 of its initial value (108 cm/sec), the rate at which the hollow closes up becomes slow.