On the Magnetic Scattering of Neutrons

forenoon but failed on June 19. Weak transmission by scattered reflections also failed. Absorption of Ftransmission from WSXAL (6060 kc/s, 650 km distant) was greater than normal on June 19. The F2 virtual heights were very high when fz,* began to increase above fp, * from 1400 to 1600 EST June 19. This example of correlation of the condition of the ionosphere with a magnetic storm corroborates previous evidence obtained by us: (1) Disturbed radio conditions correlate much better with disturbances of the Z than with disturbances of the H component. (2) A severe magnetic disturbance beginning during the daytime may show little correlation with radio data while a severe magnetic disturbance before sunrise is accompanied by disturbed radio conditions during the whole of the following day. (3) The disturbed radio conditions include lowered critical frequencies, increased absorption, and increased virtual heights, indicating a diffusion of the ionosphere. (4) During a magnetic disturbance the higher part of the ionosphere is the most disturbed. Although the forces on the neutron due to the second cause have to be assumed to be extremely much weaker than those due to the first cause, they act on distances so much larger that the scattering effect of both on slow neutrons becomes of the same order of magnitude. Treating the interaction due to both causes as small disturbances of the plane waves, which represent the incoming and scattered neutron one readily obtains a formula for the magnetic influence on the scattering process. Let B be the angle between the orientation of p and the direction of incidence of a neutron with velocity' v, yn = JM „/L(e/Mc) (k/4m) ]the magnetic moment of the neutron p, , measured in units of the Bohr magneton, divided by the ratio of masses 3II/m of the neutron and electron and q=ko —kj the difference between the vectors of propagation of incident and scattered wave, both having equal magnitude ko = k~ —2' Mv/k. The cross-section p„per unit solid angle for scattering under an angle 0 against the d'irection of incidence and an azimuth y against the common plane of p and k0 is then given by