New notations for magnetic disturbance fields are proposed, based on
the theoretical consideration of the electric current systems by which
they are produced.
A typical magnetic storm begins suddenly when the onrush of the front
of the solar gas is halted by the earth's magnetic field. This effect
(DCF field) is most markedly observed as a sudden increase of the horizontal
component of the earth's field (the storm sudden commencement,
abbreviated to ssc)— like a step function. In many cases, however, the
change of the field during the ssc is more complicated, and different at
different places. Such a complexity superposed on the simple increase
(DCF) is ascribed to a complicated current system generated in the polar
ionosphere (DP current). It is found that the changes of electromagnetic
conditions in the polar regions are communicated, without delay, to lower
latitudes, even down to the equatorial regions. It is inferred that the
equatorial jet is affected by such a change and produces the abnormal
enhancement of ssc along the magnetic dip equator.
From the extensive analysis of several magnetic storms that occurred
during the IGY and IGC, it is suggested that the capture of the solar
particles in the outer geomagnetic field occurs when irregularities
(containing tangled magnetic fields and high energy protons) embedded in
the solar stream, impinge on the earth.. Thus the development of a magnetic
storm depends on the distribution of such irregularities in the stream.
The motions and resulting currents and magnetic fields of such "trapped"
solar particles are studied in detail for a special model. It is inferred
that a large decrease (DR field) must follow the initial increase; it is
ascribed to the ring current produced by such motion of solar protons oi
energy of order 500 Kev. It is proposed that during the storm there
appears a transient 'storm-time1 belt well outside the outer radiation
belt.
It is predicted that the earth's magnetic field is reversed in
limited regions when the ring current is appreciably enhanced. This
involves the formation of neutral lines there. These may be of two
kinds, called X lines or 0 lines according as they are crossed or encircled
by magnetic lines of force. These may be entirely separated or
may be joined to form a loop, called an OX loop. It is shown that one
of them, the X line, which is connected with the auroral ionosphere by
the lines of force, could be the proximate source of th<e particles that
produce the aurora polaris. By postulating the existence of such X-type
neutral lines at about 6 earth radii, an explanation is obtained of the
detailed morphology of the aurora. This includes the auroral zones and
their changes, the nighttime peak occurrence of auroras, their thin
ribbon-like structure and their multiplicity, their diffuse and active
forms and the transition between them (break-up) the required electron
and proton flux, and the ray and wavy structures.
Among the most important phenomena associated with the sudden change
of the aurora from the diffuse to the active form are the simultaneous
appearance of the auroral electrojet and the resulting polar magnetic
disturbances (DP sub-storms). Several typical DP sub-storms are studied
in detail. It is concluded that a westward auroral jet is produced by a
southward electric field. It is shown that an instability of the sheetbeam
issuing from along the X-type neutral line can produce a southward
electric field of the required intensity. The southward electric field
produces an eastward motion of the electrons in the ionosphere. This may
be identified with the eastward motion of an active aurora and with the
westward auroral electrojet.
Besides such large changes- of the field, there often appear various
quasi-sinusoidal changes of the field, much less intense. They are
supposed to be hydromagnetic waves, some of which are generated in the
outer atmosphere and propagated through the ionosphere, where a certain
amount of their energy is dissipated. It is concluded however that Such
a dissipation is not sufficient to produce any appreciable heating of the
ionosphere.Chapter I The electromagnetic environment of the earth : The solar system in the Galaxy ; The sun and the interplanetary space ; The outer atmosphere, the Van Allen radiation belts and the ionosphere ; The earth’s permanent magnetic field ; Introduction to geomagnetic storms and auroras ; The analysis of the earth’s magnetic field – Chapter II The sudden commencement of magnetic storms : Introduction ; The studies of Sc and Si at individual observations ; A theory of the Sc of magnetic storms ; Transmission of the Sc from the inner boundary of the solar steam to the earth’s surface ; The sudden commencement DP currents – Chapter III The ring current and the van allen radiation belts : Introduction ; The motion of charged particles in the earth’s dipole magnetic field ; Electric currents in an ionized gas (general formulae) ; The steady ring current in a dipole field ; The magnetic field produced by the ring current ; The main phase of magnetic storms ; The ring current belt ; Discussion – Chapter IV A neural line discharge theory of the aurora Polaris : Introduction ; The formation of a neutral line ; The motions of charged particles close to a neutral line ; The auroral zones ; Particle injection associated with arcs ; Rayed arcs ; Instabilities of auroras – Chapter V Polar magnetic disturbances : Introduction ; The polar magnetic disturbances of 5 to 6 December 1958 (College, Alaska) ; The polar magnetic disturbances of 29 September 1957 (Worldwide) ; The polar magnetic disturbances of 23 September
1957 ; The eastward motion of auroras and the electric field of polar magnetic disturbances ; The origin of the electric field of polarmagnetic disturbances – Chapter VI Hydromagnetic waves in the ionosphere : Introduction ; Ionospheric heating by hydromagnetic waves connected with geomagnetic micropulsations – Acknowledgements -- ReferencesYe
