Ring Current Belt Research Articles

The possible relationship between the auroral breakup and the interchange instability of the ring current

Morphological evidence is presented suggesting that the auroral breakup may be the result of an instability on the boundary of the ring current belt. This suggestion is examined quantitatively by studying the consequences of a dispersion relation which includes the effects of wave particle interactions and the depolarizing effects of a finitely conducting ionosphere in a dipole magnetic field. Assuming reasonable ionospheric and magnetospheric parameters, it is shown that qualitative agreement can be obtained between predicted growth rates and wave-lengths and those observed by the all-sky camera. Connections between the auroral breakup and the polar magnetic substorm and the structure of the magnetospheric tail are suggested.

Possible consequences of the asymmetric development of the ring current belt

The consequences of an asymmetric injection of protons into the magnetosphere are investigated. A guiding center Vlasov equation is solved by a perturbation method with the solution being given in terms of an electric potential. The electric potential is determined by the condition that the drift currents plus the ionosphere currents be divergenceless. The effect of the Earth's rotation also is included. The electric potential and ionsopheric currents are seen to be critically dependent upon the ring current particle energy and ionospheric conductivity. The computations indicate substantial transfer of charge between the magnetosphere and ionosphere in auroral zone locations. The computations suggest that the ring current may have an important role in auroral processes.

Ionospheric heating associated with the main-phase ring current

Heating caused by an asymmetry in the main-phase ring current belt is examined. The heating mechanism is the joule dissipation of the ionospheric current system associated with the asymmetry. The energy dissipated in the ionosphere, coming from the particle energy contained in the asymmetry, is at a maximum during the main and early recovery phases of a geomagnetic storm. This heating should have a local-time dependence that produces maximum heating near 1800 hours local time. The consequences of a flute (or interchange) instability in the main-phase ring current plasma are also discussed, with particular attention given to the joule heating of the stabilizing currents that flow in the ionosphere. It is concluded that this heating mechanism could deposit enough heat into the ionosphere during a magnetic storm to compete with the normal solar ultraviolet heat input and thus contribute to storm-correlated increases in satellite drag.

Asymmetric ring currents and the low-latitude disturbance daily variation

An asymmetric ring current belt consisting of a symmetric ring current and a superimposed partial ring current system is proposed as the explanation for the low-latitude disturbance daily variation. The magnetic effects of the partial ring current system are derived using a scale model together with a small magnetometer as an analog computer. The magnetic field of an asymmetric ring current belt is derived by assigning an amplitude A to the partial ring current function and an amplitude S to the (constant) symmetric ring current function. The span in longitude, the initial position in local time, and the local-time drift rate of the partial ring current are also adjustable parameters in the asymmetric ring current model. Recovery phases for stations with various longitudes are derived by assuming exponential decays for the partial ring current and symmetric ring current. Measured and computed recovery phases are compared for a few magnetic storms. The comparisons show that even this very simple model of the asymmetric ring current can account for most of the low-latitude disturbance daily variation in the recovery phase.

The connection between the ring current belt and the auroral substorm

The dynamics of the DR2-radiation belt are studied based on the assumption that the DR2-belt is formed from ionization by collision of energetic neutral hydrogen incident on the Earth's upper atmosphere from the direction of the Sun. It is shown how this mechanism can lead to an asymmetric development of the DR2-belt, and it is shown that the asymmetric belt is unstable. The growing instability on the nightside of the DR2-belt can account for the quiet time auroral phenomena. The final stages of the growing instability may then result in a partial disruption of the DR2-belt with some of the belt's magnetic energy being released near the midnight meridian. The auroral activation and breakup is then a manifestation of the partial disruption of the DR2-belt, and it is assumed that in this process the DR2-belt returns to a symmetric configuration. The effect of the ionosphere on magnetospheric motions is examined, and it is found that energy dissipation in the ionosphere can account for the expansion of time of auroral forms. It is also shown how rapidly moving magnetospheric plasmas can account for the bright auroral forms during breakup.

The neutral hydrogen flux in the solar plasma flow—I

It is shown that the photo-ionization by the extreme ultraviolet radiation of the Sun is not likely to change seriously the initial degree of ionization ( x 1, see sections 4 and 5) of the chromospheric plasma during its passage to the Earth's distance. Thus, the plasma ejected from an active region of the Sun can contain an appreciable amount of neutral hydrogen atoms. The development of the main phase of geomagnetic storms and the formation of the ring current belt by such an incompletely ionized solar plasma are discussed.

A source of the energy for geomagnetic storms and auroras

Abstract It is shown that an enhancement of the ionized component of the solar plasma flow or intense turbulent motions contained in it does not introduce substantial energies into the magnetosphere for the ring current belt and auroral substorms. The role of energetic neutral hydrogen atoms is then examined as a possible source of the energy for the ring current belt. The course of the development of auroral substorms over the entire polar region suggests that their energy is not directly introduced into the magnetosphere across the boundary and that a source of their energy is stored in the magnetosphere in an invisible form before it is converted into the substorm energy. Again, the neutral hydrogen atoms are a possible source of the energy, which can be stored in the ring current belt. A possible conversion mechanism of the ring current energy into the auroral substorm energy is suggested.

On the asymmetric development of magnetic storm fields in low and middle latitudes

By a detailed analysis of the disturbance field of certain magnetic storms, including that of 13 September 1957, it is shown that there must be a fairly steady current system, partly external and partly ionospheric, which contributes a substantial portion of the asymmetry in the low and middle latitude storm field, independent of the growth and decay of auroral electrojets. A new model electric current system is presented to account for such an asymmetry. It is suggested that there is a gap in the ring current belt on the night side, and that the ring current is closed through the ionosphere.

Guiding-center approximation in the diamagnetic ring current

Guiding-center approximation for protons in the diamagnetic ring current is valid when two known conditions are satisfied. The critical energies, magnetic rigidities, and pitch angles in the geomagnetic field and the field of the ring current are studied, and the results are applied, as an example, to a model ring current belt proposed by Akasofu and Chapman. It is found that protons with energies 20–40 kev are most likely to be responsible for the belt. The lifetime of these protons in the ring current belt is estimated at 10 days, as observed on the magnetograms. The pp pulsations may, as it seems, be the cause of magnetic scattering of the ring current. This is suggested on the basis of the coincidence of commencements of pp pulsations observed by Troitskaya and the quicker increase of the H force during the main phase at equatorial magnetic stations.

The magnetic moment of model ring current belts and the cutoff rigidity of solar protons

The magnetic moment M/sub R/ of the ring current is calculated for model ring current belts, together with their magnetic fields along an equatorial radius. A graph shows the relation between the ratio M/sub R//M/sub E/(M/sub E/ = the magnetic moment of the earth) and the intensity DELTA H of the ring current field at the equator on the earth's surface. It gives possible ranges of the ratio M/sub R//M/sub E/ for observed values of DELTA H and approximate upper limits of both M/sub R//M/sub E/ and DELTA H for each belt. On the basis of diagram, the entry of low-energy solar protons is discussed, and it is shown that the ring current alone cannot produce the drastic reductions of apparent cutoff rigidity of solar protons observed by detectors carried by balloons and satellites. (auth)