Asymmetric ring currents and the low-latitude disturbance daily variation

Abstract

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.

Magnetic signature of the ionospheric disturbance dynamo at equatorial latitudes: “Ddyn”

“…[14] Cummings [1966] modeled the asymmetric ring current (symmetric ring current plus partial ring current) and noted that the asymmetric part of the storm field decays much more rapidly than the symmetric part. The asymmetry of the ring current belt would be centered about 1800 LT.…”

27-day oscillation and asymmetry in low latitude magnetic field disturbance.

“…The time variation of the amplitude of oscillation was diurnal with the maximum a little after the local noon. He suggested that this feature was associated with the asymmetric development of the ring current reported by CUMMINGS (1966), CAHILL (1966) and others.Following the technique of SUGIURA and CHAPMAN (1960), CROOKER and SISCOE (1971) studied the asymmetric part of the low latitude disturbance field. Their data was confined to 12 years of IGY, a period of very high solar activity.…”

“…The time variation of the amplitude of oscillation was diurnal with the maximum a little after the local noon. He suggested that this feature was associated with the asymmetric development of the ring current reported by CUMMINGS (1966), CAHILL (1966) and others.…”

Storm-time longitudinally propagating asymmetric modes at low latitudes

“…Akasofu and Chapman, 1964; Cummings, 1966;Frank, 1970;Love and Gannon, 2010). A remarkable dawn-dusk asymmetry is often observed during main phases of magnetic storms, which is attributed to the partial ring current on the dusk side of the Earth (Akasofu and Chapman, 1964).…”