Multiple correlation between auroral and magnetic pulsations: 2. Determination of electric currents and electric fields around a pulsating auroral patch

Abstract

The multiple correlation method has been applied to the study of concurrent auroral and magnetic pulsations on the basis of videotapes of all‐sky television camera auroral records and induction magnetometer records. The results are (1) the ground magnetic pulsations below pulsating auroras are well represented by a regression model where the magnetic change is expressed as a linear combination of auroral luminosity fluctuations at various parts of the sky, (2) the magnetic variation observed at a single station can be broken down into the magnetic contributions from various auroral patches, and subsequently, (3) the magnetic deflections at various ground points below a pulsating auroral form can be estimated even when many pulsating patches appear at the same time. It is also shown that (4) the horizontal magnetic deflections deduced from observations by use of this technique are fully explained by the combination of ionospheric and field‐aligned electric currents which are theoretically expected to be induced in and near a local enhancement of conductivity under the existence of a uniform, ambient electric field. This study thus gives a definite proof that the ground magnetic pulsation which occurs concurrently with auroral pulsations in the auroral oval is the result of successive growth and decay processes of the localized electric currents in and in the vicinity of pulsating auroral forms, which are caused by a conductivity pulsation due to the pulsating precipitation of auroral electrons in conjunction with the convection electric field. The model calculation also predicts the distribution pattern and intensity of the fluctuating electric fields below pulsating auroral patches.

Pc5 pulsations on the ground, in the magnetosphere, and in the electron precipitation: Event of 19 January 2005

“…A similar model for auroral pulsating patches was proposed by Oguti and Hayashi [1984] and Oguti [1986]. A three‐dimensional current system is associated with each patch.…”

Low‐altitude satellite measurements of pulsating auroral electrons

“…The pronounced temporal modulations (few seconds to few tens of second periods) are likely caused by groups of closely spaced individual chorus elements (lower band scattering the high-energy primaries), and these distinct patches may also be associated with field-aligned currents [Arnoldy et al, 1982;Oguti and Hayashi, 1984;Fujii et al, 1985;Hosokawa et al, 2010]. Therefore, the strong temporal modulations within distinct patches likely have upward field-aligned currents associated with them and therefore parallel potential drops which would be preventing the secondaries from leaving both the Southern and Northern Hemispheres, if the potential structure is symmetric.…”

Quantitative Studies of Energetic Particle Precipitation Using Incoherent Scatter Radar.

“…In this case the horizontal convergence or divergence of ionisation due to horizontal drifts and sharp gradients in the ionisation rate, or to sharp gradients in the electric field and hence the horizontal drift, may be important. Oguti and Hayashi (1984) have shown that sharp electric-field gradients are to be expected at the edges of pulsating patches. Another possibility is that we are not measuring true electron density with the EISCAT radar but enhanced scatter due to plasma turbulence (e.g.…”