Scenario for the formation of vortexlike structures in a presubstorm arc, taking into account changes in the arc height during its evolution

Author:

Safargaleev V. V.12,Sergienko T. I.3,Kotikov A. L.14,Safargaleev A. V.5

Affiliation:

1. Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation, Russian Academy of Sciences

2. Polar Geophysical Institute, Russian Academy of Sciences

3. Swedish Institute of Space Physics

4. Geophysical Center, Russian Academy of Sciences

5. LSR Management Company

Abstract

Activity in a prebreakup auroral arc in the form of vortexlike structures, the appearance/disappearance of which is preceded by an increase/decrease in the brightness of the arc, was studied in the context of a magnetospheric substorm, large-scale ionospheric convection, the situation in the interplanetary medium, and triangulation measurements of the arc height. The structures are observed in the premidnight hours and represent a superposition of two auroral forms: a large-scale bend in the arc that outlines the polar boundary of the diffuse auroras and smaller luminous tongues of luminosity (mini-torches) elongated along the convection on the western slope of the bends. The structures as a whole move against convection, towards substorm activity to the east of the observation area. We attribute the appearance of structures to the propagation of a disturbance deep into the magnetosphere, generated as a result of interaction of the magnetopause with a solar wind inhomogeneity, on the front of which Bz turns southward. The results of triangulation measurements show that the increase in brightness in the prebreakup arc shortly before the appearance of vortexlike structures is accompanied by a decrease in the height of the lower edge of the arc, which we explain by the appearance of a parallel electric field above the arc, which accelerates the precipitating electrons. The role of such a field in the formation of the torchlike structures is discussed in the framework of the interchange instability of the pole boundary of diffuse auroras.

Publisher

The Russian Academy of Sciences

Reference41 articles.

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