Japanese Antarctic Research Expedition
Description / Table of Contents:
A meridian scanning photometer was designed for investigating the time and space variations of auroral luminosity. With the aid of the quick-scan auroral photometer data of more than 300 clear night hours recorded at Syowa Station, Antarctica (geomagnetic lat. 69.6°S, long. 77.1°E), the following problems are studied: (1) space and time variation of auroral displays, (2) magnetic field variations associated with the space-time auroral displays, (3) relationships among auroras, magnetic field disturbance, magnetic pulsations, VLF hiss, VLF chorus and GNA during the course of substorms. Various kinds of morphological evidence obtained through the above investigations show that a polar substorm consists of the breakup phase and the post-breakup phase. The breakup phase is characterized by a sudden intensification of auroral arc(s) or band(s) and a rapid poleward movement of the intensified aurora(s) with speed of about 1 km/s (Breakup type aurora). The post-breakup phase is defined as diffused auroras or rays which still remain after the intense breakup type aurora(s) have passed away polewards (Post-breakup type aurora). Generally, the post-breakup aurora(s) move towards the equator side. A breakup type aurora is accompanied by a sharp pulsative geomagnetic disturbance (Breakup magnetic disturbance), while a post-breakup type aurora by a gradual negative bay-shape disturbance (Post-breakup magnetic disturbance). It seems that the sharp pulsative disturbance moves polewards together with the moving breakup aurora, while the gradual negative bay stays with the associated post-breakup aurora(s). Thus, the auroral electrojet can also be classified into AEJ-1, which is an intense and narrow electrojet moving together with the breakup aurora, and AEJ-2, which is a comparatively broad and weak electrojet associated with the post-breakup aurora(s). The auroral breakup phase is accompanied not only by a sharp pulsative geomagnetic disturbance but also by VLF hiss emissions, ULF emissions of PiB type and a sharp CNA phenomenon, while the post-breakup aurora is accompanied by a gradual geo-magnetic bay, a gradual, weak CNA, VLF chorus emissions and ULF emissions of PiC type. With reference to 'the space-time variations in auroras associated with geomagnetic perturbations at Syowa Station, an overall physical picture of dynamic auroral behaviors over the entire polar region is given, as a conclusion.
Type of Medium:
Series available for loan
76 S. : Ill., graph. Darst
Japanese Antarctic Research Expedition : Scientific reports : Series A, Aeronomy 10