Dawn Auroral Breakup at Saturn Initiated by Auroral Arcs: UVIS/Cassini Beginning of Grand Finale Phase

Abstract. The results of coordinated EISCAT and TV-camera observations of a prebreakup event on 15 November 1993 have been considered. The variations of the luminosity of two parallel auroral arcs, plasma depletion on the poleward edge of one of these arcs as well as electron and ion temperatures in front of a westward travelling surge were studied. It was found that a short-lived brightening of a weak zenith arc before an auroral breakup was accompanied by fading of an equatorial arc and, vice versa. A plasma depletion in the E region was detected by the EISCAT radar on the poleward edge of the zenith arc just before the auroral breakup. The plasma depletion was associated with an enhancement of ion (at the altitudes of 150–200 km) and electron (in E region) temperatures. During its occurrence, the electric field in the E-region was extremely large (~150 mV/m). A significant increase in ion temperature was also observed 1 min before the arrival of a westward travelling surge (WTS) at the radar zenith. This was interpreted as the existence of an extended area of enhanced electric field ahead of the WTS.

Download Full-text

Luminosity variations in several parallel auroral arcs before auroral breakup

Annales Geophysicae ◽

10.1007/s00585-997-0959-4 ◽

1997 ◽

Vol 15 (8) ◽

pp. 959-966 ◽

Cited By ~ 6

Author(s):

V. Safargaleev ◽

W. Lyatsky ◽

V. Tagirov

Keyword(s):

Spatial Resolution ◽

Characteristic Time ◽

Auroral Breakup ◽

Temporal And Spatial ◽

Auroral Arcs

Abstract. Variation of the luminosity in two parallel auroral arcs before auroral breakup has been studied by using digitised TV-data with high temporal and spatial resolution. The intervals when a new arc appears near already existing one were chosen for analysis. It is shown, for all cases, that the appearance of a new arc is accompanied by fading or disappearance of another arc. We have named these events out-of-phase events, OP. Another type of luminosity variation is characterised by almost simultaneous enhancement of intensity in the both arcs (in-phase event, IP). The characteristic time of IP events is 10–20 s, whereas OP events last about one minute. Sometimes out-of-phase events begin as IP events. The possible mechanisms for OP and IP events are discussed.

Download Full-text

Features of auroral breakup obtained using data of ground-based television observations: case study

Annales Geophysicae ◽

10.5194/angeo-27-1413-2009 ◽

2009 ◽

Vol 27 (4) ◽

pp. 1413-1422 ◽

Cited By ~ 8

Author(s):

E. E. Antonova ◽

I. A. Kornilov ◽

T. A. Kornilova ◽

O. I. Kornilov ◽

M. V. Stepanova

Keyword(s):

Imaging Technique ◽

Magnetic Disturbance ◽

Magnetic Fluctuations ◽

Relative Timing ◽

Expansion Phase ◽

Auroral Breakup ◽

Image Filtration ◽

Using Data ◽

Auroral Arcs

Abstract. The knowledge about the relative timing of events during the substorm expansion phase onset is very important for understanding the physics of substorms. In this work ground-based television (TV) imaging technique was used for observations of the first auroral arc brightening near zenith of TV chamber for the case of an isolated substorm. The method of the TV image filtration was used giving the possibility to analyze motion of sub visual auroral arcs. The analysis of the connection between the first auroral arc brightening and the beginning of magnetic disturbance was carried out. It was shown that luminosity disturbance is absent to the pole of breakup arc before the breakup and there exist a delay time between the brightening and start of intense magnetic fluctuations in the Pi1–Pi2 frequency ranges. The results obtained have been compared with predictions of theories of auroral breakup.

Download Full-text