Luminosity variations in several parallel auroral arcs before auroral breakup

Abstract

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.

The response of the azimuthal component of the ionospheric electric field to auroral arc brightening

“…1b, 3a, the appearance of new arc is accompanied by a fading of pre-existing one. The similar variations of the luminosity in the system of two parallel arcs were reported early by Safargaleev et al (1997).…”

“…The observed response is described in terms of polarization electric ®elds, which are generated by an elliptic inhomogeneity in the ionosphere and reduce the tangential component of background convection electric ®eld. We think that the decrease of the electric ®eld may be a reason for out-of-phase variations of the auroral activity observed by Safargaleev et al (1997) in the system of auroral arcs.…”

Ground and satellite observations of the evolution of growth phase auroral arcs

“… Bristow et al [2003] examined an isolated growth phase and, although no newly formed breakup arc was observed in their study, the presence of enhanced plasma flows ∼5 min before the arc brightening were noted by the authors. Finally, fading of growth phase arcs before onset has been discussed by several authors [see Kauristie et al , 1997; Safargaleev et al , 1997, and references therein].…”

Связь Временных Вариаций Корональных Выбросов Массы И Крупномасштабных Событий В Солнечном Ветре С Появлением SCв 23 И 24 Циклах Солнечной Активности.

“…3 представлены день за днем вариации AE индекса и интенсивности TEC флуктуаций (индекс ROTI) в течение декабря 2015 года по станции Тромсе (TRO1). Цветовыми линиями выделены интервалы 00-10 UT (голубой), 10-12 UT (красный), [12][13][14][15][16][17][18][19][20][21][22][23][24]. В целом наблюдается хорошее временное соответствие в вариациях обеих параметров.…”

“…Затем зенитная дуга вновь включается, а полюсная ослабевает. Такое противофазное поведение двух обычных дуг было описано ранее в работе [12] и объяснялось, в частности, изменением ионосферного электрического поля разгорающейся дугой. В нашем случае, можно увидеть, что при повторном включении зенитной дуги частота внутренней модуляции изменилась.…”