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Mechanisms of multiple auroral arc formation and field-aligned electron accelerationтезисы доклада
- Авторы: Antonova E.E., Stepanova M.V., Kornilov I.A., Kornilova T.A.
- Сборник: Abstract Volume 2th Scientific Assembly International Association of Geomagnetism and Aeronomy (IAGA -2013 meeting)
- Тезисы
- Год издания: 2013
- Место издания: www.iaga2013.org.mx Merida, Mexico
- Первая страница: 225
- Последняя страница: 225
- Аннотация: The splitting of auroral arc and formation of multiple arcs is a common and well-known phenomenon of auroral arc dynamics. However, it is not well studied until now. Formations of multiple structures with scales ~100 km (multiple inverted V structures) can be described as the results of the development of the instability of the band of upward fieldaligned current connected with the variation of the distribution of magnetospheric plasma pressure under the influence of the variation of magnetospheric potential. Electrostatic field-aligned potential drop located in auroral plasma cavity accelerate magnetospheric electrons in inverted V structure. Accelerated electrons have near to isotropic pitch-angle distribution excluding the source cone. Formation of multiple arcs with scales 1-10 km is ordinarily attributed to the development of the feedback instability and acceleration of electrons of ionospheric origin. Such electrons have much larger densities and form arcs which are much brighter than inverted V arcs/bands. Field –aligned electron beams produce thin auroral arcs. Field-aligned electric field of shear Alfven waves is ordinarily considered as the reason of field-aligned acceleration of cold ionospheric electrons. Difficulties of such approach are summarized including observations of electron beams at the boundaries or inside inverted V structures, the existence of upper limit of the energy of field-aligned electron beam, which does not exceed the energy of simultaneously observed inverted V electrons ets. The model named the auroral grader is developed which gives the possibility to overcome these difficulties. It is shown that the observed cases of arc splitting is possible to explain using discussed mechanism.
- Добавил в систему: Антонова Елизавета Евгеньевна