Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

NORTHERN AURORAL STRUCTURES BEFORE BREAKUP AND SOLAR WIND I.A. Kornilov, T.A. Kornilova (Polar Geophysical Institute, Apatity, Russia; kornilova@ Abstract. Rather bright auroral arcs usially appeare at the northern horizon of TV imager field o f view 30-40 minutes (substorm preliminary phase) befor breakup development at the southern arc, and are projected to 20-30 Re in the tail (breakup arc projection is at 5-7 Re). Nothem arc generates plasma fluxes and auroral structures moving eathward (so called BBF,s and streamers), pumping inner magnetosphere by hot plasma, finally yielding a breakup development. Arc position (20-30 Re) is appropriate for magnetic reconnection, but northern arc development and luminosity variations definitely are not an breakup type explosive process. It should be also noted that if breakup is a result of explosive magnetic reconnection, there is a problem, how to stop this self-sustaining and all-sufficient process. We have measured integral arc luminosity variations (about 50 cases total), and compare them with solar wind parameters (magnetic field vector mostly) registered by ACE and WIND satellites with appropriate time shift (50-60 minutes). In many cases rather good correlation between arc luminosity variations and solar wind parameters were found. We can suppouse that if northern auroral structures have magnetic reconnection nature, this reconnection is completely initiated and controled by solar wind, and actually operates as some kind o f converter, or transformer between external force (solar wind) energy, and energy o f magnetospheric plasma. Introduction Study of different solar wind parameters interconnection with magnetospheric processes started in the very beginning of cosmic science, when the first satellites were launched, and solar wind and magnetospheric tail were discovered. These investigations are rather active and nowdays. Auroral oval size and configuration dynamics, ionospheric current variations, fine detales of different period magnetic pulsations, global magnetosperic reaction on the sharp solar wind presure pulses, changes in ionospheric convection, so on. [Boudouridis, 2004; Villante, 2004; Farrugia, 2007; Shue, 2009; Juusola, 2010; Boudouridis, 2011]. Important problem o f mordem geophysics is a magnetosperic breakup divelopment. One of most popular conception of breakup is the model o f explosive magnetic reconnection in the tail. But in compare with reconnection on the dayside magnetopause, where theory and experiment are in rather good agreement, night-side tail reconnection theory faces with two serious problems. First - it is difficult to explain extremely high speed of reconnection (all main, most energetic processes o f breakup lasting couple minutes only). Second - how to stop this self-sustaining and all-sufficient process, in other words, why magnetosperic tail does not disappere at all [Akasofu, 2013]. In this paper we present some experimental results demostrating that, like on the day-side, reconnection in the tail can also be driving by external force (solar wind). For this purpose we compare magnetic field variations measured by ACE and WIND satellites with nortem auroral arc intensity variations. Experimental results Fig. 1 demonstrates some details o f northern arc luminosity variation measurements. In digital TV frame (240*240 elements matrix) 6 key points are indicated by mouse cursor (for visual control they are connected by straight lines), and these six points are interpolated by four-degree polynomial. Resulting curve shifts along the frame 20-25 points northward, forming the area of integration. Frame elements are summarized cross this area along every matrix row, forming one-dimensional vector o f arc luminosity in E-W detection, this procedure repeats for every frame of the time interval under study (usually 500-600 frames total), resulting 2-dimentional picture o f arc luminosity temporal variations (keogram in E-W direction - Fig. 2 (1 )). Rather broad integration area (usually 20-25 pixels) is useful in two aspects. First - strong noise reduction and significant dynamic range improving, second - arc can demonstrate some motion in N-S direction near northern horizon, and this fact will not change at all the result of arc luminosity integration. Summarization of all elements of every vertical keogram line (or, what is the same - integration of all frame elements inside the marked area repeated for every frame) gives one-dimensional picture o f arc integral luminosity variations (Fig. 2 (2)). "Physics o f Auroral Phenom ena”, Proc. XXXVII A nnual Seminar, Apatity, pp. 18-21, 2014 © Kola Science Centre, Russian Academy of Science, 2014 N Figure 1. Method o f northern arc luminosity Polar Geophysical Institute 18