Структура и динамика полярных токовых систем : материалы международного симпозиума «Полярные геомагнитные явления», 25-31 мая, Суздаль, СССР / Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Апатиты : [б. и.], 1988.

K.Rinnert, H.Kohl ELECTRIC FIELDS AND CURRENTS IN THE VICINITY OF AN AURORAL ARC ABSTRACT. Electric field measurements from dc to 150 Hz were performed on board the CAESAR payload which flew over a faint auroral arc just below its apogee at 703 km. The CAESAR dc-electric field together with electric fields derived from EISCAT measurements in 140 km altitude defined an electric field and current configuration associated with a local perturbation. Equatorward of the precipitation region (inverted-V-event) intense electrostatic low frequ ency noise was observed. These signals had properties of electrostatic ion cyclotron (EIC) waves. As their electric field waB predominantly polarized parallel to the Earth magnetic field, these waves are attributed to ion beam driven modes. The spatially or temporaly limited occurence cf the fluctuations gives an indication of the structure of the beams or field-aligned current system, INTRODUCTION. To study auroral arc physics the CAESAR-programme (Coordin ated Auroral Experiment Using Scatter And Rockets) was performed, which combined high resolution in-situ measurements using rocket-borne instrumenta tion and ground-based observations with EISCAT. The CAESAR rocket was launched on January 30, 1985 at 19:30 UT from the And*Sya rocket range under slightly disturbed conditions over a faint and slowly varying arc. The payload reached its apogee of 703 km just above the arc, i.e. the trajectory crossed near its apogee the magnetic field lines connected with the aro region. The rocket payload was equipped with various instruments to measure plas ma parameters as well as particle and field properties. This report concentra tes on the CAESAR dc and ac electric field measurements with a floating double probe system. Two sets of croseed boom pairs were used and the potential differences between any two probes were sampled with 312.5 Hz. Synchronous with the flight as well as before and after the plasma drift was measured with EISCAT at seven positions of a south-north scan across the expected precipitation region. MEASUREMENTS. Figure 1 shows electric field data versus flight time. The upper panel is a display of the dc electric field perpendicular to the Earth magnetic field versus flight time (bottom scale) or altitude (top scale). Ihe precipitation region between 410 s and 600 s of flight time is defined by the occurence of energetic electrons detected by the energetic particle spect rometer, The peak energy and flux of precipitating electrons was 10 keV and 4*10^ cm-2s-1SR~1 eV~1 , respectively, at about 500 s (Wilhelm, private commun ication, 1986). Each electric field vector i3 an average oyer 4 seconds. During upleg, i.e. south of the arc there is a predominantly northward direc ted electric field with a maximum of 55 mV/m. Crossing the precipitation region the electric field rotates clockwise and is reversed in the centre. 89