Координированные наблюдения авроральных явлений 1-2 декабря и 11-12 декабря 1977 г. на Кольском полуострове и в Финляндии / С. А. Черноус, Н. И. Федорова, Г. А. Логинов и др. ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т. – Препр. ПГИ-79-3. - Апатиты : [б. и.], 1979.

23 , 27 ]. and locates around the noon. 2. Hard electrons were observed together with soft ones in the morning hours. The first objection could be correct in the case of small or moderate magnetic activity however the events under con sideration took place in periods of strong disturbances. According to numerous satellite auroras and particles and ground based optical observations the equatorial cusp bo undary may extend down to rather low invariant latitudes about 70 °under the disturbed conditions [12, 28, 29 ]* There are observations the cusp manifested itself at the very low latitudes A~67° [30] and even at A~65° [31-36]. It is generally known that the longitudinal cusp extension is equal to several hours near the noon meridian very often but some of authors assume the dayside plasma flowing even up to the night sector along the magnetospheric flanks [ 20 , 23 ]. The presence of hard electron precipitation in a region of the red А-type aurora together with soft electron preci pitation caused this aurora can not contradict the cusp origin of soft precipitation since in the cusp hard electrons were registered by many authors who considered the cusp sit uated on closed field lines [21, 37]» The data of magnetic observations can show that in the regions of red auroras field-aligned currents exist with downward direction that corresponds the upward flux of ele ctrons. Such fluxes can be really observed in the cusp region [ 57 ]. Thus the considerable quantity of indirect data testify the truth of our hypothesis about the cusp origin of abnor mal А-type red auroras. However, the final conclusions can be made only when the direct measurements with the help of satellites in the magnetosphere would be obtained. The periodic structure of energy spectrum variations in the morning hours needs a special study, because the origin of the longperiod geomagnetic pulsations associated with these variations is not totally clear.