Being footprints of major magnetic storms and hence major solar eruptions, mid- to low-latitude aurorae have been one of the pathways to understand solar–terrestrial environments. However, it has been reported that aurorae are also occasionally observed at low latitudes under low or even quiet magnetic conditions. Such phenomena are known as “sporadic aurorae”. We report on a historical event observed by a scientist of the Brazilian Empire in Rio de Janeiro on 15 February 1875. We analyze this event on the basis of its spectroscopic observations, along with its visual structure and coloration, to suggest this event was a possible case of sporadic aurorae. Given the absence of worldwide aurora observations on that day as a consequence of low magnetic activity recorded on the days preceding the observation, in addition to a detailed description, the event observed can most likely be classified as a sporadic aurora. We discuss the geographic and magnetic conditions of that event. Thus, we add a possible case of sporadic aurora in the South American sector.

中文翻译：

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在里约热内卢观察到的一个可能的零星极光案例

作为主要磁暴和主要太阳爆发的足迹，中低纬度极光一直是了解日地环境的途径之一。然而，据报道，在低纬度甚至安静的磁场条件下，偶尔也会观察到极光。这种现象被称为“零星极光”。我们报告了 1875 年 2 月 15 日巴西帝国科学家在里约热内卢观察到的一个历史事件。我们根据它的光谱观察以及它的视觉结构和颜色来分析这个事件，以表明这个事件是可能的零星极光的情况。鉴于在观测前几天记录到的低磁活动导致当天没有世界范围内的极光观测，除详细描述外，观察到的事件很可能被归类为偶发极光。我们讨论了该事件的地理和磁场条件。因此，我们在南美地区添加了一个可能的零星极光案例。