气辉在西藏上空荡漾
(原标题: Airglow Ripples over Tibet)
2022-11-20
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为什么天空看起来像一个巨大的目标？大气光。4月下旬，一场巨大的雷暴过后，中国西藏上空出现了巨大的圆形波纹。这种不寻常的模式是由大气重力波造成的，这是一种交替的空气压力波，随着空气变薄，它会随着高度而增加，在这种情况下，大约在90千米的高空。与高纬度地区由高能带电粒子碰撞产生的极光不同，气辉是由于化学发光，即化学反应产生的光。气辉通常出现在地平线附近，它使夜空不至于完全变黑。
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Why would the sky look like a giant target? Airglow. Following a giant thunderstorm over Bangladesh in late April, giant circular ripples of glowing air appeared over Tibet, China, as pictured here. The unusual pattern is created by atmospheric gravity waves, waves of alternating air pressure that can grow with height as the air thins, in this case about 90-kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.
© Jeff Dai