- 封: close; seal
- 头: 5点就得动身 have to start before ...
- 过渡区: transition region; intermedi ...
- 封头过渡区半径: knuckle radius
- 过渡区: intermediate zone; intervening region; knuckle; solar transition region; transient region; transition area; transition zone; transitional area; transitional zone; zone of transition
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