As the Sun moves through the surrounding partially ionized medium, neutral hydrogen atoms penetrate the heliosphere, and through charge exchange with the supersonic solar wind, create a population of hot pick-up ions (PUIs). Until recently, the consensus was that the shape of the heliosphere is comet-like. The termination shock crossing by Voyager 2 demonstrated that the heliosheath (the region of shocked solar wind) pressure is dominated by PUIs; however, the impact of the PUIs on the global structure of the heliosphere has not been explored. Here we use a novel magnetohydrodynamic model that treats the PUIs as a separate fluid from the thermal component of the solar wind. The depletion of PUIs, due to charge exchange with the neutral hydrogen atoms of the interstellar medium in the heliosheath, cools the heliosphere, ‘deflating’ it and leading to a narrower heliosheath and a smaller and rounder shape, confirming the shape suggested by Cassini observations. The new model reproduces both the properties of the PUIs, based on the New Horizons observations, and the solar wind ions, based on the Voyager 2 spacecraft observations as well as the solar-like magnetic field data outside the heliosphere at Voyager 1 and Voyager 2.

当太阳穿过周围的部分电离的介质时，中性氢原子会穿透日光层，并通过与超音速太阳风的电荷交换而产生大量的热吸收离子（PUI）。直到最近，人们一致认为，日球的形状是彗星状的。Voyager 2的终止冲击穿越表明，日鞘（太阳风的冲击区域）压力受PUI支配。但是，尚未探索PUI对日球层全球结构的影响。在这里，我们使用一种新颖的磁流体动力学模型，将PUI视为与太阳风的热成分分离的流体。由于与日鞘中星际介质的中性氢原子进行电荷交换，PUI的耗竭使日光层变冷，'缩小'它并导致更窄的日光鞘和更小，更圆的形状，证实了卡西尼号观测结果所建议的形状。新模型重现了基于New Horizo​​ns观测的PUI的属性，以及基于Voyager 2航天器观测的太阳风离子，以及Voyager 1和Voyager 2的太阳圈外太阳样磁场数据。 。