Two-step energy transfer in space plasma Plasmas are ionized gases that contain negative electrons, positive ions, and electromagnetic fields. These constituents can oscillate in position over time, carrying energy as plasma waves. In principle, such waves could transfer energy between two different ion populations. Kitamura et al. analyzed data from the Magnetospheric Multiscale mission, a group of four spacecraft that are flying in tight formation through Earth's magnetosphere. They discovered an event in which energy was transferred from hydrogen ions to plasma waves and then from the waves to helium ions. This energy transfer process is likely to occur in many other plasma environments. Science, this issue p. 1000 Energy transfer between H+ ions, plasma waves, and He+ ions is observed in a space plasma. Particle acceleration by plasma waves and spontaneous wave generation are fundamental energy and momentum exchange processes in collisionless plasmas. Such wave-particle interactions occur ubiquitously in space. We present ultrafast measurements in Earth’s magnetosphere by the Magnetospheric Multiscale spacecraft that enabled quantitative evaluation of energy transfer in interactions associated with electromagnetic ion cyclotron waves. The observed ion distributions are not symmetric around the magnetic field direction but are in phase with the plasma wave fields. The wave-ion phase relations demonstrate that a cyclotron resonance transferred energy from hot protons to waves, which in turn nonresonantly accelerated cold He+ to energies up to ~2 kilo–electron volts. These observations provide direct quantitative evidence for collisionless energy transfer in plasmas between distinct particle populations via wave-particle interactions.

中文翻译：

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无碰撞空间等离子体中双向波粒能量转移的直接测量

空间等离子体中的两步能量转移 等离子体是包含负电子​​、正离子和电磁场的电离气体。这些成分可以随着时间的推移在位置上振荡，以等离子体波的形式携带能量。原则上，这种波可以在两个不同的离子群之间传递能量。北村等人。分析了来自磁层多尺度任务的数据，这是一组以紧密编队飞行穿过地球磁层的四艘航天器。他们发现了一个事件，其中能量从氢离子转移到等离子体波，然后从波转移到氦离子。这种能量转移过程很可能发生在许多其他等离子体环境中。科学，这个问题 p。1000 在空间等离子体中观察到 H+ 离子、等离子体波和 He+ 离子之间的能量转移。等离子体波和自发波产生的粒子加速是无碰撞等离子体中的基本能量和动量交换过程。这种波粒相互作用在太空中无处不在。我们展示了磁层多尺度航天器对地球磁层的超快测量，该航天器能够定量评估与电磁离子回旋波相关的相互作用中的能量转移。观察到的离子分布不是围绕磁场方向对称的，而是与等离子体波场同相。波 - 离子相位关系表明回旋共振将能量从热质子转移到波，这反过来又非共振地加速冷 He+ 到高达 ~2 千电子伏特的能量。