The Jovian Ionospheric Alfvén Resonator and Auroral Particle Acceleration
The Jovian Ionospheric Alfvén Resonator and Auroral Particle Acceleration
复制标题
DOI：
10.1029/2021ja029886
复制
发表时间：
2021-08
期刊：
影响因子：
--
通讯作者：
R. Lysak;Yan Song;S. Elliott;W. Kurth;A. Sulaiman;D. Gershman
中科院分区：
文献类型：
--
作者：
R. Lysak;Yan Song;S. Elliott;W. Kurth;A. Sulaiman;D. Gershman
电离层阿尔文谐振器（IAR）是行星电离层上方等离子体密度迅速下降而形成的结构。这导致Alfvén速度的相应增加，这可以提供Alfvén波的部分反射。在地球上，极光场线上的IAR与极光粒子的宽带加速有关，有时被称为Alfvénic极光。这是因为IAR中的相位混合降低了阿尔文波的垂直波长，这增强了由于电子惯性引起的平行电场。该平行电场以0.1-20.0 Hz的频率波动，与通过加速区域的电子渡越时间相当，导致宽带加速。这种宽带加速在木星的普遍存在表明，类似的过程可以发生在木星IAR。为了研究这些相互作用，已经建立了木星IAR中阿尔文波传播的数值模型，表明IAR的共振频率与地球上的共振频率范围相同。该模型描述了朱诺近木星经过期间采样的木星附近低空区域的电场和磁场的演变。特别是，该模型将朱诺号上MAG和Waves仪器的离子回旋频率以下的磁场测量和Waves的电场测量与可以加速极光粒子的相关平行电场联系起来。
The ionospheric Alfvén resonator (IAR) is a structure formed by the rapid decrease in the plasma density above a planetary ionosphere. This results in a corresponding increase in the Alfvén speed that can provide partial reflection of Alfvén waves. At Earth, the IAR on auroral field lines is associated with the broadband acceleration of auroral particles, sometimes termed the Alfvénic aurora. This arises since phase mixing in the IAR reduces the perpendicular wavelength of the Alfvén waves, which enhances the parallel electric field due to electron inertia. This parallel electric field fluctuates at frequencies of 0.1–20.0 Hz, comparable to the electron transit time through the acceleration region, leading to the broadband acceleration. The prevalence of such broadband acceleration at Jupiter suggests that a similar process can occur in the Jovian IAR. A numerical model of Alfvén wave propagation in the Jovian IAR has been developed to investigate these interactions, indicating that the IAR resonant frequencies are in the same range as those at Earth. This model describes the evolution of the electric and magnetic fields in the low‐altitude region close to Jupiter that is sampled during Juno's perijove passes. In particular, the model relates measurement of magnetic fields below the ion cyclotron frequency from the MAG and Waves instruments on Juno and electric fields from Waves to the associated parallel electric fields that can accelerate auroral particles.