Auroral Ionospheric Erosion at Jupiter

Provided here are the data that appear in the figures of the subject paper, which is published in the American Geophysical Union’s Journal of Geophysical Research: Space Physics (doi: 10.1029/2025JA034156). Abstract The generation of Jupiter’s main auroral oval is dominated by broadband-energy electron beams, in contrast with the dominance of peaked electron energy spectra at Earth. Wave-particle interactions involving Alfvén waves have been theorized to be the main mechanism driving the broadband acceleration of electrons. Alfvénic interactions are favored in the presence of density depletions and steep density gradients across adjacent magnetic field lines. Here we present electron densities above the diffuse and main auroras inferred from frequency cutoffs in plasma wave spectra measured by the Juno/Waves instrument during the first 62 perijoves. We find that the electron densities above the auroras consistently decrease towards poleward latitudes and can be depleted down to the order of 10-4 cm-3. Moreover, we show that the spatial gradient of the density depletion varies with altitude, and the peak in the density gradient occurs above 1 RJ, suggesting altitudes at which Alfvénic acceleration is most likely. Finally, we find that these auroral density gradients are much steeper than are found in the non-auroral ionosphere, indicating an active cavitation process connected with the aurora likely driven by the action of Alfvén waves. Key Points We present electron densities at low altitudes (0.3-2.8 RJ) above Jupiter's aurora that are persistently depleted towards poleward latitudes Steep spatial gradients of the depletions above 1 RJ suggest a more preferential plasma environment for Alfvenic acceleration Significantly steeper gradients than in the non-auroral ionosphere indicate ionospheric erosion by Alfven waves connected with the auroras本文所提供的数据，取自已提交至美国地球物理联合会（American Geophysical Union，AGU）旗下《地球物理研究杂志：空间物理学》（Journal of Geophysical Research: Space Physics）的待审稿论文配图。 摘要 与地球以峰值型电子能谱为主导的情况不同，木星主极光卵的生成主要由宽带能量电子束驱动。已有理论指出，涉及阿尔文波（Alfvén waves）的波粒相互作用是驱动电子产生宽带加速的核心机制。阿尔文波相互作用更易发生在相邻磁力线间存在密度耗尽与陡峭密度梯度的环境中。 本文基于朱诺号（Juno）/Waves探测仪器在前62次近木点飞行期间测得的等离子体波谱频率截止点，反演得到弥散极光与主极光上方的电子密度。研究发现，极光上方的电子密度随极向纬度升高持续降低，最低可耗尽至10⁻⁴ cm⁻³量级。此外，我们证实密度耗尽的空间梯度随高度发生变化，密度梯度峰值出现在1 RJ（木星半径，Jovian radius）以上区域，表明阿尔文波加速最可能发生于此高度区间。最后，我们发现极光区的密度梯度远陡于非极光电离层中的梯度，这表明与极光相关联、由阿尔文波驱动的等离子体空化过程极为活跃。 核心要点 1. 我们给出了木星极光上方0.3~2.8 RJ低高度处的电子密度分布，其数值随极向纬度升高持续耗空降低。 2. 1 RJ以上区域的密度耗尽具有陡峭空间梯度，表明该区域存在更利于阿尔文波加速的等离子体环境。 3. 该密度梯度显著陡于非极光电离层中的梯度，证明与极光相关联的阿尔文波作用引发了电离层侵蚀。