Ultra‐low frequency (ULF) waves can effectively accelerate ring current ions through drift‐bounce resonance. Conventional theories have been developed to understand this resonance since the dawn of the space age, which usually assume ULF waves are quasi‐steady in time. However, ULF waves would experience growth and damping stages in the real magnetosphere, which requires an adjustment of the conventional theories. Here, we attempt to reveal how ions respond to evolving ULF waves. By analyzing an event observed by Van Allen Probe A and reproducing the observations via simulation, we find the phase shift of ion flux oscillation across resonant pitch angles varies with time, when wave growth and damping cannot be neglected. As a result, the inclination angle of stripes in pitch angle spectrogram varies with time, causing “fishbone‐like” pitch angle structures. One should take into account such ion behaviors when considering the role of drift‐bounce resonance in the real magnetosphere.

Localized magnetic field depressions in the inner magnetosphere, known as magnetic dips, are produced by the diamagnetic motion of energetic ions injected via substorm activities. The magnetic dips, if deep enough, can produce a local minimum in the radial profile of the field strength to trap the injected protons. Therefore, the trapped protons would drift at the same speed as the dip propagation, which leads to the simultaneous enhancements of proton fluxes in multiple energy channels at the leading edge of the dip structure. On the trailing side, the reduction of proton fluxes shows dispersive features, which can be attributed to the energy‐dependent drift motion of the injected protons in the absence of the local field minimum. This scenario is examined based on comparisons between multi‐spacecraft observations and test‐particle simulations, and their good agreement validates the scenario to shed new light on the dynamics of the inner magnetosphere‐magnetotail coupled system.

Although foreshock transients can generate strong magnetospheric Pc5 ultralow‐frequency (ULF) waves, whether they can modulate the energy of magnetospheric ions is still poorly understood. In this study, we analyze the strong magnetospheric ion energy modulations in a foreshock transient event on October 30, 2008, based on the magnetospheric observations by the time history of events and macroscale interactions during substorms A and D in the prenoon sector. ULF wave‐induced drift accelerated the cold ions up to ∼10 keV and the enhanced ion fluxes have wave‐like patterns. There is another portion of enhanced ion fluxes from ∼0.8 to ∼10 keV but with strong energy dispersions in this event. By comparing the observations and the theoretical prediction, we for the first time found that the drift‐bounce resonances played a major role in modulating the energy of those ions with energy dispersions, during the interactions between the ions and the foreshock transient‐driven Pc5 ULF wave with growing and damping effects.

Jupiter’s magnetosphere contains a current sheet of huge size near its equator. The current sheet not only mediates the global mass and energy cycles of Jupiter’s magnetosphere, but also provides a site for many localized dynamic processes, such as reconnection and wave‐particle interaction. To correctly evaluate its role in these processes, a statistical description of the current sheet is required. To this end, here we conduct statistics on Jupiter’s current sheet, by using four‐year Juno data obtained in the 20–100 Jupiter radius, 0–6 local time magnetosphere. The statistics show the thickness of the current sheet is comparable with the gyro‐radius of ions dominating the plasma pressure. Magnetic fields in the current sheet decrease in power‐law with increasing radial distances. At given energy, the flux of energetic electrons and protons increases with decreasing radial distances. On the other hand, at given radial distances, the flux decreases in power‐law with increasing energy. The flux also varies with the distances to the current sheet center. The corresponding relationship can be described by a Gaussian function peaking at the current sheet center. In addition, the statistics show the flux of oxygen‐ and sulfur‐group ions is comparable with the flux of protons at the same energy and radial distances, indicating the non‐negligible role of heavy ions in the current sheet dynamics. From these results, a statistical model is constructed, providing us with a starting point of understanding the dynamics of the whole Jupiter’s magnetosphere.