The dispersion of shock is universal in various media, and in plasmas, standing whistler waves represent the dispersion of collisionless shocks. However, at present, our understanding of the plasma behavior and electric field properties within these waves remains limited. Using conjoint THEMIS and Magnetospheric Multiscale (MMS) observations, we report the first observation of standing whistler wave upstream of a fast shock in Earth’s magnetosheath resulting from the interaction between a solar wind tangential discontinuity and the bow shock. High-resolution MMS measurements provide unprecedented insights into these waves, characterizing their circular polarization, near-parallel propagation to the shock normal, and fixed phase relative to the shock ramp. Moreover, generated ion acoustic waves and wave‒particle interactions are observed in these waves. These findings highlight that the magnetosheath is a compelling region for investigating standing whistler wave properties.

This paper reports on the standing whistler waves upstream of Mercury’s quasi-perpendicular bow shock. Using MESSENGER’s magnetometer data, 36 wave events were identified during interplanetary coronal mass ejections (ICMEs). These elliptic or circular polarized waves were characterized by: (1) a constant phase with respect to the shock, (2) propagation along the normal direction to the shock surface, and (3) rapid damping over a few wave periods. We inferred the speed of Mercury’s bow shock as ~31 km/s and a shock width of 1.76 ion inertial length. These events were observed in 20% of the MESSENGER orbits during ICMEs. We conclude that standing whistler wave generations at Mercury are generic to ICME impacts and the low Alfvén Mach number (MA) collisionless shock, and are not affected by the absolute dimensions of its bow shock. Our results further support the theory that these waves are generated by the current in the shock.

Oxygen ions, O+, efficiently energized by weak fast shock in the mid-altitude cusp observed by Cluster on 7 November 2004 are investigated in this paper. An interplanetary fast shock hitting Earth magnetosphere was observed by Geotail at 1825 UT with a sharply increase in the solar wind dynamic pressure from 3nPa to 11nPa. There are significant fluctuations of solar wind dynamic pressure from 1930 UT to 2000 UT during this shock compressing Earth magnetosphere. During this pressure disturbance intervals Cluster 4 was located in the mid-altitude cusp, (0.43, -3.25, 3.07) RE_GSE. CODIF/Cluster 4 instrument detected O+ ions with tens keV energized by the weak fast shock with Mach number MA~1.2 in the perpendicular direction. Those energetic O+ ions have bunch or partial ring distributions in the mid-altitude cusp. Our observation results put forward confident evidences on the weak fast shock efficiently energizing heavy ions, especially, O+ ions in the cusp.