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Nine years of mesospheric wind data from two meteor radars at 52{\deg}N latitude were analyzed to investigate planetary waves (PWs) and tides by estimating their zonal wavenumber through longitudinal phase differences. Our results reveal that PW normal modes (NMs) primarily drive multi-day oscillations, showing seasonal variability and statistical associations with Sudden Stratospheric Warming (SSW) events. Specifically, a significant 6-day NM emerges in April, followed by predominant 4- and 2-day NMs until June, with peaks of 2-, 4-, and 6-day NMs spanning July to October. Furthermore, our study provides the first observational verification of frequency and zonal wavenumber of over ten secondary waves from nonlinear interactions among planetary-scale waves. One notable finding is the prevalence of non-migrating components in winter 24-hour and summer 8-hour tides, attributed to these nonlinear interactions. Our findings underscore the diverse nonlinear dynamics of planetary-scale waves, triggering a variety of periodic oscillations.

The current work investigates the Venusian solar-wind-induced magnetosphere at a high spatial resolution using all Venus Express (VEX) magnetic observations through an unbiased statistical method. We first evaluate the predictability of the interplanetary magnetic field (IMF) during VEX's magnetospheric transits, and then map the induced field in a cylindrical coordinate system under different IMF conditions. Our high-resolution mapping enables resolving structures on various scales, ranging from the thin ionopause and the associated electric currents to the classical global-scale draped IMF. Our mapping also resolves two recently-reported structures, a low ionospheric magnetization over the terminator and a global "looping" structure in the near magnetotail, both of which are not depicted in the classical draping configuration. In contrast to the reported IMF-independent cylindrical magnetic field of both structures, our results illustrate their IMF dependence. In both structures, the cylindrical magnetic component is stronger in the hemisphere with an upward solar wind electric field ($E^{SW}$) than in the opposite hemisphere. Under downward $E^{SW}$, the "looping" structure even breaks, which is attributable to an additional draped magnetic field structure wrapping toward $-E^{SW}$. In addition, our results suggest that these two structures are spatially not overlapping with each other. The low ionospheric structure occurs in a very narrow region, at about 87--95$^\circ$ solar zenith angle and 190--210~km altitude, implying that future simulation to reproduce the structure entails at least a spatial resolution of about 10 km. We discuss this narrow structure in terms of a Cowling channel., Comment: submitted to The Astrophysical Journal

Ten years of CHAMP magnetic field measurements are integrated into MFACE, a model of field-aligned currents (FACs) using empirical orthogonal functions (EOFs). EOF1 gives the basic Region-1/Region-2 pattern varying mainly with the interplanetary magnetic field Bz component. EOF2 captures separately the cusp current signature and By-related variability. Compared to existing models, MFACE yields significantly better spatial resolution, reproduces typically observed FAC thickness and intensity, improves on the magnetic local time (MLT) distribution, and gives the seasonal dependence of FAC latitudes and the NBZ current signature. MFACE further reveals systematic dependences on By, including 1) Region-1/Region-2 topology modifications around noon; 2) imbalance between upward and downward maximum current density; 3) MLT location of the Harang discontinuity. Furthermore, our procedure allows quantifying response times of FACs to solar wind driving at the bow shock nose: we obtain 20 minutes and 35-40 minutes lags for the FAC density and latitude, respectively.