Thermal and dynamic perturbations at MLT heights during the strong stratospheric polar vortex as measured by the meteor radar at 67°N and the Aura satellite are presented. Mesospheric winds are dominated by vertical shears in the zonal component and the intense alternating north- and southward flows with a period of half a month. A temperature reduction at 90 km height is observed in the mid-winter and likely associated with a localized temperature increase in the upper stratosphere. Throughout January, a long-lived ~20K inversion layer persists just below the mesopause. These features are likely indicative of considerable stratification in the MLT as well as a decoupling of the middle and upper atmosphere.

Meteoroids entering the Earth’s atmosphere produce ionized trails, which are detectable by radio sounding. Cylindrical underdense (and partly overdense) trails form a great majority of meteor echoes received by meteor radars (MR). Additionally, the long-lived non-specular (LLNS) meteor echoes are received from non-field-aligned irregularities of ionization generated along tracks of relatively large meteoroids. The occurrence and height distributions of LLNS are studied using MR observations at Sodankylä Geophysical Observatory (SGO, 67° 22’ N, 26° 38’ E, Finland) during 2008-2019. Two parameters are analyzed: the percentage and height distribution of LLNS echoes. These LLNS echoes constitute about 2% of all MR detections. However during certain meteor showers (Geminids, Perseids, Quadrantids, Arietids or/and Daytime ζ-Perseids, and Lyrids) the percentage of LLNS echoes is noticeably higher (about 6, 5, 4, 4, and 3%, respectively). Typically, the LLNSs occur ∼2 km higher than other echoes (in June-July the height difference is reduced to ∼1 km). Due to this elevation, a larger percentage of LLNSs is manifested as an upward shift of the height distribution of meteor trails during meteor showers. Moreover, during Lyrids, η-Aquariids, Perseids, Orionids, and Leonids the LLNS echoes occur noticeably, up to 3-6 km, higher than the echoes from other types of trails. Thus, enhanced heights of meteor detections during major meteor showers (Quadrantids, Lyrids, η-Aquariids, Arietids or/and Daytime ζ-Perseids, Perseids, Orionids, Leonids, and Geminids) are predominantly due to long-lived non-specular echoes from the non-field-aligned irregularities associated with large meteoroids.

On 19 October 2014, Mars experienced a very close encounter with Comet C/2013 A1 Siding Spring. Using data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express (MEX), we assess the interaction of the Martian ionosphere with the comet’s atmosphere and possibly magnetic tail during the orbit of their closest approach. The topside ionospheric electron density profile is evaluated from the peak density of the ionosphere to the local plasma around Mars Express. We find unusual, complex and rapid variability in the ionospheric profile along the MEX orbit, not seen even after the impact of large coronal mass ejections. Before closest approach, large electron density reductions predominate, which could be caused either by comet water-damping, or comet magnetic field interactions. After closest approach, a substantial electron density rise predominates. Moreover, several extra topside layers are visible along the whole orbit at different altitudes, which could be related to different processes as we discuss.