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We conducted meteor observations during the Leonid meteor shower on 16 November 2017 and 17 November 2018 with Langfang medium frequency (MF) radar (116° E, 40° N). This was the first nighttime meteor observation by MF radar in mid-latitude China. The observation period was 12:00–22:00 (UT) and the observation range was 78–150 km. By using broad vertical beams, totally 94 and 92 meteor echoes were obtained, along with their spatial, time and height distribution. Quite a few meteor echoes are within 30° zenith angles, from the southwest direction, and with a mean height of 107 km which is almost 10 km higher than traditional VHF (Very High Frequency) meteor radar observations. Initial bi-hourly and nightly averaged wind profiles were calculated, and well fitted the wind estimations by co-located VHF meteor radar at the altitude of 100–110 km. On the other side, echoes around 140 km are successfully detected in our observation, which may suggest that for most running MF radars, meteor echoes around 140 km altitude could be detected with a sampling pulse frequency less than 100 Hz. [ABSTRACT FROM AUTHOR]

During solar flares, the X-ray radiation suddenly increases, resulting in an increase in the electron density of the atmospheric D region and a strong absorption of short-wave radio waves. Based on Langfang medium frequency (MF) radar, this paper analyzed the variation characteristics of D region in the lower ionosphere from 62 km to 82 km. The analysis focused on multiple C-level and M-level solar flare events before and after the large-scale flare event at 11:53 (UT) on September 6, 2017. The results show that it is difficult to detect the electron density over 70 km in Langfang during solar flares, but the electron density value can be obtained as low as 62 km, and the stronger the flare intensity, the lower the detectable electron density height. Besides, the equal electron density height, the received power of X and O waves will also be significantly reduced during the flares, and the reduction of equal electron density height has a weak linear relationship with flare intensity. [ABSTRACT FROM AUTHOR]

Abstract: Data obtained from the newly installed MF radar at Langfang (39.4°N, 116.7°E), China, during the summer months of 2009 are used to study the short-term variability and summer averages of the mean wind and tidal oscillations in the mesosphere and lower thermosphere (MLT). Both the zonal and meridional daily winds between 80km and 98km show considerable day-to-day variability; their Lomb–Scargle spectra reveal active quasi-2-day and quasi-16-day planetary waves. The tidal large day-to-day variations have time scales of days or longer, which could be attributed to the contribution of planetary waves. The summer-averaged zonal wind is westward below 82km and eastward above 88km with the transition altitude at ∼85km. The meridional wind is dominated by the southward wind. The summer-averaged zonal and meridional semidiurnal tides exhibit amplitudes of 10–15m/s; they are larger than the diurnal tides, whose amplitudes are 5–10m/s. The phase tilt of the semidiurnal tide is downward, indicating this component is excited below the MLT. For the diurnal tide, the phase propagation is downward above 86km but it is upward below 86km, which indicates that the tide is evanescent or a mixture of evanescent and propagating modes. These wind and tide observations are compared with data from other mid-latitude stations at ∼40°N and with the HWM and GSWM models. Comparisons show that HWM-93 is better than HWM-07 in delineating the 2009 summer-averaged zonal wind over Langfang while both have systematic discrepancy in delineating the meridional mean winds. The prediction of the 2009 summer-averaged diurnal tide over Langfang by GSWM-09 is better than that from GSWM-02 but not the semidiurnal tide. [Copyright &y& Elsevier]