The Kototabang (0.20°S, 100.3°E, 10.36°S dip latitude) Equatorial Atmosphere Radar (EAR) observations of valley region field-aligned irregularities (FAI) reveal maximum percentage of occurrence (PO) of high signal to noise ratio (greater than 3 dB) type-B 150-km echoes during boreal summer (June-August) and winter (December-January) of solar moderate to minimum years 2016–2019. The PO is anomalously high in the solar minimum year 2019 and particularly during the September equinox when a major austral sudden stratospheric warming (SSW) event has occurred. Its possible relation with mesospheric tides and stratospheric ozone is investigated. The space–time spectral analysis of upper mesospheric temperature information obtained from the spaceborne radiometer instrument Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) reveals that migrating semi-diurnal tide (SW2) is dominant during June-August, when the PO of the 150-km echoes maximizes, whereas migrating diurnal tide (DW1) is dominant during equinox months. It also reveals quasi-biennial variability of the DW1 tide probably due to similar variability of the stratospheric ozone. It is suggested that the DW1 tides generated due to solar radiation absorption by stratospheric ozone and tropospheric water vapour can have phases opposite to each other, leading to the suppression of DW1 tide during September 2017 and 2019 resulting in the relative dominance of SW2 tide over DW1 tide. The meridional wind shear associated with the relatively dominant SW2 tide results in an interchange instability developed on the gradient of daytime descending ion layer along with solar minimum conditions leads to plasma irregularities responsible for these echoes. The large eastward propagating diurnal tide with zonal wavenumber 3 (DE3) observed during June-September 2019 is unlikely to cause the instability, due to its weak meridional component.

Kototabang（0.20°S、100.3°E、10.36°S 倾角）赤道大气雷达 (EAR) 对山谷区域场对齐不规则性 (FAI) 的观测揭示了高信噪比（更大）的最大发生率 (PO)低于 3 dB) B 型 150 公里回波在 2016-2019 年太阳中等至极小年的北方夏季（6 月至 8 月）和冬季（12 月至 1 月）。PO 在 2019 年太阳活动极小期异常高，尤其是在 9 月春分期间，当时发生了重大的南方平流层突然变暖 (SSW) 事件。研究了它与中间层潮汐和平流层臭氧的可能关系。使用宽带发射辐射计 (SABER) 从星载辐射计仪器探测大气中获得的上层中间层温度信息的时空光谱分析表明，迁移半日潮 (SW2) 在 6 月至 8 月期间占主导地位，此时150 公里的回波最大，而昼夜迁移潮 (DW1) 在春分月份占主导地位。它还揭示了 DW1 潮汐的准两年变化，这可能是由于平流层臭氧的类似变化。认为平流层臭氧和对流层水汽吸收太阳辐射产生的DW1潮汐可能具有相反的相位，导致2017年9月和2019年的DW1潮汐受到抑制，导致SW2潮汐对DW1的相对优势浪潮。与相对主导的 SW2 潮汐相关的经向风切变导致在白天下降的离子层梯度上形成的互换不稳定性以及太阳极小期条件导致等离子体不规则性导致这些回波。2019 年 6 月至 9 月期间观测到的大向东传播的日潮，纬向波数为 3（DE3），由于其子午分量较弱，不太可能引起不稳定。