Abstract The wave forcing from below allows the neutral atmosphere to drive short-term variability in the ionosphere. Recent modeling studies have shown that secondary waves originated from the nonlinear interaction of the atmospheric tides with planetary scale waves can contribute significantly to day-to-day variability of the ionosphere. In this study we used MLT neutral wind measured at Sao Joao do Cariri (7.4°S, 36.5°W) and ionospheric soundings performed by a digisonde installed at Fortaleza (3.9°S, 38.4°W) to investigate the presence and the induced variability by a secondary wave in the mesosphere-ionosphere system over the Brazilian equatorial region. We found evidences of the nonlinear interaction between a 3.5-day ultrafast Kelvin wave and the diurnal tide. The interaction produced a 1.3-day secondary wave that was found to propagate upward with maximum amplitude of 15 m/s and relatively long vertical wavelength (~44 km) in the MLT, which may allow it to penetrate into the ionosphere. In the ionosphere, we observed a common 1.3-day periodic variation in the virtual height (h'F) and critical frequency (foF2), which may be connected to the secondary wave observed in the MLT via modulation of the wind system in the E region dynamo. These findings suggest that secondary waves may impose additional variability to ionosphere.

中文翻译：

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由超快开尔文波和昼夜潮汐之间的非线性相互作用引起的赤道电离层的变化

摘要 来自下方的波浪强迫允许中性大气驱动电离层的短期变化。最近的建模研究表明，源自大气潮汐与行星尺度波的非线性相互作用的二次波会对电离层的日常变化产生重大影响。在这项研究中，我们使用在 Sao Joao do Cariri (7.4°S, 36.5°W) 测量的 MLT 中性风和由安装在 Fortaleza (3.9°S, 38.4°W) 的 digisonde 进行的电离层探测来研究存在和诱发的变化由巴西赤道地区上空的中间层-电离层系统中的二次波引起。我们发现了 3.5 天超快开尔文波与昼夜潮汐之间非线性相互作用的证据。相互作用产生了 1。3 天的二次波被发现在 MLT 中以 15 m/s 的最大振幅和相对较长的垂直波长（~44 km）向上传播，这可能允许它穿透到电离层。在电离层中，我们观察到虚拟高度 (h'F) 和临界频率 (foF2) 的常见 1.3 天周期性变化，这可能与 MLT 中观察到的二次波有关，这是通过 E 中风系统的调制地区发电机。这些发现表明，二次波可能会给电离层带来额外的变化。它可以通过 E 区发电机中的风系统调制与 MLT 中观察到的二次波相关联。这些发现表明，二次波可能会给电离层带来额外的变化。它可以通过 E 区发电机中的风系统调制与 MLT 中观察到的二次波相关联。这些发现表明，二次波可能会给电离层带来额外的变化。