Observations made by the Michelson Doppler Imager (MDI) and Variability of solar IRradiance and Gravity Oscillations (VIRGO) on the Solar and Heliospheric Observatory (SOHO) and by the ground-based Birmingham Solar Oscillations Network (BiSON) and Global Oscillations Network Group (GONG) have been used in a concerted effort to search for solar gravity oscillations. All spectra are dominated by solar noise in the frequency region from 100 to 1000 μHz, where g-modes are expected to be found. Several methods have been used in an effort to extract any g-mode signal present. These include (1) the correlation of data—both full-disk and imaged (with different spatial-mask properties)— collected over different time intervals from the same instrument, (2) the correlation of near-contemporaneous data from different instruments, and (3) the extraction—through the application of complex filtering techniques—of the coherent part of data collected at different heights in the solar atmosphere. The detection limit is set by the loss of coherence caused by the temporal evolution and the motion (e.g., rotation) of superficial structures. Although we cannot identify any g-mode signature, we have nevertheless set a firm upper limit to the amplitudes of the modes: at 200 μHz, they are below 10 mm s~(-1) in velocity, and below 0.5 parts per million in intensity. The velocity limit corresponds very approximately to a peak-to-peak vertical displacement of δR/solar radius = 2.3 x 10~(-8) at the solar surface. These levels which are much lower than prior claims, are consistent with theoretical predictions.
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机译：迈克尔逊多普勒成像仪（MDI）和太阳和日球观测站（SOHO）上的太阳辐射和重力振荡的变率（VIRGO）以及地面伯明翰太阳振荡网络（BiSON）和全球振荡网络组（GONG）的观测结果）已被共同用于寻找太阳重力振荡。在从100到1000μHz的频率范围内，所有频谱都以太阳噪声为主导，在该频率范围内有望找到g模式。为了提取存在的任何g模式信号，已经使用了几种方法。其中包括（1）从同一仪器在不同时间间隔收集的全磁盘数据和已成像数据（具有不同的空间蒙版属性）的相关性；（2）来自不同仪器的近同期数据的相关性；以及（3）通过应用复杂的过滤技术，提取在太阳大气中不同高度收集的数据的连贯部分。检测限由表层结构的时间演变和运动（例如旋转）引起的相干性损失设置。尽管我们无法识别出任何g模式特征，但我们为模式的振幅设置了一个固定的上限：在200μHz时，它们的速度低于10 mm s〜（-1），在百万分之0.5以下强度。速度极限非常近似地对应于在太阳表面的δR/太阳半径= 2.3 x 10〜（-8）的峰峰值垂直位移。这些水平远低于先前的权利要求，与理论预测一致。
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