Understanding the atmospheric forcing from energetic particle precipitation (EPP) is important for climate simulations on decadal time scales. However, presently there are large uncertainties in energy flux measurements of electron precipitation. One approach to narrowing these uncertainties is by analyses of EPP direct atmospheric impacts and their relation to measured EPP fluxes. Here we use observations from the microwave limb sounder (MLS) and Whole Atmosphere Community Climate Model (WACCM) simulations, together with EPP fluxes from the Geostationary Operational Environmental Satellite (GOES) and Polar-orbiting Operational Environmental Satellite (POES) to determine the OH and HO₂ response thresholds to solar proton events (SPEs) and radiation belt electron (RBE) precipitation. Because of their better signal-to-noise ratio and extended altitude range, we utilize MLS HO₂ data from an improved offline processing instead of the standard operational product. We consider a range of altitudes in the middle atmosphere and all magnetic latitudes from pole to pole. We find that the nighttime flux limits for day-to-day EPP impact detection using OH and HO₂ are 50–130 $\mathrm{protons}{\mathrm{cm}}^{-\mathrm{2}}{\mathrm{s}}^{-\mathrm{1}}{\mathrm{sr}}^{-\mathrm{1}}$ (E>10 MeV) and 1.0–2.5×10⁴ $\mathrm{electrons}{\mathrm{cm}}^{-\mathrm{2}}{\mathrm{s}}^{-\mathrm{1}}{\mathrm{sr}}^{-\mathrm{1}}$ (E = 100–300 keV). Based on the WACCM simulations, nighttime OH and HO₂ are good EPP indicators in the polar regions and provide best coverage in altitude and latitude. Due to larger background concentrations, daytime detection requires larger EPP fluxes and is possible in the mesosphere only. SPE detection is easier than RBE detection because a wider range of polar latitudes is affected, i.e., the SPE impact is rather uniform poleward of 60^∘, while the RBE impact is focused at 60^∘. Altitude-wise, the SPE and RBE detection are possible at ≈ 35–80 and ≈ 65–75 km, respectively. We also find that the MLS OH observations indicate a clear nighttime response to SPE and RBE in the mesosphere, similar to the simulations. However, the MLS OH data are too noisy for response detection in the stratosphere below 50 km, and the HO₂ measurements are overall too noisy for confident EPP detection on a day-to-day basis.

中文翻译：

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奇数氢响应阈值，用于指示中层和平流层中太阳质子和电子的撞击

了解高能粒子降水（EPP）引起的大气强迫对于十年时间尺度的气候模拟非常重要。然而，目前在电子沉淀的能量通量测量中存在很大的不确定性。缩小这些不确定性的一种方法是分析EPP对大气的直接影响及其与测得的EPP通量的关系。在这里，我们使用微波肢体测深仪（MLS）和整个大气群落气候模型（WACCM）的观测结果，以及对地静止运行环境卫星（GOES）和极轨运行环境卫星（POES）的EPP通量来确定OH和HO ₂太阳质子事件（SPEs）和辐射带电子（RBE）沉淀的响应阈值。由于它们具有更好的信噪比和更大的海拔范围，因此我们利用来自改进的离线处理的MLS HO ₂数据代替了标准操作产品。我们考虑了中层大气的高度范围以及从极点到极点的所有磁纬度。我们发现使用OH和HO ₂进行日常EPP影响检测的夜间通量极限为50–130 $\mathrm{质子}{\mathrm{厘米}}^{--\mathrm{2}}{\mathrm{s}}^{--\mathrm{1个}}{\mathrm{sr}}^{--\mathrm{1个}}$（E > 10  MeV）和1.0– 2.5×10 ⁴ $\mathrm{电子}{\mathrm{厘米}}^{--\mathrm{2}}{\mathrm{s}}^{--\mathrm{1个}}{\mathrm{sr}}^{--\mathrm{1个}}$（E  =  100–300  keV）。根据WACCM模拟，夜间OH和HO ₂是极地地区的良好EPP指标，并能在高度和纬度上提供最佳覆盖范围。由于背景浓度较高，因此白天检测需要较大的EPP通量，并且仅在中层中才有可能。SPE检测比RBE检测更容易，因为极地纬度的更广泛的受到了影响，即SPE影响是相当一致的偏北60 ^∘，而RBE影响主要集中在60 ^∘。海拔高度明智的，SPE和RBE检测有可能在≈  35-80和≈  65-75 公里， 分别。我们还发现，类似于模拟，MLS OH观测表明在中层对SPE和RBE的夜间响应清晰。但是，MLS OH数据对于在50 km以下的平流层中的响应检测来说太嘈杂了 ，而HO _2的测量总体而言对于每天进行自信的EPP检测来说也太嘈杂了。