Helios E6 (quiet-time) single detector count rates

The new Helios E6 quiet-time dataset provides full-mission time series for Helios 1 and Helios 2 based on single-detector count rates used in the SPEARHEAD Deliverable D5.3. Each record is converted to calendar datetime format and contains the midpoint time, start and end times, accumulation time, the single-detector count rates D2, D5, CE, and AN with their statistical errors, the derived ratio D2/D5, and a quiet-time flag. The flag `quiet_time` is set to 1 when the record has sufficient accumulation time (`acc > 0.2` hours) and its D2/D5 ratio lies within the Gaussian quiet-time band defined by `mean ± 4 sigma`; otherwise it is set to 0. Thus, the dataset preserves the complete mission data while making quiet-time intervals directly identifiable for further analysis.全新太阳神E6静默时段数据集基于SPEARHEAD项目可交付成果D5.3中采用的单探测器计数率，为太阳神1号（Helios 1）与太阳神2号（Helios 2）提供覆盖全任务周期的时间序列。每条记录均转换为日历日期时间格式，包含中点时刻、起始时刻与终止时刻、累积时长，单探测器计数率D2、D5、CE、AN及其统计误差，衍生比值D2/D5，以及静默时段标记。当记录满足累积时长充足（acc>0.2小时）且D2/D5比值处于由均值±4倍标准差定义的高斯静默时段带内时，`quiet_time`标记将被设为1；反之则设为0。该数据集完整保留了全部任务数据，同时可直接识别出静默时段区间以供后续分析使用。