Correcting the NOAA/MEPED energetic electron fluxes for detector efficiency and proton contamination
Correcting the NOAA/MEPED energetic electron fluxes for detector efficiency and proton contamination
复制标题
校正 NOAA/MEPED 高能电子通量以提高探测器效率和质子污染
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
K. Mursula
中科院分区：
文献类型：
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作者：
T. Asikainen;K. Mursula
NOAA/POES卫星上的中能质子和电子探测器（MEPED）仪器提供了从1978年至今的低空高能粒子观测的宝贵长期数据库。在这里，我们研究的仪器问题的NOAA/MEPED电子探测器和目前的方法来纠正他们。众所周知，MEPED电子探测器会被一定能量范围的质子污染。使用最近校正的MEPED质子通量，我们现在能够可靠地去除这种污染。使用一个简单的模拟模型来估计MEPED电子探测器对入射电子和质子的响应，我们发现由于探测器设计不同，（空间环境探测器）SEM-1和SEM-2版本的探测器的效率有很大的差异。这导致SEM-1和SEM-2测量之间的系统差异，并导致测量的MEPED电子通量的显著长期不均匀性。使用估计的效率，我们删除质子污染和纠正非理想的检测器效率的电子测量。我们讨论了MEPED测量的整个34年时间序列，并表明平均而言，校正对不同能量通道以及SEM-1和SEM-2仪器的影响不同。因此，未校正的电子通量和电子光谱由于非理想的探测器效率和质子污染而严重失真，并且它们的长期演化在没有校正的情况下被歪曲。目前对覆盖几个太阳周期的NOAA/POES测量的整个间隔内的MEPED电子通量的校正对于长期研究很重要，例如，磁层动力学、太阳活动、电离层研究和高能电子的大气效应。
The Medium Energy Proton and Electron Detector (MEPED) instruments onboard the NOAA/POES satellites have provided a valuable long‐term database of low‐altitude energetic particle observations spanning from 1978 to present. Here we study the instrumental problems of the NOAA/MEPED electron detectors and present methods to correct them. It is well known that the MEPED electron detectors are contaminated by protons of certain energy range. Using the recently corrected MEPED proton fluxes, we are now able to reliably remove this contamination. Using a simple simulation model to estimate the response of the MEPED electron detectors to incoming electrons and protons, we show that efficiencies of (Space Environment Monitors) SEM‐1 and SEM‐2 versions of the detectors have large differences due to different detector designs. This leads to a systematic difference between the SEM‐1 and SEM‐2 measurements and causes a significant long‐term inhomogeneity in measured MEPED electron fluxes. Using the estimated efficiencies, we remove the proton contamination and correct the electron measurements for nonideal detector efficiency. We discuss the entire 34 year time series of MEPED measurements and show that, on an average, the correction affects different energy channels and SEM‐1 and SEM‐2 instruments differently. Accordingly, the uncorrected electron fluxes and electron spectra are severely distorted by nonideal detector efficiency and proton contamination, and their long‐term evolution is misrepresented without the correction. The present correction of the MEPED electron fluxes over the whole interval of NOAA/POES measurements covering several solar cycles is important for long‐term studies of, e.g., magnetospheric dynamics, solar activity, ionospheric research, and atmospheric effects of energetic electrons.