We report on the annual variation of quiet-time suprathermal heavy ion spectral indices for C through Fe in the energy range 0.3–1.28 MeV nuc⁻¹ during Solar Cycle 23's rising phase through Solar Cycle 24's declining phase. These Advanced Composition Explorer/Ultra-Low Energy Isotope Spectrometer measurements cover 1998–2019. We show that the average quiet-time suprathermal spectral index across species is γ = 2.5 ± 0.3. Such observations may imply that quiet-time suprathermals are the result of a superposition of various underlying acceleration and transport processes that accelerate suprathermal ions. As such, they may be remnants of particles from discrete events like large and impulsive solar energetic particle events along with corotating interaction regions that have decayed in intensity.

中文翻译：

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第 23 和 24 太阳周期中 1 au 附近超热重离子的安静时光谱

我们报告了第 23 个太阳周期的上升阶段到第 24 个太阳周期的下降阶段期间0.3–1.28 MeV nuc ^-1能量范围内 C 到 Fe 的安静时超热重离子光谱指数的年度变化。这些高级成分探索者/超低能量同位素光谱仪测量涵盖 1998 年至 2019 年。我们表明，不同物种的平均安静时间超热光谱指数为γ= 2.5 ± 0.3。这些观察结果可能意味着安静时超热物质是加速超热离子的各种潜在加速和传输过程叠加的结果。因此，它们可能是来自离散事件（例如大型脉冲太阳高能粒子事件）以及强度已衰减的共旋转相互作用区域的粒子残余物。