Solar abundances have been historically assumed to be representative of cosmic abundances. However, our knowledge of the solar abundance of helium, the second most abundant element, relies mainly on models¹ and indirect measurements through helioseismic observations², because actual measurements of helium in the solar atmosphere are very scarce. Helium cannot be directly measured in the photosphere because of its high first ionization potential, and measurements of its abundance in the inner corona have been sporadic^3,4. In this Letter, we present simultaneous global images of the helium (out to a heliocentric distance of 3R_⊙ (solar radii)) and hydrogen emission in the solar corona during the minimum of solar activity of cycle 23 and directly derive the helium abundance in the streamer region and surrounding corona (out to 2.2R_⊙). The morphology of the He⁺ corona is markedly different from that of the H corona, owing to significant spatial variations in helium abundance. The observations show that the helium abundance is shaped according to and modulated by the structure of the large-scale coronal magnetic field and that helium is almost completely depleted in the equatorial regions during the quiet Sun. This measurement provides a trace back to the coronal source of the anomalously slow solar wind observed in the heliosphere at the Sun–Earth Lagrangian point L1 in 2009, during the exceptionally long-lasting minimum of solar activity cycle 23.

历史上一直假设太阳丰度代表宇宙丰度。但是，我们对氦的太阳丰度（第二富元素）的了解主要依赖于模型¹和通过日震观测法^2的间接测量，因为太阳大气中氦的实际测量非常稀缺。由于氦具有很高的第一电离势，因此无法直接在光球中对其进行测量，并且在内部电晕中的氦丰度测量值是零星的^3,4。在该信中，我们提出了氦的全球同步图像（缩小到3的日心距ř _⊙（太阳半径）），并且在最小周期23的太阳活动的期间日冕氢发射并直接导出氦丰度在流光区和围绕电晕（下至2.2 ř _⊙）。He ⁺的形态由于氦的丰度存在明显的空间变化，因此电晕与H型电晕显着不同。观测结果表明，氦的丰度根据大型日冕磁场的结构而定并受其调节，并且在安静的太阳期间，赤道区域的氦几乎被完全耗尽。这项测量结果可以追溯到2009年太阳-地球拉格朗日L1点日冕层中异常缓慢的太阳风的冠状源，当时太阳活动周期非常短暂，持续时间极短。