Adriani O, Barbarino G C, Bazilevskaya G A, Bellotti R, Boezio M, Bogomolov E A, Bongi M, Bonvicini V, Bottai S, Bruno A, Cafagna F, Campana D, Carlson P, Casolino M, Castellini G, De Santis C, Di Felice V, Galper A M, Karelin A V, Koldashov S V, Koldobskiy S A, Krutkov S Y, Kvashnin A N, Leonov A, Malakhov V, Marcelli L, Martucci M, Mayorov A G, Menn W, Mergé M, Mikhailov V V, Mocchiutti E, Monaco A, Mori N, Munini R, Osteria G, Panico B, Papini P, Pearce M, Picozza P, Ricci M, Ricciarini S B, Simon M, Sparvoli R, Spillantini P, Stozhkov Y I, Vacchi A, Vannuccini E, Vasilyev G I, Voronov S A, Yurkin Y T, Zampa G, Zampa N, Potgieter M S, Vos E E
University of Florence, Department of Physics, I-50019 Sesto Fiorentino, Florence, Italy.
INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence, Italy.
Phys Rev Lett. 2016 Jun 17;116(24):241105. doi: 10.1103/PhysRevLett.116.241105.
Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.
宇宙射线电子和正电子是宇宙射线传播以及银河系中粒子源的性质和分布的独特探测器。最近对这些粒子的测量正在挑战我们对宇宙射线产生、加速和传播机制的基本理解。特别引人注目的是，由太空搭载的PAMELA和AMS - 02实验收集的低能结果与早期测量结果之间存在差异，这些早期测量结果表明宇宙射线光谱的太阳调制存在符号电荷依赖性。PAMELA实验从2006年7月到2015年12月一直在测量地球上正电子和电子强度的时间变化，涵盖了从太阳活动周期23的最小值（2006 - 2009年）到太阳活动周期24最大值的中期这段时间，期间经历了2013年至2014年发生的日球层磁场极性反转。在此时间段内测量的正电子与电子比率清楚地显示了由粒子漂移引入的太阳调制的符号电荷依赖性。这些结果首次清晰且连续地观测到从太阳活动极小期到极大期，漂移对太阳调制的影响是如何随时间展开的，以及它们对粒子刚性和太阳磁场循环极性的依赖性。
