Karl‐Heinz Rädler died on the 9th of February 2020 at his home near Potsdam at the age of 85 years. He is known for his path‐breaking contributions to the development of cosmic dynamo theory. Together with Max Steenbeck and Fritz Krause, he presented a rigorous derivation of the α effect in 1966. A few years later, after their work became known in the West, many scientists around the globe applied their theory and started working on models of solar and Galactic dynamos. The field of mean‐field dynamo theory was born, and it started a new industry in astrophysics.

The roots of what is now sometimes referred to as the Potsdam Dynamo School go back to an earlier episode that started in Jena. After graduating from the University of Leipzig, Karl‐Heinz Rädler developed his lifelong interest in the origin of cosmic magnetic fields when he took up a position as an assistant at the Institute for Magnetohydrodynamics at the Akademie der Wissenschaften in Jena. He joined the group of Max Steenbeck, where the theory of averaged magnetic fields was formulated and where he defended his PhD thesis “Zur Elektrodynamik turbulent bewegter leitender Medien.” It marked the beginning of a new discipline of mathematical physics, dealing with the equations of magnetohydrodynamics in turbulent media.

In the 1970s, the research activities were moved to the Zentralinstitut für Astrophysik at Potsdam. This activity significantly shaped the profile of the Institute and contributed to its high international standing. Until today, many of the theoretical, numerical, and experimental studies of magnetohydrodynamics are based on the monograph “Mean‐field Magnetohydrodynamics and Dynamo Theory” by Krause and Rädler of 1980.

After the Fall of the Iron Curtain, owing to Rädler's scientific competence and personal integrity, as well as his democratic way of thinking, he was elected as the spokesperson of the scientific council of the Institute. Professor Rädler was chosen to become the founding director of what became the new Astrophysical Institute of Potsdam on the premises of the old observatory at Babelsberg. During that time, the Institute started collaboration with the Large Binocular Telescope in Arizona, as well as the telescope systems GREGOR and STELLA at Tenerife. It was also during this time when K.H. Rädler was active as the Editor‐in‐Chief of the Astronomische Nachrichten/Astronomical News. Another scientific highlight was his involvement in the theoretical underpinning of the Karlsruhe dynamo experiment in the late 1990s. Using the mean‐field approach, he and his team in Potsdam prepared detailed predictions for the excitation conditions and saturation behavior for the dynamo experiment.

Karl‐Heinz Rädler remained an acting master of the field until his last years. Particularly noteworthy is his work of 2005, when he devised a numerical procedure for computing the full set of turbulent transport coefficients. With that, mean‐field dynamo theory became an accurate and predictive tool beyond the realm of quasilinear theory.

In celebration of Rädler's 75th birthday, friends and colleagues presented their latest research in Stockholm on the “α effect and beyond.” Some of the contributions in the special issue of Geophysical and Astrophysical Fluid Dynamics provide a lasting memory of this. His lifelong accomplishments have been honored by the Astronomische Gesellschaft through its award of the Karl Schwarzschild medal of 2013.

His very last big contribution to the community was as one of the guest editors of the Journal of Plasma Physics of 2018 with the title “50 years of Mean Field Electrodynamics,” which fittingly characterizes a subject of which he was part of since the very first hour.

卡尔·海因茨·莱德勒（Karl-HeinzRädler）于2020年2月9日在波茨坦附近的家中去世，享年85岁。他以其对宇宙发电机理论发展的开拓性贡献而闻名。1966年，他与马克斯·斯滕贝克（Max Steenbeck）和弗里茨·克劳斯（Fritz Krause）一起提出了α效应的严格推导。几年后，在西方被人们所熟知的工作之后，全球许多科学家应用了他们的理论，并开始研究太阳能和太阳能的模型。银河动力。平均场发电机理论领域诞生了，它开创了天体物理学的新产业。

有时被称为波茨坦迪纳摩学校的起源可以追溯到耶拿开始的早期情节。从莱比锡大学毕业后，卡尔·海因茨·拉德勒（Karl-HeinzRädler）担任耶拿大学（Aenademie der Wissenschaften）磁流体力学研究所的助理，对宇宙磁场的起源产生了终生的兴趣。他加入了马克斯·斯滕贝克（Max Steenbeck）小组，在那里制定了平均磁场理论，并为他的博士学位论文“ Zur Elektrodynamik湍流的保加利亚解放者Medien”辩护。它标志着数学物理新学科的开始，该学科处理湍流介质中的磁流体动力学方程。

在1970年代，研究活动转移到波茨坦的ZentralinstitutfürAstrophysik。这项活动大大改变了该研究所的形象，并为其在国际上的崇高地位作出了贡献。直到今天，磁流体动力学的许多理论，数值和实验研究都是基于1980年Krause和Rädler撰写的专着《中场磁流体动力学和发电机理论》。

铁幕垮台后，由于Rädler的科研能力与操守，以及他的思维民主的方式，他当选为学院科学委员会的发言人。Rädler教授被选为在Babelsberg旧天文台所在地的波茨坦新天体物理研究所的创始主任。在此期间，研究所开始与亚利桑那州的大型双筒望远镜以及特内里费岛的GREGOR和STELLA望远镜系统进行合作。也是在此期间，KHRädler活跃于Nachrichten天文学/天文新闻的主编。另一个科学亮点是他在1990年代后期参与了卡尔斯鲁厄发电机实验的理论基础。使用均场方法

卡尔·海因茨·莱德勒（Karl-HeinzRädler）一直担任该领域的表演大师，直到他最后几年。特别值得一提的是他在2005年的工作，当时他设计了一种数值程序来计算整套湍流输运系数。这样，均场发电机理论就成为了准线性理论领域之外的一种精确的预测工具。

为了庆祝拉德勒（Rädler）诞辰75周年，朋友和同事在斯德哥尔摩介绍了他们对“ α效应及超越”的最新研究。在《地球物理与天体流体动力学》特刊中的一些贡献为它提供了持久的记忆。他的毕生成就获得了天文学奖（2013年授予Karl Schwarzschild奖章）的嘉奖。

他对社区的最后一项重大贡献是作为《等离子体物理学》杂志2018年的客座编辑之一，题为“平均场电动力学50年”，从一开始就恰当地刻画了他作为该学科的一员。小时。