Obituary for Prof. Giovanni Lapenta (1965 - 2024)

Annonce transmise par Carine Briand (LESIA)

From: Enrico Camporeale, Stefaan Poedts

With extreme sadness, we announce the premature passing of Prof. Giovanni Lapenta, an eminent scientist whose groundbreaking contributions to space plasmas and computational plasma physics have left an indelible mark on the field.

Gianni, as he was known among friends and colleagues, received a Master's degree (Laurea) in Nuclear Engineering in 1989 and a PhD in Plasma Physics in 1993 from the Polytechnic of Turin (Italy). He spent one year as a visiting scholar at MIT, working with Prof. Bruno Coppi. He then moved to the Los Alamos National Laboratory, initially as a Director's Postdoctoral Fellow and later as a Staff Member, where he worked until 2007. During those years, his interest shifted more and more from fusion to space plasmas.

In 2007, he was appointed full professor of Mathematics of Space Weather in the Centre for mathematical Plasma Astrophysics at KU Leuven (Belgium). He recently held a dual affiliation with his alma mater, Polytechnic of Turin, where he was also appointed full professor. Sadly, his dream to spend the final years of his career and his retirement in his beloved Turin was cut short by a devastating illness.

Gianni made fundamental and everlasting contributions in the fields of space plasmas and computational plasma physics. In particular, he pioneered some of the early studies on kinetic instabilities driving collisionless reconnection by using state-of-the-art kinetic simulations. His seminal work on the fundamental mechanisms underlying magnetic reconnection, particularly the roles of drift instabilities such as kink, lower hybrid, and tearing modes, and the interplay with turbulent reconnection has significantly advanced our understanding of plasma dynamics, influencing both theoretical frameworks and practical applications in space and laboratory plasmas.

Equally important are his contributions to the field of computational plasma physics. During his early years in Los Alamos and under the guidance of Jerry Brackbill, he became one of the major proponents of the so-called implicit moment particle-in-cell (PIC) method. This method, which became a cornerstone of the "Lapenta school," allows for the fully kinetic treatment of both ions and electrons without the numerical instabilities typical of explicit schemes (such as the CFL condition). A major milestone has been developing and releasing the 3D parallel version of the implicit PIC code, iPIC3D. Gianni was among the first in our community to embrace the philosophy of open-source code development, understanding the benefits of disseminating his computational works as widely as possible. In the last 15 years, iPIC3D has been used by a large number of researchers, all driven by Gianni's vision of extending the reach of kinetic simulations.

Throughout his career, Gianni has mentored a large number of students and early career researchers, many of which have flourished into accomplished scientists. Those fortunate enough to have worked with him remember his passion for science and his ambition to push the boundaries of knowledge.

Thanks to his clear vision, his excellent ability to communicate, and his charismatic leadership, Gianni was a leading figure in large European projects in the field of space weather and heliophysics. Among the many projects, Gianni has been a pioneer in understanding the disruptive potential of Artificial Intelligence and Machine Learning in our field, leading the AIDA (Artificial Intelligence Data Analysis) project, possibly the first EU-funded project explicitly focused on the use of AI in heliophysics. This was followed by ASAP (Automatics in Space Exploration), which is still active and focuses on deploying AI in space for robotic exploration. Recently, Gianni received an Advanced ERC (European Research Community) grant called TerraVirtualE, which promised to simulate, for the first time, a full planetary space environment with kinetic ions and electrons. Central to this project was his latest breakthrough in computational plasma physics, the Energy-Conserving semi-implicit method (ECsim), which enhances the semi-implicit PIC method with energy conservation for long-term simulations.

The frequent jest among friends and colleagues about his apparent immunity to funding challenges highlighted his ability to embrace visionary projects and push the limits of what is possible.

Gianni's untimely departure is a significant loss to the many projects he led. However, his love for science, visionary insights, leadership, and friendly demeanour will always be remembered by those who had the privilege of calling him a mentor, collaborator, and friend.