In Remembrance of Prof. Giovanni Lapenta

Italy ended research on Nuclear Energy and in response, nuclear engineering faculty at Politecnico di Torinoplaced selected students with established plasma physics groups.  Gianni Lapenta was the first.   He would spend half a year with Bruno Coppi at MIT, and half a year with me at Los Alamos.  When I met Gianni,he said he  liked Boston and Coppi and would prefer to stay there. To my surprise, he arrived in Los Alamosthe following January. I suggested a problem to Gianni,   He published his results  in:  G. Lapenta and J U Brackbill, Dynamic and selective control of the number of particles in kinetic plasma simulations,  J. Comput. Phys. {\bf{115} }(1994) 213.  In another project with semi-conductor manufacturers, we modeled the deposition of 'dust' on large-scale integrated circuits.   Our results were published in G. Lapenta, F. Iinoya and J. U. Brackbill, "Particle-in-cell simulation of glow discharges in complex geometries," in IEEE Transactions on Plasma Science, vol 23 no. 4, pp. 769-779.  We modeled the interaction of a wafer assembly and the surrounding plasma self-consistently.  Gianni did further work on dust charging in a flowing plasma and published the work in Physical Review Letters.  He modeled  particles that developed dipole moments.  Gianni became a staff member, a US citizen, and a member of the plasma physics group.  He began to apply the implicit moment plasma simulation code to study magneitic reconnection.  He brought students from Torino, to Los Alamos, among them Paolo Ricci, Stefano Markidis, Jean-Luc Delzanno, and Maria Elena Innocenti., and he published extensively on the lower hybrid instability, colllisionless reconnection, and , later, turbulence.  In 2008,  he joined the Mathematics Department at KU Leuven  as a professor in Space Weather where he remained until his death in May, 2023.  He continued to  visit the US to work with Maha Abdallah at UCLA and Marty Goldman at the University of  Colorado.  I don't know the full breadth of his work, but I know that he was excited to discover that turbulent flow generated self-sustaining magnetic reconnection.  With Stefano Markidis, he developed a plasma simulation code on  massively parallel computers , and with colleagues at the University of Michigan a method to couple magnetohydrodynamic and kinetic simulation.  My favorite paper appeared in Ap. J. in 2021 on 'Detecting reconnection sites using the Lorentz transformations for electromagnetic fields'.  His method is a simple and reliable way to identify reconnection sites in plasma simulations.Gianni and I were friends for many years.  We talked when he was diagnosed with cancer.  He was upset by the grim prognosis. So many things he had looked forward to were now out of reach, including a visit with us in Los Alamos.  He died 28 May 2023 at his home in Italy.