Event Details

Space and Planetary Physics webinar

Heliospheric plasmas have long been investigated using a fluid approach. However, a growing body of evidence indicates that kinetic processes are of extreme relevance in determining plasma dynamics in the heliosphere. Notable examples are collisionless processes that shape the velocity distribution functions of electrons and ions in the solar wind and ultimately its evolution [1]. A kinetic description is also necessary for investigating magnetic reconnection events in the heliosphere from first principles [2] and to understand turbulent dissipation at the electron scales [3]. In all these cases, the underpinning physics is intrinsically non-linear, multi-dimensional and multi-scale. Kinetic simulations based on the Particle-In-Cell (PIC) paradigm can advance our understanding of space plasmas but are very challenging especially when the aim is to model processes that span over a multitude of time and spatial scales. In this seminar, I will introduce an innovative PIC algorithm which allows for performing large scale simulations retaining a kinetic description for electrons and ions at a moderate computational cost [4]. This is obtained employing an implicit discretisation in time for particle and field equations and exploiting the moments of the distribution function. Examples showing the stability and accuracy of the code for different spatial and temporal resolutions will be discussed. Finally, fully kinetic simulations that for the first time explore the impact of electron anisotropies on the development of the proton firehose instability in the solar wind will be presented [5].

[1] Marsch, Living Rev. Solar Phys. 3, 1 (2006). Verscharen, Living Rev. Solar Phys. 16, 5 (2019).

[2] Hesse and Cassak, J. Geophys. Res. 125, e2018JA025935 (2020).

[3] Alexandrova, Saur, Lacombe, Mangeney, Mitchell, Schwartz and Robert, Phys. Rev. Lett. 103, 165003 (2009).

[4] Lapenta, Gonzalez-Herrero and Boella, Journal of Plasma Physics, 83, 705830205 (2017). Gonzalez-Herrero, Boella and Lapenta, Computer Physics Communications 229, 162 (2018).

[5] Micera, Boella, Zhukov, Shaaban, Lopez, Lazar and Lapenta, Astrophys. J. Lett. 893, 130 (2020).

If someone from outside of the SPP group would like to join the webinar, please send a request to w.gould@lancaster.ac.uk