Adapting a multi-grid method to a numerical simulation model of the interaction between Venus and the solar wind
Authors: Jariel Erwan , Aizawa Sae , Modolo Ronan , Leclercq Ludivine , Baskevitch Claire , Andre Nicolas , Persson Moa 
Published: September 2022

&lt;p&gt;Unlike Earth, Venus doesn&amp;#8217;t have an intrinsic magnetic field shielding it from the solar wind. However, an induced&lt;br /&gt;magnetic field is generated from the interaction of solar wind and the dense atmosphere of the planet. Recent&lt;br /&gt;Venus flybys by the BepiColombo mission in October 2020 and August 2021, and by Parker Solar Probe and Solar&lt;br /&gt;Orbiter, are unique opportunities to further study the interaction between Venus and the Sun.&lt;/p&gt;
&lt;p&gt;&lt;br /&gt;Observational data are essential in the study of this interaction but they are limited by the mission&amp;#8217;s trajectory,&lt;br /&gt;offering a constrained view of the processes that take place. On the other hand, simulations offer a global view&lt;br /&gt;of the interactions, allowing us to get results with physical significance that would not have been possible from&lt;br /&gt;observational data only. LatHyS is a three-dimensional parallel multi-species model using the hybrid formalism,&lt;br /&gt;that represents the electrons as a massless fluid conserving the neutrality of the plasma, and the ions by numerical&lt;br /&gt;macroparticles with variable weights. Ions and electrons are coupled together using the Maxwell equations, and the&lt;br /&gt;macroscopic plasma parameters determine the evolution of the magnetic field (&lt;em&gt;Ledvina et al. 2008&lt;/em&gt;). It was initially&lt;br /&gt;developed at LATMOS, Paris, France, for Mars (&lt;em&gt;Modolo et al. 2005&lt;/em&gt;) and later parallelized (&lt;em&gt;Modolo et al. 2016&lt;/em&gt;) for&lt;br /&gt;performance and optimization purposes. It has the advantage of having a self consistently calculated ionosphere.&lt;br /&gt;LatHyS was recently adapted to the simulations of the interaction between the solar wind and Venus at IRAP,&lt;br /&gt;Toulouse, France (&lt;em&gt;Aizawa et al. 2022&lt;/em&gt;).&lt;/p&gt;
&lt;p&gt;&lt;br /&gt;The work conducted aims at adapting a multi-grid method, initially adapted to LatHyS by &lt;em&gt;Leclercq et al. 2016&lt;/em&gt;&lt;br /&gt;for the study of Mars and Ganymede, to the case of Venus. The multi-grid refinement allows a more efficient use&lt;br /&gt;of computing resources and an improved accuracy of the simulation thanks to a spatial resolution equivalent to or&lt;br /&gt;lower than the ionospheric plasma scale height.&lt;/p&gt;
&lt;p&gt;&lt;br /&gt;First, the multi-grid method is presented. Then, simulations using the multi-grid method on the solar wind&amp;#8217;s&lt;br /&gt;interaction with Venus are conducted, and their results are compared to simulations made using LatHyS with a&lt;br /&gt;single homogeneous grid.&lt;br /&gt;Finally the outputs of the numerical simulations are compared to data on the magnetic field and charged particles&lt;br /&gt;from recent flybys and from the Venus Express mission, that orbited the planet from 2006 to 2014.&lt;/p&gt;
&lt;p&gt;&amp;#160;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Aizawa et al. 2022. &lt;em&gt;https://doi.org/10.1016/j.pss.2022.105499&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;Leclercq et al. 2016. &lt;em&gt;http://dx.doi.org/10.1016/j.jcp.2016.01.005&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;Ledvina et al. 2008. &lt;em&gt;http://dx.doi.org/10.1007/s11214-008-9384-6&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;Modolo et al. 2005. &lt;em&gt;https://doi.org/10.5194/angeo-23-433-2005&lt;/em&gt;&lt;/p&gt;
&lt;p&gt;Modolo et al. 2016. &lt;em&gt;http://dx.doi.org/10.1002/2015JA022324&lt;/em&gt;&lt;/p&gt;