Illya Plotnikov's research while affiliated with Paul Sabatier University - Toulouse III and other places

... Additionally, shock formation can occur in the presence of extreme magnetic fields, as in PWNe where the electron cyclotron frequency ω ce can exceed the electron plasma frequency ω pe , σ cold,e = ω 2 ce /ω 2 pe = B 2 /μ 0 γ 0 m e n e c 2 > 1 [12]. Several theoretical and computational studies have been performed in the astrophysics community for σ 0.1 [13][14][15][16]. However, laboratory exploration of shock formation in relativistic plasma conditions has thus far been limited to ion acceleration by laser-driven electrostatic shocks [5,17]. ...

... The large scale separation inherent to the streaming problem has also led to the development of new methods, such as MHD-PIC (Bai et al. 2015(Bai et al. , 2019Lebiga et al. 2018;Sun & Bai 2023), which has been used to study ion-neutral damping (Plotnikov et al. 2021;Bai 2022;Bambic et al. 2021). MHD-PIC describes the thermal plasma using the magnetohydrodynamic (MHD) approximation while capturing the kinetic physics of the CRs using the PIC method. ...

... Two main scenarios have been put forth to explain the observations. In the first one CME-driven shocks are proposed to be responsible for the direct acceleration of the high-energy protons far from the flaring active region, thus allowing the particles to travel from the acceleration site (close to the AR) to the chromosphere on the visible disk (Cliver et al. 1993;Plotnikov et al. 2017;Jin et al. 2018;Kouloumvakos et al. 2020;Gopalswamy et al. 2020;Wu et al. 2021). arXiv:2205.04760v1 ...

... Such models have played a tremendous role in reproducing the 3D evolution of the magnetic fields (Cheung & DeRosa 2012;Jiang et al. 2016;Inoue et al. 2018aInoue et al. , 2018bGuo et al. 2019;Y. Guo et al. 2021;Pomoell et al. 2019) and the thermodynamics (Török et al. 2018;Fan 2022;Guo et al. 2023) in the corona, as well as the ICME propagation in the interplanetary space (Pomoell & Poedts 2018;Poedts et al. 2020;Scolini et al. 2020;Verbeke et al. 2022). Here, we perform a nonadiabatic data-constrained magnetohydrodynamic (MHD) simulation of the filament eruption event that occurred on 2022 August 18, which exhibits obvious lateral drifting during its ascent, as captured by Solar Dynamics Observatory (SDO; Pesnell et al. 2012) and Chinese Hα Solar Explorer (CHASE; Li et al. 2019Li et al. , 2022 simultaneously. ...

... • Cyclotron/Synchrotron radiation: These mechanisms have been introduced to interpret FRBs within the synchrotron maser models that invoke electron gyration in ordered magnetic fields in quasi-perpendicular shocks (Lyubarsky 2014; Metzger et al. 2019;Beloborodov 2020;Plotnikov & Sironi 2019). Numerical simulations show that the narrowness of the spectrum can reach Δ / 0 ∼ 0.2 in the case that electrons are non-relativistic. ...

... The stable γ -ray emission centroid position in the two temporal intervals separated by one hour corresponds more to the flare-related origin of accelerated protons than to their shock-related origin. In the latter case, the γ -ray emission centroid position would be expected to move across the solar disk (Plotnikov, Rouillard, and Share, 2017;Kouloumvakos et al., 2020). ...

... where r down,S is the downstream gyroradius. Then, the downstream residence time of accelerated particles is roughly given by t d,S ∼ κ/c 2 (e.g., Sironi et al. 2013;Lemoine et al. 2019;Vanthieghem et al. 2020). On the other hand, the upstream residence time of accelerated particles is given bỹ Wt u,S up,S 1 (Achterberg et al. 2001). ...

... As it is seen from the numerous observations, the hydro-dynamic flow velocities and the plasma temperatures in such astrophysical objects reach relativistic values. Alexander M. et al. conducted a numerical study that examined the acceleration and transport of energetic particles in turbulent astrophysical flows [31]. In their study, Palenzuela et al. investigated the significance of the interaction between black holes and ambient magnetic fields in various highly energetic astrophysical phenomena [32]. ...

... It is well-known that relativistic shocks emit coherent electromagnetic waves [1][2][3][4][5][6][7][8], which are assumed to originate from the synchrotron maser instability (SMI) [9]. 1D particle-in-cell (PIC) simulations of relativistic shocks demonstrated that longitudinal electrostatic waves, which are called wakefields, are induced in the wake of the large-amplitude electromagnetic waves via the stimulated Raman scattering (SRS) and that nonthermal particles are generated during the nonlinear collapse of the wakefields [10,11]. ...

... In particular, the relative role of solar flares and shocks in the overall energisation process is still unclear. The advent of new techniques to derive the properties of shock waves in the solar corona based on multi-point imaging (Kwon et al. 2015;Rouillard et al. 2016;Kouloumvakos et al. 2019) has instigated new analyses on the relation between shock parameters and energetic particle events detected indirectly as electromagnetic radiation from the Sun (Plotnikov et al. 2017;Kouloumvakos et al. 2020) or directly in situ (Rouillard et al. 2016;Lario et al. 2016;Kouloumvakos et al. 2019;Kouloumvakos et al. 2023). ...