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Item Dynamics of the Storm Time Magnetopause and Magnetosheath Boundary Layers: An MMS-THEMIS Conjunction(Wiley, 2024-02-13) Rice, Rachel C.; Chen, Li-Jen; Gershman, Dan; Fuselier, Stephen A.; Burkholder, Brandon L.; Gurram, Harsha; Beedle, Jason; Shuster, Jason; Petrinec, Steven M.; Pollock, Craig; Cohen, Ian; Gabrielse, Christine; Escoubet, Philippe; Burch, JamesThis letter uses simultaneous observations from Magnetosphere Multiscale (MMS) and Time History of Events and Macroscale Interactions during Substorms (THEMIS) to address the dynamics of the magnetopause and magnetosheath boundary layers during the main phase of a storm during which the interplanetary magnetic field (IMF) reverses from south to north. Near the dawn terminator, MMS observes two boundary layers comprising open and closed field lines and containing energetic electrons and ring current oxygen. Some closed field line regions exhibit sunward convection, presenting an avenue to replenish dayside magnetic flux lost during the storm. Meanwhile, THEMIS observes two boundary layers in the pre-noon sector which strongly resemble those observed at the flank by MMS. Observations from the three THEMIS spacecraft indicate the boundary layers are still evolving several hours after the IMF has turned northward. These observations advance our knowledge of the dynamic magnetopause and magnetosheath boundary layers under the combined effects of an ongoing storm and changing IMF.Item Lower-Hybrid Wave Structures and Interactions With Electrons Observed in Magnetotail Reconnection Diffusion Regions(Wiley, 2022-04-22) Wang, Shan; Chen, Li-Jen; Bessho, Naoki; Ng, Jonathan; Hesse, Michael; Graham, Daniel B.; Le Contel, Olivia; Gershman, Daniel; Giles, BarbaraWe investigate waves close to the lower-hybrid frequency in 12 magnetotail reconnection electron diffusion region (EDR) events with guide field levels of near-zero to 30%. In about half of the events, the wave vector has a small component along the current sheet normal, consistent with known lower-hybrid drift wave properties, but the perpendicular magnetic field fluctuations can be comparable or greater than the parallel component, a feature unique to the waves inside and adjacent to EDRs. Another new wave property is that the wave vector has a significant component along the current sheet normal in some events and completely along the normal for one event. In 1/4 of the events, the 𝐴𝐴∇⋅𝑷𝑷𝑒𝑒 term has a significant contribution to the wave electric field, possibly a feature of lower-hybrid waves more likely to exist in the diffusion region than further away from the X-line. Electron temperature variations are correlated with the wave potential, due to wave electric field acceleration and crossings at the corrugated separatrix region with different amounts of mixing between reconnection inflowing and outflowing populations. The latter also leads to the anti-correlation between parallel and perpendicular temperature components. Using four-spacecraft measurements, the magnetic field line twisting is demonstrated by the correlated fluctuations in 𝐴𝐴(∇×𝑽𝑽𝐸𝐸×𝐵𝐵)|| and 𝐴𝐴(∇×𝐁𝐁)||. The lower-hybrid wave in the EDR of weak guide field reconnection may be generated near separatrices and penetrate to the mid-plane or locally generated, and the latter possibility is beyond the prediction of previous reconnection simulations.Item Dataset for "Reconstruction of electron and ion distribution functions in magnetotail reconnection diffusion region"(2020-02) Ng, Jonathan; Chen, Li-Jen; Hakim, Ammar; Bhattacharjee, AmitavaIn the diffusion region of magnetotail reconnection, particle distributions are highly structured, exhibiting triangular shapes and multiple striations that deviate dramatically from the Maxwellian distribution. Fully kinetic simulations have been demonstrated to be capable of producing the essential structures of the observed distribution functions, yet are computationally not feasible for 3D global simulations. The fluid models used for large-scale simulations, on the other hand, do not have the kinetic physics necessary for describing reconnection accurately. Our study aims to bridge fully kinetic and fluid simulations by quantifying the information required to capture the non-Maxwellian features in the distributions underlying the closures used in the fluid code. We compare the results of fully kinetic simulations to observed electron velocity distributions in a magnetotail reconnection diffusion region, and use the maximum entropy model to reconstruct electron and ion distributions using various numbers of moments obtained from the simulation. Our results indicate that using only local moments, the maximum entropy model can reproduce many of the features of the distributions: (1) the anisotropic electron distributions inside the ion diffusion region but outside the current-sheet can be modelled with 10-14 moments, (2) the electron-outflow distribution with a tilted triangular structure is reproduced with 21-35 moments and (3) counterstreaming distributions can be captured with the 35-moment model when the separation in velocity space between the populations is large.Item PIC simulation data for "Magnetic reconnection in a quasi-parallel shock: two-dimensional local particle-in-cell simulation"(2019) Bessho, Naoki; Chen, Li-Jen; Wang, Shan; Hesse, Michael; Wilson, Lynn, III2-dimensional particle-in-cell simulation data for a paper "Fully kinetic simulations of magnetic reconnection in the Earth’s quasi-parallel bow shock" Data for fig.1(a): by1250-fig1a.txt, by1563-fig1a.txt, by1875-fig1a.txt, format: x/d_i, B_y/B_0. For fig.1(b)(c)(d): az1250.txt, az1563.txt, az1875.txt, format: x/d_i, y/d_i, A_z/(B_0d_i). For fig1(e)(f)(g)(h)(i)(j): ex1875.txt, cuz1875.txt, bz1875.txt, ne1875.txt, vxe1875.txt, vye1875.txt, format: x/d_i, y/d_i, Q, where Q is each normalized field quantity (E_x, J_z, B_z, N_e, V_ex, V_ey). Normalization is given in the figure. Data for fig.2(a) for J_z, fig.2(b) for B_z, fig.2(d) for V_ex, fig.2(e) for V_ey are the same as given in fig1. For fig.2(c): cde1875.txt. For fig.2(g)(h): vxi1875.txt, vyi1875.txt. For contour of A_z for each plot, use az1875.txt. For vector plot of fluid velocities, use vxe1875.txt, vye1875.txt, vxi1875.txt, vyi1875.txt. For fig.2(f)(i): az1888.txt, az1900.txt. Format is the same as other 2-D plots. Data for fig.3(a), use ne1875.txt. For fig.3(b): ez1875.txt. For vector plot of fluid velocities, use vxe1875.txt, vye1875.txt. For vector plot of E-field: exav1875.txt, eyav1875.txt. Format is the same as other 2-D plots. For contour of A_z for each plot, use az1875.txt. For fig.3(c)(d)(e): bjc#.txt, ejc#.txt, cujc#.txt, vjec#.txt, vjic#.txt, nec#.txt, cdec#.txt, where the letter j represents a component of the field (x, y, z), and # represents a number (1, 2, or 3), format: y/d_i, Q. For fig.3(f)(g)(h)(i): fj-fig3-?#.txt, where the letter j represents e (electron) or i (ion), ? represents a figure alphabet (f, g, h, or i), and # represents a number 1 (left panel) or 2 (right panel), format: v_k/v_A, v_l/v_A, count, where v_k is the x axis of the velocity and v_l is the y axis of the velocity. Data for fig.4(a): vyi1797.txt, az1797.txt, the same format as other 2-D plots. For fig.4(b), use vyi1875.txt and az1875.txt. For fig.4(c)(d), use vyi1875.txt, vye1875.txt, for A_z contour az1875.txt, and for velocity vectors, also use vxi1875.txt and vxe1875.txt. For fig.4(e), viin-x1875.txt, for velocity vector: vxi-x1875.txt, vyi-x1875.txt, and use az1875.txt for A_z contour. For fig.4(f), vein-x1875.txt, for velocity vector: vxe-x1875.txt, vye-x1875.txt, and use az1875.txt for A_z contour. For fig.4(g)(h): bjc#.txt, ejc#.txt, cujc#.txt, vjec#.txt, vjic#.txt, nec#.txt, cdec#.txt, where the letter j represents a component of the field (x, y, z), and # represents a number (4 or 5), format: x/d_i, Q. For fig.4(i), viinc4.txt, viinc5.txt, format x/d_i, |v_i-xy|/v_A. For fig.4(j), veinc4.txt, veinc5.txt, format x/d_i, |v_e-xy|/v_A. For fig4.(k): fj-fig4-k#.txt, where the letter j represents e or i, and # represents a number 1 (top panel), 2 (middle panel), or 3 (bottom panel), format: v_k/v_A, v_l/v_A, count, where v_k is the x axis of the velocity and v_l is the y axis of the velocity.Item PIC simulation data for "Effect of the reconnection electric field on electron distribution functions in the diffusion region of magnetotail reconnection"(2018) Bessho, Naoki; Chen, Li-Jen; Wang, Shan; Hesse, Michael2-dimensional particle-in-cell simulation data for a paper, "Effect of the reconnection electric field on electron distribution functions in the diffusion region of magnetotail reconnection".