Browsing Astronomy by Author "Bessho, Naoki"
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- ItemLower-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.
- ItemPIC 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".
- ItemPIC simulation data for "Magnetic reconnection and instabilities in the Earth's quasi-parallel bow shock": foreshock region(2022) Bessho, NaokiSimulation data for a study of magnetic reconnection in foreshock waves, supported by a NASA grant 80NSSC20K1312, "Magnetic reconnection and instabilities in the Earth's quasi-parallel bow shock". Please see the data description file about details for the data.
- ItemPIC 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.
- ItemWhistler Waves Associated With Electron Beams in Magnetopause Reconnection Diffusion Regions(Wiley, 2022-09-12) Wang, Shan; Bessho, Naoki; Graham, Daniel B.; Le Contel, Olivier; Wilder, Frederick D.; Khotyaintsev, Yuri V.; Genestreti, Kevin J.; Lavraud, Benoit; Choi, Seung; Burch, James L.Whistler waves are often observed in magnetopause reconnection associated with electron beams. We analyze seven MMS crossings surrounding the electron diffusion region (EDR) to study the role of electron beams in whistler excitation. Waves have two major types: (a) Narrow-band waves with high ellipticities and (b) broad-band waves that are more electrostatic with significant variations in ellipticities and wave normal angles. While both types of waves are associated with electron beams, the key difference is the anisotropy of the background population, with perpendicular and parallel anisotropies, respectively. The linear instability analysis suggests that the first type of wave is mainly due to the background anisotropy, with the beam contributing additional cyclotron resonance to enhance the wave growth. The second type of broadband waves are excited via Landau resonance, and as seen in one event, the beam anisotropy induces an additional cyclotron mode. The results are supported by particle-in-cell simulations. We infer that the first type occurs downstream of the central EDR, where background electrons experience Betatron acceleration to form the perpendicular anisotropy; the second type occurs in the central EDR of guide field reconnection. A parametric study is conducted with linear instability analysis. A beam anisotropy alone of above ∼3 likely excites the cyclotron mode waves. Large beam drifts cause Doppler shifts and may lead to left-hand polarizations in the ion frame. Future studies are needed to determine whether the observation covers a broader parameter regime and to understand the competition between whistler and other instabilities.