Abstract
Collisionless shocks are well-known to be very efficient energizers of ions. At the first step of energization relatively low energy suprathermal ion distributions are formed in the vicinity of the quasiperpendicular collisionless shock front during ion reflection and direct transmission. These distributions are formed promptly and at the scale of the shock width mainly due to the ion interaction with the quasistationary electromagnetic structure of the front itself. Their features are intimately related to the fine structure of the shock front in the sense that they depend not only on the bulk shock parameters, such as Mach number, but also on the details of the distribution of the fields, in particular, shock width. Therefore, studies of these distributions may provide valuable information about the shock structure itself. We review the observational data collected during in situ measurements (mainly at the Earth bow shock) and compare it to the numerical simulations and theoretical developments. The developed theory of the ion dynamics in the stationary shock front relates the ion reflection and heating to the insufficient deceleration of the ions in the ramp by the cross-shock potential, as compared to the expected downstream drift velocity, required by the Rankine-Hugoniot relations. As a result, the direct flow energy it transferred into the gyration energy, leading to the gyration of the ion distribution as a whole and enhanced spread in the velocity space, that is, effective collisionless heating. Anisotropy and nongyrotropy are typical features of ion distributions at both low and high-Mach number shocks, which is confirmed by observations. Time-dependent fields, which are not considered in the stationary shock model, are thought to provide subsequent smoothing and isotropization of the ion distributions. These processes occur at scales substantially larger than the shock width.
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Balikhin, M. A. and Wilkinson, W. E.: 1996, 'Ion heating within the ramp of quasi-perpendicular subcritical collisionless shocks', Geophys.Res.Lett. 23, 1063–1066.
Blandford, R. and Eichler, D.: 1987, 'Particle acceleration at astrophysical shocks: A theory of cosmic ray origin', Phys.Rep. 154, 1–75.
Brinca, A. L., Borda de Agua, L. and Winske, D.: 1993, 'On the stability of nongyrotropic ion populations: A first (analytical and simulation) assessment', J.Geophys.Res. 98, 7549–7560.
Burgess, D., Wilkinson, W. P. and Schwartz, S. J.: 1989, 'Ion distribution and thermalization at perpen-dicular and quasi-perpendicular supercritical collisionless shocks', J.Geophys.Res. 94, 8783–8792.
Farris, M. H., Russell, C. T. and Thomsen, M. F.: 1993, 'Magnetic structure of the low beta, quasi-perpendicular shock', J.Geophys.Res. 98,15,285–15,294.
Forslund, D. W., Quest, K. B., Brackbill, J. U. and Lee, K.: 1984, 'Collisionless dissipation in quasi-perpendicular shocks', J.Geophys.Res. 89, 2142–2150.
Fuselier, S. A. and Schmidt, W. K. H.: 1994, 'Hand He heating at the Earth's bow shock', J.Geophys.Res. 99, 11,539–11,546.
Galeev, A. A., Krasnoselskikh, VV. and Lobzin, V. V.: 1988, 'Fine structure of the front of a quasiper-pendicular supercritical shock wave', Soy.J.Plasma Phys. 14, 697–702.
Gedalin, M.: 1996a, 'Ion reflection at the shock front revisited', J.Geophys.Res. 101, 4871–4878.
Gedalin, M.: 1996b, 'Noncoplanar magnetic field in the collisionless shock front', J.Geophys.Res. 101 11,153–11,156
Gedalin, M.: 1996c, 'Transmitted ions and ion heating in nearly-perpendicular low-Mach number shocks', J.Geophys.Res. 101, 15, 569–15,578.
Gedalin, M.: 1996d, 'Particles at quasiperpendicular collisionless shocks: Dependence on the shock scale', Multiscale Processes in Space Plasmas, in T. Chang and J. R. Jasperse, (eds. ), Physics of Space Plasmas (1995), Number 14, (MIT Center for Theoretical Geo/Cosmo Plasma Physics, Cambridge, MA, 1996) (to appear).
Gedalin, M., Balikhin, M. and Krasnosselskikh, V.: 1995, Electron heating in quasiperpendicular shocks', Adv.Space Res. 15(8/9), 225–233.
Gedalin, M. and Zilbersher, D.: 1995, 'Non-diagonal ion pressure in nearly-perpendicular collisionless shocks', Geophys.Res.Lett. 22, 3279–3282.
Giacalone, J., Jokipii, J. R. and K´ota, J.: 1994, 'Ion injection and acceleration at quasi-perpendicular shocks', J.Geophys.Res. 99, 19, 351–19,358.
Goodrich, C. C.: 1985, 'Numerical simulations of quasi-perpendicular collisionless shocks', R. G. Stone and B. T. Tsurutani (eds. ), Collisionless Shocis in the Heliosphere: Reviews of Current Research, Geophys.Monogr.Ser., vol. 35, AGU, Washington, D. C., pp. 153–158.
Goodrich, C. C. and Scudder, J. D.: 1984, 'The adiabatic energy change of plasma electrons and the frame dependence of the cross shock potential at collisionless magnetosonic shock waves', J.Geophys.Res. 89, 6654–6662.
Gosling, J. T., and Robson, A. E.: 1985, 'Ion reflection, gyration, and dissipation at supercritical shocks', R. G. Stone and B. T. Tsurutani (eds. ), Collisionless Shocis in the Heliosphere: Reviews of Current Research, Geophys.Monogr.Ser. vol.35, AGU, Washington, D. C., pp. 141–152.
Gosling, J. T. and Thomsen, M. F.: 1985, 'Specularly reflected ions, shock foot thicknesses, and shock velocity determinations in space', J.Geophys.Res. 90, 9893–9896.
Gosling, J. T., Winske, D., and Thomsen, M. F.: 1988, 'Noncoplanar magnetic fields at collisionless shocks: A test of a new approach', J.Geophys.Res. 93, 2735–2740.
Greenstadt, E. W.: 1985, 'Oblique, parallel, and quasi-parallel morphology of collisionless shocks', in R. G. Stone and B. T. Tsurutani (eds. ), Collisionless Shocks in the Heliosphere: Reviews of Current Research, Geophys.Monogr.Ser., vol. 35, AGU, Washington, D. C., pp. 169–184.
Gurgiolo, C., Parks, G. K., Mauk, B. H., Lin, C. S., Anderson, K. A., Lin, R. P. and Reme, H.: 1981, 'Non-E _ B ordered ion beams upstream of the Earth's bow shock', J.Geophys.Res. 86, 4415–4424.
Jokipii, J. R., K´ota, J., and Giacalone, J.: 1993, 'Perpendicular transport in 1-and 2-dimensional shock simulations', Geophys.Res.Lett. 20, 1759–1762.
Jones, F. C. and Ellison, D. C.: 1987, 'Noncoplanar magnetic fields, shock potentials, and ion deflec-tion', J.Geophys.Res. 92, 11,205–11,207.
Jones, F. C. and Ellison, D. C.: 1991, 'The plasma physics of shock acceleration', Space Sci.Rev. 58, 259–346.
Kennel, C. F., Edmiston, J. P. and Hada, T.: 1985, 'A quarter century of collisionless shock research', in R. G. Stone and B. T. Tsurutani (eds. ), Collisionless Shocis in the Heliosphere: A Tutorial Review, Geophys.Monogr Ser., vol. 34, AGU, Washington, D. C., pp. 1–36.
Lee, L. C., Wu, C. S. and Hu, X. W.: 1986, 'Increase of ion kinetic temperature across a collisionless shock, 1, A new mechanism', Geophys.Res.Lett. 13, 209–212.
Lee, L. C., Mandt, M. E., and Hu, X. W.: 1987, 'Increase of ion kinetic temperature across a collisionless shock, 2, A simulation study', J.Geophys.Res. 92, 13, 438–13,446.
Leroy, M. M.: 1983, 'Structure of perpendicular shocks in collisionless plasma', Phys.Fluids 26, 2742–2753.
Leroy, M. M., Winske, D., Goodrich, C. C., Wu, C. S., and Papadopoulos, K.: 1982, 'The structure of perpendicular bow shocks', J.Geophys.Res. 87, 5081–5094.
Livesey, W. A., Russell, C. T. and Kennel, C. F: 1984, 'A comparison of specularly reflected gyrating ion orbits with observed shock foot thicknesses', J.Geophys.Res. 89, 6824–6828.
Li Xinlin, Lewis, H. R., LaBelle, J., Phan, T.-D., and Treumann, R. A.: 1995, 'Characteristics of the ion pressure tensor in the earth's magnetosheath', Geophys.Res.Lett. 22, 667–670.
McKean, M. E., Omidi, N., and Krauss-Varban, D.: 1995, 'Wave and ion evolution downstream of quasi-perpendicular bow shocks', J.Geophys.Res. 100, 3427–3437.
Mellott, M. M. and Greenstadt, E. W.: 1984, 'The structure of oblique subcritical bow shocks: ISEE 1 and 2 observations', J.Geophys.Res. 89, 2151–2161.
Mellott, M. M. and Livesey, W. A.: 1987, 'Shock overshoots revisited', J.Geophys.Res. 92, 13, 661–13,665.
Newbury, J. A. and Russell, C. T.: 1996, 'Observations of a very thin collisionless shock', Geophys.Res.Lett. 23, 781–784.
Paschmann, G., Sckopke, N., Bame, S. J., and Gosling, J. T.: 1982, 'Observations of gyrating ions in the foot of the nearly perpendicular bow shock', Geophys.Res.Lett. 9, 881–884.
Paschmann, G., Loidl, H., Obermayer, P., Ertl, M., Laborens, R., Sckopke, N., Baumjohann, W., Carlson, C. W., and Curtis, D. W.: 1985, 'The plasma instrument for AMPTE/IRM', IEEE Trans.Geosci.Remote Sens. GE-23, 262–266.
Quest, K.: 19898, 'Theory and simulation of collisionless parallel shocks', J.Geophys.Res. 93, 9649–9680.
Russell, C. T., Hoppe, M. M. and Livesey, W. A.: 1982a, 'Overshoots in planetary bow shocks', Nature 296, 45–48.
Russell, C. T., Hoppe, M. M., Livesey, W. A., Gosling, J. T., and Bame, S. J.: 1982b, 'ISEE-1 and-2 observations of laminar bow shocks: Velocity and thickness', Geophys.Res.Lett. 9, 1171–1174.
Scholer, M. and Fujimoto, M.: 1993, 'Low-Mach number quasi-parallel shocks: Upstream waves', J.Geophys.Res. 98, 15, 275–15,283.
Schwartz, S. J., Thomsen, M. F. and Gosling, J. T.: 1983, 'Ions upstream of the Earth's bow shock: A theoretical comparison of alternative source population', J.Geophys.Res. 88, 2039–2047.
Sckopke, N., Paschmann, G., Bame, S. J., Gosling, J. T., and Russell, C. T.: 1983, 'Evolution of ion distributions across the nearly perpendicular bow shock: Specularly and nonspecularly reflected-gyrating ions', J.Geophys.Res. 88, 6121–6136.
Sckopke, N., Paschmann, G., Brinca, A. L., Carlson, C. W., and L¨ uhr, H.: 1990, 'Ion thermalisation in quasi-perpendicular shocks involving reflected ions', J.Geophys.Res. 95, 6337–6352.
Scudder, J. D., Mangeney, A., Lacombe, C., Harvey, C. C., Aggson, T. L., Anderson, R. R., Gosling, J. T., Paschmann, G., and Russell, C. T.: 1986a, 'The resolved layer of a collisionless, high β, supercrit-ical, quasi-perpendicular shock wave, I, Rankine-Hugoniot geometry, currents, and stationarity', J.Geophys.Res. 91, 11,019–11,052.
Scudder, J. D., Mangeney, A., Lacombe, C., and Harvey, C. C.: 1986b, 'The resolved layer of a collisionless, high β, supercritical, quasi-perpendicular shock wave, 2, Dissipative fluid hydro-dynamics', J.Geophys.Res. 91, 11, 053–11,073.
Thomsen, M. F., Gosling, J. T., Bame, S. J., and Mellott, M. M.: 1985, 'Ion and electron heating at collisionless shocks near the critical Mach number', J.Geophys.Res. 90, 137–148.
Wilkinson, W. P.: 1991, 'Ion kinetic processes and thermalization at quasi-perpendicular low-Mach number shocks', J.Geophys.Res. 96, 17, 675–17,688.
Wilkinson, W. P. and Schwartz, S. J.: 1990, 'Parametric dependence of the density of specularly reflected ions at quasiperpendicular collisionless shocks', Planet.Space Sci. 38, 419-435.
Wilkinson, W. P., Pardaens, A. K., Schwartz, S. J., Burgess, D., L¨ uhr, H., Kessel, R. L., Dunlop, M., and Farrugia, C. J.: 1993, 'Nonthermal ions and associated magnetic field behavior at a quasi-parallel Earth's bow shock', J.Geophys.Res. 98, 3889–3905.
Woods, L. C.: 1969, 'On the structure of collisionless magnetoplasma shock waves at super-critical Alfven Mach numbers', J.Plasma Phys. 3, 435–447
Woods, L. C.: 1971, 'On double structured, perpendicular, magneto-plasma shock waves', J.Plasma Phys. 13, 281.
Wygant, J. R., Bensadoun, M., and Mozer, F. C.: 1987, 'Electric field measurements at subcritical, oblique bow shock crossings', J.Geophys.Res. 92, 11, 109–11,121.
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Gedalin, M. Ion Dynamics and Distribution At the Quasiperpendicular Collisionless Shock Front. Surveys in Geophysics 18, 541–566 (1997). https://doi.org/10.1023/A:1006509702173
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DOI: https://doi.org/10.1023/A:1006509702173