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Publication list

 Refereed journal articles and refereed review articles
  1. Diffusion and Concentration of Solids in the Dead Zone of a Protoplanetary Disk (2018)
    Yang, C.-C., Mac Low, M.-M. & Johansen, A., The Astrophysical Journal, vol. 868, p/id 27
    1 citations

  2. Streaming instability of multiple particle species in protoplanetary disks (2018)
    Schaffer, N., Yang, C.-C. & Johansen, A., Astronomy and Astrophysics, vol. 618, p/id A75
    0 citations

  3. Stellar abundance of binary stars: their role in determining the formation location of super-Earths and ice giants (2018)
    Bitsch, B., Forsberg, R., Liu, F. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 479, p/id 3690
    0 citations

  4. Slowing Down Type II Migration of Gas Giants to Match Observational Data (2018)
    Ida, S., Tanaka, H., Johansen, A., Kanagawa, K. D. & Tanigawa, T., The Astrophysical Journal, vol. 864, p/id 77
    3 citations

  5. The dynamical evolution of transiting planetary systems including a realistic collision prescription (2018)
    Mustill, A. J., Davies, M. B. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 478, p/id 2896
    2 citations

  6. Towards an initial mass function for giant planets (2018)
    Carrera, D., Davies, M. B. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 478, p/id 961
    0 citations

  7. Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt (2018)
    Eriksson, L. E. J., Mustill, A. J. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 475, p/id 4609
    5 citations

  8. Pebble- isolation mass: Scaling law and implications for the formation of super-Earths and gas giants (2018)
    Bitsch, B., Morbidelli, A., Johansen, A., Lega, E., Lambrechts, M. & Crida, A., Astronomy and Astrophysics, vol. 612, p/id A30
    20 citations

  9. Jupiter Analogs Orbit Stars with an Average Metallicity Close to That of the Sun (2018)
    Buchhave, L. A., Bitsch, B., Johansen, A., Latham, D. W., Bizzarro, M., Bieryla, A. & Kipping, D. M., The Astrophysical Journal, vol. 856, p/id 37
    6 citations

  10. Giant Planet Formation and Migration (2018)
    Paardekooper, S.-J. & Johansen, A., Space Science Reviews, vol. 214, p/id 38
    2 citations

  11. Debris disc constraints on planetesimal formation (2018)
    Krivov, A. V., Ide, A., Löhne, T., Johansen, A. & Blum, J., Monthly Notices of the Royal Astronomical Society, vol. 474, p/id 2564
    4 citations

  12. The growth of planets by pebble accretion in evolving protoplanetary discs (Corrigendum) (2018)
    Bitsch, B., Lambrechts, M. & Johansen, A., Astronomy and Astrophysics, vol. 609, p/id C2
    7 citations

  13. Harvesting the decay energy of 26Al to drive lightning discharge in protoplanetary discs (2018)
    Johansen, A. & Okuzumi, S., Astronomy and Astrophysics, vol. 609, p/id A31
    2 citations

  14. Concentrating small particles in protoplanetary disks through the streaming instability (2017)
    Yang, C.-C., Johansen, A. & Carrera, D., Astronomy and Astrophysics, vol. 606, p/id A80
    29 citations

  15. The origin of the occurrence rate profile of gas giants inside 100 d (2017)
    Ali- Dib, M., Johansen, A. & Huang, C. X., Monthly Notices of the Royal Astronomical Society, vol. 469, p/id 5016
    6 citations

  16. Atmospheric signatures of giant exoplanet formation by pebble accretion (2017)
    Madhusudhan, N., Bitsch, B., Johansen, A. & Eriksson, L., Monthly Notices of the Royal Astronomical Society, vol. 469, p/id 4102
    20 citations

  17. Forming Planets via Pebble Accretion (2017)
    Johansen, A. & Lambrechts, M., Annual Review of Earth and Planetary Sciences, vol. 45, p/id 359
    28 citations

  18. Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles (2017)
    Blum, J., Gundlach, B., Krause, M., et al., Monthly Notices of the Royal Astronomical Society, vol. 469, p/id S755
    12 citations

  19. Radially resolved simulations of collapsing pebble clouds in protoplanetary discs (2017)
    Wahlberg Jansson, K. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 469, p/id S149
    3 citations

  20. The effects of external planets on inner systems: multiplicities, inclinations and pathways to eccentric warm Jupiters (2017)
    Mustill, A. J., Davies, M. B. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 468, p/id 3000
    25 citations

  21. K2-111 b - a short period super-Earth transiting a metal poor, evolved old star (2017)
    Fridlund, M., Gaidos, E., Barrag√°n, O., et al., Astronomy and Astrophysics, vol. 604, p/id A16
    12 citations

  22. Planetesimal Formation by the Streaming Instability in a Photoevaporating Disk (2017)
    Carrera, D., Gorti, U., Johansen, A. & Davies, M. B., The Astrophysical Journal, vol. 839, p/id 16
    30 citations

  23. The Role of Pebble Fragmentation in Planetesimal Formation. II. Numerical Simulations (2017)
    Wahlberg Jansson, K., Johansen, A., Bukhari Syed, M. & Blum, J., The Astrophysical Journal, vol. 835, p/id 109
    5 citations

  24. The Role of Pebble Fragmentation in Planetesimal Formation. I. Experimental Study (2017)
    Bukhari Syed, M., Blum, J., Wahlberg Jansson, K. & Johansen, A., The Astrophysical Journal, vol. 834, p/id 145
    10 citations

  25. Initial mass function of planetesimals formed by the streaming instability (2017)
    Schäfer, U., Yang, C.-C. & Johansen, A., Astronomy and Astrophysics, vol. 597, p/id A69
    24 citations

  26. Dust Evolution and the Formation of Planetesimals (2016)
    Birnstiel, T., Fang, M. & Johansen, A., Space Science Reviews, vol. 205, p/id 41
    45 citations

  27. Survival of habitable planets in unstable planetary systems (2016)
    Carrera, D., Davies, M. B. & Johansen, A., Monthly Notices of the Royal Astronomical Society, vol. 463, p/id 3226
    14 citations

  28. Terrestrial Planets across Space and Time (2016)
    Zackrisson, E., Calissendorff, P., Gonz√°lez, J., Benson, A., Johansen, A. & Janson, M., The Astrophysical Journal, vol. 833, p/id 214
    8 citations

  29. Forming Chondrules in Impact Splashes II Volatile Retention (2016)
    Dullemond, C. P., Harsono, D., Stammler, S. M. & Johansen, A., The Astrophysical Journal, vol. 832, p/id 91
    2 citations

  30. Long-term stability of the HR 8799 planetary system without resonant lock (2016)
    Götberg, Y., Davies, M. B., Mustill, A. J., Johansen, A. & Church, R. P., Astronomy and Astrophysics, vol. 592, p/id A147
    14 citations

  31. Integration of Particle-gas Systems with Stiff Mutual Drag Interaction (2016)
    Yang, C.-C. & Johansen, A., The Astrophysical Journal Supplement Series, vol. 224, p/id 39
    11 citations

  32. Spontaneous concentrations of solids through two-way drag forces between gas and sedimenting particles (2016)
    Lambrechts, M., Johansen, A., Capelo, H. L., Blum, J. & Bodenschatz, E., Astronomy and Astrophysics, vol. 591, p/id A133
    9 citations

  33. Influence of the water content in protoplanetary discs on planet migration and formation (2016)
    Bitsch, B. & Johansen, A., Astronomy and Astrophysics, vol. 590, p/id A101
    15 citations

  34. Fossilized condensation lines in the Solar System protoplanetary disk (2016)
    Morbidelli, A., Bitsch, B., Crida, A., Gounelle, M., Guillot, T., Jacobson, S., Johansen, A., Lambrechts, M. & Lega, E., Icarus, vol. 267, p/id 368
    45 citations

  35. The growth of planets by pebble accretion in evolving protoplanetary discs (2015)
    Bitsch, B., Lambrechts, M. & Johansen, A., Astronomy and Astrophysics, vol. 582, p/id A112
    99 citations

  36. The Destruction of Inner Planetary Systems during High-eccentricity Migration of Gas Giants (2015)
    Mustill, A. J., Davies, M. B. & Johansen, A., The Astrophysical Journal, vol. 808, p/id 14
    28 citations

  37. How to form planetesimals from mm-sized chondrules and chondrule aggregates (2015)
    Carrera, D., Johansen, A. & Davies, M. B., Astronomy and Astrophysics, vol. 579, p/id A43
    90 citations

  38. The formation of the solar system (2015)
    Pfalzner, S., Davies, M. B., Gounelle, M., Johansen, A., M√ľnker, C., Lacerda, P., Portegies Zwart, S., Testi, L., Trieloff, M. & Veras, D., Physica Scripta, vol. 90, p/id 068001
    18 citations

  39. Growth of asteroids, planetary embryos, and Kuiper belt objects by chondrule accretion (2015)
    Johansen, A., Mac Low, M.-M., Lacerda, P. & Bizzarro, M., Science Advances, vol. 1, p/id 1500109
    118 citations

  40. The structure of protoplanetary discs around evolving young stars (2015)
    Bitsch, B., Johansen, A., Lambrechts, M. & Morbidelli, A., Astronomy and Astrophysics, vol. 575, p/id A28
    93 citations

  41. New Paradigms for Asteroid Formation (2015)
    Johansen, A., Jacquet, E., Cuzzi, J. N., Morbidelli, A. & Gounelle, M., Asteroids IV, vol. p/id 471
    8 citations

  42. Forming the cores of giant planets from the radial pebble flux in protoplanetary discs (2014)
    Lambrechts, M. & Johansen, A., Astronomy and Astrophysics, vol. 572, p/id A107
    110 citations

  43. Separating gas-giant and ice-giant planets by halting pebble accretion (2014)
    Lambrechts, M., Johansen, A. & Morbidelli, A., Astronomy and Astrophysics, vol. 572, p/id A35
    103 citations

  44. The PLATO 2.0 mission (2014)
    Rauer, H., Catala, C., Aerts, C., et al., Experimental Astronomy, vol. 38, p/id 249
    448 citations

  45. Forming Chondrules in Impact Splashes. I. Radiative Cooling Model (2014)
    Dullemond, C. P., Stammler, S. M. & Johansen, A., The Astrophysical Journal, vol. 794, p/id 91
    12 citations

  46. Formation of pebble-pile planetesimals (2014)
    Wahlberg Jansson, K. & Johansen, A., Astronomy and Astrophysics, vol. 570, p/id A47
    32 citations

  47. On the Feeding Zone of Planetesimal Formation by the Streaming Instability (2014)
    Yang, C.-C. & Johansen, A., The Astrophysical Journal, vol. 792, p/id 86
    21 citations

  48. A fossil winonaite-like meteorite in Ordovician limestone: A piece of the impactor that broke up the L-chondrite parent body? (2014)
    Schmitz, B., Huss, G. R., Meier, M. M. M., et al., Earth and Planetary Science Letters, vol. 400, p/id 145
    9 citations

  49. Giant Planet and Brown Dwarf Formation (2014)
    Chabrier, G., Johansen, A., Janson, M. & Rafikov, R., Protostars and Planets VI, vol. p/id 619
    59 citations

  50. The Multifaceted Planetesimal Formation Process (2014)
    Johansen, A., Blum, J., Tanaka, H., Ormel, C., Bizzarro, M. & Rickman, H., Protostars and Planets VI, vol. p/id 547
    135 citations

  51. Ice condensation as a planet formation mechanism (2013)
    Ros, K. & Johansen, A., Astronomy and Astrophysics, vol. 552, p/id A137
    111 citations

  52. Gravoturbulent Planetesimal Formation: The Positive Effect of Long-lived Zonal Flows (2013)
    Dittrich, K., Klahr, H. & Johansen, A., The Astrophysical Journal, vol. 763, p/id 117
    50 citations

  53. Magnetically Levitating Accretion Disks around Supermassive Black Holes (2012)
    Gaburov, E., Johansen, A. & Levin, Y., The Astrophysical Journal, vol. 758, p/id 103
    26 citations

  54. Can Planetary Instability Explain the Kepler Dichotomy? (2012)
    Johansen, A., Davies, M. B., Church, R. P. & Holmelin, V., The Astrophysical Journal, vol. 758, p/id 39
    59 citations

  55. Rapid growth of gas-giant cores by pebble accretion (2012)
    Lambrechts, M. & Johansen, A., Astronomy and Astrophysics, vol. 544, p/id A32
    269 citations

  56. An abundance of small exoplanets around stars with a wide range of metallicities (2012)
    Buchhave, L. A., Latham, D. W., Johansen, A., et al., Nature, vol. 486, p/id 375
    343 citations

  57. Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities (2012)
    Johansen, A., Youdin, A. N. & Lithwick, Y., Astronomy and Astrophysics, vol. 537, p/id A125
    77 citations

  58. Planetesimal Formation Through Streaming and Gravitational Instabilities (2011)
    Johansen, A. & Klahr, H., Earth Moon and Planets, vol. 108, p/id 39
    10 citations

  59. High- resolution simulations of planetesimal formation in turbulent protoplanetary discs (2011)
    Johansen, A., Klahr, H. & Henning, T., Astronomy and Astrophysics, vol. 529, p/id A62
    59 citations

  60. Prograde rotation of protoplanets by accretion of pebbles in a gaseous environment (2010)
    Johansen, A. & Lacerda, P., Monthly Notices of the Royal Astronomical Society, vol. 404, p/id 475
    86 citations

  61. Particle Clumping and Planetesimal Formation Depend Strongly on Metallicity (2009)
    Johansen, A., Youdin, A. & Mac Low, M.-M., The Astrophysical Journal, vol. 704, p/id L75
    164 citations

  62. Zonal Flows and Long-lived Axisymmetric Pressure Bumps in Magnetorotational Turbulence (2009)
    Johansen, A., Youdin, A. & Klahr, H., The Astrophysical Journal, vol. 697, p/id 1269
    185 citations

  63. Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks (2009)
    Lyra, W., Johansen, A., Zsom, A., Klahr, H. & Piskunov, N., Astronomy and Astrophysics, vol. 497, p/id 869
    112 citations

  64. Standing on the shoulders of giants. Trojan Earths and vortex trapping in low mass self- gravitating protoplanetary disks of gas and solids (2009)
    Lyra, W., Johansen, A., Klahr, H. & Piskunov, N., Astronomy and Astrophysics, vol. 493, p/id 1125
    88 citations

  65. Embryos grown in the dead zone. Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids (2008)
    Lyra, W., Johansen, A., Klahr, H. & Piskunov, N., Astronomy and Astrophysics, vol. 491, p/id L41
    66 citations

  66. High accretion rates in magnetised Keplerian discs mediated by a Parker instability driven dynamo (2008)
    Johansen, A. & Levin, Y., Astronomy and Astrophysics, vol. 490, p/id 501
    45 citations

  67. Gravoturbulent planetesimal formation (2008)
    Klahr, H. & Johansen, A., Physica Scripta Volume T, vol. 130, p/id 014018
    2 citations

  68. A coagulation-fragmentation model for the turbulent growth and destruction of preplanetesimals (2008)
    Johansen, A., Brauer, F., Dullemond, C., Klahr, H. & Henning, T., Astronomy and Astrophysics, vol. 486, p/id 597
    33 citations

  69. Global magnetohydrodynamical models of turbulence in protoplanetary disks. I. A cylindrical potential on a Cartesian grid and transport of solids (2008)
    Lyra, W., Johansen, A., Klahr, H. & Piskunov, N., Astronomy and Astrophysics, vol. 479, p/id 883
    54 citations

  70. Rapid planetesimal formation in turbulent circumstellar disks (2007)
    Johansen, A., Oishi, J. S., Mac Low, M.-M., Klahr, H., Henning, T. & Youdin, A., Nature, vol. 448, p/id 1022
    587 citations

  71. Survival of the mm-cm size grain population observed in protoplanetary disks (2007)
    Brauer, F., Dullemond, C. P., Johansen, A., Henning, T., Klahr, H. & Natta, A., Astronomy and Astrophysics, vol. 469, p/id 1169
    83 citations

  72. Protoplanetary Disk Turbulence Driven by the Streaming Instability: Nonlinear Saturation and Particle Concentration (2007)
    Johansen, A. & Youdin, A., The Astrophysical Journal, vol. 662, p/id 627
    161 citations

  73. Protoplanetary Disk Turbulence Driven by the Streaming Instability: Linear Evolution and Numerical Methods (2007)
    Youdin, A. & Johansen, A., The Astrophysical Journal, vol. 662, p/id 613
    126 citations

  74. Turbulent diffusion in protoplanetary discs: the effect of an imposed magnetic field (2006)
    Johansen, A., Klahr, H. & Mee, A. J., Monthly Notices of the Royal Astronomical Society, vol. 370, p/id L71
    47 citations

  75. Dust Sedimentation and Self-sustained Kelvin-Helmholtz Turbulence in Protoplanetary Disk Midplanes (2006)
    Johansen, A., Henning, T. & Klahr, H., The Astrophysical Journal, vol. 643, p/id 1219
    81 citations

  76. Gravoturbulent Formation of Planetesimals (2006)
    Johansen, A., Klahr, H. & Henning, T., The Astrophysical Journal, vol. 636, p/id 1121
    93 citations

  77. Dust Diffusion in Protoplanetary Disks by Magnetorotational Turbulence (2005)
    Johansen, A. & Klahr, H., The Astrophysical Journal, vol. 634, p/id 1353
    117 citations

  78. Simulations of dust-trapping vortices in protoplanetary discs (2004)
    Johansen, A., Andersen, A. C. & Brandenburg, A., Astronomy and Astrophysics, vol. 417, p/id 361
    96 citations

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Click here to see my publication list on ADS (sort by citations). My Google Scholar page can be found here.

Press coverage

Movies

Asteroid formation at high resolution
The movie shows a high-resolution computer simulation of asteroid formation by the streaming instability. The metallicity starts at Z=0.01. Particles of 10 cm in size sediment to form a thin mid-plane layer, but the mid-plane layer gradually puffs up due to turbulent stirring. The movie makes a jump from a time of 50 to a time of 200 when the metallicity is slowly increased to Z=0.02. This triggers the formation of dense filaments at a time of around 250. After the dispersal of the second filament the particle self-gravity is activated. The next filament collapses gravitationally to asteroids with a wide range of sizes. Their Hill radii are indicated on the top right panel and their radii on the bottom right panel.
File size: 19.1 MB
References: Johansen et al. (2015)
Long time-span simulation of planetesimal formation
Previous simulations of particle clumping in protoplanetary disc turbulence have only been able to follow planetesimal formation for a few orbital periods. With a computing grant for 4096 core years at the Jugene supercomputer in Jülich we recently were able to run high-resolution simulations (5123) and long time-span simulations (at 2563) of magnetorotational turbulence with particles. The movie shows a simulation where self-gravity was started at the same time as releasing the particles. In this cold start initial condition planetesimals form slowly over the next 13 orbits. The circles indicate the Hill spheres of the bound clumps and the number their mass in units of the 1000-km-diameter dwarf planet Ceres.
File size: 41.9 MB
References: Johansen, Klahr, & Henning (2011)
Prograde rotation of asteroids and protoplanets
The predominantly prograde rotation of terrestrial planets and large asteroids is difficult to explain through the classical picture of planet formation, since run-away accretion of planetesimals leads to slow, retrograde rotation. The tendency for prograde rotation of large asteroids is often attributed to giant impacts and pure chance. However, if asteroids grow primarily by accreting small pebbles embedded in the protoplanetary gas disc, rather than km-sized planetesimals, then prograde rotation is natural. Pebbles approaching the Hill sphere of a protoplanet lose energy by friction with the gas, fall towards the protoplanet, acquire prograde spin from the Coriolis forces and enter a prograde particle disc. The protoplanet obtains prograde angular momentum from particles accreted through the circumplanetary disc.
File size: 15.1 MB
References: Johansen, & Lacerda (2010)

Metallicity controls planetesimal formation
Exoplanets are found primarily around stars that are rich in heavy elements. This is normally attributed to the efficiency of forming several Earth mass cores in short enough time to attract gaseous envelopes and become gas giants. However, already the earlier stages of planet formation, where dust particles grow to km-sized planetesimals, are affected by the metallicity of the disc. Particle clumps that form spontaneously in turbulent flows can become gravitationally unstable and contract to form planetesimals. This clumping, in turn, is highly dependent on the metallicity. The first movie shows a simulation of particle sedimentation, starting at a metallicity equal to that of the sun. The gas is removed on a 30 orbits time-scale. Color contours show particle density, with bright regions containing many particles and blue regions few. Initially there is almost no clumping in the particle component, but as the metallicity is increased, strong clumping sets in. The second movie shows the formation of planetesimals in a simulation with two times the solar heavy element abundance. Seven gravitationally bound clusters, containing pebbles of a few cms in radius, condense out of the overdense filament.
File size: 67.1 MB, 9.2 MB
References: Johansen, Youdin, & Mac Low (2009)

The Parker instability in a strongly magnetised accretion disc
Strongly magnetised accretion discs are unstable to the Parker instability. The movie shows the vertical field strength at the sides of the simulation box. Typical Parker instability modes of short radial wavelength and long (about five scale heights) azimuthal wavelength are visible. As the initial azimuthal field rises in big arcs, vertical field is created, which in turn becomes unstable to the magnetorotational instability. The mid-plane also shows signs of magnetorotational instability in the azimuthal field. The turbulent state has high accretion torques, with an alpha-value of around 0.1. A large scale radial field appears due to the stretching of field lines as matter streams down the inclined field lines. The radial field component in turn re-creates the azimuthal field by stretching in the Keplerian shear. This way the azimuthal field stays confined to the disc, and the high accretion rate can be maintained.
File size: 18.9 MB
References: Johansen & Levin (2008)

Formation of gravitationally bound clusters of boulders
The movie shows the column density of boulders in a protoplanetary disc. Initially the particles have been allowed to evolve without feeling each other's gravity, but at the onset of the movie self-gravity is turned on. The radial contraction of the boulder component leads eventually to a full non-axisymmetric collapse into a gravitationally bound cluster, containing a mass in solids that is comparable to the dwarf planet Ceres. The inset shows an enlargement around the densest point in the simulation. Clear accretion features are visible as the clump consumes the remaining boulders in the box. A second massive clump condenses out at a time of around 3.5 orbits when the first clump interacts with a dense filament of particles.
File size: 10.0 MB
References: Johansen, Oishi, Mac Low, Klahr, Henning, & Youdin (2007)

The radial drift of solids is unstable to the streaming instability
It is a notorious problem of planet formation that m-sized boulders drift into the central protostar because of the friction with the gas disk. But Youdin & Goodman (2005) showed that the flow of dust and gas is linearly unstable to the streaming instability (confirmed numerically in the simulations by Johansen, Henning, & Klahr 2006). The two movies show how the radial drift flow turns turbulent, creating high density particle clumps. The first movie is from a 3-D simulation where the particles represent m-sized boulders. The flow shows initially the linear growth of the streaming instability, but the wave patterns eventually go non-linear and turbulent on a time-scale that is shorter than the radial drift. The second movie shows a 2-D simulation where the particles represent 10 cm rocks. Here the drift flow is weaker, and the turbulence sets in almost instantaneously through the creation of rapidly expanding voids.
File size: 29.1 MB, 4.8 MB
References: Johansen & Youdin (2007); Youdin & Johansen (2007)

Pebbles, rocks and boulders moving in Kelvin-Helmholtz turbulence
The three movies show particle density contours in a two-dimensional azimuthal-vertical slice of a protoplanetary disc, for three different particle sizes (cm-sized pebbles, dm-sized rocks and m-sized boulders). There is no global turbulence in the disc, so the solid particles sediment unhindered towards the disc mid-plane. Due to a radial pressure gradient through the disc, the gas rotates at a speed that is slightly below the Keplerian value. However, as the particles settle around the mid-plane, the gas is forced by the solids to rotate more and more Keplerian, inducing a vertical dependence of the rotation velocity of the gas. This shear flow is unstable to the Kelvin-Helmholtz instability, forming beautiful breaking waves in the dust layer. In the self-sustained state of Kelvin-Helmholtz turbulence the solid particles are transported away from the mid-plane at the same rate as they fall, but the particle density is nevertheless very clumpy because of a clumping instability that is caused by the dependence of the particle rotation velocity on the local solids-to-gas ratio.
File size: 14.3 MB, 18.6 MB, 11.2 MB
References: Johansen, Henning, & Klahr (2006)

Boulders trapped in magnetorotational turbulence
The movie shows the locations of 100,000 of a total of 2,000,000 meter-sized solid particles moving around in magnetorotational turbulence. Large concentrations are seen, up to a factor of 100 in solids-to-gas ratio, due to trapping of boulders in transient high pressures that have a few percent overdensity in the gas. A global gas pressure gradient is causing particles to migrate inwards. This also contributes to the concentrations by loading gas overdensity regions with migrating boulders.
File size: 11.9 MB
References: Johansen, Klahr, & Henning (2006)

Dust settled in magnetorotational turbulence
The movie shows dust density contours at the sides of a simulation box representing a local, corotating coordinate frame in a protoplanetary disc. The radial direction is towards the right, the rotation direction towards left and the vertical direction upwards. The dust is concentrated around the mid-plane due to vertical gravity, but the configuration is now in an equilibrium where the turbulent gas transports dust away from the mid-plane at the same rate as the settling. The scale height of the dust grains allows determination of the diffusion coefficient of the turbulent flow.
File size: 8.7 MB
References: Johansen & Klahr (2005)

This page was last modified on 7 January 2019.