Skip to main content


We’d like to understand how you use our websites in order to improve them. Register your interest.

Drag forces in the near and distant solar system


Like the solar photons the solar wind particles induce a drag force onto the zodiacal dust grains in the heliosphere. For the distant solar wind with high Mach numbers the drag coefficient is a constant, but close to the Sun, where Mach numbers become small, the drag coefficient is a complicated function of the ion sound speed, density and temperature. We discuss the dynamics of dust particles due to this drag force and compare it with that in the distant solar wind. Especially in the near solar wind the eccentricity varies in a complicated way with the inclination of the orbits, also the semimajor axis decreases faster closer to the Sun. These variations are quite different in the distant solar wind.

In addition, we apply an analogous mathematical formalism to the dust dynamics in the outer region of the heliosphere (>20 AU) where the neutral gas density becomes comparable or larger than that of the solar wind plasma. Here the neutral hydrogen gas induces a drag force onto the dust particles similar to the plasma Poynting-Robertson effect. But different to the radial solar wind, the velocity of the interstellar gas is mono-directional, and hence with respect to the inflow direction of the interstellar material this introduces an axial-symmetric force onto the dust particles. This force acts asymmetric in the orbit, and causes the eccentricity to increase fairly fast. The lifetime for dust grains in the Edgeworth-Kuiper Belt is no longer determined by the electromagnetic Poynting-Robertson lifetime, but by that of the neutral gas and is in the order of half a million years for a 10 μm sized particle.


  1. Banaszkiewicz, M., H. J. Fahr, and K. Scherer, Evolution of dust particle orbits under the influence of solar wind outflow asymmetries and the formation of the zodiacal dust cloud, Icarus, 107, 358, 1994.

  2. Bougeret, J. L., J. H. King, and R. Schwenn, Solar radio burst and in-situ determination of interplanetary electron density, Sol. Physics, 90, 401–411, 1984.

  3. Bzowski, M., H.-J. Fahr, D. Rucinski, and H. Scherer, variation of neutral hydrogen moments in the heliosphere during the solar cycle, Astron. Astrophys., 1997 (in press).

  4. Fahr, H.-J., The interstellar gas flow through the heliospheric interface region, Space Sci. Rev., 78, 199–212, 1996.

  5. Fahr, H.-J., K. Scherer, and M. Banaszkiewicz, The evolution of the zodiacal dust cloud under plasma drag and Lorentz forces in the latitudinally asymmetric solar wind, Planet. Space Sci., 43, 301, 1995.

  6. Fahr, H.-J., K. Scherer, and M. Banaszkiewicz, The evolution of the zodiacal dust cloud under plasma drag and Lorentz forces in the latitudinally asymmetric solar wind, Planet. Space Sci., 43, 301, 1995.

  7. Frisch, P. C., Characteristics of nearby interstellar matter, Space Sci. Rev., 72, 499–592, 1995.

  8. Geiss, J. and M. Witte, Properties of the interstellar gas inside the heliosphere, Space Sci. Rev, 78, 229–238, 1996.

  9. Gor’kavyi, N. N., L. M. Ozernoy, J. C. Mather, and T. Taidakova, Quasi-stationary states of dust flows under Poynting-Roberston drag: New analytical and numerical solutions, Astrophys. J., 488, 268, 1997.

  10. Kausch, T. and H. J. Fahr, Interstellar gas filtration to the inner heliosphere under the self-consistent influence of a pick-up ion modulated termination shock, Astron. Astrophys., 325, 828–838, 1997.

  11. Muhleman, D. O. and J. D. Anderson, Solar wind electron densities from Viking dual-frequency radio measurements, Astrophys. J., 247, 1093–1101, 1981.

  12. Northrop, T. G., Dusty plasmas, Physica Scripta, 45, 475–490, 1992.

  13. Northrop, T. G. and T. J. Birmingham, Plsama Drag on a dust grain due to Coulomb collisions, Planet. Space Sci., 38, 319–326, 1990.

  14. Osterbart, R. and H.-J. Fahr, A Boltzmann-kinetic approach to describe the entrance of neutral interstellar hydrogen into the heliosphere, Astron. Astrophys., 264, 260–269, 1992.

  15. Rucinski, D. and M. Bzowski, Modulation of interplanetary hydrogen density distribution during the solar cycle, Astron. Astrophys., 296, 248, 1995.

  16. Rucinski, D., A. C. Cummings, G. Gloeckler, E. Möbius, and M. Witte, Ionization processes in the heliosphere—Rates and methods of their determination, Space Sci. Rev., 78, 73, 1996.

  17. Scherer, K., Drag forces on interplanetary dust grains induced by the neutral gas, Icarus, 1998 (submitted).

  18. Scherer, H., H.-J. Fahr, and J. T. Clarke, Refined analysis of interplanetary H-Lyman-Alpha spectra obtained with the Hubble-Space Telescope GHRS spectrometer, Astron. Astrophys., 325, 745–754, 1997.

  19. Scherer, K., I. Mann, and G. Reaves, On the dynamics of the zodiacal dust cloud near the Sun, in NASA Conference Publication 3343: From Stardust to Planetsimals: Contributed Papers, edited by M. E. Kress, A. G. G. M. Tielens, and Y. J. Pendleton, pp. 209–212, 1996.

Download references

Author information



Corresponding author

Correspondence to Klaus Scherer.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Scherer, K., Fahr, H. Drag forces in the near and distant solar system. Earth Planet Sp 50, 545–550 (1998).

Download citation


  • Dust
  • Solar Wind
  • Mach Number
  • Drag Force
  • Dust Particle