The 10 January 1986 Disconnection Event in Comet Halley

  1. Alan Johnstone
  1. Malcolm B. Niedner Jr.1,
  2. John C. Brandt2 and
  3. Yu Yi2

Published Online: 26 MAR 2013

DOI: 10.1029/GM061p0153

Cometary Plasma Processes

Cometary Plasma Processes

How to Cite

Niedner, M. B., Brandt, J. C. and Yi, Y. (1991) The 10 January 1986 Disconnection Event in Comet Halley, in Cometary Plasma Processes (ed A. Johnstone), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM061p0153

Author Information

  1. 1

    Laboratory for Astronomy and Solar Physics, NASA-Goddard Space Flight Center, Greenbelt, MD 20771

  2. 2

    Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309

Publication History

  1. Published Online: 26 MAR 2013
  2. Published Print: 1 JAN 1991

ISBN Information

Print ISBN: 9780875900278

Online ISBN: 9781118663660



  • Comets;
  • Space plasmas;
  • Astrophysics


The disconnection event (DE) in the plasma tail of comet Halley on January 9–12, 1986 is examined. We measured the distances between the comet head and the disconnected tail for a series of images for that time period and then extrapolated to the nucleus to determine the disconnection time, Td = January 9.60 +/- 0.2 days. The approximate solar-wind conditions at the time of the DE were obtained by corotation of IMP-8 satellite data in Earth orbit to comet Halley. At the time of the DE, comet Halley is inferred to have been close to a magnetic sector boundary and a high-speed stream compression region, circumstances which are consistent with models invoking magnetic reconnection in response to either sector boundary crossings or increases in solar-wind plasma pressure (sunward and tailward reconnection, respectively). However, a heliographic latitude separation of 22 degrees (between the comet and IMP-8), gaps in the IMP-8 data, and other, more minor disconnection activity slightly preceding the January 9–10 DE, render a more definitive statement about the linkage of the DE to external conditions quite difficult. In particular, it appears not possible at this time to resolve the effects of magnetic changes associated with the sector boundary and plasma pressure in the compression region. Resolution of conflicting DE theories will likely require a statistical treatment of many events.