COMPARISON OF THE WAVE ENERGY-TRANSPORT AT COMETS P HALLEY AND P/GIACOBINI-ZINNER/

Using magnetic field, plasma density and flow observations from spacec raft flybys of two comets, variables are determined in order to study, wave propagation directions. The inbound path of the Giotto spacecraf t flyby of comet p/Halley is investigated outside the bow shock (betwe en 10:36 and 19:11 LUT on March 13, 1986, corresponding to distances f rom 3.3 x 10(6) to 1.2 x 10(6) km from the nucleus) and inbound path o f the ICE spacecraft flyby of comet p/Giacobini-Zinner is investigated outside of the bow wave (between 00:00 and 9:24 UT and between 12:25 and 23:30 UT on September 11, 1985, corresponding to distances from 8. 5 x 10(3) to 1.2 x 10(5) km from the nucleus and from 1.0 x 10(5) to 9 .3 x 10(5) km from the nucleus respectively). The interaction of comet ary pick-up-ions and the solar wind expected to generate waves which a re assumed to be dominated by field-aligned propagating Alfven waves. This predicted wave propagation combined with wave modes generated by the ion cyclotron resonance instability are compared with observed wav e properties. Three mhd-modes are possible: right-hand polarized waves propagating toward the Sun (RH(-)) and left-hand polarized waves prop agating toward (LH(-)) and away from the Sun (LH(+)). Plasma condition s dictate that the RH(-) mode is the most unstable mode and satisfacto ry agreement is found between observed and predicted energy flow direc tions in regions outside the bow shock at Halley and the bow wave at G iacobini Zinner, where local cometary ion pick-up conditions dominate. Copyright (C) 1996 Elsevier Science Ltd