The variable nature of the comet-solar wind interaction

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:5220160

Flammer, K R

The different modes of interaction of the solar wind with a Halley-type comet as it approaches the sun are discussed. At large heliocentric distances the solar wind penetrates unimpeded onto the surface of the comet nucleus. This causes electrostatic charging and expulsion of fine dust from the comet surface; a process which is modulated by the local solar wind flux. The observed irregular brightness variation of comet Halley between 11 and 8 AU (inbound) are explained in terms of this mechanism. As the comet moves closer to the sun (within 4 AU), mass loading of the solar wind by the heavy cometary ions causes the flow to slow down, thereby enhancing the convected interplanetary magnetic field significantly. This magnetic field enhancement is the earliest and most sensitive signature associated with the solar wind mass loading. Still farther in ({le} 3 AU), as the mass loading approaches a critical value, a weak collisionless standing shock forms, which recedes upstream of the nucleus as the comet approaches the sun. The cometary atmosphere becomes dense enough so that a well-defined ionopause forms which separates the cometary ionospheric plasma from the contaminated solar wind plasma only when the comet is within {approx} 2.2 AU from the sun. The stability of the ionopause is examined under the framework of linear magnetohydrodynamic taking into account the effects of ion-neutral drag, sources, curvature and compressibility. Both Kelvin-Helmholtz and Rayleigh Taylor modes are excited. The growth rates of these modes are determined from various shears and density jumps at the ionopause and under different solar wind conditions. A quasi-linear theory is then used to examine the evolution of the unstable modes to finite amplitudes.

• Research Organization: California Univ., San Diego, CA (USA)
• OSTI ID: 5220160
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BRIGHTNESS
CHARGED PARTICLES
COMETS
COSMIC DUST
DUSTS
FLUID MECHANICS
HALLEY COMET
HELMHOLTZ INSTABILITY
HYDRODYNAMICS
INSTABILITY
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
IONS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MAIN SEQUENCE STARS
MECHANICS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLASMA
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
RAYLEIGH-TAYLOR INSTABILITY
SHOCK WAVES
SOLAR ACTIVITY
SOLAR WIND
STARS
SUN
VARIATIONS