SHORT CIRCUITS IN THERMALLY IONIZED PLASMAS: A MECHANISM FOR INTERMITTENT HEATING OF PROTOPLANETARY DISKS

Journal Article · Mon Dec 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/761/1/58· OSTI ID:22140045

Hubbard, Alexander; McNally, Colin P.

Many astrophysical systems of interest, including protoplanetary accretion disks, are made of turbulent magnetized gas with near-solar metallicity. Thermal ionization of alkali metals in such gas exceeds non-thermal ionization when temperatures climb above roughly 1000 K. As a result, the conductivity, proportional to the ionization fraction, gains a strong, positive dependence on temperature. In this paper, we demonstrate that this relation between the temperature and the conductivity triggers an exponential instability that acts similarly to an electrical short, where the increased conductivity concentrates the current and locally increases the Ohmic heating. This contrasts with the resistivity increase expected in an ideal magnetic reconnection region. The instability acts to focus narrow current sheets into even narrower sheets with far higher currents and temperatures. We lay out the basic principles of this behavior in this paper using protoplanetary disks as our example host system, motivated by observations of chondritic meteorites and their ancestors, dust grains in protoplanetary disks, that reveal the existence of strong, frequent heating events that this instability could explain.

• OSTI ID: 22140045
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 761; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ALKALI METALS
ASTRONOMY
ASTROPHYSICS
COSMIC DUST
ELECTRICAL FAULTS
GAIN
HEATING
INSTABILITY
IONIZATION
MAGNETIC RECONNECTION
MAGNETOHYDRODYNAMICS
METEORITES
METEOROIDS
PLASMA
PROTOPLANETS
TEMPERATURE DEPENDENCE