Ambipolar drift of spatially separated electrons and holes

2001 ◽  
Vol 64 (8) ◽  
Author(s):  
M. Beck ◽  
D. Streb ◽  
M. Vitzethum ◽  
P. Kiesel ◽  
S. Malzer ◽  
...  
Keyword(s):  
Ambipolar Drift

scholarly journals Constraint on ion–neutral drift velocity in the Class 0 protostar B335 from ALMA observations

2018 ◽  
Vol 615 ◽  
pp. A58 ◽  
Author(s):  
Hsi-Wei Yen ◽  
Bo Zhao ◽  
Patrick M. Koch ◽  
Ruben Krasnopolsky ◽  
Zhi-Yun Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Drift Velocity ◽  
Large Scale ◽  
Ambipolar Diffusion ◽  
Neutral Drift ◽  
Neutral Gas ◽  
Mhd Simulations ◽  
Ambipolar Drift ◽  
Velocity Drift ◽  
The Magnetic Field

Aims. Ambipolar diffusion can cause a velocity drift between ions and neutrals. This is one of the non-ideal magnetohydrodynamics (MHD) effects proposed to enable the formation of large-scale Keplerian disks with sizes of tens of au. To observationally study ambipolar diffusion in collapsing protostellar envelopes, we compare here gas kinematics traced by ionized and neutral molecular lines and discuss the implication on ambipolar diffusion. Methods. We analyzed the data of the H13CO+ (3–2) and C18O (2–1) emission in the Class 0 protostar B335 obtained with our ALMA observations. We constructed kinematical models to fit the velocity structures observed in the H13CO+ and C18O emission and to measure the infalling velocities of the ionized and neutral gas on a 100 au scale in B335. Results. A central compact (~1′′–2′′) component that is elongated perpendicular to the outflow direction and exhibits a clear velocity gradient along the outflow direction is observed in both lines and most likely traces the infalling flattened envelope. With our kinematical models, the infalling velocities in the H13CO+ and C18O emission are both measured to be 0.85 ± 0.2 km s−1 at a radius of 100 au, suggesting that the velocity drift between the ionized and neutral gas is at most 0.3 km s−1 at a radius of 100 au in B335. Conclusions. The Hall parameter for H13CO+ is estimated to be ≫1 on a 100 au scale in B335, so that H13CO+ is expected to be attached to the magnetic field. Our non-detection or upper limit of the velocity drift between the ionized and neutral gas could suggest that the magnetic field remains rather well coupled to the bulk neutral material on a 100 au scale in this source, and that any significant field-matter decoupling, if present, likely occurs only on a smaller scale, leading to an accumulation of magnetic flux and thus efficient magnetic braking in the inner envelope. This result is consistent with the expectation from the MHD simulations with a typical ambipolar diffusivity and those without ambipolar diffusion. On the other hand, the high ambipolar drift velocity of 0.5–1.0 km s−1 on a 100 au scale predicted in the MHD simulations with an enhanced ambipolar diffusivity by removing small dust grains, where the minimum grain size is 0.1 μm, is not detected in our observations. However, because of our limited angular resolution, we cannot rule out a significant ambipolar drift only in the midplane of the infalling envelope. Future observations with higher angular resolutions (~0. ′′1) are needed to examine this possibility and ambipolar diffusion on a smaller scale.

Ambipolar drift and breakdown of oscillistor effect in strong magnetic fields

1977 ◽  
Vol 23 (12) ◽  
pp. 939-941
Author(s):  
V.M. Bondar ◽  
V.V. Vladimirov ◽  
V.P. Doskoch ◽  
E.A. Chaban ◽  
A.I. Schedrin
Keyword(s):  
Magnetic Fields ◽  
Strong Magnetic Fields ◽  
Ambipolar Drift

Ambipolar Drift in α Ag2S

1981 ◽  
Vol 50 (6) ◽  
pp. 2050-2053 ◽  
Author(s):  
Shin-ya Miyatani ◽  
Akira Tabuchi
Keyword(s):  
Ambipolar Drift

Ambipolar Drift, Deformation, and Diffusion of a Plasma in a Magnetic Field

1973 ◽  
Vol 51 (5) ◽  
pp. 564-573 ◽  
Author(s):  
Richard L. Monroe
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Effective Magnetic Field ◽  
Theoretical Problem ◽  
Direction Parallel ◽  
Transverse Diffusion ◽  
Weakly Ionized ◽  
Plasma Diffusion ◽  
Ambipolar Drift ◽  
And Diffusion

The theoretical problem of a weakly ionized, constant temperature, three particle plasma in an externally generated magnetic field is reformulated by transforming the set of 14 macroscopic plasma equations (continuity and momentum equations for ions and electrons plus Maxwell's equations) in 14 unknowns (ion and electron number densities and velocities plus the effective electric and magnetic fields) into an equivalent set of 4 integral equations in 4 unknowns. In the course of this transformation, it is shown that the plasma behavior can be interpreted in terms of three ambipolar processes : drift, deformation, and diffusion. Plasma diffusion is characterized by two diffusion coefficients : the usual Schottky formula applying in the direction parallel to the effective magnetic field and a new expression for the ambipolar transverse diffusion coefficient applying in directions perpendicular to the effective magnetic field. The new ambipolar coefficient differs markedly from the familiar ambipolar coefficient associated with the names of Bickerton, Lehnert, Holway, Allis, and Buchsbaum; and, in general, it gives values for the transverse diffusion coefficient which are two orders of magnitude larger than those given by the latter. It is concluded that ambipolar diffusion can produce a transverse diffusion coefficient large enough to account for the diffusion rates measured by Bohm, Burhop, Massey, and Williams in argon arc discharges.

ERRATUM: “AMBIPOLAR DRIFT HEATING IN TURBULENT MOLECULAR CLOUDS” (2000, ApJ, 540, 332)

2012 ◽  
Vol 755 (2) ◽  
pp. 182 ◽  
Author(s):  
Paolo Padoan ◽  
Ellen Zweibel ◽  
Åke Nordlund
Keyword(s):  
Molecular Clouds ◽  
Ambipolar Drift

Propagation of Ion‐Acoustic Waves in a Plasma Subject to an Ambipolar Drift

1969 ◽  
Vol 40 (6) ◽  
pp. 2674-2675 ◽  
Author(s):  
S. Aksornkitti ◽  
H. C. S. Hsuan ◽  
K. E. Lonngren
Keyword(s):  
Acoustic Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic ◽  
Ambipolar Drift

Discontinuities in drift solutions due to reversal in ambipolar drift. Injection and accumulation of hot carriers

1978 ◽  
Vol 46 (1) ◽  
pp. 45-53 ◽  
Author(s):  
A. P. Dmitriev ◽  
A. E. Stefanovich ◽  
L. D. Tsendin
Keyword(s):  
Hot Carriers ◽  
Ambipolar Drift
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