Changes between Version 6 and Version 7 of u/adebrech

Timestamp:

05/26/16 15:08:26 (9 years ago)

Author:

adebrech

Comment:

—

u/adebrech

@@ -2 +2 @@
 [[PageOutline]]
 
-= Christie paper =
+= [http://arxiv.org/pdf/1206.5003v3.pdf Tremblin & Chiang], Computational Charge Exchange =
+Followup to 2008 and 2010 studies of charge exchange between planetary and stellar winds, which used Monte Carlo simulations of 'meta-particles' that were computationally obstructed by bow shocks. Here they use the hydrodynamic equations (no magnetism, Coriolis and centrifugal forces, or tidal gravity). A slow stellar wind (130 km/s) was chosen to approximate the solar wind, and the isothermal planetary wind was initialized as 80% ionized, following Murray-Clay et al. The planetary wind incorporated photoionization/recombination and advection. To incorporate charge exchange, the hydrodynamic code was augmented with chemical reaction solvers - 4 equations relate x,,i,,, i=1-4 representing each possible combination of hot or cold and neutral or ionized hydrogen, and n,,H,, with beta, the reaction rate. These equations take reverse exchange into account, so as not to overestimate neutral hydrogen too greatly (still slightly overestimated). x,,i,, is also included in the hydrodynamic equations.
+
+[[Image(TremblinEqns.jpg)]]
+
+
+
+= [http://iopscience.iop.org/article/10.3847/0004-637X/820/1/3/pdf Christie] paper =
 2.5D spherical simulations of planetary and stellar wind interactions, including charge exchange, were performed. Hydrodynamic simulations were performed, with density fixed at the base of the planetary wind and an inflow boundary condition on one half of the simulation serving to emulate the stellar wind. In addition to charge exchange, advection, photoionization and recombination, and collisional ionization were included. The escape parameter lambda was used to categorize the models; it was found that there were two distinct regimes, with a transition region between. With lambda <= 4 (high planetary temp), the planetary wind becomes transonic before colliding with the stellar wind, creating a large tail that takes a significant amount of time to mix. With lambda >= 6 (low planetary temp), the planetary wind has no chance to become transonic before it encounters the stellar wind, and the winds mix turbulently rather than collide, resulting in a well-mixed, barely evident tail. The transition region between these is also shown clearly in the calculated mass-loss rates of the simulations.