Update 1/31

Qual

  • What should I be reviewing?
  • What should I focus on in the brief (10 journal-style pages)?
    • Should I try to work in all of the papers, tell the story so far in limited detail? Focus on just one?

​Radiation pressure paper

  • Sent an email around with information related to our previous discussion. I've begun incorporating some of the information where appropriate. Body of email copied below for reference.
  • Could use some brainstorming on alternate ways to make the same point as these measurements:
    • Comparing the average speed of a particle being significantly affected by radiation pressure to the escape speed of the system
    • , , comparison (could also compare pressures, if I can figure out a good length scale to convert volumetric radiation force to radiation pressure)

Even using the high-memory nodes on the visual partition, VisIt either crashes (at end of trying to load Chombo) or hangs (while processing) when trying to make the necessary plot. Possible to load all of the VTKs created when saving 3D plot in python, maybe?

  • Cherenkov et al 2017 ionization procedure:
    • This is the entirety of what they say about their ionization procedure: “In the grey approximation, the last term in equation (6), the rate of photoionization, can be written in the form , where h is the Planck constant, σUV = 6.3 × 10−18 cm2 is the photoionization cross-section at the Lyman limit frequency ν0, FUV = F0 (apl2/l2) is the intensity of ionizing radiation at distance l from the star centre, F0 = 884 erg cm−2 s−1 is the radiation intensity at the planet orbital distance, apl, (Schneiter et al. 2016) and τ is the optical depth.”
    • Sections 2.3 and 2.4 talk about the radiation transfer model they use, but only in the context of the radiation pressure (Lyman-alpha line). My assumption would be that they intend for this to extend to the ionizing radiation, but they never make this explicit.
    • None of the previous studies that could reasonably be considered to be by their group use self-consistent ionization
  • Launch conditions from Bourrier et al.
    • Bourrier et al 2013 launch metaparticles of neutral hydrogen only, and stop tracking ionized hydrogen—this may have a significant effect on the dynamics, since much of what is being pushed on (indirectly) is ionized
    • Their highest density is at launch radius, and is ~107 /cm3. Around the same location (Mach surface/Hill sphere at ~2.8 Rp), we have a total density of ~6x106 /cm3, with a neutral density of ~8.5x104 /cm3 (for no-flux simulation). So their optical depth to Lyman-alpha radiation is significantly higher.
    • They say “the number of atoms in a meta-particle is calculated to keep a low value of the corresponding optical depth dτ in front of a fraction of the occulted stellar surface.” Unclear to me what exactly this means.
    • Their metaparticles are launched randomly in every direction with thermal speed of 11000 K (much higher than our temperature at this point).
  • HD 209458 vs. other stars' Lyman-alpha fluxes
    • From Wood 2005, Lyman-alpha fluxes for other G0 V stars normalized to HD209458b orbital distance, in erg/s/cm2: 18344, 18955, 14374, 23836; HD209458 = 6409
    • So it’s on the low side, by a factor of ~3
  • Optical depth in wings (near planet)
    • At 3 Rp in +y, 50 km/s ± 2km/s bin, optical depth of 1.66 (in high flux case)
  • What happens as we transition between ionizing flux regimes?
    • From Sec 5.3 of John's paper: While in E-limited, neutral fraction constant, density higher, so total neutral density (and therefore optical depth) higher. Crossing into R-limited, neutral fraction reduces as 1/F1/2, and density increases at the inverse rate, so optical depth becomes constant. At some point, wind may start turning around to create the swirly arms – at this point, optical depth should ~double from previous.
  • Local ionization equilibrium
  • Effect of averaging over bubbling in high-flux case
    • Very small effect, mostly deeper center transit in the phase where the wind is expanding out of the Roche lobe. See ​attenuation and ​observation comparisons.
  • Plots of velocity, neutral density
    • ​Final attached plot is neutral mass density with velocity contours plotted over. Contours are: blue, 1x105 cm/s; red, 5x105 cm/s; cyan, 1x106 cm/s; yellow, 5x106 cm/s; magenta (none present), 1x107 cm/s

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