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yeah so I'll be talking about snow lines

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in external evaporated Florida flank

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readers that's my shorter title so

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actually the previous speaker gave give

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a really nice introduction to what I'm

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going to be talking about and I thank

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off for that so to motivate my talk

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basically I'm listed here a couple of

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like the water content by weight of some

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of the bodies in our solar system and

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you can kind of see that they really

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vary from a word like say point one

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percent or tens of percent and

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impossible exhaust successful our

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planetary I mean whatever else you you

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could probably have like up to fifty

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percent of water by weight so what

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really decides the water content of you

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know the planets and to get into this

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question we talking about snow lines the

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last bit again like introduces so a snow

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line is basically the region that kind

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of demarcates where water condenses his

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eyes and where where it doesn't so you

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can kind of see a snow line on a

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mountain here and but in a

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protoplanetary disk what is sublimates

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at once empty Kelvin and so this was

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initially thought to exist at like two

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point seven EU from the Sun and so here

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shown us here so it was theorized that

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you know bodies that formed within this

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snow line would be whatever dry and the

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bodies that formed outside fit would be

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water rich and subsequently a lot of

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more like detailed / a plant various

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models that kind of assume more accurate

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dust properties and temperature profiles

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in this kind of came to the conclusion

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that

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the snowline need not necessarily be at

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this value it could be much more closer

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in even as close as one AU and also

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subsequently models found that like

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temperatures probably not the only

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criterion but a radial transport of

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volatiles across the snow line also

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matters so probably the picture of the

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snow line is not a static and clear as

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this but probably something a little bit

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more murky so what do I mean by radial

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transport of volatiles there could be

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like different types of like wall tile

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processes happening across this new line

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you could have a continuous output

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diffusion of vapor outside this new line

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and then you could have like an inward

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drift of icy particles which kind of

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orbit at the different frequency orbit

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like yeah at a different frequency than

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the pressure supported gas and because

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of which they would like spiral inwards

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and upon reaching the snow line they

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would melt and kind of you know so you

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would have liked cyclically like

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transport of water vapor outside and

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inside the snow line and to this

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scenario if we were to add the process

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of external for evaporation let it could

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be a little bit more complicated so what

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what external photo operation is is that

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the Sun was born in a massive it's very

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likely that the Sun was born in a

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massive star forming region and it's

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disc was sort of intensely irradiated by

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radiation from nearby massive stars so

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if that was the case then it could you

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know frustrate this inward drift and

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kind of enhanced in outward a wall tile

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transport like outside from the outer

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edge of the disk so we kind of consider

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this process as well in our modeling of

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this structure so what what what this

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project is about is basically riedl

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transport of Walter's would be

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sort of intimately connected to the

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destruction of the protoplanetary disk

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and we kind of probe the dress structure

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a little bit more so to very simply

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represent our density structure and it

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is you kind of like a call it by a

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radial power log with with an exponent

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of fee or here and this density

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structure would be like very intimately

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connected with the temperature in a disk

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so if you represent that as well as a

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power loss with with Q we go back to a

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result by like 2k chicken Lynn who say

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that if the sum of these two exponents

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is greater than two then the net volar

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transport is likely to be outward and we

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kind of test what this is likely to be

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so if you assume like a standard value

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of the temperature power law are you

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know over the q of point five so we are

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like left to determine what is P and the

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previous speaker again spoke about the

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minimum master intervenor model where

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each of the giant planets kind of like

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smear in their current annuli and you

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you can infer surface density profile

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the slope of 1.5 with with such a model

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just shown here later dash 2007 kind of

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included the positions of the giant

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giant planets from the nice model and he

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found a slope that was more steeper for

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the surface density profile he basically

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thought that okay the nice model a

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position the giant planets is a more

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reasonable assumption to make because a

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lot of migration in the planets like

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father word after from hundreds of

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millions of years so we so basically in

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in this project we model destruction and

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evolution and try to see what effects de

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structure how for the operation of extra

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structure and also we consider a

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non-uniform as a viscosity of LP

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explaining so we take an account the

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standard

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equations of bisque evolution by Lynn

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melanin belen Pringle and where this

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equation our talks about the evolution

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of the surface density and the rate of

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mass flow and we also assume like this

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the standard viscosity parameterization

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where a new is given as alpha times San

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speed squared divided by orbital

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frequency and so mostest models just

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assume just an invariable alpha offers

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the same throughout the disk with height

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and width or radius and it's and it's

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also the same with time but we kind of

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kind of derive this alpha from Magneto

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rotation instabilities and kind of find

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that it varies quite a bit and this has

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to be considered in risk evaluation

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models so magneto rotational

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instabilities simply put is like in a

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fluid instability that occurs in a

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creationist it occurs only if there's

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the if the region in the discus like

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sufficiently ionized and so for this we

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calculate the ionization state at each

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region in the disk so we consider

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ionizations by x-rays and cosmic rays

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and we consider recombinations of these

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ionic species and electrons and the gas

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phase is this dust green surfaces I

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could I could talk about more details

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later so what we do then is we consider

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the treatment treatment of buyin stone

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2011 well be basically determine the

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Alfred each each region in the disk from

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the ionizing ionization state and we

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find that on incorporating these

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equations in our disk model that alpha

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does really change a lot like oh for

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more do some attitude throughout the

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radius of the disk from about likes a

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point or less than point 5 15 the flower

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here I'm sorry 10 to the 10 to the minus

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5 and 2.1 in the outer regions the disk

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and it also changes

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dramatically with time so and finally we

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also include photo operation using the

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the treatment and the result of Food

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Association models from Adams at all

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where they basically the massless rates

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your for evaporation mainly depend on

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the the disc radius at ya on the disc

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radius as well as G naught which is kind

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of like the parameter for describing the

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radiation intensity that the disc point

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is finds itself in so here we find we we

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use a value of a GNote of a thousand to

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be be considered that to be typical of

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what this are likely to face and in like

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rich star forming regions and finally do

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go to our results so I'm showing you the

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first sort of viscously evolving disc

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case and to kind of describe this graph

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a little bit this is the surface density

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on a log-log with a log-log plot with

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the radius so the radius curve goes from

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point 1 au to 180 here and each of these

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um so this is the initial the door line

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or the dashed line is in is the initial

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profile of the disc and each of these

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lines are solid lines at each subsequent

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here or milliner of evolution from 1

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million years 10 min years so you can

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see that the disc obviously becomes less

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massive with time and you can also see

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it sort of expand outwards that's what I

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viscously evolving this without any of

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the effects that i described about good

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what kind of I mean react so so after 10

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million years of evolution

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only like half of the disc remains and

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you could kind of like keep keep in mind

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this number as I show you different

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cases so then so the other thing we do

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is we also track the slope of the

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surface density profile between five and

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thirty you and here we find that the

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slope p is about one so next we go to a

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photo operated case so it's basically a

219
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viscously evolving disk without Amara

220
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alpha with with for with for evaporation

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and you can see that this the slope that

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we keep track off between five thirty au

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it's slightly steeper right now and the

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disc is less less massive even more only

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five percent of the disc remains after

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ten million years of evolution and it's

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also truncated to about fifty fifty a

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you so the other interesting thing that

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you can find in this this type of disc

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is that is the behavior of the

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transition radius so in a in a viscously

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evolving disk this transition radius

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usually moves outward with time and we

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find that this this radius which is

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basically the radius where the net mass

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flow changes from inward operational

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flow to outward this moves inward with

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time and in in this disk it actually

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moves as closes 17a you from the start

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so basically what this means is that

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mass as close as 17 au is drawn out

242
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words from from the outer edge of the

243
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disk then we take the third case where

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we include MRI azva and 40 operation and

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we find that the disk rapidly dispatch

246
00:13:01,120 --> 00:12:58,040
within just seven point seven point five

247
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million years of evolution so what what

248
00:13:05,980 --> 00:13:03,589
happens is the slope becomes really

249
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really steep and most of the disk is

250
00:13:13,569 --> 00:13:09,380
just gone in within 7.5 million years

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and but when we include dust in the

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scenario the previous case do not have

253
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any dust in it it kind of has it

254
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has an totally opposite effect from what

255
00:13:29,390 --> 00:13:26,430
we just saw what we see here is the dust

256
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kind of stalls the inner disk evolution

257
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by sort of absorbing charges in the

258
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theory of the disk and the rest of the

259
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disk just files on on top of the inner

260
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disk kind of erecting this really steep

261
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profile you know where p is like much

262
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greater than 3 and so this is kind of

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really interesting of course we don't

264
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include grain growth here so that is an

265
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important caveat so conclusions for

266
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evaporation does cause steep profiles so

267
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we get a large p and this is likely to

268
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create like more outward transferred

269
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from the result by decay chain then my

270
00:14:13,610 --> 00:14:10,500
alpha is very sensitive to the presence

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of dust and dust causes the style

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evolution of the inner disk it doesn't

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let it evolve disk dispersal would

274
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require would require grain growth which

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we don't model here and the transition

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radius moves in so the gas is removed

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from the inner disk and in this previous

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case it moves as close as three a year

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which is why it's very important from

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the for the terrestrial planet region

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point of view so dehydration of the

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inner disk especially wood is important

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especially for dis in rich clusters so

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huh so um have you done a sensitivity

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studied to see if you turn off the MRI

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alpha and just include the dust if it

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essentially reproduces the same shaped

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is just completely overwhelmed the alpha

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variability no actually that would be

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interesting to see all right let's thank