Valentin Aslanyan (University of Dundee) chats about his article on the Sun, and where we can go from here given the published article.
A Near-half-century Simulation of the Solar Corona
https://ui.adsabs.harvard.edu/abs/2024ApJ…961L…3A/abstract
Valentin’s web presence:
https://www.dundee.ac.uk/people/valentin-aslanyan
The intended audience for the AAS Journal Author Series is active researchers.
Hello everyone welcome back to the double as YouTube channel this is part of the good stuff this is the double as Journal author series and I am very happy to have Val aslanian with us today hello Val hi there um those are some great equations over your right
Shoulder those are pretty famous yes they were in no way planted there of course not never never never uh yeah so we we uh we will be uh I’ll be mentioning some of uh Magneto hydrodynamics a bit of plasma physics a bit of electromagnetism um so we we will uh
Just briefly touch on that uh and see some of the applications some of these equations in the wild in the wild okay very good uh and Val where where are you located at what’s your geolocation uh yes so right now I’m in uh the city of dunde the original one in Scotland
United Kingdom uh so and I’m in a at a lovely uh School of Science and Engineering here um I am part of the uh mathematics division here uh so we we do a lot of Applied Mathematics but as you’ll see we do very much like to uh relate that rather
Abstract those abstract Notions to the real world and you will see some uh real world examples very cool uh let’s see dendi we’re fairly far got Northern latitude there is there snow in dundy do you get snow uh there is some snow right now um we are uh of course well we have
The Gulf Stream of course so it’s it’s maybe not as as cold as some of the the latitudes uh in the US equivalently um we we it does get dark quite early we I think are just about out of out of the range of latitudes where you can observe the ISS with the
Naked eye so nice nice just just die out so I do have to go south to see the okay uh let’s see it is January 18th 2024 as we record this and I’m in Phoenix and Phoenix is definitely in its winter mode um so we get a little above
Freezing in the morning and then it’ll warm up to a very pleasant day so it’s all good and Val what do you like to do for research uh well uh I I have a background in plasma physics um I was began uh almost lifetime ago uh that
Doesn’t seem that long maybe it does seem longer uh in uh the uh study of controlled Fusion but now I have moved on to uh to a a as people tell me a working Fusion reactor studying our very own Sun um and many other the model for many
Other Fusion reactors many other stars of course in our uh universe so uh I’m studying um the sun specifically the uh the sort of outer layers of the Sun the the sun’s atmosphere the sun’s Corona and that’s what we’re going to be uh discussing today cool so let’s go ahead
And get into it and see I’m gonna do a share desktop on this one and there we go this one is an apj letter it is open access it’s the Open Access era people go ahead and grab a copy for free a near half century simulation of the
Solo Corona and V take us away yes so thank you so first of all I would certainly like to uh thank and acknowledge my co-authors uh my boss uh Karen May here at dunde is also um a lot of experience studying a solar phenomena um uh I have a close collaborator Roger
Scott who’s currently at the US Naval research laboratory but he was also previously here at dunde and I’ll I’ll highlight um a particular piece of work he’s done um for this and finally uh our collaborator Anthony Yates um at the at darham University darham again the the
UK one not the uh yes American one I’m afraid to say the original and the best perhaps um and again I’ll I’ll very much highlight um his part uh in this so um I’ll I’ll point out what they’ve done so if you don’t mind I’ll I’ll jump straight into it
As I mentioned we we’re going to be talking about the Sun and we’re going to be talking about the sun’s Corona so this is the the region just above that burning ball of gas that you normally see uh this is a a region of course uh
Filled with plasma but it is one which is dominated by the magnetic field of the sun uh and indeed there is an interaction of course between the plasma and the magnetic field Mutual sort of interaction uh and so it’s utterly Domin ated by the magnetic field and so the
Way to model this region um there are there are a couple of established approaches so on the one hand uh you have what is called the uh potential uh field approach so this is one where uh you largely ignore the influence of the plasma it’s it’s also called a force
Free approach or current free approach so you largely ignore that plasma with the exception of you’re probably familiar that there is a solar wind an outflow of plasma from the Sun so that’s the only way that the plasma is kept in that model and other than that it is
Basically a magnetostatic model yeah okay and um it’s a model where um because you’re not considering the effects of the plasma you are not considering the History either so you can kind of take a single snapshot and simulate the whole Corona without knowing what has happened before or what
Will happen in the future you just have this snapshot and that of course is that’s a double-edged sword on the one hand you’re missing some of this dynamics of course there is histo a history and a historis within the Corona and on the other hand uh on the other on
The on the positive side though because you don’t need to know all that history you can uh run this model very quickly yeah on the complete other end of the scale you have the Magneto hydrodynamic approach which should be familiar to all sorts of plasma physicists and other
Researchers um so this treats the plasma as a fluid which interacts self-consistently with the magnetic field okay uh and uh you know and these these models can get almost limitlessly complex and complicated so you know you can have a volume the size of my little finger uh filled with plasma being
Simulated by an entire superc computer for you know for only 0. one of a second or so of real time might take you days it can get really really complicated of course it doesn’t have to be that way but right the Magneto hydrodynamic models they are very uh intensive and uh
Complicated indeed and um and so what we have is a Magneto friction model I’ll talk about that in just a moment but the the long and short of it is this lets us keep some of those Dynamics but it also uh is simple enough that we can run it quickly enough that
We as the title suggests we have done a uh we have simulated the uh the Ser Corona for a total of 47 years continuously with time resolutions of of order second so you know a time step every few seconds nice it’s Dynamic so each time step informs the next one
There is a history there time step to time step um so clearly uh that’s a a very large and interesting data set there that we have you know that sort of small resolution the whole Corona uh in a whole in a single case for that length
Of time and so and let me let me ask what is the um what is the spatial resolution um so the so we we have about uh it actually does say it lower down but it’s about one degree um so one degree and in two angular directions
Okay and then we have 60 so you know it’s it’s enough and you’ll see you’ll see some of the effects here so it’s you know it’s not the the tiniest resolution it’s not the size of my little finger by any means but it is enough to capture
Some of the important Dynamics cool um and uh so the the real purpose one of the main purposes of this uh letter is to kind of make the scientific Community aware of this and more importantly to solicit uh suggestions collaborations you know feedback Etc how can we use
This data set and this study to help you answer some of your science questions what can we do with this we have a lot of ideas we have you know we’re writing um several longer more involved articles to follow this up but we would definitely like to to hear from you um
Any any suggestions from from the scientific community may your inbox fill up um so what is this uh Magneto frictional approach that we have taken and uh there’s code that’s been developed called dumri um to solve this so the idea is um to take the Magneto hydrodynamic equations which as I say
They have a fluid component and uh to basically ignore the or or rather simplify the uh inertial term okay so there’s an inertial term in the mhd equation and we’ll simplify that into a a frictional term so what this means firstly it means that we can eliminate the uh the density
We don’t need to worry about the density anymore there’s just a friction you know the the the bulk of the plasma just causes a friction and what it also means is we can eliminate the velocity as an independent parameter as an independent variable um and you can see there in
Equation two that the velocity now becomes just a function of the magnetic field so as I mentioned the magnetic field is is dominant so we have subordinated all the other variables to it we solve just for the magnetic field we can either well in fact we solve
Through the um through the uh Vector potential but as you know if you’re if you’re familiar with this as you know from the vector potential we can very readily get the magnetic field itself y so um so I say we’ve effectively eliminated the the density and the fluid velocity
As a as an independent variable we’re solving just for the magnetic field uh but we get this Dynamic effect and I’ll so I’ll show you uh this and and and all of this has been we have developed all this into you know working code now I
Should also say the the the the word we that I just used there in last few sentences is doing a lot of heavy lifting so um this the development of this code has been uh you know a decadal work by our co-author Anthony yeets and of course many others involved with him
At uh darham University um so um uh and we’ve we’ve included we’ve included references to some of the early works if you want to know more about the the technical imp implementation some of the mathematics the history Etc you can read uh some of those past papers and and and other
References there in okay nice good here’s my from question there we go yes exactly so there is a there is and you can see it’s the in radius we we’re logarithmic and so on so this is this is fairly standard for this kind of model okay so as I’ve mentioned um yeah if
You’d like to go to figure one if you don’t mind abolutely so as I mentioned we have 47 years of data of magnetic field and uh we can infer from it the velocity um as you are probably aware even if you’re you know not um super into uh coronal physics you’re probably
Aware that uh the sun there are these things called coronal mass emissions or FL solar flares so very frequently there are these giant enormous uh expulsions of of plasma from the Sun these violent very rapid events that happen uh they happen quite regularly you know we’re talking every week every month Etc it
Varies we’ll we’ll talk about that in a moment but these happen very frequently so we had better hope that in our model you know in these 47 years we had better hope that there are you know hundreds of these and indeed there are so indeed there are hundreds of eruptions and and
Various s the dynamic events happening and so one thing that uh when I was looking at this one thing that I wanted to do is to try and localize each of these in space and in time so we could uh you know we have this kind of almost semi-automated way of detecting we’ve
Got an eruption that happened on this exact day uh in this exact location and of course then we want to check that against uh you know against Real records right um so what I’ve added to this code um if you look in the the bottom right
Of this figure so panel D um what I’ve done is I’ve taken the outer uh if you imagine that this is the outer boundary so there’s a sphere that encompasses our simulation encompasses our Corona okay and what I’ve done with that sphere is I’ve split this up into um into Parts
These are strictly called caps so if you imagine a kind of dome right a dome like shell so part of a sphere um here that kind of would form a dome if you took it off this is called a a spherical cap yes you can have various
Ones with different sort of it’s kind of the end of a cone right you could think of it as the end of a cone so you can have a various opening angles and so on and so I picked one and I what I’ve done is I’ve broken up uh you know just in
Terms of computation I’ve broke not in terms of the actual grid just but I have kind of yeah um I have grouped parts of it into these caps I’ve I’ve kind of stuck a bunch of caps onto the outside of our uh of our simulation domain I’m waiting and within each of
These caps as a function of time I’m calculating a quantity um I’ll explain what this is in the moment but it’s it’s called a holisti um flux well I’ll talk about that but basically for each cap I have a quantity as a function of time so
You can see an example of that in panel B right and this quantity um just by you know by deduction and also by just observation having having you know played around with this and and run this this quantity shows a peak exactly when an eruption happens and um uh so most
Specifically uh it might actually help here if you if you went uh to the movie of this yeah we got some very cool animations in this article and so let’s go ahead and pull up the first one here and away we go yes so um as as it shows there we
Have we have a a time period of three days uh and we are on the cap you can see on on the in the figure on the left we have this cap so within that cap we have this quantity that’s changing um and what I’m showing is I’m
Showing a number of magnetic field lines that are evolving within this uh within our simulation the these magnetic field lines go through that cap and what you’ll see you’ll see just in a moment there what you’ll see is you have see the magnetic field lines twist themselves into this bird’s nest yes and
This bird’s nest is then expelled out of the SIM ation domain so that that of course is is quite realistic in in uh in the real Sun we would expect uh eruptions to happen where indeed this is what happens the magnetic field sort of twists itself up and material and those
Magnetic field runs are effectively expelled outwards into the broader solar system so reconnection it’s going now there is reconnection happening and and you know this is um so in order to have that in order for a um a magnetic field line I’ll probably talk about that in a
Subsequent figure but in order for a magnetic field line to First be connected to the Sun and eventually disconnect and be expelled in that way there has to be magnetic reconnection and this is you know of course not all models capture that the pfss model would
Not be able to capture that we can do with wing to frictional this clearly shows that um but yeah so some of these magnetic field they reconnect they get expelled out and an eruption happens and I should stress that this is um you know I’m showing a period of 3 days but there
These are are three kind of real calendar days that uh you know we could look up Etc and uh they you know really happened um so now this eruption is driven um you can also see in the in the plot on the left the actual sphere itself the sphere
Of the sun uh is colored by the radial magnetic field okay okay and you can um so you can see that uh so the extreme uh bright and extreme dark are the the most intense so where you have a a dark patch or a bright patch that’s the most
Intense magnetic field and you can see that the the magnetic field lines the where that sort of bird’s nest of uh material appears um it begins at um a pair of like a a sort of you know a bright region next to a dark region this
Is what’s called an active region yes so of course um you need to um you know one of these equations up there tells you that you have to have a negative polarity for every positive polarity right you have no magnetic monopoles so an active region is a region on the sun
Of uh hopefully balanced positive a negative but strong in both cases so Net Zero but strong in in either direction yeah um magnetic field this is magnetic field that has sort of bubbled its way up it was U it’s it was generated inside the Sun there were some turbulent motion uh
Some currents were created and this was bubbled its way to the surface of the Sun um this would have been observed by a you know a an observatory on Earth or in space we we have certain sources and this effectively forms a boundary condition to our model so we we need
Someone to go out there and observe and see um where these active regions these regions of strong magnetic field emerge from the Sun and then we take that as an input to our model and what we produce then is something like this we show what happens to the magnetic field then in
The corona cool and so generally not always um but generally these kind of eruptions and flares and things are caused by these active regions these regions of intense magnetic field Co very nice beautiful um but so the the the thing here is that this approach um of of calculating this quantity again
I’ll come to that in a second but this quantity the uh Hy flux uh this can be calculated um from the magnetic field yes and as you can see it causes a spike exactly uh as the eruption passes through the outer simulation domain and this approach by
The way could be taken and used in something like an mhd model you know or any other model so you know this this could be readily transferred to a more complicated model it should work there and it should tell you the time that an eruption is happening and it should also
Because you’ve broken up your uh your uh outer boundary into these caps it should tell you where it’s happening so you can very readily you know you can say it’s it’s happening right here if I can somewhat digress uh when I was making this um I was sort of thinking of uh you
Know the uh the Star Trek TV show um I was sort of thinking you know you might be uh sort of sitting there you know saying Captain we have an an eruption in sector 3G or something you know um so that that’s the kind of idea here we we
Can we can sort of localize this as if you were you know a captain of a Starship those spherical caps are you know the the protective layer and you know protect it all it’s very cool good exactly so anyway but this is so this is approach lets us uh localize in time and
In space and eruptions of which we have many in our in our model um now what is this uh what is this uh quantity here this H with a um H dot um if you go back to the uh to the paper that’s that’s defined let’s go back it was up a little
Bit H dot there’s yeah exactly um so um this is to do with the change in magnetic helicity yes um so the magnetic helicity is a is a sort of twist uh of the magnetic field I won’t go too far into detail again there are references and so on that you can read
But the important thing here is that you can calculate this from local quantities on that cap so you you know in practice if you are running a simulation all you need to know is about the local plasma quantities at the outside of the uh of your simulation domain and then you can
You know only choose the ones in a particular area a particular cap that’ll uh and it’s an instantaneous quantity so that will tell you uh what is happening and you only need to know a kind of instantaneous time slice in order to be able to compute this quantity very cool
Okay all right so One um I think that’s all I have to say about that so we can move on to figure two yeah let me zoom out people can see a global of this so this is the mean electric current densities okay and other things yeah so what this is this
Is now a uh this is basically you know a snapshot of our entire simulation so we you can see that on the on the um the labels on the x-axis are years so this is you know this is running from uh 1976 to uh you know some way into
2023 um so uh this is kind of a a simulation as I mentioned uh we take as a as an input as a bound condition we take these uh these active regions that emerge uh from the the inside of the interior of the Sun and so in Gray um is
Given for every month or so uh in Gray is given the amount of emerging flux now again as as I mentioned technically uh this would be the modulus of the flux right because uh technically you have zero flux at any given time it has to be
Balanced by uh by Max equations but uh this is the amount of magnetic flux uh that’s emerging from the Sun in a number of active regions yes these emerge uh you know when they emerge but and we take them as an input we we rely on observations either from as I mentioned
The Earth or or there are now space-based observations par yeah that uh that that gives give us observations of where and when active regions are emerging we take them as an input and when we calculate of course the magnetic fields I mentioned in the corona but we can draw out uh and again
This is this happens potentially at every time step so we have this with a a few seconds of resolution we have quantities such as uh I have here in blue the average electric current through the corona uh these are both scaled just to to be on the same uh
Scale you know I can I can provide absolute values of course but um just to kind of give an indication here that they’re scaled and in red is the total magnetic energy uh in the corona at any given time okay um so um these these have both
A short and a longterm Trend so the the long-term trend is one that should be probably familiar to to people who are you know familiar with the sun is that in the sun there is a roughly 11year cycle so I’m I’m labeling by um what is
You know it’s a global cycle number this is this began with the work of Carrington observing the Sun so uh in the 70s we’re in cycle 21 and so on so there’s a global cycle where at the start of each cycle there is a general minimum in the emerging flux there is a
Quiet period there’s not much solar activity and as we go through the cycle we ramp up uh you know Crescendo to a Max roughly in the middle of each cycle and then Decay away again so that that’s a generic um that’s a generic feature of the sun uh but of
Course then what we are calculating is how the Sun responds that so we um with each of those emerging active regions we inject magnetic energy into the system yes and then some of it decays away as as these eruptions happen as they eject uh you know and straighten the magnetic
Field some some of that uh energy then decays away and we create we stir up electric currents in the corona uh yes which uh also it on a on a broad scale the the currents of the magnetic energy take their peaks when the um when the solar activity PE but you can also
See a very kind of short scale um very short scale activity so for example that the the current there you know it’s very spiky very of um oscillatory yep so each of those spikes broadly speaking not always but um those spikes typically correspond to those eruptions that I
Showed you so you know when there’s a when there’s a ramping up of the current you’ll have some sort of uh activity uh and they are driven uh by uh by emerging active regions no though not always and this is something that’s I haven’t put this on this spot but it’s
Quite interesting to see if we overplot also uh specifically if we zoom in and we look at when do the active regions emerge sometimes as soon as an active region emerges you get a spike in the current but sometimes active you know you might get a spike in
Curr but then you have uh when there are no emerging active regions you’ll also get a spike in a Curr you may get an eruption that is delayed and that of course happens in the real sun too you you sometimes you have an region that has emerged it’s maybe quite quiet for a
While but then only then do you get some activity happening so we kind of uh pick this uh this these aspects up as well um now we also what I’ve done here just as a very you know very simple bit of data analysis and and sort of filtering is
What I’ve done is I’ve uh you can see there at the bottom of the the blue curves which the current I have a little yellow um a yellow line that sort of what I’ve tried to do there is kind of take the Minima or you know fit to the
Minima to sort of lay a baseline for the uh for the current ah okay got it uh and so then so we have a longterm and slowly varying Baseline and we have uh we have the the actual spikes of current above that so you can see uh a particular you
Know just less than a month uh a a detail there of uh what happens this this is where an active region will emerge you have the both the energy and the current spiking um but you can see just how that Spike goes above that yellow sort of Baseline that I’ve just
You know fit to the to the curve which lets us then you know if we subtract that Baseline then we can see exactly when and and relatively how strong each current Peak is nice so that that again helps us to to sort of process that it
Helps us to say when exactly we have an eruption and then then we can look into that hallisy uh flux and and and you know look at all the caps and so on and see when we get an eruption so than beautiful that that so this forms the
The uh the data set a core data set for uh this simulation which as you can see is a good half century nearly of of solar activity that’s awesome very good okay okay um now so what we really want to do is to fit some you know to to Really
Compare this to uh actual solar activity of course you know it’s all well and good running models so here I’ve attempted to compare uh an eruption that happens within our model to an eruption and solar activity that happened and was recorded for it so in the in the top right figure uh
Panel C we have a real image of the sun now firstly if you’re listening to this please do me a favor never look directly at the sun it will damage your eyes even when there’s an eclipse coming even when there’s eclipse coming it’ll damage your eyes and it’ll damage your telescope and
So on uh if you aren’t careful if you aren’t using the correct uh filter you know filters and so on yeah uh now if you did have those filters and you looked at the sun you still wouldn’t see quite what we have there in the top
Right because what we have there is uh a an image in the extreme ultraviolet part of the spectrum our eyes aren’t sensitive to this and this light doesn’t get through the atmosphere anyway so you would have to go to space with special instruments to see this which is exactly
What’s happened so we are seeing the uh extreme ultraviolet emission from the Sun it is emitted largely from areas of plasma that are hot and dense relatively speaking yes so you know you you you see quite a a difference right you see quite a bit lot of structure there in the Sun
And in particular yes you can see uh the the brighter regions uh are uh regions of of uh higher and hotter plasma high density and water plasma and they happen to be these active regions regions with intense magnetic field so yes you’re you’re highlighting there in in the
Bottom sort of middle left slightly uh that sort of triangle of of really bright material yes those are a pair of active regions there’s also uh on the top right there are a couple the sort of it’s kind of almost almost turned away from us in the bottom right there’s regions so
There’s a few active regions here at this time this is at a particular time this is um on uh the 8th of September 2021 you know that that image is taken an exact time uh you know so a tangible time if you like that that you can look up uh so we we
Have we have active regions on the sun and I’m particularly uh focusing here on the one that’s just south of the equator in the sort of middle those pair in fact of active regions there yeah um and so it might be worthwhile now to go to
The to the animated version of this just so you can see what happens there let’s put this in motion and window figure two and here we go bang ah so this is from the perspective of the earth so relative to the Earth the Sun is turning first of
All which you’ll see and and and the the simulation view is is kind of calibrated to that and so what you’re seeing in our simulation on the say the the left there is you I’m showing a bunch of magnetic field lines and what what’s happening is first the magnetic field lines are in
These closed Loops they leave the Sun and come back to it but as an active region in our model emerges these magnetic field lines open up they sort of force themselves open they they become uh they start at the Sun and now they’re they’re open to to go out into
The wider uh solar system so this is this is again what happens in an eruption you have closed magnetic field lines and they open up this it this is a process that requires uh magnetic Rec connection which we have in our model and it is a it involves as I
Mentioned it involves going from a closed this kind of closed loop of a magnetic field line to an open one because plasma follows those field lines when you have an open field line the plasma is then free to stream out into the Widder solar system so what I’m
Showing in the bottom middle kind of panel here is I’m showing firstly the there’s a there’s an orange Sun there that that corresponds to you know the the that uh Sun of course um yeah the ball of the Sun the Photosphere and so on um and what I’m showing around that
Is a 3D surface that’s obviously varying in time and this 3D surface is what I call the last closed flux surface so this is a an imaginary surface around the Sun okay inside which so inside it are the closed field lines right and outside it as where we are where we’re
Seeing it are the open field lines so plasma is able to stream towards us you know at at the Earth or wherever it’s able to stream from the regions where the where we can see through to the orange ball that is Regions where there is an a field an open field then that
Goes from us to the sun everything underneath this sort of surface there the surface is cover is colored by uh how far away from the Sun it is so by the the solar radius there um everything inside it is is closed all the magnetic field lines are closed and
So the plasma in principle should be confined so inside that uh inside that volume that’s that’s enclosed by this uh by this surface there should be relatively dense relatively hot plasma that’s confined it cannot leave the sun in principle what we are seeing though is uh is the Dynamics there we’re seeing
How there’s this sort of of course what what’s happening we know is there’s an eruption happening what we’re seeing is that um that last closed flux surface is kind of bulges outwards and then sort of it’s like a balloon it inflates and then it pops back down so magnetic the the
Closed magnetic field lines kind of extend outwards and then they reconnect then they then material is left to uh to be expelled and it sort of Retreats back down so this is a kind of the bottom there is a kind of way to to sort of
Visualize what is happening at a at a glance what is happening to the magnetic field and the where um where for example the plasma is trapped and where it is not trapped so right so roughly it’s about two and a half times the solar radius or that confined surfaces and of
Course right now now the the the maximum there is in some ways a model parameter because because we only simulate out to two and a half solar radi that has to be um within the but that is that is kind of that is what is observed is generally
Out to about um two and a half solar Radia maybe three or so that’s where the there are closed field lines which contain hot dense plasma relative um to it now those of you who are kind of more familiar with this will uh look immediately at the in the top right the
Actual uh IM images of the Sun the E image um and you’ll recognize that there are dark regions on that which are what are called coronal holes these are regions that are colder and less dense precisely because the field lines there the magnetic field lines there are open
And plasma is able to escape and you can kind of see that at a glance from our model two you can see regions that where there’s open uh and they kind of correspond now it’s not perfect of course but they correspond at the poles and and some places down below
The the equator to the coronal holes cool so so this is a way and I’m trying to kind of promote this as well as a way at a glance of visualizing the structure of the coronal magnetic field it shows you where where it’s closed where it’s
Open so that’s that and and let me just question what was the what was the sofware used to make that uh animation on the bottom uh so the the basic software is uh it’s python there’s a python Library called mayavi okay so it’s it’s just a 3D plot now um just to
Promote a few things uh firstly to calculate this you know now you you’re welcome to uh to visualize it how you like because I’m I’m producing a you know a general 3D file something like an STL or something that you many 3D uh modeling uh pieces of software can
Produce um but to to actually to actually produce this of course you have to look at where the open and closed magnetic field lines are you have to trace magnetic field lines um so I have a code I’ve developed a code that um that traces magnetic field lines for
Many different coronal codes this is going to be published in future you know very soon in fact the code itself is published but um and it should be able to so for example it should be able to take an existing an output of an existing image decode and so on and
Produce something like this almost directly and I’m making all that publicly available uh now the other thing is that um uh I uh this this sort of this plot of the last closed flug service I had a student um you know this is this is nice as a kind of scientific visualization
But I had a student uh come along and make and again this is publicly available um make a very nice sort of public uh you know something that looks cool for the kids as it were a nice visualization animation using more uh kind of more involved more commercial uh
Visualizing software so there are there are ways to make this kind of look even more neat um Co Good Very but anyway so that and the last thing I want to say on this is that um as I mentioned what we have so the the in the top right the these images
From the Sol Dynamics Observatory they are you know real tangible they happen at a given time you know a few years ago um uh each one has a very specific time that it was taken and we are matching this with our model so again our model
Also has of course you know it has a real time there’s there’s not just a an arbitrary sort of simulation right so many units of normalized time we we are talking about real comparable right this 8th of September in our model versus the 8th of September in reality now um the and and
The the oh the final thing I should say so the we are seeing an eruption but there really was an eruption uh at uh whatever it was 528 on the 8th of September um there’s another piece of uh sort of data that I’m not showing here but there are
Other satellites that observe the sun in the X-ray and when they get an x-ray Spike which they did at that time um there is they have an eruption and so so we were able to in this case very precisely to about you know to within an hour or so half an hour
To have an eruption happen in our model and in real life now that I must stress that that is probably that level of accuracy is probably fatuous probably we can’t guarantee that level of accuracy but in principle you know our models uh we could probably get you know
Within a few hours a day or so of a real eruption happening and an eruption happening in in our model of course we’re limited by that resolution we don’t have infinite resolution uh you know we have we’re limited by other uh other problems and other observations
But but that that’s you know that that’s what we can get in in this magn frictional model love it love it love it love it okay let’s go back to the article fig three right so um yeah so that’s um uh that’s that and then the final
Thing I guess we have one more figure MH um and this one now if you this one is a bit involved so this one is really for the for the um experts for the well for the connoisseurs you know you really want to if you’re listening along at home I’ll
Try and explain it in in in general terms but you know you might want to make yourself comfortable get a hot chocolate with some marshmallows or something because I have hot chocolate or actually have an espresso but okay right so this one’s going to get a bit
Involved so um and in fact what you might like if you don’t mind is just to zoom can you see there’s a a yellow border we have you know three figures that are on one particular date the 28th of at the the top you if you just zoom
In on those three for now maybe just as the top three yeah okay how about that okay thank you very much yeah so uh what we have here firstly what do we actually show what what is what are our you know scales right so we’re showing three
Plots uh and maybe maybe the the one in the bottom right of this three is is the one to to start with okay so we have along the bottom we have radius so yeah um we we’re in that axis we’re moving outwards in radius from one solar radius
At the start of our model to two and a half where our model terminates OKAY in the Y we have uh Theta which is the uh latitude okay so north to south so this this one panel is at a constant longitude so if you imagine you are you
Know uh I believe right let’s say you’re in Dundee where I am and you’re moving North and as you’re moving vertically in this figure you’re moving North and South so what we’ve done is we’ve taken a sort of anulus from the North Pole down to the South Pole and outwards in
Radius a sort of annulus around the Sun and we’ve kind of stretched it into just you know we’ve deformed it into a a rectangular rectal plot so we have again we have radius on the x-axis latitude on the y axis okay next um next let me talk about what
The colors represent so what uh we have red and blue so let’s let’s let’s pick let’s pick one of the latitudes and let’s move outwards let’s say zero right so so at the equator that’s zero Theta and we’re moving outwards in radius so the red represents closed field okay and
The blue is open field so as we move we first start off in a region where all the magnetic field starts and ends on the sun and as we move outwards to the to the outside eventually we get to a place where one end or or in fact
Possibly both ends of our uh magnetic field line do not start on the Sun so it may be it may start on the sun and go outwards and then out into the into the uh solar system or it may uh it may start on the outside come into our
Simulation domain and leave so it’s it’s a loop that it’s then a loop that never reaches the sun it starts out in the broader solar system comes into our simulation domain leaves so this could be one of those eruptions when an eruption is happening it could be the
The bottom of that eruption where the magnetic field just dips into our simulation Dom and out and then there’s a closed loop outside the sun okay gotta so that’s the red versus blue and what is what is what is the technical definition of so so firstly
The the Q is called a squashing Factor this should be familiar hopefully to cop physicist it’s a squashing Factor I’ll explain what the what that actually means the the SLO is signed logarithm so the sign we keep and the sign we have positive for closed negative for open
That’s a convention uh that we have yep um so what but what is the magnitude what is that what’s called squashing Factor what does that represent what does the you know if you have it very red or very blue what does that mean so the squashing factor is a property of
The magnetic field um where where it’s high it means that the magnetic field is highly um it’s either sort of uh it’s topologically very complicated so it either diverges perhaps or it’s very kind of twisted up it may be very uh you know in homogeneous so where you have very
Bright colors where you have a very high logarithm of that squashing factor in you know in in absolute terms that is where the magnetic field diverges or is is kind of um very topologically mixed up so for example okay for example this quantity formally where you have a a bit
Of red touching a bit of blue yes that is the interface so on one side of that then you have closed field lines they they start and end on the sun um on the other side you have open so formally there that this squashing Factor Q goes through a singularity goes to Infinity
Because those field lines diverge one goes out to Infinity the other curves back to the sun right so these are these are highly Divergent uh magnetic field lines but so so that so it’s it’s it’s infinite there but you can also have um either very high or even infinite uh
Within one of two colors so for example you might have closed magnetic field but one Loop goes one way and the other loop goes the other way so you have diverging from a point so there that quantity is infinite so this is this of course shows you where the the closed versus open
Field line is but it also shows you where the field is very stressed very tangled up and so on and these are important from the point of view of um you mentioned magnetic reconnection this should happen where you have a very high Q um and other kind of Dynamics should
Happen there so when you have an eruption you and we’ll see this you will have regions of highq very uh magnetic field line that’s or magnetic magnetic field that is very Tangled and very messy and complicated I’m with you very so that was that one panel now the other
Two panels if you if you slightly zoom out the other two panels there then um the one on the top is one at uh constant latitude so if you imagine this is one of the like on Earth this would be a Tropic this would be a sort of line
Around the Sun uh right going at a a Conant latitude and then out in radius um so there again we see uh at lower radi in some places it’s open and it’s closed and as you move outwards you have these structures that are you have these kind of Domes that are closed um
But as you move out in radius it becomes all open um yes okay exact yeah exactly and these are these are called um helmet streamers you can actually see them physically uh when you when you look at the Sun and Corona especially during an eclipse where the main you know the very
Bright disc is a um included you can actually see some of these now of course again these are kind of um this isn’t GE we’ve sort of uh deformed it somewhat um because we’ made it into this rectal linear plot in reality it’s this kind of
Annular conical ribon uhuh uh but uh if you uh if you actually saw this in real life you could see these kind of um domes these sort of spiky uh uh regions of closed field now remember the the closed field is typically brighter in in optically because it has more Plasma in
Its dens well that’s very cool I mean have now I have something to hump for come April uh okay yeah exactly right and uh yeah so yeah and again just to advertise this the way to generate these um so this was using a a code that’s a bit clunky to
Actually generate just these plots from our magnetic field um it’s using an existing code um called hqv seg that was developed I believe in France but I now have a slightly more user friendly version that will be published it has been published but the paper behind it will be published soon um
Finally in the the yeah the middle the larger of the panels there this is at constant radius so it’s latitude versus longitude this is on Earth this would be called a maor projection yes um and it is at the uh at the outside of our simulation domain 2.5 yep um you can see
It’s all blue meaning it’s all open this is by definition because of course once you get to the outside everything there is kind of open and everything this is um to do with the that Sol the yeah the solar wind model the um the Parker solution and so on so basically
Everything once you get to the two and a half solar radi all the magnetic field lines there leave the Sun and go out to Infinity you know to The Wider solar system okay uh so it’s all it’s all open but the what the uh the magnitude of the
Squashing Factor there there are these um sort of arcs and um now there’s a there’s a kind of um going on the left it’s at 60 can you see a sort of it’s It’s a light it’s white but then there’s blue on either side there’s a kind of line that snakes its
Way it starts at um zero f equals z and uh theta equals z and then snakes its way down if you see what I mean um this one here no no uh above that this one yes and can you see how it snakes its way from one side to the other that is
The heliospheric current sheet that is where the magnetic field um polarity flips it is a separatrix because um magnetic field lines from above it map to one part of the Sun from below it to the other so it is a it is a line of infinite
Q um but but but there there there are other regions where the magnetic field line or the magnetic field sign may not um flip but they are INF these are these are the other kind of blue um arcs and things like that these are regions where
Um on one side the magnetic field you know goes to one part of the Sun and on the other it goes to another part of the Sun for that reason the magnetic field diverges there and so we have infinite squashing Factor infinite Q there okay
Um and so what this kind of plot in the uh technical terminology U might be called is the separatrix web the S web yes uh so this is a concept in solar physics um where uh the this on the outside of the sun there are these um kind
Of there are these regions where the magnetic field diverges um there also as I mentioned High Q High squashing Factor corresponds to where uh magnetic reconnection happens and so because the field is stressed it’s it’s uh you know Divergent and so on um and so these are regions where it is
Hypothesized and I’ve done some work and many others have done work on this where uh the slow solar wind as opposed to the fast solar wind if you’re aware of that sort of dichotomy that’s where that is generated um and so so cool this this
Kind of at a glance tells you the the sort of structure of the magnetic field the really topology of the magnetic field okay beautiful so there’s the three PS and so of course that is that is at one time that is just at one time and I’m showing then uh three days later
Uh it has somewhat changed very interestingly if you go to the the middle panel okay um you can see a kind of pair of little swirls that uh 5120 yeah exactly so this is where an eruption has happened and where the these two swirls are the kind of ends of material being
Ejected um you can see there’s a lot of dynamism and so on so um many people are used to the separ to seeing the separatrix where maybe from one of those pfss models I mentioned this is a very kind of static as I mentioned there’s no dynamism happening there here it’s
Really busy Dynamic this is you know it’s it’s very kind of interesting as a as a scientist to see this to there there are signatures of reconnection there there are signatures of plasas uh you know plasma being ejected and so on um now okay so at this
Point it might be to to explain the very bottom this point it might be worth to to flip to the movie of this okay let’s go to the animation on this one this is a big one um okay yeah fine so what the bottom panel in this case what the
Bottom panel you’ll see there’s just red and white and so the red regions in the bottom panel here in the movie um they correspond to where the Q in the in the um constant radius plot where the Q is above some threshold large amount okay so they these are these are regions of
High Q this is what we call a High Q volume now we have a and this is where the the co-author Roger Scott this is very much his work um he’s developed an algorithm it’s not just we’re showing you a kind of slice through it but he’s
He’s calculating where the Q is high in a volume in a volumetric sense throughout the entire simulation domain where the Q is high he’s also kind of showing this is a bit technical but um he’s showing where that high Q is connected to a um a null magnetic null
This is important for again reconnection considerations and things like that yep or where it’s connected to multiple NY there’s a very um there’s a complicated kind of taxonomy that I’m not quite showing here um but uh there is a reference to to some of Roger’s other
Work where you get into the full gory details we will also publish uh further studies on this but what it’s what I’m showing here is just where the Q is high yeah so this is where um the that s web is where you have these regions of perhaps a rapidly reconnecting magnetic
Field where you are having perhaps emission of slow solar wind and I’m showing how that change in this case I’m showing how that changes in time so if we look if you now watch through this is looping if we now watch through one of the loops we will see some parts let’s
Say at um 5 = 240 and Theta = 60 so the top there uh this SP here uh no five five equals 240 degrees so kind of 180 degrees right of oh here we go so you can see that AR that Arc is largely unchanged at this time so if you
If we watch through a whole cycle it’s basically it stays there exactly as it is yeah but other regions let’s say a i 120 right you can see you can see stuff is happening there stuff is going on there’s an eruption probably happen in fact there is an eruption there’s
Probably a corresponding active region stuff is happening there so some parts of this separatrix web this s web some during this moment at least are fairly stable fairly unchanging and other parts are very much in flux very rapidly changing five um yeah right okay and so finally if we
Return to the static figure now okay I got it okay if we go to the bottom uh panel what we now have what this is now is a sort of um a kind of synthesis of all that data so what I’m showing is Regions colored uh the the red is where
Where that hqv is only is only appears there for a brief amount of time and the golden sort of yellow orange is where that high Q volume persists for a long time for many days this is only a slice of six days so there six is the maximum
Sure so what we’re showing is some regions that that sweb is very persistent it’s just staying there it’s it’s fairly static but in other regions there’s a kind of Continuum where it’s more Dynamic it Chang changes it’s rapidly evolving it only persists maybe some of it persists for 3 Days some of
It persists for only briefly of course we have a certain time resolution here as well but so this is um for the again as say for The Connoisseur for the real um you know people who really enjoy this stuff and and are experts in this field this should be quite interesting because
It’s showing a previously rather unstudied aspect of the S just how it evolves how certain you know how persistent it is how um how dynamically it changes and so on so um yeah so hopefully that sort of answers that so I think I think that’s
All we have to show so this this last bit as I mentioned a lot of that um is uh very much thanks to Roger Scott my my co-author and future I’m sure we will be publishing a bunch of papers as well and I think that kind of brings us to the
End uh finally of this paper awesome awesome Val I want to thank you so much for walking us through this very awesome letter very cool uh let’s see and you touched on it uh a couple of times uh in various ways uh so first of all I really look forward to your public
Releases of these codes to help do this analysis I think that’s great um uh but where do you think we go from here uh given the given the published work uh is there stuff in the way to do a full Century or two centuries how about a
Millennium uh of of the sun uh there plans to do maybe other stars is there other observations or analysis to you so just sort of next steps on where do we go with this topic over the next couple years yes so firstly yes uh just over
One century is what I can promise and that is very much in the pipeline we are you know we’re funded in part to look at historical data so we as I mentioned what’s really limiting us is the knowledge of what’s happening at the surface of the sun because we really
Can’t peer any deeper we can’t predict when one of these active regions is going to emerge so we have data going back to 1916 so that is the next step for us is going to be to run uh from 1916 to let’s say start of
2024 just over A Century Of course uh of solar activity again we very much much welcome any inputs um you know now there there’s a lot of technicals including of course by the the review of this article asked us certain things so this during these 47
Years has helped us to iron out a lot of the kind of Technical and some of the you know scientific as well features so we’re now much more much better informed about what we’re looking for in this future Century of uh of St Sun evolution cool as I mentioned this study has also
Helped us to write some codes that should be of of broader use for analysis and particular of the magnetic field and its topology especially um so the this has helped us help us to make that some of that is we’re making available some of it is already available uh we’ll be
Certainly in the you know in a very near future we’re hoping to publish kind of a a technical description and very long article to to explain some of these codes for the scientific Community to then use um and going yes to other stars we do have um now one thing I’m also
Looking at at the moment is um I I should mention that all of this as many codes um this is kind of the the simulation runs within the uh the frame of the Sun so the sun is rotating it’s actually rotating differentially meaning that the poles are rotating slower than
The the equator but within a frame called the carington frame so the average rotation um of the Sun that we observe we’re kind of in that frame and we’re imagining that the sun is other than that differential rotation is not rotating right um but to fully address
This in in this kind of frame what we need to then do is consider the coris effect and the coris force the uh fical fictitious forces that arise from being in a rotating frame so actually where I’m coding that into the uh the dumri code now we will look at that and as
Well now the I I already have early results basically that say that we’re up to where we’re simulating up up to about two and a half solar radi the corona rotates largely rigidly the corus force is fairly negligible relative to all other forces it has a very low
Effect however and and you know so we’re going to um we’re going to do a full publication on this we’re going to finish off our studies and you know cross the t’s do the eyes whatever on that uh front but what we’re going to then do is we’re going to try and extend
That to other perhaps younger stars that are rotating much more rapidly and there we do perhaps expect to see some effect from uh the rotating Corona we’ll see um you know that remains to be seen that’s we’ll report that to you uh to the scientific community in in due time um
Yeah so and and just finally again as I said at the beginning we what we really are looking for is any sort of collaborations anyone that wants to you know suggest something do is there some fairly simple like metric or something that we can calculate uh some derived
Quantity that as a function of time or do you you know during an eruption something like that can is there something that can help you answer a scientific question do some good science there please let us now of course the you know there’s a way to contact us so
This is you know this is very much open to the scientific Community yeah I think you can find this email in the opening part of the article so won’t be hard to find B thank you so much that was really awesome thank you once again and that
Will do everyone and I hope this made your astronomy day just a little bit better and we will see you on the next one Byebye