 Hello, everyone, from wherever you're joining. Thank you for being here today for this NCAR Explorer Series lecture, The Lower Fringes of Outer Space, The Thermosphere and Ionosphere with Dr. Li Yingqian. It's been a challenging time for our community, and so we really appreciate all of your flexibility in rescheduling this event. My name is Dr. Dan Zitlow, and I'm an education specialist here at the National Center for Atmospheric Research, or NCAR, which is a world-leading organization dedicated to understanding Earth system science, including our atmosphere, our weather, our climate, our sun, and the importance of all of these systems to our society. I'm really excited to be with you all today to learn more about space weather and space climate. So for this event, we'll be taking all the questions at the end of the lecture, but please definitely submit any questions you may have throughout the talk using the Slido platform. So if you scroll down this webpage just a little bit, you can see the Slido window just below where you are seeing the live stream video of this event. Also be sure to join Slido so that you can add your thoughts to our work cloud question. What do you think of when you hear space climate or space weather? This lecture is also being recorded and will be available on the NCAR Explorer Series website. Now, before I introduce our speaker, let's go ahead and check out your thoughts on our work cloud. Paula Brett, could you go ahead and show that for us? Yeah, so right away I see solar wind, cold, plasma. I love the NCAR exclamation point. Magnetic field, aurora, drive, space weather, electromagnetic activity, RF propagation, variable, cosmic. The final frontier, that's a great one. Yeah, I'm seeing so many great thoughts on here and thanks for adding them. All right, so with us today, we have NCAR scientist Dr. Liying Shen. Liying joins us from the High Altitude Observatory or HAO at NCAR where she focuses her research on the physics and dynamics of our Earth's atmosphere. Liying holds a bachelor's and master's degree in atmospheric sciences from Nanjing University and the Chinese Academy of Science, a master's degree in computer science from the Pennsylvania State University and a PhD in meteorology also from Penn State. She's currently investigating such questions that is how the composition of the thermosphere changes with the seasons and how the global electric field impacts the ionosphere and the equatorial and low latitude regions of our planet. And so with that, please join me in welcoming Dr. Liying Shen. Okay, so I will first share my screen. Sorry, I need to start my video first. No problem, there you are. And as we get set up, I also just wanna add, I see a new comment on our work class. We're gonna need a bigger umbrella. I love that, that's fantastic. Okay, so welcome to this NCAR Explorer lecture. Today we will explore the lower fringe of outer space, the thermosphere and ionosphere. So we probably have all heard about outer space, but the thermosphere and ionosphere is probably not something that we talk about in our everyday life. So when I say the thermosphere and ionosphere, you might have questions like, where is the thermosphere and ionosphere? What is in it? What is happening in there? Why do we care about it? And how do we get to know it? These are the questions that I will talk about today, along with some fun facts. So first, where is the thermosphere and ionosphere? So this is a NASA image that shows the atmosphere of the Earth. So if we look at the bottom, we see some landscape and maybe some tree. And then we see clouds and an airplane. So this is the lowest layer of the atmosphere. That's where we live. It's called as troposphere. Above troposphere is a stratosphere. Stratosphere is where the ozone layer is. And above the stratosphere is the mesosphere. Mesosphere is where all the meteors that come into our atmosphere get burned up. And above the mesosphere, from about 60 miles to 400 miles, that's where the thermosphere is. So this is these blue parts. And now the ionosphere, this yellow color. So ionosphere is not a separate layer. It occupies the same space as the thermosphere. And it also overlaps with parts of the mesosphere and parts of the atmosphere above the thermosphere called the exosphere. So the thermosphere and the ionosphere is where the low Earth orbiting satellite flies. So we're probably all familiar with the International Space Station. So that's where the International Space Station flies. It flies at about 400 kilometers. So now in the nature, there isn't really a boundary where the Earth's atmosphere ends and the outer space begins. But the airplane and the spacecraft, they are under different jurisdiction. They under subject to different law, different regulation and treaties. So it is necessary to have a boundary to define where the atmosphere ends and the space, outer space begins. So FAI, which is International Standard Setting Body, they defined a boundary at 100 kilometers called the common line. This is about 62 miles. So that's exactly where the thermosphere begins. So this is a common line defined where the airplane above this line, the airplane will, the areas become too thin for airplane to fly. So here, so we see that the thermosphere and ionosphere is right at the lower fringe of the outer space. So you might ask why for the same space we called two names, thermosphere and ionosphere. So that is what I will talk about in terms of what is in it. So it all starts with the thermosphere. So this is a NASA image that is taken by the International Space Station. So this part is the Earth and this is the orange color is the sunset and then troposphere and then goes up is the stratosphere and goes up the hemisphere and then this blue color fade into the dark darkness. And so this area is the thermosphere. So this is the air particles that is in the thermosphere. It is oxygen and nitrogen. That's the same air particles that we have in the troposphere where we live. But in the thermosphere, there's one more thing, one more particle. It is atomic form of the oxygen. So now the sun, sun's radiation coming into the thermosphere and this sun's radiation gave energy to this air particles and knock or which knock off the electron that is in this molecular and atoms and make the ions. And these ions also go through some chemical reaction. And in the end, we get these ions and the electron and also in this process, in this process, there's a heat that is released into the atmosphere and it heats the thermosphere, makes the atmosphere very hot. So now in this space, we have neutral particles, we have charged particles. So we use the name thermosphere to call this neutral part of the neutral part of this space and the ionosphere call to use ionosphere to call this part that is the charged particle. And later on, we will see it's good to have two names to distinguish this neutral part and the charged particle of this space. And we know that this air in this space is very thin. And so the amount of this particle and how they change are very important because they enable and also impact our space technology. So here in this space, we know that we all know this is an international space station flying in this space and the SpaceX Starlink internet satellites also fly in this region. And this space flight, commercial space flight will also come into the lower part of the thermosphere and take passengers to experience zero gravity. And this GPS and the high frequency radio signal, they transmit through the ionosphere, which is a charged part, charged particle, charged part of this space. So now what is happening in there? So here, this is a NASA image that shows a hurricane. So this is this one of our weather phenomenon. And this is also NASA image that shows the Arctic ice. And because of the global warming, so this ice area become less and less. So now in the space, we similar, we have also have a space weather and a space climate and even space climate change. So on the left, this image shows Aurora, which is also called the northern lights, but in the southern and Arctic, there's also Aurora, we can also see Aurora. So this is probably the only way that we can see the space weather with our naked eye. And on the right, this image is also NASA image that shows the space object that is in the space. And because of, later on, we will talk about because of the space climate change, this space object, which most of them is our space debris and they accumulate faster and faster, which cause a problem and which later on I will talk about. So this space and the space weather and the space climate, what are the causes of the space weather and the space climate and space climate change? Well, the cause are the sun, the earth and the weather and the climate that is in the sun and the sun's atmosphere and the earth and the earth's atmosphere. So this NASA image that shows called what we call the 11 year solar cycle. So this is the sun's climate. So these bright spots are the active region. So in 1996, we see this sun is very quiet and then it become more and more active by the year 2001. So we see that sun is the most active in this cycle and then it become quieter and quieter again and then finally it become very quiet and then goes on next cycle. So this is climate of the sun and it will cause space climate. And then now in the sun and the sun's atmosphere, there's a weather. So the two most important weather phenomenon it's called a solar flare and a corona mass ejection. So they usually happen in the area of sunspots. And so we probably have heard about solar storms. So when we talk about the solar storm, it is mostly it is caused by this, we are talking about the solar flare and the corona mass ejection. So here, this is a NASA image that shows a solar flare. So these bright spots, that's a solar flare and this solar flare happened on October 28th, 2003. And actually this is a very active period of the sun. It lasted for a period of more than one and in that one week, there was several solar flares and several corona mass ejection. And because this is close to the halloween, so we actually causes those storms, halloween storms. And now you may ask, how does a solar flare cause space weather? So remember earlier, I talked about the sun's radiation coming into the thermosphere, gave energy to the air particles there and make this charged particles and also gave the heat to the thermosphere. So what happens during a solar flare happens is there was a burst of increased solar radiation in the part that is absorbed by the thermosphere. And this burst of solar radiation caused a burst of the heat into the, which heats the thermosphere and that can cause the satellite to lose altitude. And also it caused a burst of the making of this charged particles and so which we call the ionosphere, what's in the ionosphere. And now the GPS signal and also the high frequency radio signals, they transmit through the ionosphere. Their transmission is affected by how much the charged, these charged particles are in the ionosphere. In the ionosphere. So this burst of the increased charged particles will disrupt those GPS signal and radio signals and even cause a blackout. So that's how solar flare cause space weather and affect our space technology. And another space where the phenomenon from the sun is the corona mass ejection. So this corona mass ejection is this very hot gas stream of the hot gas that erupts from the sun. And in this hot gas, there are very high energy charged particles and these charged particles are magnetized. So come with them are the magnetic field. And when they are released from the sun, they go into the space and they goes all directions. And this stream of hot gas, we call it solar wind. So if a stream of the solar wind travel towards the earth and so it will after two to four days, it will come to the earth. And we are, so this is a high energy charged particle and they are very harmful to us. We are pretty much for the most part, we are protected by the earth's magnetic field because the earth is a giant magnet. So it has magnetic field. So they protect us from the solar wind but this protection is not complete. So when this magnetic field in the solar wind and magnetic field of the earth, when they aligned in a certain way, they connect, they become one. And that open a channel that allow the high energy particle from the solar wind coming into the thermosphere through that channel. And also this charged particle has electromagnetic energy and this electromagnetic energy also coming into the thermosphere and ionosphere through that open the channel. And when this energy coming into the thermosphere and ionosphere, they again, they heats the thermosphere and ionosphere cause that light to lose the altitude and they change, they cause a burst of those, again cause a burst of the charged particle, they change the amount of the particle, they move around everything, they cause disturbance in the ionosphere. And then you can imagine that will cause disruption to the GPS signal and those high frequency radio signals. So that's how a CME corona mass ejection cause space weather and affect our space technology. So now let's talk about the earth, the earth's weather and the earth. So here, this image here, we have a thunderstorm, cyclone and even volcanoes from and also the topography, which is a mountain. So this process, this phenomenon, they can excite waves and we call these waves gravity wave. And also the sun heats the earth during the day and not at night. And that difference of the heating between day and night, that also excite waves and we call that wave tides. And this gravity wave and the tides, they are waves. So they propagate. So they certainly propagate upward towards the thermosphere and ionosphere. They can propagate all the way to thermosphere and ionosphere and how the waves can cause space weather. So here in this image, this orange color representing the ionosphere. And so when the wave travel into the into the thermosphere and ionosphere, they cause something like that. They cause disturbance in the ionosphere, look like that and look like a bubble. So actually we call it plasma bubble. So this is a GPS satellite. So it sends out GPS signals. When this signal travel transmit through this undisturbed part of the ionosphere, this airplane receive this, have a clear reception of the GPS signal for its navigation and the positioning. But when this GPS signal transmit through this bubble, then at the ground, when we receive this signal, it will be distorted and there's a fuzziness. So this is how the wave can cause space weather and affect our space technology. So now another thing that is also from the earth is the greenhouse gas. So we probably are familiar with carbon dioxide, methane, water vapor, ozone, but it's the one that cause the most problem cause the largest space climate change is the carbon dioxide. So we know that the carbon dioxide cause a global warming in troposphere, in the atmosphere where we live. And this global warming in the troposphere is a 0.3 degree Fahrenheit per 10 years. So it sounds very small, but we know the consequences are larger. We already see this ice at Arctic is shrinking, the amount of the mass shrinking. But now you may ask, what about the atmosphere above the troposphere? Well, above the troposphere, actually it's global cooling. So in the stratosphere and the mesosphere, it's about two degree Fahrenheit per 10 years. But in the thermosphere and the ionosphere, it is the largest. It's a four degree Fahrenheit per 10 years. So it is more than 10 times of the global change that we experience here in the troposphere. So now you, so actually it's easier for us to find the evidence of this global cooling in the thermosphere and ionosphere because it is a lot bigger. And so now how does the same carbon dioxide, it cause global warming in the troposphere and cause a global cooling above the troposphere? So where the answer is here. So these two images, this here is a lower image representing what happens in the troposphere and the upper image representing what's happening in the atmosphere above the troposphere. So here in the troposphere, this is a carbon dioxide molecular. So carbon dioxide receive energy from the earth surface. So earth surface radiate, this carbon dioxide radiate to infrared radiation. And when the carbon dioxide absorbs this energy, it has two ways to lose this energy. One way is through chloride with the air particles and gave this energy to air particles and the heats atmosphere. And the other process is the other way to lose this energy is just simply radiate into the space and lose this energy. And it's a matter, so which process to, so which way for carbon dioxide to lose energy, it depends on how fast, which one is faster. So in the troposphere, because the air is much denser, much more than much denser. So there's a lot of air particle. So this process, the first process is faster. So this energy is, so the carbon dioxide gave this energy to the air particle and the heats the thermosphere. So that's why in the thermosphere, the carbon dioxide has a warming effect cause a global warming. But in the upper atmosphere, in the atmosphere above the area much thin, the process that carbon dioxide side actually gets its energy through the very few collision with the air particles. And after it gets this energy, again the same two process, it loses energy in the same two ways. But in the upper atmosphere, the air molecules are very few air molecules. So before carbon dioxide can give back this energy, this radiation just happened faster. So you'd already lose this energy through the radiation into the space. So carbon dioxide has a cooling effect. So it causes a global cooling in the atmosphere above the troposphere and has the largest cooling in the thermosphere and ionosphere. And another way that the Earth can cause space climate change is through the magnetic pole movement. So this image shows the magnetic pole. This is the position is here in 1900. And now it's here. So this is a slow movement of the magnetic pole over a long period of time. And the reason this process can cause global space climate change is because it's mostly through the ionosphere because the ionosphere has a charged particle. Charged particle, how they move, the magnetic field affect how the charged particle move. So when the magnetic pole moves, it changes the magnetic field. So it changes how those charged particle move. So that's how this magnetic pole movement can cause space climate change. So now, so you may ask, why do we care about this? So in the past, the space technology might be so used in the military, in the aviation. But now we have entered in a new era where the space technology is becoming more and more relevant to our daily life. In a way, maybe we're not really aware of. So first, the GPS navigation and the positioning now is ubiquitous. It's not only used in military aviation. It's used in our daily life. And our cell phone has more or less have the GPS capability to receive a GPS signal for the same thing, its navigation and the positioning. And there are more and more satellites are orbiting the Earth as SpaceX and other companies seek to create satellite cluster that provide low latency and broadband internet service. Not only in this coverage is global and low latency, but also it reaches all the remote area, all over the globe. And the space tourism is on the cusp of becoming an industry. And we all know that at least Virgin Galactic and Blue Origin, these two company has already both conducted test flight to take passengers to the lower part of the hemisphere. So it will be, I think it's in the very near future, it will go into the commercial to take people to the lower hemisphere to experience zero gravity. And also the Earth observing fleet and constantly monitors our environment and those Earth observing fleet, there are a lot of them are the low Earth orbiting satellites. So here for example, so this shows the COVID-19 Earth observing fleet and these satellites, some of them from United States, some of them from other countries and also some are commercial satellites. They fly in the low Earth orbit and they monitors during the COVID-19 last year and this year they monitors how the change in people's behavior changes the Earth's environment. And this is GPS positioning and navigation. So these are the GPS satellites. They send out the GPS signals and it is received by the airplane for the aviation, for the ships in the ocean and on the ground for our car and used in the farming and for the ground communication infrastructure that transmits the data and for the phone and satellite phone. And when space weather happens, it affects all these things. It damages cost damages to the electronics in the satellites, in the airplane and we know that it affects the GPS signal and the high frequency radio signal and cause blackout, radio signal blackout. And also we know that ionosphere is a charged particle. So the charged particles have current, electric currents and those currents during space whether there's a sudden change of the currents and that can induce currents in here, in our power grid cause damages, cause problems in our power grid. And another problem of the space weather is satellite tracking. So here it shows this yellow is this sudden jump it shows there was a storm, there was a solar storm. So this blue bar shows the number of lost satellite. So before the storm, so this is the amount of the lost satellite. And when after this storm, the number of lost satellite tripled and it take about a week to be able to find those extra lost satellite and it goes back to before the storm level. And also actually this same storm, which is actually it's March 13, 1989. This same storm caused the entire province of Quebec, Canada to have electrical power blackout and that lasted 12 hours. So the power grid industry, they developed technology to be able to weather this kind of power search that is caused by space weather. And I want to talk about a little more about satellite tracking. So the US military is in charge of keep track of the trackable space objects. So currently in the current catalog, they are more than 22,000 trackable objects and only 5% are functioning satellites and 95% are non-functioning which is essentially space debris. And some of them are empty, rocket in body after they send the satellites and some of them are from, most of them are coming from collisions. So I want to give one example of how this collision, one of the examples of this kind of collision. So we know this company, Iridium Communication Inc. They own this Iridium Communication Satellites constellation and in this constellation there are 66 satellites and they fly in the lower orbit and they are very good being in the lower orbit, the latency is very low. And in 2009, one of the Iridium satellites collided with a Russian spacecraft. And that collision caused more than 2,000 large pieces of debris and the small ones, untrackable ones, small one is even more. And now the NASA Orbital Debris Program Office, they are in charge of monitoring untrackable populations. So this is a NASA image that shows the space objects that is in outer space. And so the amount of the objects that is larger than 10 centimeter is about more than 34,000 and the space object with the size between one to 10 centimeter is about 900,000 and the object that is greater than one millimeter is 170 million. So the small amount of those are the functioning satellites and most of them are space debris. And so the next slide is an awesome NASA image that shows that is before 1957, this you can hardly see anything in the outer space. And this is 1980 and this is 2000 and this is 2018. And so you see how fast the space objects are accumulating. And one of the reasons, of course, we are launch more and more satellites. Last year in 2020 alone, the United States launched 955 satellites. But most of them is actually the accumulation of the space debris. And so the space climate just makes this a problem worse. So why is space climate change can make this problem worse? Remember space climate change is global warming or global cooling. And when the surface will become cooler, that means actually the air become even thinner. And when it is thinner, that means there's less air particle and that cause less drag on the satellites and also on the space debris. And so that allows the space debris staying in the thermosphere much longer time because if without the thermosphere become cooler, the space debris would lose the altitude faster and then eventually coming into the lower atmosphere where the atmosphere is denser. And so they would burn up. So when there's global cooling, the space debris accumulate faster and faster. So that's why it cause makes the problem worse. But this is really something that is worrisome because SpaceX alone, they plan on launch about 30,000 to 40,000 internet satellites. They will all be in the lowest orbits. And the space of this satellite space debris is about 17,500 miles per hour. So they travel very fast. So even a small piece of space debris, they can cause significant damage if we collide with a satellite. So, and the people probably largely have not really realized this problem yet. Certainly have not realized the problem that will be caused by the space climate change. And then now how do we get to know the thermosphere and ionosphere? So there are two ways scientists try to, for scientists to gain understanding of the thermosphere and ionosphere. So one way is through observations. Another way is through computer program, which we call models and modeling. So you might have heard about that. And so there are different ways for observations. The first is through the satellites. So these are the satellites that is in the space, in the outer space. And some of them is far away, far, far away from the earth that monitors, even monitors the sun. And some of them monitors the space between the sun and the earth. And some of them monitors the earth's magnetosphere here. And some of them monitors the thermosphere and ionosphere. And so here there are two, these two satellites, those are recent, very recent NASA machine called the gold and icon. So several people from NCAR are involved in this two NASA satellite mission. And these two satellites monitors how, what's the population of the charged particle in the ionosphere? What are, how are they moving? And what are their temperature even? And so, and also they monitor, so what's the population in the, in the thermosphere and how they move and what are their temperature? And the second way to do the observation is using the radar. So these are some of the radar stations. And this radar they monitors, they mainly monitors the ionosphere, they monitor the charged particle, looking at their population, looking at how they move and yeah, look at how they move. And the third way is the GPS network. So the GPS signal not only help us to do the navigation and the positioning, but they also comes with this gave us the information of how many plasma is on the path of the GPS signal. So, so this GPS network, the data from this GPS network is very good because it's a global, it's all over the whole world. So they give us the information all over the globe. But one drawback is this ground GPS network ground infrastructure and they are, they are on the land. And so they cannot be in the ocean. So we would not get data in the ocean in this area. So that's the drawback. And the third way is the fourth way is the satellite catalog data from the satellite catalog. So the satellite tracking not only maintain the, where is the satellites, but also it comes with the information about the satellite drag. And from the satellite drag, we can know what is the mass density of the service sphere. So that's how the satellite catalog is the one of the ways of the observations. Also these are the four main ways of the observations. And now the modeling. So, so there are different kinds of models that study the sun, the earth. Some model just study the sun. And the sun model study the space between the sun and the earth called the heliosphere. And the sun model study the earth's magnetosphere. That's where the magnetic field are. And some of them study the thermosphere and ionosphere. And some of them just study the atmosphere from ground all the way to the magnetosphere. And some yet some of them in the future it will be models from the sun. They call from sun to mud essentially from the sun all the way to the earth is including everything. And NCAR has a long history of this developer, this atmosphere model and has a lot of heritage and as a national institute and NCAR develop this model and provide for the community to use. And so we call this model community model. So it's free for everybody else to use. So at NCAR we have a model that, so there's a model that is developed at NCAR that studies the thermosphere and ionosphere. And there's a model that developed at NCAR that studies the whole atmosphere from the earth's surface to the top of the thermosphere and the ionosphere and actually can go all the way to the magnetosphere. And some of the community model are reside at the NASA community coordinated modeling center for the CCMC. So NCAR model, one of the NCAR model is also at CCMC. So now I want to talk about three examples that my colleague and I use these observations and models to study the thermosphere and ionosphere. So the first example here we study how the solar flare change the total amount of plasma on the path of the GPS signal. So actually we call it total electron content. So on the left, that is from the GPS network. So this shows the electron content on the GPS signal path. So that is before the flare. And we see that the data at over the ocean, there was no data that I talked about earlier. So that's the drawback, but the good thing is all over the globe. So that's very nice. So this is the electron content before the flare. This is when the flare is happening and this is the change because of the caused by that the solar flare. And okay, I forgot to say this is the flare that is one of the flare that during that Halloween storm period that is in 2003. And so now on the right, this is a model calculated to electron content. This is a model that is developed at NCAR. So this is before the flare. This is at when the flare happened was happening. And this is a change because of the flare. So we see that the model overcome that problem of the data missing data in the ocean. So it covered everywhere. So during this flare, this flare caused the electron content in the ion sphere increased more than 20%. So you can imagine that burst of sudden increase of more than 20% of charged particle, how much they can disrupt the GPS signal and the radio signals and cause a distortion of those signals. So the second example here, we look at the mass density how they change over a solar cycle and how they changes over the year over a year. So this is a mass density at 400 kilometers. So remember this 400 kilometers is where the, that's where the international space station fly. And so this black is from the satellite drag, which is come from satellite catalog, satellite to drag information. So this is black is from that as a mass density at 400 kilometers. That's how it changes over the solar cycle and from 1996 to 2013. This is more than one solar cycle. And this is how they change over the year. And this red is calculated by this model that is developed at NCAR. It's a community model. And it is at the NASA CCMC that everybody can use this community model. So now, so this model and this observation allow us to know how the mass density at 400 kilometers, how they behave over a solar cycle, how they behave over a year. And this model calculation, they also allow us to understand why the mass density behaves the way they behave. And the third example is that we are looking at to use the whole atmosphere that is developed at NCAR, looking at the climate change in the whole atmosphere. So here, this is from zero to 400 kilometers here, looking at the altitude. So here is the latitude. So this negative latitude, negative 90 to zero, this is equator. So this is a southern hemisphere. So here, this is a northern hemisphere. So we know that this, so this is actually, so the border, actually the border, border Colorado, the baseline, baseline road actually is exactly at 40 degree north, northern hemisphere, it's exactly here. And so here, this is a color. So this warm color is that representing the increase of the temperature, which is warming. And this cold color representing the negative change of the temperature, which is cooling. So we here see that over the globe and in the lowest layer is a chop sphere. We see this warm color. So this is a global warming in the chop sphere. And above the chop sphere, see this is a cooling, negative change of the temperature, global cooling. And here, now here goes to the thermosphere. We see the very largest cooling in the thermosphere. So that's all the three examples that my colleague and I use the observations and the model to study the thermosphere and ionosphere. So now some fun facts. So first some fun fact. So is the thermosphere hot? So thermosphere, so it's actually thermosphere gets its name from a Greek word, thermus. So thermus means heat. So thermosphere is hot. The thermosphere can reach a temperature of 3,000 degree Fahrenheit. And so this is hot because like today, our temperature is probably in the 40s, 40 degree Fahrenheit. So this is a 3,000 degree Fahrenheit. So it is hot. But you would not feel hot. You would actually feel cold. So why? So this is because the heat, they only transferred when particles touch each other. So in the thermosphere, the area is so thin, there are so small number of particles. So one air particle will need to travel more than half miles before they can see another particle. They collide with another particle. So that's why there are so little energy is transferred. That's why the air feels very cold in the thermosphere. So now what is the color of the thermosphere and ionosphere? So first let's look at the color of the aurora. So earlier we talked about when the magnetic field in the solar wind and then the magnetic field of the Earth, when they align with each other in a certain way, they connect, become one and open a channel to allow the high energy particle from the sun, which is in the solar wind now. They travel down through that channel into the thermosphere. And when those high energy particle coming into the thermosphere, they gave that energy to the air particle in the thermosphere. And this air particle become excited, very excited, higher energy. And when those air particle calm down, they gave off lights. And the different air particle gave different color. And also even the same particle, they can be excited different extent. So when they calm down, they gave off different color. So that's why when we see aurora, we see different color. Sometimes it's green, sometimes we see red, sometimes even purple, blue, purple. So that's the color that we can see from the aurora when there's a space weather. And now this is a space hurricane. So you might say, we have never seen this. We see aurora, but we have never seen space hurricane. So you are right. And nobody have ever seen space hurricane. And we will not be able to see space hurricane with our naked eye. So the reason is that space hurricane actually is one kind of aurora. And this aurora always happen in the daytime, very close to the Arctic, not in the Antarctic, in Arctic. And it's in the daytime daylight. So that's why we will not be able to see it with our naked eye. So now how is this space hurricane different and similar compared to the hurricane, our weather hurricane in the troposphere? So well, the hurricane in the troposphere and the space hurricane, both of them have very high wind. The difference is the troposphere hurricane has high wind of air, the air is high wind of air. And in the space hurricane, these are the high swirling wind of plasma. And both space hurricane and the troposphere hurricane has a center eye that is still. And also hurricane bring us a very heavy rain. And the space hurricane also has a heavy rain except that the rain here is the rain of a water drop. And in the space hurricane, that rain is the high energy particles from the solar wind, which is from the sun. So that's how space hurricane and the hurricane in the troposphere, how they are same and how they are different. So those are the color that when there's a space hurricane when there's a space weather, but what about, what's the color when it's quiet, when there's nothing going on, when there's no weather. So this is an image, NASA image, that is from International Space Station that is looking at the horizon of the Earth. So this is the Earth and this orange sunset. And then it goes to the stratosphere and the atmosphere and the fade into the darkness. So here, so if you're looking from International Space Station looking at the horizon, so you will see the dark, that's the color of the thermosphere and ionosphere. However, if you look down, look down instead of looking at horizon and you can see this air glow and they are visible light. So first at the lower place here, there's a very thin, if you look carefully, this very thin layer of the green color. So those are the color at the very bottom of the thermosphere. And then if you go higher, so bottom of the thermosphere, that's 62, 60 miles and if you go higher at about like 200 kilometers, you will see red color, so green and red. So that's the color that you can see. If you see from the space and looking down, you can always see this green and red color. Okay, so these are the some fun facts of the thermosphere and ionosphere. So that's today's lecture. So now I will stop this nice screen share and take a question, go back to late then, take over and also take questions. Yeah, thank you so much for sharing all that. Super interesting, you know, especially for me as a geophysicist, I spend a lot of time looking down, so it's nice to look up sometimes. And before we dive into some of the audience questions, I'm super curious how leading did you get interested in studying space weather, space climate, the atmosphere? What kind of led you down that path? So my bachelor's degree, I studied the atmosphere that was in the troposphere and that's the weather forecast, this kind of thing. And when I work on my PhD, you know, the atmosphere, they are all, actually they are all connected. Today we have learned that the thermosphere and ionosphere is affected by the troposphere, but the troposphere can also be affected by a thermosphere and ionosphere. So they are all connected. So that's how I like start to look from the troposphere and it goes higher and higher all the way to the thermosphere and ionosphere. That's so cool. Great, yeah, diving into the question. So it looks like our top rated question right now is from Theo. Let's see if I can highlight this. There we go. So you would talk a lot about, you know, there's a lot of trackable debris in the upper atmosphere right now, but only about 5% of that is actually operational satellites. So Theo is wondering if there's any promising efforts to clean up space debris? So I think there is. I'm not, you know, the details of those programs, but they do have a program. They do have technologies to clean up the space debris. So I think they use, I think they use some fuel, they use satellites and use satellites and use some kind of technology to move the space debris and either into the higher, way from the low earth orbiting or I think they mostly move them to the higher altitude. And I don't know the details of this technology, but I heard that they work on this because it's really a very serious problem, especially when in the future, you know that even just the SpaceX is going to launch like 30,000, 40,000 low earth orbiting satellites. So it's really will become more and more severe problem. Which I see a follow-up question in here from Curious about how can a commercial space flight not collide with space trash? So space trash actually, they only orbit, they can maintain the orbit in all the commercial flights. When they launch the space commercial flights, they certainly need to know what's in their path. They need to develop, I think they have technology to mitigate these kind of effects, make sure that they don't collide with a space junk. Yeah, I just have this vision of, I guess for licensing we can't say this, but the animated movie about a robot when they kind of blow through the atmosphere of all the space junk, that's what I think of it now. Great, so our next question is from Fio again. So can charge particles from a solar storm damage our satellites? So you talked a little bit about how it could possibly damage the electronics, but is there any other type of damage that could happen to the satellites? They probably, the charged particle should not directly damage the satellites, they can damage those electronics. And it's just that during a solar storm the change of those charged particle, when there's a change of the charged particle, there also comes with the change of the heat, there's a lot of heat, and those heat can cause satellite to lose altitude. I think that's one of the, actually it's always happens. Satellite orbits is always affected by this, by this solar storm, cause them to lose altitude and spin faster and faster. So that's the direct effect on the satellites. And does it take a lot to completely knock a satellite out of orbit, or is it just like a little bit of radiation from the sun that could really cause major damage to the satellite orbit? They would not knock them all the way into the, into the massive sphere, so that they could not even be able to maintain their orbit. So it would not, because they fly about like 400 kilometers, 500 kilometers, they lose some altitude, but they can still maintain at the lower altitude. And also these solar storms usually, like solar flare is probably like one hour, two hours effect of it. And so one orbit for this, the time take this satellite to do one orbit is like 90 minutes. So it probably, it will go through like one or two of it and there's a solar storm effect will be gone. So satellites would be still be able to maintain their altitude. And the corona mass ejection is taken longer and can take a day and several hours to a day. And but still this take one day is like 15 orbits. So the satellites would still be able to maintain their orbits in the lower, so in the, in that altitude that keep on orbiting. And then the usually satellites has them, they have fuel carries this, propel whatever, you know, this thing and then they get boosted to higher altitude. So they have this kind of technology. Well, that's good, no, I guess. So our next question, and I apologize if I'm not saying your name correctly, is from Nachiket, who's wondering, can upward propagating waves associated with sudden stratospheric warming events or polar text breakdown also affect higher layers of the atmosphere? Yes. Yes. Actually, this upward propagating wave, you know, during sudden stratosphere warming events, you know, it's not not only cause stratosphere warming, but it, the effect goes all the way to thermosphere and ionosphere and change, change the, how much this neutral particle there are, changes the wind and changes the, how much of the charged particles and the amount of the charged particles and the, changes the, changes the currents, electric currents, all of those. So definitely, actually during sudden stratosphere, spherical warming, this wave, those waves will cause more change in the thermosphere and ionosphere. So actually you can say this sudden stratosphere warming is a weather events that cause space weather. Awesome. And maybe staying on the theme of waves and kind of going back to what you were mentioning about how, all of our earth systems are interconnected, you know, they all impact each other. So Mark is wondering, you know, are the gravity waves that disrupt the ionosphere, the same type of gravity waves that are detected by LIGO, the Laser Interferometry Gravitational Observatory. So the LIGO, the laser, so those, those probably they detect the gravity wave probably at a lower, lower altitude. And then, yes, those gravity wave, they can, some of them, not all of them, some of them can propagate all the way to thermosphere and ionosphere, some, some of them, you know, they can get filtered, what you call filtered, you know, when their propagation speed is certain, amount of speed and when they are very similar to what the wind in the stratosphere, in the mesosphere, they will disappear. They can't propagate higher. But some of them can propagate all the way to the thermosphere and ionosphere. A lot of them, they break at the very bottom of the thermosphere and ionosphere and actually cause a lot of turbulence there. And some, some of them, they can propagate all the way to higher, like higher 400 kilometers, you know, upper part of the thermosphere and ionosphere. So, yes, they can be the same gravity wave. Actually, this, you know, this data that is detected by LIGO, right? LIGO. And they can be used together with the data that, that is observed for the thermosphere and ionosphere to, for scientists to study how the gravity wave, because, you know, when you look at this data at the lower altitude and the higher altitude, you can find out, figure out if they are the same gravity waves. And by doing that, you can figure out what kind of gravity waves, where the, what kind of gravity waves affect the thermosphere and ionosphere, how high they go. So this would be very useful observation to be used together with those observations that observe the higher, the outer space. Yes, that's very, that's very good. It's also just really interesting to think about how, you know, so many natural systems like volcanic eruptions and earthquakes and storms gave off gravity waves. Like that's to me, that's to me, that's really cool. Great. So our next question is from Frank. How large are space hurricanes and what are the causes? This is something I had not heard of before actually. So I'm super curious to hear more about space hurricanes. Yeah, actually space hurricane, you know, it has a, they are not, they don't happen very often. And so how large is the space hurricane, you know, this space hurricane, you know, just like, because they are a space, a special type of Aurora. So their size is just so it's not super big, but you can say it can be like several hundred kilometers, you know, in radius several hundred, several hundred kilometer to yeah, several hundred kilometers in diameter probably. And the cause of it is, and also space hurricane always happens in the Arctic, you know, very, very, actually very polar, you know, polar region, Arctic region further into the Arctic compared to the Aurora that we can see. And and this, the cause of this is very similar to the Aurora that we can see. So basically the solar wind that traveled towards the Earth and and I talked about this magnetic field in the solar wind and magnetic field of the Earth when they align in a certain way. So this, the difference between this space hurricane and the other Aurora is the alignment of this magnetic field. So this is a very special alignment of the magnetic field. They align with each other just in the perfect way. That is very close to the magnetic pole actually. That's why it is further into the Arctic and they align with each other. Actually that's anti-parallel to each other in that particular region, in the Arctic region. And then they connect, they become one, become so that, that when they become one, so there's that open that channel. So the now the high energy particles in the solar wind, they can travel down from that open the channel into the thermosphere and give that energy to the air particles, excites them. And again, when they, when they come down, they give, give off these lights that is that is that is Aurora. So that's how this happens. So it's a special form of of Aurora. And actually, you know, in the from in the, in the past decades, you know, probably we have seen about maybe a dozen of space hurricane. So it does not happen very often. And you can see it from the satellites, only can see it from satellites. You cannot see it with naked eye, because it's on the daytime. You can cannot see this color. Cool. So our next question. And again, I apologize if I miss pronouncing your name. It's from not to get. Do you have any advice for prospective graduate students interested in space climate and whole atmosphere modeling. Thank you for this fascinating presentation. And thanks for being here with us today. So, okay, so so my advice is it would be so it's great that that that you are interested in space climate and a whole atmosphere modeling. So you can I would say start from we have like so in our in this space science community actually every every year we have this this meeting. And actually this year it's always in June and there's a lot of students. We particularly we have even have financial support to encourage students to come into this meeting and interact with scientists and and other students. So that would be a very good thing to do to attend a meeting like that. That is a very has a lot of focus on students and and if you are interested in atmosphere atmosphere modeling. So it's very important to to know the computer programming because and actually it's atmosphere model. We use a lot of fortune code code, you know, F-O-R-T-R-A-N. So very old computer language. So you need to understand this language and do computer programming familiar with computer programming and and also the yeah, this is actually very helpful to NASA NASA and also NCAR and the NOAA has a space where the prediction center and they have NOAA has a website that has introduced a lot of space climate space, weather information. So that's very good. And NASA has has a lot of this kind of has a website that gave a lot of this information about knowledge about space and that is really that would be very good for students to understand the space science and know a lot of things about space weather space climate and NCAR have a website like that too. So yes, so number one goes to the website of NOAA and NASA and NCAR to search for space where the space climate and you would see a lot of very good information. Number two get familiar with computer programming and number three come to this meeting. It's if you go to NCAR website you would be able to see this meeting and you can also contact me to go to this meeting that is very much focused on students and have financial support for students for students to interact with scientists and other students. Yes, so so far I have these three advices. Yeah, thanks for sharing all that. I totally agree, you know, just to start talking to people. The Earth and atmospheric scientists tend to be fairly friendly, so just start talking to us. Great, so our next question is from Edward and it's about ozone in the upper atmosphere. So if ozone is destroyed, what will be the effect on the warming or possibly cooling of the upper atmosphere? Actually ozone. So ozone, you know, actually it's slightly different from other greenhouse gas. Ozone, actually when you have more ozone, ozone can cause warming in the stratosphere cause ozone cause a warming effect in the because ozone layer most of ozone is in the stratosphere. So if you have more ozone, actually it can cause make the stratosphere warmer. And in terms of the upper atmosphere, the ozone does not have a lot of effect in the thermosphere and ionosphere. It's a very small effect. So if you have most of the most of the effect in the thermosphere and ionosphere come from carbon dioxide. So ozone, yeah, ozone does not have much effect. Great, thanks. So it's like our next question is from William. At lower solar activity levels, there are often bright patches in hydrogen alpha images called plagues. Can solar particles reach Earth from them? So these are the patches in the sun. With this alpha image. I'm not particularly not know if this H alpha image is on the on the sun or yeah, it should be looking at the sun. Can solar particles reach Earth from them? So I'm not sure if this bright patch is on the solar disk. So but regardless, even at very low solar activity, there's still there's still there's like this hot gas coming out of the the sun actually constantly actually erupts this kind of high hot gas. And now we have earlier I talked about in the lecture, I talked about too recent to mission gold and icon. And so so this past two or three years actually is a very low solar activity level. What we see is even at this very low solar activity level actually it's like solar minimum super low, but we still see this effect from the sun that is coming from this solar wind. That is they coming into the thermosphere and the atmosphere and reaching Earth. Yes, definitely. Yes. At low solar activity level and this solar particle can still reach Earth through the same process except at less smaller degrees, smaller magnitude, smaller amount. So, so yes, the answer is yes. Great. Thanks for sharing all that and building on on that it looks like our next question is kind of related so it may or may not be within your your search realm, but Bob's wondering how about incoming cosmic rays not from the sun so maybe outside of our of our solar system and their impact on the ionosphere. What is the interplay between incoming solar radiation and cosmic rays? So this cosmic ray actually what they do not ionize they do not work impact at that high altitude actually cosmic ray they have they come to lower altitude lower atmosphere and so so and so they they don't they their impact is not is not in the ionosphere they come into the lower atmosphere I don't know exactly which which part probably goes to layer like stratosphere this kind of altitude not as higher in the ionosphere or maybe part of it to actually yes, the ionosphere actually overlap with the atmosphere so maybe some of them can have impact the ionosphere in the in the atmosphere part is the lowest part of the ionosphere the interplay between the solar radiation and the cosmic ray so interplay so the solar radiation in the part that impact the the thermosphere and ionosphere is actually the this is a very shortest waverance part you know the which is also the part of the solar spectrum that has the highest energy that we call like x-ray, soft x-ray and extreme ultraviolet so those parts are the other parts that absorbed in the thermosphere and so but cosmically they cosmic ray they come to a lower altitude so so I there isn't so they affect different parts of the atmosphere so essentially great thank you thank you so much for sharing all that again and if there's no more questions that come in definitely thank you to everybody for putting some questions in there and really sparking some some great conversation and discussion about space weather and space climate and again this this conversation this lecture is being recorded and will be posted up on our NCAR Explorers series website hopefully within the next couple days if not sometime by next week and we also just want to you know again thank Liying for being here with us today and sharing all your knowledge so thank you so much for being here Liying okay then I seems to see there was a question they're asking if this presentation can be available yeah so we've been answering a couple of the questions right within the chat so this so the presentation will definitely be available the next couple of days yes this is available and a lot of the image I get it from NASA and I there's a each image you know it has a credit so just keep this credit just to be able to credit properly yes definitely definitely yeah so you know thank you so much for being here and thank you everybody for joining us we definitely look forward to hanging out next time at our next Explorers series event so have a good rest of your evening or good morning wherever you happen to be thank you