- Good evening and welcome to Space Place.
This is one of our monthly guest presentations here, and our
speaker tonight is someone who's spoken here at Space Place
a couple of times before, one of our regulars, and that is
Professor Alex Lazarian of our astronomy department
of the UW-Madison Astronomy Department.
Professor Lazarian is an expert in many areas of astronomy, has
particular interests in cosmic phenomena, he was telling me,
cosmic rays and things like this.
But he has a much more specific topic for us tonight.
And I was going to mention that Alex was a Humboldt,
recipient of the Humboldt Award a few years ago in 2012.
So he's very distinguished, very well known
in the field of astrophysics.
So tonight Alex is going to talk to us about solar activity
and its influence on us, so we should welcome Alex.
[applause]
- Thank you for coming to my lecture.
And I'm going to talk about something
that the nearest star is doing to us.
And, as you know, nearest star is the sun.
Sun is giving life to the surface of the Earth.
Interestingly enough, you can't have life without sun.
And probably the life was born inside our planet
and only after that it moved to the surface of our planet.
Nevertheless, for any advanced forms of life, sun is essential.
And, therefore, sun was the god or goddess for many people.
There's an Egyptian sun god Ra.
Apollo was the sun god for Greeks.
There are gods of suns for other nations.
Indian god and there is Mayan god of sun.
So sun was worshipped.
For us, sun is the center of our solar system,
which consists a part of our planet, other planets.
The sun, as we are, was also born at some moment.
And it was born from the contraction of huge masses
of gas and dust, as it's shown on this diagram.
Initially you have a cloud of gas, it's getting more
and more compact, and then it forms the planet,
the protoplanetary system,
and then it develops in the modern planetary system.
Sun, at some point, was very active.
It had the accretion disk near it, and it had a jet.
For both components, the magnetic fields that I'm going
to mention in my talk were essential.
This is another view of the protoplanetary disk, and you see
there is a disk of dust and gas around the protostar.
There are some--
Well you can imagine that this is our early sun,
and there are planets being formed around.
And you see there are these collisions
of planets and planetesimals.
So it was a pretty violent place.
What is the energy of the sun?
We all know that the energy of the sun
is coming from thermal nuclear reactions.
In these thermal nuclear reactions,
we have four hydrogen atoms,
which are coming together, eventually,
to create the nucleus of helium.
There is a difference of masses between those
four hydrogen atoms and the nucleus of the helium.
It's really tiny. You see?
It's a small number.
Nevertheless, this small amount of mass, when it transfers
to the energy according to Einstein's formula, E=MC2,
produces a lot of energy.
This is, by the way, also the source of energy
for the thermal nuclear bomb.
Unfortunately, it happened all through all history of humanity.
People were faster to produce weapons
from whatever discoverer
than to use it for peaceful purposes.
For instance, the use of mechanical energy of gases in
cannons happened many centuries before it was used to,
for example, drive our cars.
The same is happening with thermal nuclear energy.
We have thermal nuclear bombs, but we still cannot have thermal
nuclear reaction controlled.
Our sun was born, as I told you,
and it is going through its cycle.
Now it is in its middle age, in its middle of its lifetime.
And it's an average type of star.
Eventually it will go to the red giant.
And at this point, even Madison will be a very hot place,
[laughter] because the radius of this red giant may be
very close to the orbit of the sun.
Well, after that, eventually our sun will be a white dwarf.
It's just a cooling star, which is a small,
pretty luminous per unit area,
but pretty faint if we look at it from outside.
What is the relation of the sun and the Earth?
The simplest one is related to the energy that the sun
is producing and supplying to our planet.
And it's interesting that our planet is not absorbing
this energy like a simple rock.
It has its atmosphere, and, therefore, the energy which is
coming to the surface is not simply emitted.
It's emitted and it's reflected and reabsorbed
and emitted back by the atmosphere.
This is what is shown here.
So we have radiation flux of the sun coming toward the surface
of the Earth, but not all the energy is getting back.
It's a very interesting process because the amount of energy
which is absorbed by the Earth depends on many factors.
One is, for example, how much is the snow coverage
or ice coverage of the planet?
Another factor is how much the atmosphere reabsorbs
and reemits the radiation back.
This is related to the greenhouse effect.
Also it relates to how much clouds we have, and clouds at
different layers of our atmosphere act differently
in terms of changing the temperature of our planet.
So in the case of the Earth,
I claim we have a very nice balance.
Nice balance for whom?
For us because our planet is perfect place for us to live.
Is it really necessary to be that way?
No, it may not be necessary.
Our planet would be much cooler if not for the greenhouse gases.
Greenhouse is, as you see here,
is some room which has this glass,
and glass has a special property.
It does not, it allows sunlight to enter but the infrared
radiation from the surface is being reabsorbed by glass,
and, therefore, you have hot or warmer environment
within the greenhouse.
The same is happening in our atmosphere.
We have water vapor, we have carbon dioxide,
and these gases act as greenhouse gases.
In fact, the greenhouse effect is essential
for our well-being on this planet
because it increases the temperature of our planet.
It does not allow real rapid changes of the temperature
at day and night.
However, everything should be in good proportion.
For example, the same greenhouse effect
makes the temperature of Venus really, really intolerable.
Why is that happening this way?
Well, in fact, you can have an effect
of runaway greenhouse effect.
What is it?
For example, our Earth has oceans.
And the mass of the oceans, the mass of water in oceans,
is much larger than the mass of water in the atmosphere.
But if we increase the temperature of the Earth,
this water will go into the atmosphere.
And, as a result, it will increase significantly
this greenhouse effect.
As a result, the temperature can go, you know, not even dozens
but maybe hundreds of degrees,
which will make the surface of Earth
not useful for any at least higher-level organisms.
At the same time, for Mars it was
not enough greenhouse effect, and what happened?
It happened that the atmosphere started condensing.
We have CO2 ice at the polar caps of Mars.
And as a result of no greenhouse gases, Mars is a very cold.
So there's an illustration of Venus.
What it has, it has 97% carbon dioxide
and temperature 860 degrees Fahrenheit.
So Mars, at some point it had running water.
When it had the greenhouse effect, it was not so cold,
but now it lost it, and we don't have any running water on it.
So the problem of us not to overheat our planet,
and this is an important issue.
And I will be discussing what are the processes
that affect this heating.
I'm going to now talk about magnetic fields.
Magnetic fields are very important for our sun.
This is the picture of the magnetic activity
of the solar surface.
Let me say a few words about magnetism in general.
I would like to first quote a Roman poet who wrote:
"Those restless minds study the world's structure,
"surge the beginning of things,
"should inquire into the origin of magnet."
Interestingly enough, yes there's poetry, but philosophers
in Roman and Greek time, every scientist was a philosopher,
was supposed to write their papers as poetry.
I'm very fortunate I don't need to do this.
[laughter]
Okay, so humans were facing magnetism and were
fascinated by magnetism probably for thousands of years.
Nevertheless, the first written description of magnets
is dated by 6th century BC.
I'm sure that humans knew magnets for longer.
What were these magnets?
Lodestone is a natural magnet.
And it is, you know, believed that these are pieces
of iron ore which are magnetized by lightning.
So they're pretty rare.
But nevertheless, you can imagine how fascinating
it was for people to see magnetic events.
Magnet gets its name from Magnesia,
which was a Greek city.
Magnets were used by humans for different purposes,
mostly to find their prey and to deceive people.
In China, it was used to deceive people.
How?
Fortune tellers would use the small bort,
saying this is your destiny,
and, you see, I know your destiny.
You see, I'm changing the direction
of this bucket of water,
but your destiny cannot be changed.
I can tell you what to expect.
So you can play this and make such an experiment yourself,
magnetizing it.
Vikings did not believe in fortunetelling.
They believed in robbery and killing.
And one of the favorite place for them to visit was England.
And they did not want to go, as Greek would go, along the coast.
Too much trouble. Too long.
And they invented different navigation instruments,
and magnet was one of them.
So they could come, kill, and return with booty.
Okay, we will not be talking about such bloody things.
We will be talking about solar physics.
And for solar physics it's important that we have plasma,
ionized gas, and this gas is turbulent and it is magnetized.
This is a picture of that you see.
Turbulence, magnetic field, and plasma.
What do we see here? We see sunspots.
Sunspots were observed by Greek scientists.
They were also observed by Indian
and Chinese astronomers.
But for a while they were not observed.
And this while was the dark ages in Europe
because people were not looking at anything.
They were too much suppressed, I think.
Then they were rediscovered by Galileo.
And Galileo found the sunspots.
Actually, you should understand that Galileo invented telescope,
but he was smart enough not to look
and watch the sun with a telescope
because there is a joke that you can watch the sun
with a telescope but only twice. [laughter]
With your left eye and then right eye.
[laughter]
Well, why do we care about the sunspots?
They are just tiny things.
In Galileo's time, it was important, surely,
because the sun was considered an ideal object,
and suddenly it has spots.
Well, we also care about it.
And it definitely affects a lot,
and it affects our climate.
For example, this plot shows the number of sunspots
from the time people started observing the sunspots.
And there is a special place, in terms of years,
when there were no sunspots.
And I will tell you what it meant for the Earth.
Sunspots are caused by magnetic fields.
So we are coming back to magnetic fields.
These are places where we have some
very strong magnetic fields.
By the way, on this picture sunspots are dark.
But if we bring the material of the sunspot here,
it will be shining like crazy.
It's very hot. Everything simply in comparison.
The sunspots are dark in comparison
with the surrounding media.
Magnetic fields are also coming out of the surface of the sun,
and they create this prominence.
This is the cartoon and this is
the actual photograph of the prominence.
And this prominence is much larger than,
for example, our planet.
They are comparable with the size of the sun.
And these are also important because, I will tell you, that
they are bringing, producing high energy particles, which are
come to the Earth and induce a lot of phenomena on our planet.
So this prominence is also related
to the coronal mass ejection.
So when you have this magnetic activity,
some part of the plasma
is getting energized,
and they produce high energy particles,
and this energized plasma can be ejected.
Well, solar activity that we in fact enjoy is related to aurora.
And you can see Madison is sufficiently north, and,
therefore, we can see, from time to time, aurora events.
Well, how these events are produced?
Usually you have some solar flare eruption,
ejection of high energy particles, and then
there's particles transferred together with a solar event
and interact with the magnetic field of the Earth.
Magnetic field of the Earth shields us from
the direct effect of those particles.
In fact, it shields better the equatorial parts of the Earth
compared to the, for example,
southern and northern part of the Earth.
But, nevertheless, it shields.
Depending whether we observed aurora in the north or south,
it's aurora stratus or aurora borealis.
Very spectacular events.
This is aurora seen from the space.
You can really see what's happening.
These energetic particles come and interact
with the atmosphere, creating these spectacular events.
Interestingly enough, aurora is not only peculiar to our planet.
It's also common for other planets
which also have magnetic fields.
There's aurora for Saturn. There's an aurora for Jupiter.
There's even for Uranus. Well, this is good.
This is nice, especially if you have, you know,
polar night and you have these flashes.
Is there any other effect apart from this spectacular flares?
Yes. And it can be really pernicious.
What's happening?
These energetic particles are coming to the Earth,
and they start interacting with everything,
including our equipment.
For example, if we have space station satellites,
this equipment is sensitive to the effects of radiation.
And, as a result, this equipment can be destroyed.
It also can interfere with
the signals with radio communications.
Exposure by this energetic particles can be pernicious
for human beings, especially human beings on the planes.
You know that to get from one place to another, for example
from Madison if you are flying to Asia or Europe,
usually the shortest path, not straight,
but curved path going closer to the north pole.
By the way, that's why Titanic was sank,
because the captain of Titanic
wanted to have this blue ribbon.
This is a special prize or honor for the fastest ship.
Therefore, it was going to the north, and, therefore,
it collided with the iceberg.
But, at the same time, this is a usual routine for all planes.
But during solar activity, the amount of radiation
may be dangerous, and it can cause cancer.
As a result, when it's happening,
the companies advise not to save time,
not to save fuel, but not go too much north.
Moreover,
the energetic particles can induce
some currents, and they can induce
short circuiting of electric grid.
There are many other effects and the damage of such solar
activity can be billions and billions of dollars.
So what we want to know, whether we know
when it is going to happen. Why?
In this case, we can switch off our sensitive equipment
on the satellites and make them not susceptible to the damage.
We can also maybe give the warning to the companies
not to fly over the North Pole.
Well, in terms of energetics,
the solar flare is maybe hundreds of billions times
the world's annual consumption of energy.
And solar flares can be really, really strong, dramatic.
Current event which happened in 1859 is the well-known recorded
event of very strong solar flare.
At that time this aurora was seen
even at the equatorial regions of our planet.
But this is not the most dramatic event.
The studies of the cedar by Japanese scientists
found that around 774
there was an even bigger, more dramatic event.
Such events can really cause a lot of damage for humans.
And this was happening with our sun.
So it happened one time, it can happen in another time.
So the idea of the space weather is to predict these events.
These energetic particles, although they are energetic,
they are not moving very fast to our planet
because they are diffusing.
They're interacting with the magnetic field
within the solar wind, and, therefore,
we have a couple of days.
So the idea is we look at the sun and say,
"Oh, there was a solar flare,
"but it's okay if solar flare not something dramatic."
We'll not switch our equipment, switch off our equipment.
But this solar flare, "Oh, this is very bad, we should prepare."
So this is the idea.
But to realize this idea, we need to understand
which solar flare accelerates more particles.
We need to understand the physics because you may not
necessarily have very bright solar flare, but it can have
a lot of energetic particles accelerated.
So we'll discuss the effect of magnetic activity and climate.
So this is ultraviolet image of sun.
And in terms of ultraviolet image or ultraviolet emission,
solar flares change a lot.
For example, the total radiation of the sun
during a flare cannot be changed.
But in terms of UV, it can very important.
And UV radiation affects the atmosphere, especially upper
part of the atmosphere, affects atmospheric chemistry,
and we actually don't really know all the effects.
It's a complex system.
And in this complex system it's really difficult to predict what
is happening, what is the exact effect that we are dealing with.
We also know that this accelerated particles
are influencing ozone layer.
Again, we know that ozone layer is protecting us
from UV radiation, so effects can be bad
in terms of our getting skin cancer.
But it's not only that.
There are many other effects that the changes in the ozone
layer can have on the overall atmospheric state.
For example, it is established that the solar cycles influence
La Nina effects, and they change the temperature in the Pacific
regions and they change also precipitation.
So this is well-established fact.
Let's discuss another thing on a global scale.
This Maunder Minimum. I mentioned it.
This is the range of years where there were no sunspots.
Interestingly enough, this time to respond to the so-called
Little Ice Age on our planet.
The temperatures were really, really
dropping during this time.
This time is also known as the time of big conflict. Why?
Hungry humans fight.
And there are more problems which is happening.
Also, this is, by the way, the paintings.
[inaudible] paintings.
You see people are playing on the frozen canals.
Nowadays it's not possible.
This is the time of low solar activity.
Interestingly enough, by the way, we're still living in the
Ice Age because the temperatures of the Earth now,
if we take this mean temperatures of the Earth
so it's more recent history, are lower than its mean.
Well, sometimes those changes of the climate, even temporal,
play bad tricks with kings or emperors.
This is Napoleon.
And, look, this is Maunder Minimum.
And there's another minimum here.
He's pointing to his infamous campaign in Russia.
Russia would be called for French soldiers anyhow.
But this particular time was the worst.
It was extremely, extremely cold winter.
In fact, it was not only French army that lost all its cavalry
during the [inaudible], it's also Russian army
which was following, it also lost
a lot of its artillery because it was too cold.
In any case, for the great army, it was a disaster.
So Napoleon was supposed first to consult astronomers who would
tell him no, just wait a dozen of years and then invade.
There are scientists who believe
that there is a very tight correlation between the climate
and the cosmic and the solar activity.
They relate it to the cosmic ray flux coming from the galaxy.
And the solar activity changes the [inaudible]
around the solar system, which is called heliosphere.
And this is the way how we can change the number or density of
cosmic rays that are coming and interacting with atmosphere.
What's happening when the cosmic rays are interacting?
Cosmic rays are very energetic particles which are coming
mostly from outside of our solar system.
When these cosmic rays are interacting with the atmosphere,
they create droplets in the upper parts of the atmosphere.
And, as a result, the sun radiation gets reflected.
So when we have active sun,
the protection over all our solar system is better.
And as a result, less cosmic rays interacting
with the atmosphere and creating these droplets.
And as a result, our planet is getting more radiation
and it's warmer.
But when we don't have solar activity,
in this case the planet is getting colder.
So this is essentially the idea.
And it explains, for example, this Maunder Minimum.
So we have solar activity that's due to
the solar interaction with the cosmic rays.
We can change the flux of the cosmic rays
coming to our planet and change, as a result, our climate.
And these people find good correlation between the changes
of the climate and the solar activity.
Well, interestingly enough, the changes of the climate
which are important, and through some analysis we can know
how fast the changes temperature were happening.
It can happen sometimes in a very dramatic way,
and this can be pretty bad for the ecosystem.
Well, these scientists, for example,
predict that as our galaxy is going through,
our sun is moving through the spiral arms of the galaxy,
we should have changes of the climate.
And they obtained a fair correlation between the changes
of the Earth's climate with this passage through the spiral arms.
Nevertheless, we don't have such a good correlation
for the recent years.
And this is an indication that indeed the human activity
may be important in changes of the climate.
So my message is there are other reasons apart
from human activity that act on the climate.
And so the sun magnetic activity is probably the primary culprit.
However, more recently we see not a good correlation,
which is maybe suggestive no, we should be very worried.
We don't want to put a lot of greenhouse gases
into our atmosphere.
Well, where are we in terms of this climate?
Well, we're not in the most warmest part.
You see there's the change of the climate
over the last 12,000 years.
There were warmer periods and there's some of those periods
that are pointing to all this so-called optimal climate.
Should we be happy with the change of the climate?
I would be very worried about that.
And why I would be worried?
Because usually changes of the climate induce wars.
The problem is that if the climate was good in some place,
usually the density of population is higher there.
Then when the climate changes, well these people
try to move somewhere else.
One of the reasons that there was this huge invasion
of Europe, not only Europe, Asia,
by Mongols was a change of climate.
For many, well for around 200 years,
there enough precipitation in this Mongolia step,
and the population of local nomads increased significantly.
And after that, when the climate went to its usual dry stage,
there was a big invasion, a lot of problems. Okay.
How do we study this activity? There are different ways.
Observations of the sun, and I will show you a number
of pictures in UV and X-rays is one of the ways.
There is also a way of studying magnetic activity in C2.
So by having props.
And MMS is special mission which as four props
which are acting as, you know, team.
And this team is intended to for studying processes
which are called magnetic reconnection.
Magnetic reconnection can be illustrated
by this simple demonstration.
Assume that these are two magnetic flux tubes.
In plasma, magnetic fields act differently from,
for example, not ionized gas.
And if you take a bar magnet, you cannot form a flux tube.
But if you put a magnetic field in the conducting plasma,
magnetic fields start moving together with the gas.
And, as a result, we can consider flux tubes.
And these flux tubes can interact with each other,
and, as a result, they can create these knots.
And whether these knots are resolved or not depends on a
particular process which is called magnetic reconnection.
If they're not resolved, you see, energy is being released.
And as energy is being released,
you can accelerate particles and explain, for example,
solar activity, solar magnetic activity.
This is a picture of one of the objects,
and this is an illustration of reconnection.
You see these magnetic flux tubes, magnetic flares lines,
they interact, and they reconnect.
So that's what's happening.
Okay, this is what's happening in terms of our planet.
When we have this reconnection, there could be energizing
of plasma, and this is what is being started.
A connection is one of the topics
that I am studying myself.
And what I suggested with my colleague, Ethan Vishniac,
is a model of a connection in turbulent fluids.
Why in turbulent fluids?
Because most fluids in astrophysical media
are turbulent, and, therefore, it is important
to understand what's going on with those fluids.
Let me show some illustration of another mechanism that we
theoretically described and here we are numerically testing.
These are two fluxes of magnetic field.
And then they start interacting.
And as they interact, they annihilate
and they create turbulence.
I'm also again showing you.
As a result, the energy which was stored in magnetic field
is being released.
This energy can accelerate energetic particles,
and it can create heating, it can be responsible for flares.
This is another illustration of this process, what's going on
if we move through this reconnection layer.
There is a lot of turbulence and this turbulence
is initiating a connection.
There's two processes which bootstrap each other.
A connection is also started in Madison,
for example, experimentally.
There's this special device which has been built
in the department of physics, and it is dedicated
for studies of magnetic reconnection.
I was telling you about the sun and how it is important for us.
However, sun is also our laboratory because studying sun
phenomena on the surface of the sun, magnetic phenomena,
we can get insight about different exotic processes.
The most energetic processes in the modern universe
are related to the gamma ray bursts.
If we have, for instance, two neutron stars colliding,
they're not only producing the gravitational weight
like those which were detected by LIGO
but they can also produce this gamma ray burst.
And gamma ray bursts very much depend on magnetic activity.
As I told you, these jets
are usually associated with magnetic fields.
And gamma ray bursts create a very narrow jet.
And if we have a narrow jet like that happening in, you know,
in our quarter of the galaxy and this jet
is directed towards to us, we can be cooked here.
So it's so much powerful.
There are these magnetars with neutron stars
with a critical magnetization,
and this is also a magnetic phenomena.
There are pulsars which are routine to study now
but still mysterious.
And studying sun, we can understand some of these effects
because magnetic fields are universal.
And the magnetic phenomena, therefore,
which we understand on the sun
can be used to explain other exotic processes.
Thank you very much for your attention.
[applause]