- [Jim Lattis] Good evening and welcome to UW Space Place.
Tonight is another one of our guest lecture
series on the second Tuesdays of the month.
And tonight I'm very pleased to introduce
Professor Alex Lazarian of the
UW astronomy department.
Alex is a worldwide known expert on
astrophysical magnetic fields, and has
been honored, among other things, with
a Humboldt Prize, from the Humboldt
Foundation in Germany, and he's here to talk
to us tonight about interesting aspects
of interstellar and intergalactic,
and I don't know what else,
magnetic fields.
So join me in welcoming Professor Lazarian.
(applause)
- Thank you very much.
I will be talking about
magnetic fields in the universe.
And here we see magnetic fields
of the galaxy, and this is magnetic fields
of a Bohr magnet.
I will start my lecture showing you
an experiment which
clarifies the importance of magnetic fields.
For example, this is a magnet,
this is a metallic tube.
So, look.
Listen.
Normal magnet.
Again.
Why is that?
Because magnetic field
of this magnet induces currents in
this tube, and the interaction of
these currents and magnet makes
the motion of,
slows down the motion of
the magnet.
I'll give this tube
and you may play while I'm giving the lecture.
(audience laughing)
Just return it to me later.
Yes, it's copper.
Right.
This is also a citation:
Those whose restless minds study the world's
structure, search for the beginning
of things should inquire into the origin
of murmur magnet.
And this is the
citation from an
ancient Roman writer.
So, in the
University we have particular installations
which use magnetic fields to
confine plasma.
And I would claim that
this is the future of
energy industry, because
this is the
unlimited source of energy, and if we
think about what humanity was always
limited by, it was energy.
And this development would be
as remarkable and as important, and
more important than the
use of fire by human beings.
But let's talk about history
of magnets.
Okay.
Lodestone was the first natural magnet,
and it is
presumably produced naturally during lightning,
when we have
more iron
ores in the earth, and there is lightning.
Why it is called magnet?
It is from the place which
called Magnesia.
And there are two theories where this
Magnesia was situated.
One is that it was situated in the
northern Turkey, and another is
it was not probably far from Athens
in Greece.
But there the first magnets were
found and described
by people.
What were the first practical use of magnets?
We have actually two
uses.
One was by
Chinese fortune tellers, and another is
by Vikings.
What were Chinese fortune tellers doing?
They were putting
a boat, or in a bucket of water, and would say
this is your destiny.
And then they move this bucket of water,
but the boat would still
point in the same direction.
This would be very convincing way
to persuade people that they
have some magic powers,
and for some limited sum of money,
you can know what's your future.
You can play with this
and predict future this way,
by taking
cork and having magnetized needle
put into it and you will see
the same effect.
What about the
Vikings?
Vikings were using them
for seafaring.
They were actually a pest of Europe.
They would,
for example, plunder Britain,
and to get the
quickest way to Britain they needed
some navigation, and they were using
different navigation tools.
Magnet was one of them.
What do we know about strength
of magnetic fields?
We have really
a big variety of magnetic field strengths.
For example, Earth magnetic field,
you can say that it's ballpark
value is one gauss.
It's in fact 0.5 gauss.
But the magnetic fields
in between the stars, in the interstellar media,
is a million times less.
Some spot on the magnetic field,
on the contrary, is a thousand times more,
but this is not the limit.
In the laboratory, you can
in some explosion devices,
reach magnetic fields which are
10 million times stronger than
the Earth magnetic field.
But this is essentially nothing compared
to the magnetic fields of magnetars,
which can be 10 to 15 gauss.
And the scales,
scales are really
of wide range.
They can be a million, or 10 million
light years.
So such scale of magnetic fields.
And I mentioned to you already
the applications
were fortune tellers in China
in 200 BC, and
the navigation by Vikings.
The first description,
detailed description, of magnet and its properties
is in the
manuscript by
a monk in 1269.
And the first theory of magnetism
was suggested by Rene Descartes.
Descartes was a really remarkable man,
and his Latin name is
related to this Cartesian system of reference,
because it was he who really introduced it.
At the same time,
a particular discovery of his
is not associated with his name.
I can now ask you what is the
measure of
atmospheric pressure.
And you answer to me, Pascal's.
Because it was,
it is associated with Blaise Pascal.
However, it was Rene Descartes
who devised this experiment.
The experiment was that you put mercury
in a tube, go to the
mountain and see the change of the
level of the mercury, and this is the
pressure of the atmosphere.
It was devised by
Descartes, but he
did not have a small thing,
well actually, a big thing, a mountain.
He was living in Holland.
It's pretty flat.
He could not make such an experiment.
He could surely travel somewhere,
but he thought why
I not write to my friend Pascal,
and to describe he's living exactly
near the mountain. He did it.
Well, Pascal
performed all that Descartes
was writing to him.
Then he wrote
his scientific paper, which had
one small deficiency.
He forgot to mention whose idea it was.
(laughter)
Well, in any case,
this is again the citation,
and this is the
portrait of Descartes.
Well, Descartes
actually was
chosen to be
a tutor of
Swedish queen,
Christina, who comes to the throne at 19,
was very active.
And actually, this is the tragedy of Descartes
because here they become lovers.
Well, you would say
it's not a tragedy,
but, you know,
Christina was 19 and he was a middle-aged man,
and Christina was very active.
She would dance
'till two with Descartes,
and in the morning at six o'clock
she would wake him up to have
some, for example, horse riding,
and the guy got sick,
and he dies of pneumonia.
Christina becomes very
desperate.
She abdicated very soon.
She actually kept his head
with her.
So only the body of Descartes was
buried, and head was kept
and preserved with Christina.
(audience laughing)
Well, he still
surely was pretty naive.
The actual theory of magnetism was
suggested by James Clark Maxwell.
And these are the
creations of Maxwell.
Well, then it became some business.
You have them on the mugs.
And some students have them on
tattoos and T shirts,
and this lady has it on the back,
probably it will help her fellows
on the exam.
(audience laughing)
What we have in astrophysics,
in astrophysics we have not only
magnetic fields but also we have
ionized gas, or plasma.
And plasma and magnetic fields
are inseparate in
the case of
astrophysical phenomena.
Plasma follows magnetic fields,
and magnetic fields follow gas.
So they...
I mean plasma and magnetic fields behave
like this cord.
If you move plasma, magnetic field
is moving.
With this device, we can
explain many properties of
magnetic fields.
For example, we can explain how to
increase the strength of magnetic fields.
Magnetic field strength,
is, in this case, may be represented by
the thickness of this cord.
But what I'm doing now,
I'm doing an experiment which is called
Zeldovich dynamo.
So I am
twist,
this band,
then I fold,
and I stretch.
What do I have?
I have twice the magnetic field.
I can do this again and again,
and increase the strength of magnetic field.
This is the way plasma, moving
plasma can enhance magnetic field,
and create magnetic fields.
Magnetic fields that we see
in the universe
are not primordial.
They are generated.
The sun is generating magnetic fields,
and magnetic fields are related to plasma.
The plasma
activity is
really a magnetic activity related to,
for example, this solar spot.
The solar spots are particular places,
for example, this is a solar spot,
this is also the solar spot,
and these are places where magnetic fields
are enhanced.
And I will be telling a bit later
that the number of the solar spots
may be related to the
temperatures that we experience
on the Earth, and to the Earth's climate.
Solar spots were discovered by
Galileo, and they contain
very intense magnetic field lines.
These are actually spots
that we see as
dark, but if you bring the material
of the solar spot in this room,
it will be shining.
It's just relative temperature
of the solar spot is less
than the temperature of the ambient plasma.
Their size can be much larger
than the size of our planet, and
they actually
contain very intensive magnetic fields
which are measured by Zeeman splitting.
Solar spots present
one example of magnetic activity.
There are other examples.
For example, these are arches,
plasma arches,
that we see.
And they are formed also by magnetic field.
Plasma is moving along magnetic fields.
These arches can be stable for some time,
but then they can destabilize
and eject
high-energy particles.
And for example, here we see this
arch, prominence, and this is Earth
for comparison.
These are really huge events,
and this is,
they're comparable to the size of
the Sun.
These are examples of magnetic phenomena.
These magnetic phenomena are related
to ejection of energetic particles,
and these energetic particles can create
a lot of effects
for us.
Aurora is one of these effects,
and this is an example of aurora.
We can see different
examples here,
some of them are called Aurora Australis,
in the Southern Hemisphere,
and Aurora Borealis in the Northern Hemisphere.
This is our
planet, and this is the
aurora around the Pole.
I can also
show you
some of the pictures
from the Space Station,
from the International Space Station,
as it,
you see, flies.
And you see the
spectacular event.
What is the cause of them?
You have
energetic particles which interact
with atmosphere.
For example, red and green light
are related to
oxygen, atomic oxygen.
And there can be
also blue light related to molecules.
We see, for example here, mostly green light.
Interestingly enough, this aurora
can happen not only for our planet.
The planets which have
magnetic fields,
also experience similar
events, and this is Aurora Jupiter.
You see, even at Uranus
you have aurora.
Well, the boundaries of aurora
in the Northern Hemisphere are shown
here.
These are...
They depend on the intensity of aurora.
So, for example, this red light,
red line corresponds to most
intensive aurora.
Well, these are
interesting, spectacular phenomena,
and sometimes aurora can be so bright
that you can read a newspaper
at night, but
it also can be
pretty pernicious.
And it's important to understand
this event
to, for example, save
equipment on satellites.
This is the subject of space weather.
So, the idea is very simple.
You have the
generation of energetic particles
by Sun, and these particles then
propagate towards the Earth.
They're diffusing or
moving together with
the solar wind.
And it gives us
hours, around 18 hours, to
for example, switch off
equipment on our satellites
to prevent short-circuiting.
Well, but we should not switch
our equipment all the time.
The satellites-- they are not for fun.
They should work.
We should switch them off
only when it is necessary.
And to predict when it is necessary,
we need to know how intensive
is this event that is coming.
And this is space weather idea.
This is an illustration of
these particles,
and their interaction
with Earth's magnetosphere.
Magnetic field of the Earth protects
the planet, does not allow
these energetic particles to come
directly to
the planet.
And this is good,
but at the same time.
the perturbances in magnetic field
can create a lot
of problems,
because, for example, you can have
short-circuiting
of electric equipment;
you can have induction of
currents in these
cables;
you can have
disruption of communications
between satellites and airplanes.
And this is a very, very
serious issue.
It is estimated that the
effect of
such events could be,
could cost, usually,
several billions of dollars per year.
And as we have more sensitive equipment
in space, the price
may go up.
Well, sometimes we have
flares, which are unusually
bright.
For example, a typical solar flare
releases one hundred million times
of the world's consumption of energy.
But there can be
solar flares much more powerful.
One of these, or actually,
the most powerful recorded solar flare,
is the so called Carrington Event.
And this, when this solar flare
happened, it was,
aurora was seen near Equator.
And to such an event, if it happens
nowadays, can probably destroy
most of the equipment
in the orbit,
even if it's switched off.
But these are not probably the most
dramatic solar flares associated
with our Sun.
For example, the studies of
a particular isotope, Carbon 14,
in cedar, Japanese cedar,
revealed that
at that time, probably between
774, 775, there was an event
which was a thousand times
more energetic than Carrington Event.
This such event actually is
dangerous not only for
electronic equipment, but it's also
dangerous for biosphere.
And such solar superflares are observed,
in fact, for other stars similar
to our sun.
If you have a
substantial sample of stars,
and you observe them, from time to time
you see such events.
Well, let me touch
upon a rather
sensitive topic,
which is relation of solar activity and climate.
Well, solar activity.
Formerly, during
the solar cycle
as we have change of
the number of the sun spots,
we have a
substantial change of the solar flux.
But because of magnetic activity,
we can have a substantial
influence on what's happening on the Earth.
For example, if we are talking
about extreme UV, in this case,
the change of the flux of the
UV radiation is not 0.1%
as in just visible light,
but in extreme UV, it can be substantially
larger factor, factor 10 or more.
And this can have an appreciable
effect on ozone layer.
And it's very difficult, actually,
to understand the consequences of
all these changes, but we know that
during these
flares you have this change of the concentration
of ozone, and it can
have different consequences.
I will mention one of the consequences,
and it's related to La Nina
event in the Pacific.
It was found that
you change substantially precipitation
and temperatures in the Pacific region
during these solar flares,
and this is a result of a complex
processes change.
It's triggered by changes in the
ozone concentration, or the
ozone column densities.
Another important event
that we know
took place
in history
is the change in the number
of solar spots.
As I told you, Galileo was the first
who discovered
these solar spots.
Earlier on, they were also observed
in ancient Greece
and also in China, but then
no one was looking at Sun, somehow.
But Galileo found them.
Actually, he was using his telescope
but not his eye.
There is a joke that you can
watch your sun with your eye,
but only twice.
Once with your left eye,
then with your right eye.
(audience laughing)
So, he was not as stupid as that.
He was projecting this
on a screen and was experimenting.
And after that, the number of the
sun spots was studied.
And we know that there was a period
which is called Maunder Minimum,
during which there were essentially
no sun spots,
and interestingly enough,
this period coincides with
the so-called Small Ice Age.
This is
a picture of Holland.
You see, everything is frozen.
You travel to Holland
and you'll see it's not, nowadays.
Well, there was some other period of
low solar activity.
And this is Napoleon
in Russia.
The particular winter of 1812,
was extremely, extremely cold.
We know that Napoleon
lost his great army,
but it's less known that
Russian army lost
nearly all its cavalry
and guns, because it was so cold.
Well, there are scientists
who believe that there is
quite a relation between the
changes of climate and the
solar activity.
And this is related, actually,
not with the energetic particles of
the Sun, Sun also emits energetic particles,
but it's related to the energetic particles
related to the galaxy.
What would you say relation
of the solar activity and galactic flux?
The relation is through the solar wind.
There is a wind coming from the Sun
and its intensity depends on the
solar activity.
If you have strong wind,
you have a plarion around the solar system,
and less cosmic rays are coming from
the outside,
and less cosmic rays interact
with the Earth's atmosphere.
People
believe that this creates,
this is the key to the relation
of climate and solar magnetic activity.
What's happening?
If you have more galactic cosmic rays coming
into our atmosphere,
these cosmic rays passing through the
atmosphere ionize atmosphere, and this
creates the seeds for
drops of water.
Creates clouds.
And these clouds, when they are
at lower atmosphere,
reflect solar light.
If they're in the upper atmosphere,
the effect is opposite, interestingly.
They act more like
a blanket, not allowing
the Earth to lose its heat.
But in the lower atmosphere,
they create clouds, and decrease the flux
of solar radiation towards
the Earth.
And this is what they show.
They show that
there is
variation of
galactic flux
detected,
galactic cosmic ray flux detected
in the Earth and the cloud,
amount of clouds in the atmosphere.
They also claim, and this is
controversial, I will show some
data by other researchers,
that you can
essentially explain most of the
changes of climate
by this effect.
In terms of the
variations of climate, it's also interesting
that sometimes these variations of climate
are pretty rapid.
For example, they can happen in,
as here explained, in dozens of years,
which somehow acts
against a competing theory which tries
to explain the variations of climate
by the changes of
the procession of the Earth,
or some variations in the Earth's orbit.
Interestingly enough, this research
is also related to the Ice Ages,
to the motion of the solar system
within our galaxy.
As you know, our galaxy is a spiral galaxy,
and as the solar system moves,
it goes through this
spiral, and then space between the spirals.
And the intensity of cosmic rays is
known to be different in spirals
and outside spirals.
It's stronger in the spirals.
And so, this graph shows
the intensity of
this epochs of glaciation,
the periods of
Ice Age on the Earth.
Incidentally, we are still living in the ice age,
because ice age is defined by
the part of Earth history
where we have either
South Pole or North Pole, or both,
covered with ice.
And this relates to the
times of this glaciation,
and the flux of the cosmic rays
which was detected by a particular procedure
of studying meteorites.
So these people believe that
we can explain, essentially, all the changes
of the climate by
the flux of cosmic rays,
both in the during previous history,
through millions of years,
these are millions of years,
and on the time scale of
dozens of years and years.
So, in fact, in their papers they say
at least two-thirds of the variations of
the climate of our planet
can be explained.
Well, this is not an accepted point of view.
For example, there are some studies
which show that,
indeed, if we look at the
records of
solar activity, this is solar activity averaged
over an 11-year period, which is the cycle,
and this is the temperatures,
also averaged over 11 years.
And they say okay, this is
probably not bad correlation between
these activities up to, maybe, 1960,
even maybe further,
but later, we see a decorrelation
between this.
So the present warming is not due
to the cosmic rays,
and it's probably we humans
are responsible.
Well, accepting this,
the authors of the theory that I
showed you
do not agree.
They have different data,
and I will not go into all those details.
But what I believe, still, is not controversial,
is that there is still correlation
for earlier.
Maybe now, it's not correlated.
We are emitting
too much of
these greenhouse gases
in the atmosphere,
but we could not, probably,
deny the fact that there is correlation
between these activities.
And also, I showed you these
plots of the
clouds and cosmic rays, and these are
also plots from people who
argue against this
present correlation.
They say no, there is no correlation right now.
But nevertheless, for a substantial period,
you see this correlation.
So I think this is
difficult to deny that
this is an important fact,
and it's an important process to study,
and this is related to magnetic activity.
Well, if we think about climate variations,
it's really interesting.
We see really big changes
of the climate.
And irrespectively,
what is happening now,
it's a big scientific problem to understand
why we had these
big variations of climate
through the history.
Well, let me change the gear
and discuss something different,
but still magnetic.
And this is related to pulsars.
Our Sun is
magnetic star,
but there are stars
which are much more magnetic.
In some sense, pulsars cannot
be called stars, they should be
called corpses of stars.
Because these are the objects which
are created during
the death of the stars,
when the star dies, producing a supernova.
Interestingly enough, these
objects show very strong magnetism,
and they are observed
because it's magnetism.
So we have
neutron star.
This is probably 10-kilometer object,
with a mass
higher than the solar mass.
And all the matter is compressed
into neutrons.
So, electrons are squeezed into
the nucleus, and everything
forms neutrons.
And there are currents
in such a system which creates magnetic field,
and there is beam radiation
along the magnetic axis
of such a star.
And as this neutron star rotates,
from time to time this beam will be
pointing towards our planet
and we'll see
these pulsars.
There are, in fact,
more magnetized objects than pulsars,
and they are called magnetars.
In this object, their
magnetic forces are comparable
with the gravitational forces
which actually squeeze electrons into nucleus.
So, these are really remarkable objects,
and we have some evidence of their existence.
Interestingly enough, I showed you
the solar activities
in terms of the solar flares.
Now we believe that
similar to solar flares,
we can have flares on magnetars.
And it is also believed that the processes
similar to solar flares,
may be the source of
gamma-ray bursts.
These are the most energetic
events in the present universe.
In fact, if
a similar gamma-ray burst happens
somewhere in the vicinity of the star,
our Sun, meaning in the vicinity,
the galactic vicinity,
we would be completely exterminated.
There is no way to
be saved.
I talked about the corpses
of the stars,
but what about young stars?
Young stars also show a lot
of magnetic activity.
In particular, young stars
show jets, and jets
are ubiquitous phenomena
for different objects.
It's somehow related to the processes
of accretion,
and accretion is also
a magnetized process,
and when you accrete material,
part of this material will be ejected
along these jets.
And these jets can be collimated,
And they can be collimated for example, for galactic jets
over the distance of
many dozens, and sometimes hundreds,
of light-years, they're collimated,
they're directed,
and magnetic fields are responsible for this.
So, we have many
magnetic processes
also happening on the scale of
the galaxies.
And even our galaxy is
something that we
still need to understand.
Interestingly enough, the particular
event, or particular phenomenon,
of really gigantic proportions,
was discovered quite recently,
and it's called Fermi Bubble,
because it was discovered with a Fermi satellite.
This is a picture
representation of our galaxy.
And this is the cloud
of magnetized plasma,
this was discovered.
And you see this cloud
is comparable to our galaxy.
So, I touched upon,
in my lecture,
different phenomena,
on different scales.
And we are discovering more and more
magnetic phenomena
in astrophysics.
Let me just, in the last couple of minutes,
mention, for example, what I am doing
in relation to this big picture.
What I am doing is
related to
the process of annihilation
of magnetic fields.
So, we may have magnetic fields
of different direction,
and when they are frozen in plasma,
they have their own life.
And if these magnetic fields of different
direction come together, they reconnect.
This is the source of energy
for solar flares, for all these magnetic
processes that I was describing.
Interestingly enough, the process
of reconnection is still mysterious.
We don't have good,
well, it's not agreed upon,
I would put it this way,
what is the process which makes
the connection fast.
Interestingly enough, to explain solar flares,
it's not enough to have
a connection fast.
It also should be slow.
So, look how
mysterious is it.
Sometimes it's fast,
sometimes it's slow.
Why it should be slow?
Because we know that accumulation
of the magnetic flux for the solar flares
happening for weeks, and magnetic fields,
in this case, are in contact, and they are
reconnecting probably very slowly.
And then suddenly they start
reconnecting fast.
So, with my collaborator
we suggested a particular model which
develops the classical textbook model
of the process.
There this upper panel shows
this classical model of reconnection.
It's called Sweet-Parker reconnection
after the researchers who introduced this model.
This is the model in which
you have magnetic fluxes
in the opposite direction.
And the plasma, which is coming
in the vertical direction, is being ejected from
this slot of the size delta,
in the horizontal direction.
And you have the annihilation
of magnetic field
in this region.
What's the problem with this model?
It can explain slow reconnection,
but it cannot explain fast reconnection.
Why?
Because if you think about this,
what is this scale?
This is the scale of your magnetic flux tubes,
and this is astrophysical scale.
Big scale.
And what is
the other scale?
The other scale is microphysical.
It is determined by your plasma properties.
And this disparity of the scale
makes, through the conservation of your
matter, a connection velocity slow,
it's the velocity of the ejection
of the material,
times a very small factor.
Well, what we suggested,
we suggested to add
a natural phenomenon,
which we know exists in nature,
which is turbulence.
The real plasma
is not calm.
When we observe solar flares, we see
turbulent motions, turbulent plasma.
Actually, air in this room is also turbulent.
Blood in your big vessels
is also turbulent.
Turbulence is everywhere.
And the larger the scale, the more
turbulent phenomena we see.
We added this, and because of that,
we managed to explain
the processes of fast reconnection.
Because when you have turbulence
you can have much
larger outflow velocity.
And in some sense, this is
very natural process.
Turbulence is known
to accelerate processes of,
for example, mixing.
If you rely on
simple process of
molecular diffusion, you would need
four months for your coffee to become sweet.
You don't wait four months!
You just mix the coffee,
you create turbulence,
and that's it.
Okay.
I can show you
also, as the final note,
some simulations of
this turbulent reconnection.
And this shows
turbulence naturally develops
when we bring magnetic fluxes,
but use very
big boxes.
So this was testing of our idea.
And do you see this development
of turbulence, and enhancement of
reconnection, which is
related to it.
What we see actually,
and this is interesting,
such patterns sometimes you see
in the sky
with clouds.
This is Kelvin-Helmholtz instability.
We also see this
instability in these
turbulent layers.
I don't have time to describe you
the consequences of this
fast reconnection.
And we suggested a new theory
of star formation related to
this fast reconnection,
and also provided an explanation
of anomalous cosmic rays,
which were detected by voyagers.
But this is probably the subject of
more specialized lectures
I can answer your questions
if you have,
but for the time being,
thank you for your attention,
and I will be happy to answer your questions.
Thank you.
(applause)