RAW TRANSCRIPT -- NOT YET REVIEWED FOR CORRECTIONS BY CASSINI PERSONNEL

**FTS-NASA-VOICE**

**Moderator: Trina Ray**

**May 29, 2007**

**1:00 pm CT**

Coordinator: Excuse me. Today's conference is being recorded. If you
have any objections, you may disconnect at this time.

Ma'am, you may begin.

Amanda Hendrix: Thank you.

My name is Amanda Hendrix. I'm at JPL, and I'm the host of today's CHARM
telecon. And I'm pleased to introduced Dr. Wayne Pryor from Central
Arizona College.

Dr. Pryor has been involved in many lines of research, in particular,
studying aurora from Jupiter and Saturn using data from Galileo and
Cassini and Hubble Space Telescope spacecraft.

And today, he's going to be telling us about Cassini measurements of
Saturn's aurora, in particular, from the Ultraviolet Imaging
Spectrograph.

So, Wayne, please go ahead and start whenever you're ready.

Wayne Pryor: Okay. Well let me get started.

Amanda Hendrix: Thank you.

Wayne Pryor: I'm speaking today from Coolidge, Arizona. Nice, warm day
here. I'll be talking about Saturn's auroras from the Cassini
Ultraviolet Imaging Spectrograph.

I guess you're on Page 1.

Man: (Yeah).

Wayne Pryor: I'm going to click to the second page now. I'll be talking
a little bit about background of what auroras are in comparison of
Earth, Jupiter and Saturn auroras; then I'll get specifically into some
of the results we've been getting.

The auroras are important. For one reason they're important is because
we think they create a great deal of polar haze at Jupiter and Saturn.
I'll mention that and where we think that haze is coming from. We'll
also talk about how the solar wind varies, how that affects the auroras
and how they vary.

Next, in comparisons with Hubble Space Telescope data, and I'll present
some very recent data we've gotten, which shows some unique perspective
with Cassini above the pole of Saturn. We get a very nice view of the
auroral ovals.

Okay. So we go to the next slide. With that, we'll review, first off,
what the solar wind is. The solar wind is a stream of charged particles
coming out of the sun at several hundred kilometers per second.

The low density, it's not very much (stuffed) in the solar wind, a few
particles per cubic centimeter at the Earth. The main ingredients in the
solar wind are protons and electrons.

And then when those charged particles strike planetary atmospheres,
there's the potential for auroral emissions, which usually show up at
high latitudes on planets.

Go to the next slide, please.

Now, the auroras are not showing up everywhere on the Earth because the
Earth has a magnetic field, and it turns out charged particles do not
easily cross magnetic field lines. Instead, they tend to spiral up and
down magnetic field lines.

So on the Earth, which is more or less a (bar) magnet in the middle,
(access) if there was one (bar) magnet in the middle. It's difficult for
charged particles from the sun to strike at low latitudes; however,
there are places where they can hit at high latitudes, which leads to
the auroral displays we'll talk about. The actual field of the Earth is
produced by churning iron down deep inside the core of the Earth.

Okay next slide, please.

As the solar wind reaches the Earth, very complicated structures get set
up. We called (up the old) structure the magnetosphere. There's a
shockwave, (upwind), as the solar wind slowed as it gets near the Earth,
and then the magnetic field of the Earth is distorted by the interaction
with the solar wind, and you get this extended tail going downstream
from the Earth.

And then you can see up near the top of the Earth and the bottom of the
Earth, there are regions kind of - we call it the (cuff), where material
might be able to go in directly from the sun and strike and make
auroras. Other material from the tails may eventually work its way back
in and make auroras.

Okay, next slide.

This gets us up to Slide 6. As I said, the charged particles typically
do not cross the field lines very much. Most of these spiral up and
down. And there are certain active field lines that have currents
flowing on.

The currents flow up and down the magnetic field. And then when those
currents strike the atmosphere, light is emitted kind of like, you know,
fluorescent tube where electrons strike gases and make emissions of
light.

So next slide, please.

So on the Earth, the auroras, these beautiful displays, as you can see
at high latitudes are often colorless; but if you have particularly
bright one, it may seem to have color to you, red or green, very
complicated displays of (unintelligible) (and curtains). Mostly, what
you're seeing are electrons, striking the gases in the atmosphere of the
Earth, lighting things up.

Man: Somebody's at my door.

Wayne Pryor: Going to Number 8, if you can get above the Earth and look
down the aurora, you'll see that it actually has a lot of structure to
it. This is a shuttle image, which says the aurora is organized as kind
of a long, extended wall of light. One interesting thing here is the top
of the emission is red.

There are other colors further down, blues and greens. These are
different emissions of the atmospheric gases near the atmosphere. And
this picture is taken from 300 kilometers altitude.

If you go to Slide 9, the view you get from much further back where you
can now see the Earth as a whole, the oval shows up. That is, the
auroras are showing up as a big oval around the pole, and you can see
the - if you live, say, in northern edge of Alaska or somewhere in
Central Canada, you get a pretty good chance of seeing the light
displays. It's rare to see them further south.

And the aurora really - or really is organized as kind of a circle
around, not true north of magnetic north to somewhat offset from the
North Pole.

So let me go to Slide 10 now.

Now, my research interest is primarily not the Earth, but you may see
some similarities between what you see in Slide 10 or what you saw on
the previous slide.

Jupiter and Saturn also have very remarkable auroras, and they're quite
strong. The ones at Jupiter are much stronger than the ones at the
Earth, and the ones at Saturn are intermediate in strength between the
ones at Jupiter and the Earth.

If you look at the Jupiter aurora, which is shown in the image on the
right, you'll see that it looks different at the two different ends of
the planet.

The one on the south end, the bottom end, you see mostly (grayed)
against the edge of the planet.

The one in the north, you can see quite a bit more emission. You see an
oval facing you more.

And the reason they're quite different, north and south, is because the
magnetic field of Jupiter is quite distorted. It's not a simple dipole
magnet field.

The one on Saturn, as you can see, is more confined at the polar region
of both poles. They're somewhat simpler magnetic fields.

(One thing) I want you to notice in these pictures is that, you get away
from the light that's showing up at the ends of the planet, the
background clouds are actually kind of dark at high latitudes. That's
true for both Jupiter and at Saturn.

And we think those background clouds are dark because the chemical
reactions that are triggered by the auroras and make dark material in
the atmosphere.

Going to Slide 11.

Amanda Hendrix: So, Wayne, when you're talking about the dark material,
it's kind of in the area surrounding the aurora (with)...?

Wayne Pryor: Yes.

((Crosstalk))

Amanda Hendrix: Okay.

((Crosstalk))

Wayne Pryor: It's kind of like the smoke around a fire. So you can see
those bright emissions in the picture, and the dark material near it is
sort of the smoke that's been produced as the result of reactions in the
aurora.

Amanda Hendrix: Okay.

Wayne Pryor: Okay. Number 11 kind of summarizes some of the differences
between the three planets we're talking about. On the Earth, the aurora
seemed to mostly be controlled by the solar wind. It's kind of organizes
everything it produces and most the material that's involved in the
auroras.

On Jupiter, it's quite a bit different. Most of the material that
surrounds there actually comes from one of the moons of Jupiter, the
moon Io, which has active volcanoes, which are spitting out sulfur and
oxygen, some of which makes it out into space and then fills the region
around Jupiter.

And the plasma created from that sulfur and oxygen is what ultimately
ends up hitting the atmosphere and making the auroras you saw in that
previous slide.

Now, in Saturn, we're still trying to figure out what's going on a bit
more. But it seems to be true that there is solar wind effect on Saturn,
as we'll show it later. And there's also a lot of internal material
there at Saturn that is stuffed around Saturn, mostly oxygen and
hydrogen, which come from water.

And the source of that water is a couple of places \-- one place in
Saturn's rings, which are rich in water ice, and the other is the moon
Enceladus, which we've learned from Cassini, has active geysers that are
shooting out water in space.

So those are sources for a lot of the material that's going to show up
in the magnetosphere and some of that material later (ionize) and then
strike Saturn and makes the auroras on Saturn.

Amanda Hendrix: So the material from Io or Enceladus then can get sort
of picked up and travel along the field lines into the polar region?

Wayne Pryor: That's it, yeah.

Amanda Hendrix: Okay.

Wayne Pryor: Okay going to Slide 12. I'll be mentioning today mostly
data from the Cassini UVIS. I'll also briefly mention something from
VIMS. These are a couple of the instruments bolted to the Cassini
orbiter, which is shown in the picture on the left.

The UVIS is in sort of pink color there, the arrow pointing to it. It's
bolted to the spacecraft. If you want to look at something, you have to
turn the whole spacecraft.

On the right is the blowup of the instrument, the Ultraviolet Imaging
Spectrograph, which has several channels on it. I'll be talking about
results from a couple of the spectral channels today \-- the extreme
ultraviolet and the far ultraviolet channels. And there you can see the
Buffalo on there, that's the University of Colorado mascot. This is
built at the University of Colorado.

Going to Number 13 now, we've got some sample data from this instrument
from two of the channels \-- the extreme ultraviolet channel and the far
ultraviolet channel.

And it's really complicated. What you're seeing is data on the detectors
for each channel, making an array, which in one axis or one dimension is
spatial information along this spectrometer's entrance slit. The other
axis is spectral information \-- information about the different
wavelengths of light that's present

And in the - one on the left, it's the EUV channel. You'll see towards
the middle, something like spatial pixel 32, 33, somewhere in there, you
see a bright band of light going left to right. Those are emissions
coming from Saturn. Those are excited emissions from hydrogen molecules
in the atmosphere.

Similarly, in the figure on the right, you follow over pixel 32, 33 -
spatial pixel 32, 33, you'll see again yellow emissions going left to
right, which are again hydrogen that's been excited at Saturn. The
hydrogen is excited by electrons hitting it, primarily, in the auroral
regions.

You'll also see a blob a little further down that's over - in the right
side over near 1800 Angstroms and spatial pixels like 20 to 30, that's
reflected the sunlight from the Planet Saturn. So we have information
that reflected sunlight as well as information about the auroras coming
in to the instrument.

Also, notice around 1200 Angstroms just to the right of 1216 Angstroms,
you see a yellow stripe going up and down all the way across the spatial
direction, and that's hydrogen, atomic hydrogen in space near Saturn.
Also some of it is on Saturn.

Okay going to Number 14, which shows the slit I mentioned previously,
(pasted) on the planet. In this case, you're pointing at Saturn, and
then data is recorded up and down that slit, and different spatial
pixels are 64 spatial pixels along the slit. And then, for each spatial
pixel, we get a spectrum.

Sometimes we just do this, (obtain) spectra this way. Other occasions,
the slit is slowly moved back and forth sideways, which allows us to
build up images. So in some cases, we have images of Saturn and spectra
for each location of the images. So there's lot of information the data
sets.

Now, in the picture you see in front of you, there's a little bit of
green inside the slit. Those are actually emissions from Saturn showing
up there. In the northern end, it's aurora light. In the southern end,
it's auroral light. In the middle, there's some reflected sunlight
showing.

The auroral emissions are showing up from molecular hydrogen and from
atomic hydrogen. The reflected sunlight you see is actually created by
scattering in the atmosphere of cloud particles and of molecular
hydrogen.

And on top of that, there are actually some absorption features we can
pull out of the data. The absorption features tell us about gases in the
atmosphere. One of the main ones we've spotted there is acetylene,
which - acetylene is C2H2 \-- a hydrocarbon gas.

Okay, so going to Slide 15 now. I mentioned you can make images. Here is
an example where images were constructed just about the time Cassini got
to Saturn, that's July 2004.

The image on the top is an ultraviolet image of Saturn at the atomic
line of hydrogen. The image in the bottom is molecular bands of H2, and
they look a little bit different. And the reason for that is because
there is atomic hydrogen out in space around Saturn and not much
molecular hydrogen.

Atomic hydrogen in space, if you look at the top picture, you can see
there's sort of blacky region around Saturn, outside of the rings. It's
a little bit brighter than the rest of the frame.

And that's actually atomic hydrogen in extended region around Saturn.
When atomic hydrogen fills that region, eventually some of that will be
ionized and available to make auroral emissions of the planet.

The source of that hydrogen we're not so sure about, but some of it is
coming from the rings and some of it is probably coming from the
atmosphere of the planet. How much of each we're still trying to figure
out.

And at the end of the planet, you can see the auroras showing up in both
the top and the bottom picture.

Okay going to Slide 16. We're taking a look at how extended that
hydrogen cloud is. And what is shown here is how much light is present
as you move away from Saturn in the hydrogen channels. And that the
black one is probably the most interesting one here.

It shows that if you look at the black curve, which is an equatorial cut
across the previous sorts of pictures, that the amount of hydrogen
decline as you go away from Saturn, but there's hydrogen present all the
way out to at least 40 Saturn radii out. So there's a big cloud of
hydrogen extending out in space (the ring of) Saturn.

Okay going to Number 17. We've also obtained a lot of UVIS images that
emphasized atomic oxygen, which shows up that 1304 Angstroms or 130
nanometers. And again, it has sort of this wider and tall appearance
where you see material, which is atomic oxygen in the region around
Saturn.

Saturn is marked here as a circle. You can see the rings are marked on
here. And there are a couple of yellow blobs well away from Saturn,
which are atomic oxygen out in space.

So again, this is a water product, oxygen like hydrogen can come from
water, and it's filling the magnetosphere and it's available there and
become ionized and then some of that material can move up and down the
field lines and strike Saturn and make auroras.

Okay. Going to Number 18 showing you the kinds of spectral information
we get. Here we've compared Jupiter's spectrum and Saturn's spectrum.
And you can look hard for differences, and there aren't very many.
They're both very similar in terms of just the up and down variations.

There are many wiggles there. Those are different wiggles, which are due
to transitions in molecular hydrogen from a couple of the band systems
of molecular hydrogen, the Werner and Lyman band systems.

There is, however, a significant difference between the two. We've had
to scale them. Jupiter was reduced in brightness. Saturn was increased
in brightness because, generally, the Jupiter auroras are much brighter
than the Saturn auroras, (like a factor) of 100 or more. Jupiter has
very intense auroral emissions.

Going to Number 19.

Man: Before you leave 18...

Wayne Pryor: Yes.

Man: ...could you tell me what the intensity is measured in, kR/A?

Wayne Pryor: Okay. The units are kiloRayleighs per angstrom.

Man: Okay.

Wayne Pryor: A Rayleigh is a measure of brightness.

Man: Yeah. Thank you.

Wayne Pryor: Okay, going to Number 19.

Here's another spectrum of Saturn. This one I want to just show that
it's - a spectrum of Saturn is actually somewhat similar to a laboratory
spectrum obtained in the laboratory of Colorado, where they took the
instrument into the lab, put in the vacuum chamber and run a current
through hydrogen gas, and that produced the red spectrum. It is rather
similar to the black spectrum you get from Saturn. There are a few
differences.

The long wavelengths are quite a bit different, because Saturn also has
reflected sunlight, which is what shows up at the long end.

Another difference is that there are absorbing gases in the atmosphere
of Saturn, primarily methane, which absorbs some of that shorter
wavelength light on Saturn, and we can actually model that, which is
shown as the sort of a brownish orange color. We've added some methane
into the model, put it above the lab spectrum.

And the comparison is pretty good to the actual data. There are some
discrepancies we argue about to maybe the other absorbers, but we're
still trying to figure some of that out.

Okay. Going to Number 20, extreme ultraviolet spectrum of Jupiter and
Saturn are shown here. The solid is Saturn. The dash is Jupiter. Again,
they're very similar.

There's also a dotted spectrum shown at the top curve there, which is
the lab spectrum, again, where electrons were fired through hydrogen gas
and (unintelligible) the instrument.

Some differences there - but again, it is - they are similar enough to
be convinced it's molecular hydrogen. The differences are pretty well
understood in terms of self-absorption, and they're very thick hydrogen
gas on these gas giant planets. And I'll show models of that later where
we can actually fit that spectrum.

Number 21, here's the case where we were able to do extremely good
imaging of Saturn, where the UVIS slit was moved up and down. It was
aligned east west and moved up and down to create two images of Saturn.

And these are bit fairly heavily processed, but this is real data where
it's been color-coded here so that the orange shows reflected sunlight
coming from the rings of Saturn and the atmosphere of Saturn. And the
blue is showing the atomic and molecular hydrogen emissions from the
auroras.

These two images were taken about an hour apart, and you can see by
comparing the two that the blue region at the bottom is changed
somewhat.

Different parts of it are brighter in one than the other. Particularly,
the changes are most obvious inside the oval where we think the auroras
are more directly tied to changes in solar wind conditions. And those
things change fairly quickly.

We were actually able to use deconvolution. It turned out to make these
images look fairly crisp (using some canned) deconvolution algorithms
that are available in the language IDL.

((Crosstalk))

Wayne Pryor: And we could tell - sorry?

Man: Pardon me, I have a question.

Wayne Pryor: Please.

Man: Could you clarify what you just said a minute ago that the -
earlier you mentioned that the particles of the aurora were not from the
solar wind particles.

They were from, you know, particles that are near Saturn, but I think
you just mentioned that solar wind does play a - it does play a part in
the auroras of Saturn. Could you clarify the difference between that?

Wayne Pryor: Yeah. I wish I could. We're still trying to figure out
what's what here, and I went to a meeting last week in (Iowa), where we
argued about what's what in there.

Man: Okay.

Wayne Pryor: But it's usually true that the stuff right near the pole is
more likely to be solar wind material.

Man: Okay.

Wayne Pryor: And the stuff further from the pole is more likely to be
tied to the magnetospheres of Saturn and the material from the Enceladus
or the rings. So the main ring there may be more tied to Saturn-related
material, and then the center stuff might be more tied to changes in the
solar wind. We're still trying to decide if that's true or not.

Man: Okay great, great.

Does - do the two interact? Does the - can the solar wind cause
variation in the other particles as well?

((Crosstalk))

Wayne Pryor: It probably does. It probably compresses the whole field,
which will affect how many precipitate, how many (come on) down to the
atmosphere.

Man: Great, thank you so much.

Wayne Pryor: Okay.

Okay going to Number 22, where I've shown with the latitude grid, more
or less, where the auroras are coming from. In this case, it's something
like 70 to 75 degrees south, so it's fairly close to the pole on the
oval. This is pretty high latitude emission.

Going to Number 23, now we're using images from a different instrument.
This is the imaging - the camera on UVIS not - sorry, the camera on
Cassini \-- the ISS.

And I want to call your attention, first off, to the fact that it's
generally kind of dark in the polar region, and there's something very
strange right in the middle of that dark area.

There's a concentration of dark material right at the south pole of
Saturn, which is pretty interesting stuff. And I think it has something
to do with the auroras, as I'll try to explain in a minute here.

Let's go to Number 24. This is a better view from the camera of that
south polar storm. I like to think that this is like a bathtub drain. I
think it's a region of downwelling or material is going down and being
concentrated.

I think dark material that was produced over a large region (seeing
that) the auroras have now been concentrated inside this sort of tunnel
and making the (circles) seem rather dark. I really love this picture.
It's a beautiful storm.

It turns out the spectrum we got right at the spot was quite a bit
different than our other spectrum. I've been trying to understand that
for a while now.

Going to Number 25, we'll talk a little bit more now about this haze
business. As I mentioned earlier, there seemed to be a lot of haze
around the auroral zones. The figure on the lower right is information
from two older - two previous spacecraft at Jupiter.

One was from Voyager, which is the Photo-Polarimeter. It's called PPS
here, and the other was data from the Galileo ultraviolet spectrometer.

What is shown there are cuts across planet going north south, showing
how reflective the atmosphere is at different latitudes. And what it's
showing you is that at very high latitudes at both poles, it gets quite
dark, and it's a dark absorbing haze material.

And on Jupiter, the dark absorbing haze material is dark over a wide
range of latitudes near the North Pole down to, say, 40 or 50 north. On
the South Pole, it's not quite so extended in latitude.

And that difference we think has to do with the difference in the
auroras. That is the aurora is spread over a lot of latitudes in the
north; the aurora is confined to polar latitudes in the south.

So it leads to a broader region of haze in the north and a smaller
region of haze in the south. And that was seen at the - from a couple of
spacecraft almost 20 years apart.

Okay. Going to Number 26, on Saturn, again, there's a relationship
between the aurora and the haze. You see in the Hubble picture and - now
I've got - on the right, I've got Voyager data for two planets \--
Jupiter, which I just showed you and now I've got Saturn on there also.

Saturn also gets dark towards the poles over by 90 on the right
latitude. You can see the reflectivity \-- I over F drops down below
0.1.

The only (first) - (for a) limited range of latitudes, that is only at
higher latitudes on Saturn, these are much of this haze. It's fairly
well confined to the region near the aurora oval.

So we think there\'s a connection between the aurora and the haze. So
far it's just coincidence in geography, but there - I think there\'s
more to the story than that.

If you go to 27, it talks about a little bit about modeling efforts that
have been made to understand this haze-making process. A number of
groups have worked on this.

And the story seems to be that if you take methane and you ionize it in
the auroral regions that chemistry started that leads to formation of
polymers, that is, long-chain hydrocarbons that eventually can make
hazes.

And so, we think that those dark regions are full of hydrocarbon haze in
the upper atmosphere of Jupiter and Saturn.

One of the important molecules that is expected to come out of this
process is benzene, the basic ring compound in organic chemistry. It got
six carbons and six hydrogens.

And we think that benzene would be a good starting place to make a
multiple rings \-- polymers and produce haze particles and some of the
chemists who have looked at this think that benzene should be very
important.

So we had looked at the data set we had from 2005, Day 172, which I
showed you a minute ago that was the one that was - had an orange planet
and blue haze at the poles - I mean, and blue auroras at the poles.

(Now, it) had a very nice spectrum right at the polar region, which we
were able to test to see if there were any usual compounds in that.

So I\'m going to Number 28 now. What is - this is one where the PDF file
is a little bit perturbed. You'll notice that the wavelength numbers are
not in a straight line anymore, that (broadens) to be fixed eventually.
But what is shown there are images at different wavelength bins from the
Cassini UVIS data.

The one on the left shows wavelength 1738-1816. If you look hard there
you\'ll notice it's extremely dark right at the pole in both of those
tests across the pole it's quite dark.

If you look at the next one over, which is supposed to read 1816-1894
Angstroms, it's actually been - it's overlapping some other words (in
mind), unfortunately. This one did not a show dark spot right at the
pole, although generally dark.

The third image shows the ratio of those two images emphasizing there\'s
a very dark spot right at the pole. This is unexpected. This was just
something I was looking around to see what kinds of things were in the
data. We found there was a wavelength bin, the on the left, 1738-1816,
where it was quite a bit darker right at the pole.

And then, the fourth image shown there, shows you where the aurora is.
You can see the dark spot is actually - dark spot in the third image is
actually somewhat inside the auroral region.

And we think that dark spot there corresponds to that dark (eye) I
showed you a minute ago in the camera images. It was showing up there\'s
an unusual ultraviolet feature as well as an unusual camera feature.

Then the spectrum shown here is a ratio spectrum and we\'ve compared the
spectrum of that dark spot to the region around it. And the data is kind
of noisy. I would like to get more spectral like this and clean it up
later. But there is a general broad dip centered around 1715.

And we think that that general broad dip is due to benzene, which is
concentrated. It's produced by the aurora and then concentrated by the
circulation pattern and concentrated right at the south polar spot.

Going to Number 29, it turns out we have good sensitivity to benzene in
our data. The bottom panel shows how strongly benzene absorbs at
different wavelengths. It turns out it absorbs quite strongly at the
wavelength where we're seeing our dip.

Also shown the absorption cross-section (unintelligible) acetylene that
is C2H2, which has a lot more structure, a lot of wiggles in it. And we
think both of those are contributing to what we actually see on Saturn.

So on the - the top one, we\'ve actually modeled the dip. The way we
modeled the dip is to put some benzene in and put some acetylene in, and
we can actually fit the absorbed spectrum by putting a fair amount of
benzene right at the pole. We think, again, that benzene is produced by
the auroras.

So this is kind of a Cassini discovery. We think there\'s enhanced
benzene right at the pole on Saturn. Benzene had previously been
detected and the global average from - I believe, it was the ISA
spacecraft.

Okay, going to Number 30...

Amanda Hendrix: Quick question, Wayne.

Wayne Pryor: Yes.

Amanda Hendrix: When you say it's a mixing model with, you know,
particular amount of benzene...

Wayne Pryor: Yes.

Amanda Hendrix: ...is it easier to tell us what the other stuff is that
you put in there?

Wayne Pryor: It's also got acetylene. It got two absorbers.

Amanda Hendrix: Okay, just the two? Okay.

Wayne Pryor: Yeah. And that seems to fit what\'s going on.

Amanda Hendrix: Okay, cool, (right).

Wayne Pryor: Okay going to Number 30, there\'s another instrument on the
spacecraft, which should be able to see benzene, that's Cassini CIRS,
the infrared instrument.

And I checked with them to see if they were seeing enhanced benzene at
the polar region and they also reported seeing enhanced benzene at the
polar region, so that's a confirmation that there seemed to be more
benzene there being produced by the auroral chemistry.

And that's - shown here there\'s a C6H6 on this figure, up and down bar
pointing to our little feature in the spectrum. I guess, (it's near
wave) number is 674, where they confirmed they are seeing some benzene
there, near the polar region, this is that (80 south) in their data. So
I think that story is coming together that there is enhanced benzene at
the polar region.

Okay going to Number 31, now I\'m going to start talking about solar
wind time dependence in the aurora.

Here we got some data taken during an unusual opportunity when the
spacecraft was out in the solar wind and we are able to observe the
aurora at the same time. So we could see what\'s happening in the solar
wind and then see how that affects the aurora itself.

Most of the mission we can\'t do this. But for this brief period, we had
the right geometry to do this, over about 50 days.

Going to Number 32, it's a little hard to explain but what\'s shown here
is the brightness seen in UVIS as a function of day and a function of
spatial pixel, you know, see that about spatial pixel 30 going left to
right across, there\'s a bright band, that's the South Pole in southern
aurora on Saturn.

There\'s also on arc moving across, which is also bright going from the
(in) on the left side to the (in) on the right side, that's the northern
auroral oval.

And these sides of the planet changed over this period on the detector
because the spacecraft was moving with respect to Saturn, sometimes it's
bigger, sometimes it's smaller.

And I marked on there, a solar wind shock, you could select day 2007.
And the response of that solar wind shock when a pressure pulse came by
in the solar wind, the auroras got substantially brighter.

And there are other examples in there, where (a brightening) of that -
when it brightens at one pole, it seems to brighten both poles, which
you might expect.

Okay going to Number 33, here we have the same information from UVIS
(unintelligible) in the top panel, that is how bright the aurora was on
different days.

And again, I\'ve got that shock marked. Shock is marked on the bottom of
this and there's actually the second shock showing up here where you can
see brightening events in the UVIS data.

So it's interesting to see what else was going on. There are other
instruments on the spacecraft that can tell us about solar wind
conditions.

The second panel shows what\'s labeled SKR. This is radio data from the
spacecraft. And the radio data is sensitive to the auroras also because
the auroras produce radio noise. And I think you can see that during the
shock event, there is a little bit of extra radio noise produced.

The third and fourth panel show the magnetic field changes. Again, about
where that shock is marked, you can see the magnetic field jumps
strongly and stays high for a while.

(Tapers off) and then jumps again about a day to 30 something. You can
see at least a couple of shocks in here where the magnetic field jumps.

The bottom two panels are showing the solar wind conditions, in this
case, the proton densities and velocities. You can see the densities
jump dramatically at those shocks. So you suddenly have a lot more
protons, higher magnetic fields, and that increased pressure seems to
drive the aurora to bright.

Going to Number 34, several times during the mission, we\'ve been able
to coordinate Hubble observations in Saturn with Cassini observations.
The slide had some details on the first of these campaigns when Hubble
with the ACS, an instrument which is now (unintelligible) on Hubble, was
able to image the Saturn aurora the same time Cassini was imaging the
northern aurora or taking spectrum of the northern aurora, I should say.

And going to Slide 35, you can see auroral images from Hubble. These are
a little bit better spatial information than we ever get out of Cassini
so you can get some idea of - some of the details you can see.

The arcs are not entirely complete. Some patches of the arcs are
brighter than others and from frame to frame, things change. In general,
this was considered a weaker aurora day. There have been days when a lot
more was going on on Saturn's auroras.

Going to Number 36, this shows where the UVIS was looking at the same
time. So while the camera was looking at the sunlit pole, we were
looking at the night side pole with UVIS.

And going to 37, shows where we\'ve obtained data. I marked on here in
red, places where we saw the aurora, in green are places where we did
not see the aurora. And again, you can see that the auroras are showing
out at latitudes between, say, 70 and 80 latitude.

In this case now, it's this - the northern aurora as seen from UVIS.

Going to Slide 38, it shows - the spectrum I got at this time, which
looks - again, looks a lot like a spectrum you get in the laboratory,
electrons hitting hydrogen.

So during this campaign, we succeeded in getting a nice spectrum to go
along with the images from Hubble. And we'll be working that up with
some detailed models.

Okay. If you go to Slide 39, this shows one of the detailed models
produced by (Jack Gustan) at the University of Colorado, where he\'s
been able to fit the details of the extreme ultraviolet spectrum with
the solid brown being the model, black being the data and very good
agreement as seen in fitting the features in there. The features that
are showing up - show up as a result of the process called
self-absorption in hydrogen gas.

Dash line shows you what you would see if there was no self absorption,
and it's quite a bit of different from the spectrum we've seen, which
tells us that the aurora is showing up from a significant column of
hydrogen, that is, it's produced fairly deeply in the atmosphere and a
hydrogen column of about five times 10 to the 20th per square centimeter
and at a temperature in the upper atmosphere of about 500 Kelvin. The
upper atmosphere is fairly warm there.

Okay. Going to Number 40, some of their fairly recent stuff. Here's an
image obtained when the spacecraft was finally able to get well above
the plane of Saturn rings and look down the auroras as a whole.

And this nice image shows that the ring is - auroral arc makes a pretty
much complete oval, with even nice little bright spot inside of it,
which again is probably tied to things in the solar wind - features in
the solar wind. We haven\'t got very many of these images yet, but
they're very valuable to look at.

Going to Number 41, this is a piece of a movie we got on Day 96 at this
year. And I\'m showing the geometry in this slide. We're looking at the
northern aurora and that little frame in there with the red and the blue
actually shows the aurora emissions on the planet.

((Crosstalk))

Amanda Hendrix: So is this a similar geometry to the one on the - or on
Slide 40?

Wayne Pryor: Say again.

Amanda Hendrix: Is it a similar geometry - are we looking at the same
kind of thing then?

Wayne Pryor: Similar sorts of geometry to the previous one, yeah.

Amanda Hendrix: Okay. (So just) give it a color scheme. It's showing...

Wayne Pryor: Yeah. I'm playing with colors.

Amanda Hendrix: Okay.

Wayne Pryor: The nice thing about this newer one is there were nine
images obtained and I'll show those in a minute, which is enough to look
for variations.

And the images - each one took about two hours to obtain, and they're
obtained over long enough period as Saturn had completely rotated and
started to repeat itself. So we could start to look for a fix to the
Saturn rotation.

Okay, so going to Number 42, which shows those nine frames in this first
movie we got. And these frames are, again, are about two hours apart.
Saturn is rotating something like 10 hours, so this is long enough that
you get more than one rotation of Saturn showing - slightly more than
one rotation and the pattern starts to repeat.

And you could see the patterns are different from frame to frame.
There\'s a lot going on in here. We're trying to figure out this
picture.

A few things I can say about from looking at it here, there are some
spiral structures that show up. There are multiple arcs that up, more
than one auroral arc.

In a couple of cases, you can see the light inside the oval. There's a
lot of fun things to try to figure out. And then, as I'll show in a
minute, some of the patterns actually repeat after an orbit - after a
rotation rather.

Going to Number 43, this one is a polar projection of the data that was
previously shown, where now I\'ve got things laid out so that the
repeating patterns are above each other.

So for example, the one at the top left goes with the one on the bottom
left. The next one over goes with the one below it. And so, I was trying
to see if things repeat, and there definitely are some repetitions
showing up in the - patterns as going on.

In general, the auroras are brighter on the dawn side, but some things
seen to be rotating around.

So to help the eyeball on that, I\'ve drawn a little spiral on there in
black, which is at the fixed set of latitudes and longitudes, tracing
out some of the brighter features and I watch to see it rotate around to
see if those features would, in fact, rotate around.

And it looks to me like there is some stuff rotating around, but as of
doing so, it becomes dimmer as it gets around to the bottom which is the
dusk side, then becomes brighter, again, when it gets back around the
top of the dawn side.

So we think on the dawn side, things are more compressed and that seems
to drive auroral emission, whereas in the dusk side things are more
expanded in their list likely to have auroral emission. But there are
(blobs) rotating around in this movie clip we got.

Okay, going to Number 44, this is the same movie now, shown in the
bottom, frames going well across from one through nine. And above it
now, is data from a different instrument, the INCA instrument, which is
measuring energetic neutral hydrogen near Saturn, in the magnetosphere
of Saturn, in the ring plane.

And what I want you to notice is that their data has spiral structures
in it. And the UVIS data spiral structures in it, and we're in the
process of trying to see if they're related.

So for example, if you look on their top row there, the second frame
over shows a fairly bright orange and red (blobs) were over five frames
to the right, you again see a fairly bright orange and red (blob), sets
of patterns repeated after a rotation.

Similarly, if you go down and look at the UVIS frames, the patterns kind
of repeat after about five. If you look at the one in the bottom left
and you go over five frames, the pattern, again, is kind of repeated.

So you think things are rotating around and then become active when they
get to the dawn side?

And we think there are connections between what seen in the ring planes
and what's seen in the auroral zone, which is telling us in this case
that we think that the auroral emission is tied to the ring plane
emission and not more - not directly to the solar wind, which was kind
of puzzling. Some people who've been putting the other story forward
that it was more solar wind controlled.

Going to Number 45, this shows the orbit that was involved for this
period. It's showing where Cassini was moving in space during this
period. The date in question was Day 96, which I think if you're - may
be a little bit small to see here, but if you can find Day 96 on there
and you can see where the spacecraft was at that time.

And the reason we carefully looked at the spacecraft trajectory is we're
trying to see if Cassini was anywhere near the right place to be sitting
on an active field line, that is a field line that's creating the
aurora.

You would love to be on - at one of those situations where you're on the
auroral field line measuring the particles, at the same time, you're
watching the aurora in the atmosphere and we haven't pulled that up yet.
It turns out we just missed on this occasion.

Going to Number 46, it shows you where the trajectory maps on to the
planet. And it turns out that on Day 96, which is the date of the
observation, the spacecraft was not actually on the field line that was
making light. It was actually somewhat inside of it. So I marked in red
there at the bottom of all of this.

That we were just inside the UVIS oval at that time, that is the
spacecraft was not sampling active field lines. So the particle in field
instruments can't tell us too much about the aurora on that day.

Although we'll keep trying during the rest of the mission to see if we
can get a coordinated observation where we get the auroral emissions. At
the same time, we measure the fields and particles of data from the
spacecraft on that field line.

Amanda Hendrix: So the plot on Page 46 is showing us how...

((Crosstalk))

Wayne Pryor: Showing you where on the auroral - where on the planet,
where on the ionosphere the field line hits. So if you've seen Number 96
there, Day 96, you see that that falls between 5 degrees and 10 degrees
from the fall, something like 7 or eight degrees.

And at that time, the auroral emission was not getting that close to the
fall. So we were not on an active field line that day, assuming of
course that the model for the magnetosphere is reliable.

But as I'll show in a minute, it looks like we really did have a quite
day in the magnetic field, not much was happening that day.

So I'm going to go to the number of...

((Crosstalk))

Amanda Hendrix: ...showing me the trajectory of Cassini maps on to
this...

((Crosstalk))

Wayne Pryor: Mapped on to the ionosphere on to the planet itself.

Amanda Hendrix: Oh okay.

Wayne Pryor: I wasn't that clear on that, sorry.

Okay going to Number 47, this shows some of the magnetic field data for
this day. And Day 96 is the day in question. Magnetic field does not
change much on that day.

There's not a whole lot going on. There were other days when there was a
lot more activity if you look along in time and those might have been
days when we actually - we're on active field lines.

The Day 96, when we have the good auroral observations was not a good
day in terms of the particle and field measurements.

Going to 48, it emphasizes that point. Again, we've blown up that period
in magnetic field data.

And there's a little bit of action about our four, but really not very
much is happening in the purple region. It's a pretty quiet day in the
magnetic field, not a lot going on. You can try that experiment a few
more times to see if we can actually catch an active field line while
we're looking at the auroral emissions.

Okay. So the Number 49 kind of summarizes the results from that first
auroral movie we've got. Again, it's a nine frame movie, shows the
auroras at times who have multiple arcs, a fair amount of spiraling
structure, the auroras are showing up at 70 to 80 north, generally
brighter on the dawn side.

And it looks like we missed being on an active field line, that is, we
did not actually catch the auroral particles, the auroral fields while
we're measuring that aurora.

The INCA comparisons were kind of interesting. INCA showed spirals,
directionally spiraling outwards, while the spirals that we see are
spiraling inwards, and that sounds strange.

For what that actually turns out to make sense is that if you get
further out from the planet, the field lines actually map in closer to
the pole.

It turns out that the pattern and the spirals we're seeing kind of makes
sense, although we have not yet done the detailed mapping to see if we
can map one structure directly on to another. That's work in progress.

We also saw some repeating patterns. It suggests their (blob) is
rotating around in longitude. So it's - things are kind of controlled by
the magnetosphere. It is so rotationally controlled.

But the fact that we saw it always brighter on the dawn side says, there
also is some roll, the solar wind is playing. It controls local (time)
effects like that.

In the future, we'll be able to use spectral information, try to decide
just how energetic those electrons were to make that map. And we'll do
that in the future.

Okay going to Number 50, reminding you that there are other instruments
on the Cassini. Here's another one called the VIMS, is also getting
auroral images.

This one was provided by Kevin Baines, showing you - this other
instrument is also showing nice auroral images. This is - in this case,
emissions from H3+ ions in the atmosphere of Saturn.

So we're still trying to coordinate to get (these) images, while they're
getting (these) in images that they don't always work out that well
because they have different strategies than we do. But it's nice that
there are more than one instrument available to take this kind of image
of the aurora on Saturn.

Okay, Number 51, since I turned this presentation in to Amanda last
week, we've actually gotten two more of these movies, which are not on
your PowerPoint, but I'll tell you. We've got them in hand. They look
nice, so we're going to have more of these movies to release in the
future.

One nice thing I'm seeing in this stuff is there's a lot of activity
right in the middle of the auroral oval again, perhaps more so than
before. So we're going to have fun figuring out what we're seeing there.

So this is an active period for the aurora right now. Unfortunately, we
had some - apparently some rain yesterday, some of the data was lost,
but I guess that's the luck of the draw.

Okay going to Number 52, summarizing the talk. We've been able to image
the aurora from UVIS. The VIMS instrument has also been imaging it. We
can fit what we're seeing in the spectrum with models that include
self-absorption molecular hydrogen and hydrocarbon absorbers, primarily
methane.

We've seen the aurora's respond to solar wind changes. We've identified
the small spot in the data right at the South Pole (where there's a
storm on) Saturn and that spot seems to have enhanced acetylene and
probably benzene, which is showing up in that dark spot, a certain
wavelength range.

And the nice thing that's going on now is Cassini is finally at high
latitudes, and we're getting direct views of the Auroras. So we're going
to be able to file it on, learn a little bit more about what's
controlling the auroras, how are they controlled internally from
material - from (unintelligible) in the rings, or is it solar wind
driven stuff.

And what I think is going on now is probably a little bit of both that's
going on. At dawn, things get brighter, with a lot of the (blobs) are
materially repeating from orbit to orbit.

And I think that concludes my talk. Slide 53, just has a list of
references, and I should open the floor to any questions you guys have.

Amanda Hendrix: Thanks a lot, Wayne, that's really interesting.

Are there questions?

Man: (Mute off).

Man: Yes, I have a question.

((Crosstalk))

Man: Can you hear me?

Wayne Pryor: Yes.

Man: When you talk about the different days and dawns and so forth, how
are you measuring a day on Saturn?

Wayne Pryor: Okay...

Man: What's the reference point of this with the current...

((Crosstalk))

Wayne Pryor: We usually do our planning in terms of Earth days
(unintelligible) Day 96, and I said that refers to Earth Day 96, which
is 24-hour Earth days.

Man: Okay.

Wayne Pryor: And not a Saturn day.

Man: Thanks.

Amanda Hendrix: So when you - (let me chime in) with a question here.

When you say that there's (probably) contribution from both the solar
wind and the Saturn system stuff like the ring and Enceladus, you're
saying that the contribution from the solar wind is evidenced by the
(tightening) that in the dawn location?

Wayne Pryor: Yeah.

Amanda Hendrix: And then the sort of (blobs) that moved around would be
the - maybe the Enceladus materials that accumulated?

Wayne Pryor: That's right.

Amanda Hendrix: Okay.

Wayne Pryor: I think, yeah, you understand as well I do, which is not
too well (unintelligible).

(Don Mitchell) said that we just happened to get lucky and get one day
when there was a structure that was moving around that was well
organized for that movie. Mostly - most of the time, it's more chaotic
than that.

Amanda Hendrix: You expect that if there are contributions from
Enceladus materials that that would be a way to track Enceladus activity
or...?

Wayne Pryor: You saw that doesn't really track all that well, so I guess
it feeds in over a long enough period of time. It's not bursting enough
that you can easily trace it to Enceladus...

((Crosstalk))

Amanda Hendrix: Right, but the Enceladus - well we don't know if
Enceladus is bursting or not, right?

Wayne Pryor: Okay.

Amanda Hendrix: But (if you)...

Wayne Pryor: More to learn.

Amanda Hendrix: Yeah exactly. I mean, I guess that would be a really,
really long-term experiment.

Wayne Pryor: Yeah. (When) he said that it's not that easy to instantly
trace it to Enceladus location. There are other things that are going
on.

Amanda Hendrix: Right. Right, because it's the (blob) for - is it like
an Enceladus footprint like an Io footprint?

Wayne Pryor: There was a search for an Enceladus footprint reported on
the meeting I attended. Apparently, student at (unintelligible) during
her thesis on that, and if there is a footprint from Enceladus, it's
very faint. It's not a bright - it's not like there's a strong current
between Enceladus and Saturn like there is for Io and Jupiter.

Amanda Hendrix: So it'd be more just the material is lost from
Enceladus?

Wayne Pryor: Yeah, and it takes part...

Amanda Hendrix: Okay.

Wayne Pryor: ...takes some time to ionize it after at least...

((Crosstalk))

Amanda Hendrix: Right. Right, right, right, (right).

(Are there other) questions?

Man: Yeah, I have a question. Can you hear me okay?

Wayne Pryor: Yes, great.

Man: How do we know that the Earth aurora isn't from, you know,
particles that are other than the solar wind?

Wayne Pryor: There is some contribution from Earth's upper atmospheric
gasses also. And there's some mixture of material in there, on the
Earth.

But when I say it's solar wind controlled, that mostly is referring now
to the fact that things are usually so strong. At local time effects,
the aurora seemed brighten up toward midnight, and they're strongly tied
to the local time rather than blobs rotating around in longitude.

Man: Thank you.

What about (varying), you know, large variations of solar wind or things
going on in the sun, has there been any studies of what that
relationship (pattern to) aurora?

Wayne Pryor: Yeah. I think I showed a couple of those where - I
mentioned (shocks) going by, those are basically outburst on the Sun
that is propagated all the way out there. It takes a few days to get out
there. And once they get out there, it shows up as a pressure (pole).

This is - originally, it was a coronal mass ejection of the sun and it
takes - after some days it gets out to earth (and then) eventually out
to Saturn and you can see a pressure (pole) as that material finally
goes through and you get more density and more magnetic field usually.
And that seems to trigger the brightening in the aurora, which would...

((Crosstalk))

Man: ...I wasn't quite sure if the - if that (pole) was from a coronal
mass ejection...

Wayne Pryor: I think so.

Man: Okay great.

Wayne Pryor: In some cases, those (poles) actually end up being for more
than one coronal mass ejection because it kind of catch up with each
other.

Man: Okay.

Amanda Hendrix: Another question.

Man: I have a question. As Cassini gets to higher latitudes, is that
going to help yet greater resolution or spectral data on that polar dark
spot?

Wayne Pryor: Yeah, I keep hoping we get better information on that polar
dark spot. It seems to have been a very ideal observation we got on that
one day. And so far it's the best data I've seen on. But we're - I'm
going to try to get more data like that to at least that good quality...

Man: Thank you.

Wayne Pryor: ...so we can get the - I want that spectrum cleaned up, so
I'm working on that.

Man: (Okay), thanks.

Amanda Hendrix: Speaking of the polar dark spot, is - I don't really see
it jumping out at me in the VIMS image. I see a ring but I don't see a
dark spot. Is there any...

((Crosstalk))

Amanda Hendrix: here?

Wayne Pryor: Oddly enough...

((Crosstalk))

Wayne Pryor: ...I wasn't going to get into it, but oddly enough, that
VIMS image is the other end of Saturn...

((Crosstalk))

Wayne Pryor: ...and they did a press release recently. I shouldn't be
the one to give this so - but they get a press release recently where
they saw a hexagon.

Amanda Hendrix: Okay, right. But that's...

Wayne Pryor: ...at the northern end. So the northern end of Saturn has a
hexagon, the south end has an (eyeball and a drain).

Amanda Hendrix: (Got you) (unintelligible).

Wayne Pryor: Whatever that means, I don't know yet.

Amanda Hendrix: (I see). Your dark spot is at the South Pole.

Wayne Pryor: Right.

Amanda Hendrix: Wow.

((Crosstalk))

Man: Regarding the dark spot at the South Pole, I thought it - so in the
press release that had mentioned that we're seeing deeper - part of the
reason it's dark is we're able to see deeper into - better into
atmosphere from the downwelling. And from what you described here with
the benzene, that's - that may not be the case...

((Crosstalk))

Wayne Pryor: Well my ideas may be wrong on that, too. (We still have) -
we sought to sort out what we're seeing, (what depth it's set). But it -
downwelling regions in general cause clearings in the clouds, so you
would see the deeper depths.

Man: Okay got it.

Wayne Pryor: And that would lead to more absorption at certain
wavelength. You're absolutely right about that.

Man: Thanks.

One more question, do you have anything to say about this hexagon? Any -
what...

Wayne Pryor: I have no idea why it's there or why it really does look
like a hexagon.

Man: All right.

Wayne Pryor: It's not something you normally expect in a fluid. But it
was there in the Voyager also. So it's a persistent feature, maybe one
helpful thing because whatever it is, it's been there a long time.

Amanda Hendrix: Okay any final questions?

Well thanks again so much, Wayne, for this really interesting talk and
for giving us all the latest info on your research.

Wayne Pryor: My pleasure.

Amanda Hendrix: Thanks, Wayne.

Wayne Pryor: Okay. Bye.

Amanda Hendrix: And to everybody else, thanks for calling in. And we
will see you or hear from you, hopefully, next month when we'll have the
third anniversary CHARM telecon with the overview of all of the results
or the highlights of the missions to date over the last three years.

So that will be happening in the last Tuesday in June. I think it's the
29. I don't have my calendar with me. It's the 26th - June 26, so we'll
be sending out an email about that.

So thanks very much and we'll talk to you next time.

Man: And thanks a lot.

Amanda Hendrix: Bye. Thanks.

END