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Title: Detection of lightning in Saturn's Northern Hemisphere
Authors: Mohsen Hassanzadeh Moghimi

During Cassini flyby of Saturn at a radial distance 6.18R_s (Saturn Radius), a signal was detected from about 200 to 430 Hz that had the proper dispersion characteristics to be a whistler. The frequency-time dispersion of the whistler was found to be 81 Hz1/2s. Based on this dispersion constant, we determined, from a travel time computation, that the whistler must have originated from lightning in the northern hemisphere of Saturn. Using a simple centrifugal potential model consisting of water group ions, and hydrogen ions we also determine the fractional concentration and scale height that gave the best fit to the observed dispersion.

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Saturn's Lightning
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Cassini Spots Daytime Lightning on Saturn

Saturn was playing the lightning storm blues. NASA's Cassini spacecraft has captured images of last year's storm on Saturn, the largest storm seen up-close at the planet, with bluish spots in the middle of swirling clouds. Those bluish spots indicate flashes of lightning and mark the first time scientists have detected lightning in visible wavelengths on the side of Saturn illuminated by the sun.
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Saturn's atmosphere
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 Cassini Shows Why Jet Streams Cross-Cut Saturn

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Turbulent jet streams, regions where winds blow faster than in other places, churn east and west across Saturn. Scientists have been trying to understand for years the mechanism that drives these wavy structures in Saturn's atmosphere and the source from which the jets derive their energy.
In a new study appearing in the June edition of the journal Icarus, scientists used images collected over several years by NASA's Cassini spacecraft to discover that the heat from within the planet powers the jet streams. Condensation of water from Saturn's internal heating led to temperature differences in the atmosphere. The temperature differences created eddies, or disturbances that move air back and forth at the same latitude, and those eddies, in turn, accelerated the jet streams like rotating gears driving a conveyor belt.
A competing theory had assumed that the energy for the temperature differences came from the sun. That is how it works in the Earth's atmosphere.

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Cassini Captures Images and Sounds of Saturn Storm

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Scientists analysing data from NASA's Cassini spacecraft now have the first-ever, up-close details of a Saturn storm that is eight times the surface area of Earth.
On Dec. 5, 2010, Cassini first detected the storm that has been raging ever since. It appears approximately 35 degrees north latitude of Saturn. Pictures from Cassini's imaging cameras show the storm wrapping around the entire planet covering approximately 4 billion square kilometres.
The storm is about 500 times larger than the biggest storm previously seen by Cassini during several months from 2009 to 2010. Scientists studied the sounds of the new storm's lightning strikes and analysed images taken between December 2010 and February 2011. Data from Cassini's radio and plasma wave science instrument showed the lightning flash rate as much as 10 times more frequent than during other storms monitored since Cassini's arrival to Saturn in 2004. The data appear in a paper published this week in the journal Nature.

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Saturn Storm
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Updrafts of Large Ammonia Crystals in Saturn Storm

This false-colour infrared image, obtained by NASA's Cassini spacecraft, shows clouds of large ammonia ice particles dredged up by a powerful storm in Saturn's northern hemisphere. Large updrafts dragged ammonia gas upward more than 50 kilometres from below. The ammonia then condensed into large crystals in the frigid upper atmosphere. This storm is the most violent ever observed at Saturn by an orbiting spacecraft.
Cassini's visual and infrared mapping spectrometer obtained these images on Feb. 24, 2011. Scientists colorized the image by assigning red to brightness detected from the 4.08-micron wavelength, green to brightness from the 0.90-micron wavelength, and blue to brightness from the 2.73-micron wavelength. Large particles (red) reflect sunlight well at 4.08 microns. Particles at high altitude (green) reflect sunlight well at 0.9 microns. Particles comprised of ammonia -- especially large ones -- do not reflect 2.73-micron sunlight well, but instead absorb light at this wavelength.

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Credit:    NASA/JPL/Univ. of Arizona

The storm here shows up as yellow, demonstrating that it has a large signal in both red and green colours. This indicates the cloud has large particles and extends upward to relatively high altitude. In addition, the lack of blue in the feature indicates that the storm cloud has a substantial component of ammonia crystals. The head of the storm is particularly rich in such particles, as created by powerful updrafts of ammonia gas from depth in the throes of Saturn's thunderstorm.

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Skydiving on Saturn

Daredevils regularly bail out at high altitude to skydive through Earth's atmosphere but what would it be like to skydive on Saturn?
Would you jump in summer into an atmosphere shrouded in a yellow-ochre haze, aim for winter when the planet is tinged blue, or maybe leap into the shadow of those famous rings?

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Cassini and Telescope See Violent Saturn Storm

NASA's Cassini spacecraft and a European Southern Observatory ground-based telescope tracked the growth of a giant early-spring storm in Saturn's northern hemisphere that is so powerful it stretches around the entire planet. The rare storm has been wreaking havoc for months and shooting plumes of gas high into the planet's atmosphere.
Cassini's radio and plasma wave science instrument first detected the large disturbance, and amateur astronomers tracked its emergence in December 2010. As it rapidly expanded, its core developed into a giant, powerful thunderstorm. The storm produced a 5,000-kilometer-wide dark vortex, possibly similar to Jupiter's Great Red Spot, within the turbulent atmosphere.

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Looking Deep into a Huge Storm on Saturn

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Credit ESO

ESO's Very Large Telescope (VLT) has teamed up with NASA's Cassini spacecraft to study a rare storm in the atmosphere of the planet Saturn in more detail than has ever been possible before. The new study by an international team will appear this week in the journal Science.
The atmosphere of the planet Saturn normally appears placid and calm. But about once per Saturn year (about thirty Earth years), as spring comes to the northern hemisphere of the giant planet, something stirs deep below the clouds that leads to a dramatic planet-wide disturbance.

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Saturn from Cassini's VIMS spectrometer.



Animation of southern hemisphere of Saturn from distance ~1.1 mil. km, made from 21 image cubes in observation VIMS_063RI_SUBML05MP001.
Images were resampled to size 360x360 from original 64x64 size (real original resolution ~500 km/pix).
Colors are from channels 351 (R, Saturnian thermal radiation), 225 (G) and 96 (B). 5.11 (R), 3.01 (G) and 0.88 (B) in microns. Timewarp ~400x.
Date: 3.4.2008. Time: 16:01:48 - 22:37:43./



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Cassini Sees Saturn Electric Link with Enceladus

NASA is releasing the first images and sounds of an electrical connection between Saturn and one of its moons, Enceladus. The data collected by the agency's Cassini spacecraft enable scientists to improve their understanding of the complex web of interaction between the planet and its numerous moons. The results of the data analysis are published in the journals Nature and Geophysical Research Letters.
Scientists previously theorised an electrical circuit should exist at Saturn. After analysing data that Cassini collected in 2008, scientists saw a glowing patch of ultraviolet light emissions near Saturn's north pole that marked the presence of a circuit, even though the moon is 240,000 kilometres away from the planet.
The patch occurs at the end of a magnetic field line connecting Saturn and its moon Enceladus. The area, known as an auroral footprint, is the spot where energetic electrons dive into the planet's atmosphere, following magnetic field lines that arc between the planet's north and south polar regions.

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