In June 2008, the original work program of the Xsini spacecraft was completed. Since the spacecraft functioned to the satisfaction of its planners and researchers, it was decided to extend its activity for two years with an option for another two years until 2012. Many findings, some of them surprising, were broadcast to Israel. This set of data allows a global view of this planet. First article in the series
After we reviewed in the previous reviews you The spectacular rings of Saturn It is also time to take care of the planet Saturn in his own right.
Saturn's axial velocity
Measuring the axial velocity of Saturn has been problematic for years because it is covered by clouds and it is not possible to observe what lies beneath them. What was missing was a solid reference point based on which it would be possible to perform this type of measurement. This is of great importance since it allows us to learn a lot about the internal structure of the star. Although there was an estimate regarding the axial speed of Saturn, it lacked the dimension of precision. The approach that was decided to be used is radio waves created by Saturn's magnetic field. It has been known for a long time that electric charges trapped in this field emit radio waves at a frequency of 100 kHz. The magnetic field itself is created inside the planet, so changes in the emission of radio waves can indicate its speed Saturn's axial speed. This method proved to be successful when the axial speed of Jupiter was measured. This technique was used when the Voyager spacecraft passed by Saturn and the result obtained was 10 hours, 39 minutes and 24 seconds. Another measurement made 15 years later by the Ulysses spacecraft showed that the radio wave emission changes over time and the tests made by the Cassini showed that Saturn's axial velocity is 10 hours, 45 minutes and 45 seconds. This meant that during the years between the spacecraft's passes, the axial speed of Saturn slowed down by 6 minutes. It was clear that what he was doing was affecting the emission of radio waves from Saturn. The slowdown in Saturn's rotation speed did not seem reasonable. An explanation is required. According to one explanation, changes in the speed of the solar wind cause changes in the emission of radio waves. According to a second explanation, particles from the geysers of Enceladus affect the magnetic field by causing them to be dragged around Saturn. Examining the data showed that the significant cause is the solar wind. It turned out that there is a pattern according to which there is a permanent change in the emission of the short radio waves every 25 days, very close to the time of the sun's revolution around itself, every 26 days, although an additional explanation is needed to arrive at a complete answer(1).
Magnetic field and radiation bands
It turns out that Saturn's magnetic field has more in common with the Sun than with Earth. This can be explained by the fact that part of the magnetic field that controls the emission of radio waves has moved towards higher latitudes in the last two decades. This hypothesis is based on the fact that the sun's magnetic field does not rotate the sun like it does with a solid body. The duration of the rotation changes with the variation of the latitudes. The radio sounds like heartbeats (2). At a distance of 5 radii from Saturn, a phenomenon was found that was previously detected near the Earth and near Jupiter. Electrons that move from Saturn onward and are therefore called antiplanetary electrons. It turned out that the phenomenon occurs at the poles, in a place where the polar glow is of low intensity and collides with the magnetic field lines, which are also of minimal intensity. The spread width of these electrons is 10°, which allows researchers to place the exact point of formation above the pole within a maximum distance range of 5 Saturn radii(3).
Saturn's magnetosphere is unusual in its structure and behavior. In terms of dynamics, it is similar to that of Jupiter. In some places, its chemistry is similar to the plasma of water vapor surrounding comets. 4 plasmatic regions have been distinguished that differ from each other in their chemical structure and have properties characteristic of liquids. Earth has two such regions , one receiving plasma from the ionosphere and the other receiving it from the solar wind. Up to a distance of 24,000 km the terrestrial plasma rotates with the Earth. In Saturn this plasma reaches a distance of 1.6 million km and within this space are Titan, most of the ice moons and the rings. All of them are suppliers of plasma with different chemical compositions. It turned out that Saturn has 3 sources of plasma that the Earth does not have and there is a chemical and electromagnetic interaction between them. This has several results. The moons and rings are covered every time anew with different chemical mixtures and part of Titan's atmosphere has been removed.
With the help of ultraviolet energy from the sun, the plasma is constantly renewed. Photons from the sun and electrons from the plasma hit the surface of the moons and rings. The intensity of the impact is so high as to release ions and molecules such as water and sometimes also the nitrogen buried in the ice. The ionized material is accelerated by the high rotation speed of Saturn's magnetic field in a cyclical manner. At great distances in the magnetosphere, the plasma is made of water ions torn from the surface of the moons similar to those found in the corona of comets(4).
the color of the planet
In an earthly observation of Saturn using a home telescope, the planet appears yellow. Cassini, when viewed closely, showed that it is different. The color of the sky is blue. The molecules in the upper atmosphere scatter the sunlight. Although the atmospheres of the Earth and Saturn are different from each other in terms of their composition, the result is the same. There are other colors, but blue is the dominant one. The name of the phenomenon is Rayleigh scattering. Blue dominates in the northern hemisphere. In the southern hemisphere the dominant color is yellow. It may be that the sky in this hemisphere is cloudier and hence its different color (5). One of the ways What the researchers use to monitor the star's atmosphere is repeated observation of different places and the production of films from a sequence of photographs. Another way is shadowing. Since the upper layer of clouds and the haze do not allow a deep look into the atmosphere, visible and infrared light photographs were combined in a method that allows a look inside. In this way, the clouds The inner ones are illuminated against the background of the emission of heat from the interior of the star(6).
Sources
1."The planetary scientists close to Saturn's elusive rotation" 12.12.2007
http://www.spaceflightnow.com/news/n0712/12saturnrotation
2."Saturn lighting rotation discoveries made" 20.12.2004
http://www.spaceflightnow.com/cassini/041220lighting.html
3. "Cassini detects backward electrons on Saturn" 8.3.2006
http://www.saturndaily.com/reports/ Cassini_Detects_ Backward_ Electrons _On_ Saturn.html
4. "Saturn's uniquely complex magnetosphere" 24.2.2005
http://www.spacefkightnow.com/cassini/050224magnetosphere.html
5. Philips T.-"Blue skies on Saturn" 23.2.2005
http://www.spacedaily.com/news/cassini-05zb.html
6."Chinese lantern technique helps track clouds at Saturn" 6.10.2006
http://www.saturndaily.com/reports/ Chinese_ Lantern _Technique_ Helps_ Track_ Clouds_ At_ Saturn_999.html
