[Saturn's magnetosphere that sweeps on the Surface of Titan at high speed]
Titan's orbit has a radius of about 1.2 million km, and Saturn's magnetosphere
is 1.1 million km. So, 95% of its orbits through Saturn's magnetosphere.
The rotation period of the magnetosphere was in 10.7 hours. The speed on
charged particles captured by magnetic field is 195.6 km/sec at Titan's
orbit.
Those charged particles are coupled by its magnetic interactin and the
life of the plasma is long. On the other hand, Titans of Saturn's moon
orbits around Saturn pariod of 16-day cycle, and Titans' orbiting speed
is 5.5 km/sec. So, the charged particles trapped by the magnetic flux sweep
the surface of Titan at 190.1 km/sec. H+ with a speed of 190.1 km/sec collides with h N2 or CO2 of Titan’s atmosphere.
A part of H+'s collide witTitan’s surface. H+ sputters by the kinetic energy (1/2) mv2=189 (eV), The substance is decomposed to atoms and ions, and those are
released to the atmosphere. NH3 is synthized, when N2 collided with H+. The collision between
CO2 and H+ synthesizes H2O and CH4.
Since Titan's surface temperature is Ttitan =93K (=-180°C) , NH3 or H2O
stays as solid crust. N2 is accumulated in the atmosphere because melting point of N2 is 63
K and the boiling pointis 77 K. The melting point of CH4 is 91 K and the boiling point is 112 K. As for C2H6, melting point is 90 K,
and boiling point of is 185 K. Those molecules of hydrocarbons accumulate
on the surface of the Titan in a liquid state. N2 is accumulated in the atmosphere as a gas because the melting point is
63 K and the boiling point is 77 K. In this way, Titan had a thick atmosphere
composed mainly of N2, and a lake of CH4 was created. Now, the thick atmospheric composition is N2 (97%), CH4 (2.7 ±
0.1%), and H2 (0.1 to 0.2%).
[Titan's atmospheric super-rotation]
Since melting point of H2 is 14K and boiling point of H2 is 20K, H2 can
rise into upper sky and it is released into the space. But H+ is replenished
continuously by the solar wind. The amount of H+ reaching Titan directly
can be estimated by the ratio of the spherical surface of the distance
to Saturn's position centered at the Sun to the cross section of the Titan.
The cross section of Titan is STitan=π/(2.575x106)2. And Ssphere is 4π(
9.55x1.5x1011)2. By using the data 109 kg/sec on the amount of H+ emitted
from the Sun, the amount of H+ that reach to Titan is calculated as 0.81x10-3 kg/sec.
The amount corresponds to 70kg per a day, and it corresponds 25.5t per a year. The amount of hydrogen ions reached during 4 billion years is 102 billion tons.
That amount is one billionth of that of Titan's mass of 1.345 x 1020 t. This is an evidence that the super rotation of Titan's atmosphere is
driven by the rotation of the magnetosphere, not by rotational componets
of the solar wind.
There is a difference in the distance from Saturn between the facing
Saturn side near Titan's equator and the back side. Therefore, since there is
a difference of ±2.1x10-3 in the speed at which H+ caught in the magnetosphere
collides. The maximum difference of speed is 822 m/sec. The difference of speed on the movements atmosphere generates Titan’s super
rotation.
index -4.4-