Properties of Saturn’s ULF Wave Foreshock: Observations by Cassini

NAHUEL ANDRÉS; DANIEL O. GOMEZ; CESAR BERTUCCI; CHRISTIAN MAZELLE; MICHELLE DOUGHERTY

Cancun

Congreso; American Geophysical Union, Meeting of the Americas 2013; 2013

When the supersonic solar wind plasma from the Sun encounters Saturn’s magnetic field, a bow shock is formed. At the bow shock, a fraction of the solar wind particles (electrons and ions) are reflected in the sunward direction. The region of space upstream of the shock, magnetically connected to the shock and filled with particles backstreaming from the shock is known as the foreshock. The combination of the solar wind and this counterstreaming component, can be subjected to a number of plasma instabilities (Convery & Gary 1997), bow shock leading to the generation of ultra-low frequency waves, which are in fact detected by the magnetometer on board Cassini. Just behind the tangent field line is the electron foreshock, where backstreaming electrons are observed. Backstreaming ions are observed behind the ion foreshock boundary. Therefore, ULF wave foreshock region is expected within the ion foreshock and there must be a second boundary within the ion foreshock confining the region of ULF wave activity, known as the ULF wave foreshock boundary. In the case of the Earth, Greenstadt & Baum (1986) using single spacecraft techniques, introduced the solar foreshock coodinates (SFC) μ-ν, where the position of the ULF foreshock boundary can be foreshock. In particular, the occurrence of ULF foreshock waves is determined. We adopted this technique to study the morphology of Saturn’s foreshock. All wave events described are clearly associated to Saturnas restricted to a region defined by bow shock normal angles smaller than ∼ 45 degrees. We discuss these results in the light of previous studies on possible wave generation mechanism.