SCARI Science

SCARI will be used to study the interaction of our Solar System with the gas and dust that exists in between the stars, called Interstellar Medium , or ISM. The ISM, and everything else in the Galaxy, is rotating about the center of the Galaxy. This motion of the ISM with respect to our own motion about the Galaxy causes an interstellar wind. Our Solar System consists of the Sun, the planets and planetesimals, as well as all the gas and dust streaming out from the Sun, called the solar wind . The solar wind streams out radially from the sun, until it is balanced by the interstellar wind. The point at which SCARI can detect at the Lyman-alpha transition in the UV. This gas has passed from the ISM into our solar system, through the heliopause and interface region. By studying the temperature, density, and velocity of the hydrogen, and comparing it to known values of the ISM well outside the solar system, we can learn more about the interaction itself (Baranov and Malama, Journal of Geophysical Research,100,14755).

The upper atmosphere of the Earth consists of mostly Hydrogen. The same solar radiation which excites the hydrogen streaming into the solar system from the ISM, also excites hydrogen within our own atmosphere. SCARI will also see this hydrogen, which is called the Geocorona. The top of this region is where hydrogen can escape completely from the atmosphere, called the Exosphere, and starts above 500 km in altitude. By looking at the Geocorona, SCARI will be studying hydrogen escape from the Earth's atmosphere.

The hydrogen flux , or density and speed at which hydrogen escapes Earth's atmosphere, is critical to understanding the upper atmosphere. Predicted fluxes fall short of those observed, meaning that the escape mechanisms known must be more effiecient, and/or there must other escape mechanisms at work. SCARI will be able to measure the speed and temperature of the escaping hydrogen, which will help narrow this gap (Hodges & Brieg,Journal of Geophysical Research,96,769).