SPRG Seminars
September 9, 2008:
"The role of energetic neutral atoms in shaping the heliosphere"
Dr. Jacob Heerikhuisen, IGPP, UC Riverside
The Sun emits a continuous stream of charged particles known as the solar wind. As the solar wind plasma expands, it feels the presence of the ionized gas of the local interstellar cloud. The two plasmas do not mix, but instead flow around each other, creating a bubble of solar wind plasma known as the heliosphere, with an associated heliotail due to the motion of the Sun through interstellar space. This plasma-physics interaction is complicated by the presence of neutral atoms (mainly Hydrogen) of interstellar origin which propagate throughout the heliospheric interface and are weakly coupled to the plasma through charge-exchange. In this talk I will introduce the problem of the interaction between the solar wind and the local interstellar medium, and present results from our global computational models. Particular emphasis will be on so-called "energetic neutral atoms" (ENA's) that originate from particular regions of the heliosphere and which may be used to remotely diagnose those regions. ENA's have recently been observed by the STEREO spacecraft and will soon be observed by the IBEX spacecraft. I will show how observations of ENA's can be used to unravel the structure of the heliosphere with the help of global models.