Heliosphere and Local Interstellar Medium

IBEX, Heliosphere

(left) Illustration of the heliosphere formed from the solar wind's interaction with the local interstellar medium. Credit: NASA/IBEX/Adler Planetarium. (right) IBEX ENA data painted onto an illustrated surface of the heliopause. Credit: McComas, D. J., et al. (2009), Science, 326, 959-961.

The heliosphere is created by the interaction of the outward-flowing solar wind with the interstellar medium. The solar wind, traveling at speeds between ~300 and 800 km s-1, is slowed and compressed at the solar wind termination shock, located approximately 100 au from the Sun. Beyond the termination shock, the solar wind plasma continues to flow away from the Sun until it is diverted around the heliopause, the boundary separating the solar wind and interstellar plasmas. The Sun is moving with respect to the local interstellar matter, creating a comet-like heliosphere. The interstellar plasma is compressed and diverted at the heliospheric bow wave, but neutral atoms such as hydrogen, helium, oxygen, and neon can traverse inside the heliosphere and interact with the solar wind plasma via charge-exchange. These interactions create non-thermal ions that are "picked up" by the solar wind, and energetic neutral atoms that propagate ballistically through the heliosphere.

Relevant Observations:

  • Energetic neutral hydrogen atoms from the heliosphere (IBEX)
  • Neutral hydrogen, helium, oxygen, and neon atoms from the interstellar medium (IBEX)
  • Interstellar pickup ions in the solar wind and at interplanetary shocks (SWAP)

Examples of Research Topics:

  • Role of energetic particles in the heliosheath
  • Properties of the interstellar neutral gas and magnetic field
  • 3D structure of the heliosphere and heliotail