Wednesday, October 26, 2022 - 2 p.m. to 3 p.m.
Morse Hall rm 301 OR Zoom
Speaker: Jeff Linsky
Joint Institute for Laboratory Astrophysics (JILA), University of Colorado and National Institute of Standards and Technology (NIST), Boulder
Abstract: High-resolution ultraviolet spectroscopy is a critical tool for understanding the structure, physical properties, and kinematics of the local interstellar medium. Past studies have identified 15 partially ionized clouds within about 10 pc from the Sun and measured their velocity vectors, hydrogen column densities and approximate shapes. We now find that the Local Interstellar Cloud (LIC) and other nearby clouds have a wide distribution of internal temperatures and turbulent velocities. These appear to be randomly distributed and can be fit with Gaussians. These properties do not depend on spatial coordinates and magnetic field orientation. The size scale for thermal inhomogeneities is less than 5,100 AU, the distance that the Sun travels in 1,000 years. The total pressures (thermal, turbulent, magnetic, suprathermal, and ram) in the heliosheath, outer heliosphere, LIC, and Local Cavity appear to be consistent with the Galactic gravitational pressure. The LISM gas immediately surrounding the heliosphere appears to be different from the LIC. We present evidence that within 4 pc space is completely filled with LISM clouds, and that beyond 4 pc the clouds become separated with ionized gas between the clouds.
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