29 research outputs found
Is the Sun Embedded in a Typical Interstellar Cloud?
The physical properties and kinematics of the partially ionized interstellar
material near the Sun are typical of warm diffuse clouds in the solar vicinity.
The interstellar magnetic field at the heliosphere and the kinematics of nearby
clouds are naturally explained in terms of the S1 superbubble shell. The
interstellar radiation field at the Sun appears to be harder than the field
ionizing ambient diffuse gas, which may be a consequence of the low opacity of
the tiny cloud surrounding the heliosphere. The spatial context of the Local
Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at
International Space Sciences Institute, October 200
Suitability of linear quadrupole ion traps for large Coulomb crystals
Growing and studying large Coulomb crystals, composed of tens to hundreds of
thousands of ions, in linear quadrupole ion traps presents new challenges for
trap implementation. We consider several trap designs, first comparing the
total driven micromotion amplitude as a function of location within the
trapping volume; total micromotion is an important point of comparison since it
can limit crystal size by transfer of radiofrequency drive energy into thermal
energy. We also compare the axial component of micromotion, which leads to
first-order Doppler shifts along the preferred spectroscopy axis in precision
measurements on large Coulomb crystals. Finally, we compare trapping potential
anharmonicity, which can induce nonlinear resonance heating by shifting normal
mode frequencies onto resonance as a crystal grows. We apply a non-deforming
crystal approximation for simple calculation of these anharmonicity-induced
shifts, allowing a straightforward estimation of when crystal growth can lead
to excitation of different nonlinear heating resonances. In the axial
micromotion and anharmonicity points of comparison, we find significant
differences between the compared trap designs, with an original rotated-endcap
trap performing slightly better than the conventional in-line endcap trap
Physical Processes in Star Formation
© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00693-8.Star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. Stars and star formation are key pillars in observational astronomy from local star forming regions in the Milky Way up to high-redshift galaxies. From a theoretical perspective, star formation and feedback processes (radiation, winds, and supernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individually and of their interactions. In this review we will give an overview of the main processes that are important for the understanding of star formation. We start with an observationally motivated view on star formation from a global perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key process to close the cycle. After that we focus on the thermal and chemical aspects in star forming regions, discuss turbulence and magnetic fields as well as gravitational forces. Finally, we review the most important stellar feedback mechanisms.Peer reviewedFinal Accepted Versio