Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present the first observation of a solar filament formed by magnetic reconnection, associated chromospheric evaporation, and subsequent coronal condensation. Driven by shearing motion during flux emergence, a sequential tether-cutting reconnection process occurred and resulted in an M1.3 confined flare accompanied by the formation of a sigmoid structure. It is found that the flare had conjugate compact footpoint brightenings, which correspond to the footpoints of the sigmoid. Furthermore, observational evidence of explosive evaporation is well diagnosed at the conjugate footpoint brightenings in the impulsive phase of the flare. After the flare, continuous cool condensations formed at about the middle section of the sigmoid and then moved in opposite directions along the sigmoid, eventually leading to the formation of the filament. These observations suggest that magnetic reconnection can not only form the magnetic field structure of the filament but also heat the chromospheric footpoints during their formation and drive chromospheric evaporation. As a result, the heated chromospheric plasma may be evaporated into the magnetic field structure of the filament, where the accumulated hot plasma might suffer from thermal instability or nonequilibrium, causing catastrophic cooling and coronal condensation to form the cool, dense material of the filament. This observation lends strong support to the evaporation–condensation model and highlights the crucial role of magnetic reconnection in forming both the magnetic field structure and the cool, dense material of the filaments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new simulations of the formation of the Magellanic Stream based on an updated first-passage interaction history for the Magellanic Clouds, including both the Galactic and Magellanic Coronae and a live dark matter halo for the Milky Way. This new interaction history is needed because previously successful orbits need updating to account for the Magellanic Corona and the loosely bound nature of the Magellanic Group. These orbits involve two tidal interactions over the last 3.5 Gyr and reproduce the Stream’s position and appearance on the sky, mass distribution, and velocity profile. Most importantly, our simulated Stream is only ∼20 kpc away from the Sun at its closest point, whereas previous first-infall models predicted a distance of 100–200 kpc. This dramatic paradigm shift in the Stream’s 3D position would have several important implications. First, estimates of the observed neutral and ionized masses would be reduced by a factor of ∼5. Second, the stellar component of the Stream is also predicted to be &lt;20 kpc away. Third, the enhanced interactions with the MW’s hot corona at this small distance would substantially shorten the Stream’s lifetime. Finally, the MW’s UV radiation field would be much stronger, potentially explaining the H<jats:italic>α</jats:italic> emission observed along most of the Stream. Our prediction of a 20 kpc Stream could be tested by searching for UV absorption lines toward distant MW halo stars projected onto the Stream.</jats:p>