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1. Tidal disruption discs formed and fed by stream–stream and stream–disc interactions in global GRHD simulations

   https://doi.org/10.1093/mnras/stab3444  

   Andalman, Zachary L. ; Liska, Matthew T. P. ; Tchekhovskoy, Alexander ; Coughlin, Eric R. ; Stone, Nicholas ( November 2021 , Monthly Notices of the Royal Astronomical Society)

   When a star passes close to a supermassive black hole (BH), the BH’s tidal forces rip it apart into a thin stream, leading to a tidal disruption event (TDE). In this work, we study the post-disruption phase of TDEs in general relativistic hydrodynamics (GRHD) using our GPU-accelerated code h-amr. We carry out the first grid-based simulation of a deep-penetration TDE (β = 7) with realistic system parameters: a black hole-to-star mass ratio of 106, a parabolic stellar trajectory, and a non-zero BH spin. We also carry out a simulation of a tilted TDE whose stellar orbit is inclined relative to the BH midplane. We show that for our aligned TDE, an accretion disc forms due to the dissipation of orbital energy with ∼20 per cent of the infalling material reaching the BH. The dissipation is initially dominated by violent self-intersections and later by stream–disc interactions near the pericentre. The self-intersections completely disrupt the incoming stream, resulting in five distinct self-intersection events separated by approximately 12 h and a flaring in the accretion rate. We also find that the disc is eccentric with mean eccentricity e ≈ 0.88. For our tilted TDE, we find only partial self-intersections due to nodal precession near pericentre. Althoughmore »these partial intersections eject gas out of the orbital plane, an accretion disc still forms with a similar accreted fraction of the material to the aligned case. These results have important implications for disc formation in realistic tidal disruptions. For instance, the periodicity in accretion rate induced by the complete stream disruption may explain the flaring events from Swift J1644+57.

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2. Exploring dissolved organic carbon cycling at the stream–groundwater interface across a third-order, lowland stream network

   https://doi.org/10.1007/s10533-017-0404-z  

   Ruhala, Sydney S. ; Zarnetske, Jay P. ; Long, David T. ; Lee-Cullin, Joseph A. ; Plont, Stephen ; Wiewiora, Evan R. ( January 2018 , Biogeochemistry)
3. Destabilization of a planar liquid stream by a co-flowing turbulent gas stream

   https://doi.org/10.1016/j.ijmultiphaseflow.2019.103121  

   Jiang, Delin ; Ling, Yue ( September 2019 , International Journal of Multiphase Flow)
4. Seeing the light: urban stream restoration affects stream metabolism and nitrate uptake via changes in canopy cover

   https://doi.org/10.1002/eap.1941  

   Reisinger, Alexander J. ; Doody, Thomas R. ; Groffman, Peter M. ; Kaushal, Sujay S. ; Rosi, Emma J. ( July 2019 , Ecological Applications)
5. Along-Stream Evolution of Gulf Stream Volume Transport

   https://doi.org/10.1175/JPO-D-19-0303.1  

   Heiderich, Joleen ; Todd, Robert E. ( August 2020 , Journal of Physical Oceanography)

   Abstract The Gulf Stream affects global climate by transporting water and heat poleward. The current’s volume transport increases markedly along the U.S. East Coast. An extensive observing program using autonomous underwater gliders provides finescale, subsurface observations of hydrography and velocity spanning more than 15° of latitude along the path of the Gulf Stream, thereby filling a 1500-km-long gap between long-term transport measurements in the Florida Strait and downstream of Cape Hatteras. Here, the glider-based observations are combined with shipboard measurements along Line W near 68°W to provide a detailed picture of the along-stream transport increase. To account for the influences of Gulf Stream curvature and adjacent circulation (e.g., corotating eddies) on transport estimates, upper- and lower-bound transports are constructed for each cross–Gulf Stream transect. The upper-bound estimate for time-averaged volume transport above 1000 m is 32.9 ± 1.2 Sv (1 Sv ≡ 106 m3 s−1) in the Florida Strait, 57.3 ± 1.9 Sv at Cape Hatteras, and 75.6 ± 4.7 Sv at Line W. Corresponding lower-bound estimates are 32.3 ± 1.1 Sv in the Florida Strait, 54.5 ± 1.7 Sv at Cape Hatteras, and 69.9 ± 4.2 Sv at Line W. Using the temperature and salinity observations from gliders andmore »Line W, waters are divided into seven classes to investigate the properties of waters that are transported by and entrained into the Gulf Stream. Most of the increase in overall Gulf Stream volume transport above 1000 m stems from the entrainment of subthermocline waters, including upper Labrador Sea Water and Eighteen Degree Water.« less