TY  - JOUR
A1  - Nishikawa, Ken-Ichi
A1  - Frederiksen, J. T.
A1  - Nordlund, A.
A1  - Mizuno, Y.
A1  - Hardee, P. E.
A1  - Niemiec, J.
A1  - Gomez, J. L.
A1  - Dutan, I.
A1  - Meli, A.
A1  - Sol, H.
A1  - Pohl, Martin
A1  - Hartmann, D. H.
T1  - EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH
kKHI AND THE WEIBEL INSTABILITY
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - In the study of relativistic jets one of the key open questions is their interaction with the environment. Here. we study the initial evolution of both electron-proton (e(-) - p(+)) and electron-positron (e(+/-)) relativistic jets, focusing on their lateral interaction with ambient plasma. We follow the evolution of toroidal magnetic fields generated by both the kinetic Kelvin-Helmholtz and Mushroom instabilities. For an e(-) - p(+) jet, the induced magnetic field collimates the jet and electrons are perpendicularly accelerated. As the instabilities saturate and subsequently weaken, the magnetic polarity switches from clockwise to counterclockwise in the middle of the jet. For an e(+/-) jet, we find strong mixing of electrons and positrons with the ambient plasma, resulting in the creation of a bow shock. The merging of current filaments generates density inhomogeneities that. initiate a forward shock. Strong jet-ambient plasma mixing prevents a full development of the jet (on the scale studied), revealing evidence for both jet collimation and particle acceleration in the forming bow shock. Differences in the magnetic field structure generated by e(-) - p(+) and e(+/-) jets may contribute to the polarization properties of the observed emission in AGN jets and gamma-ray bursts.
KW  - acceleration of particles
KW  - plasmas
KW  - radiation mechanisms: non-thermal
KW  - relativistic processes
KW  - stars: jets
KW  - Sun: magnetic fields
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/820/2/94
SN  - 0004-637X
SN  - 1538-4357
VL  - 820
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Thomas, Jessica E.
A1  - Carvalho, Gary R.
A1  - Haile, James
A1  - Rawlence, Nicolas J.
A1  - Martin, Michael D.
A1  - Ho, Simon Y. W.
A1  - Sigfusson, Arnor P.
A1  - Josefsson, Vigfus A.
A1  - Frederiksen, Morten
A1  - Linnebjerg, Jannie F.
A1  - Castruita, Jose A. Samaniego
A1  - Niemann, Jonas
A1  - Sinding, Mikkel-Holger S.
A1  - Sandoval-Velasco, Marcela
A1  - Soares, Andre E. R.
A1  - Lacy, Robert
A1  - Barilaro, Christina
A1  - Best, Juila
A1  - Brandis, Dirk
A1  - Cavallo, Chiara
A1  - Elorza, Mikelo
A1  - Garrett, Kimball L.
A1  - Groot, Maaike
A1  - Johansson, Friederike
A1  - Lifjeld, Jan T.
A1  - Nilson, Goran
A1  - Serjeanston, Dale
A1  - Sweet, Paul
A1  - Fuller, Errol
A1  - Hufthammer, Anne Karin
A1  - Meldgaard, Morten
A1  - Fjeldsa, Jon
A1  - Shapiro, Beth
A1  - Hofreiter, Michael
A1  - Stewart, John R.
A1  - Gilbert, M. Thomas P.
A1  - Knapp, Michael
T1  - Demographic reconstruction from ancient DNA supports rapid extinction of the great auk
JF  - eLife
N2  - The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species' geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.
Y1  - 2019
U6  - https://doi.org/10.7554/eLife.47509
SN  - 2050-084X
VL  - 8
PB  - eLife Sciences Publications
CY  - Cambridge
ER  -