TY  - JOUR
A1  - Pena-Angulo, D.
A1  - Nadal-Romero, E.
A1  - Gonzalez-Hidalgo, J. C.
A1  - Albaladejo, J.
A1  - Andreu, V
A1  - Bagarello, V
A1  - Barhi, H.
A1  - Batalla, R. J.
A1  - Bernal, S.
A1  - Bienes, R.
A1  - Campo, J.
A1  - Campo-Bescos, M. A.
A1  - Canatario-Duarte, A.
A1  - Canton, Y.
A1  - Casali, J.
A1  - Castillo, V
A1  - Cerda, Artemi
A1  - Cheggour, A.
A1  - Cid, Patricio
A1  - Cortesi, N.
A1  - Desir, G.
A1  - Diaz-Pereira, E.
A1  - Espigares, T.
A1  - Estrany, Joan
A1  - Fernandez-Raga, M.
A1  - Ferreira, Carla S. S.
A1  - Ferro, Vito
A1  - Gallart, Francesc
A1  - Gimenez, R.
A1  - Gimeno, E.
A1  - Gomez, J. A.
A1  - Gomez-Gutierrez, A.
A1  - Gomez-Macpherson, H.
A1  - Gonzalez-Pelayo, O.
A1  - Hueso-Gonzalez, P.
A1  - Kairis, O.
A1  - Karatzas, G. P.
A1  - Klotz, S.
A1  - Kosmas, C.
A1  - Lana-Renault, Noemi
A1  - Lasanta, T.
A1  - Latron, J.
A1  - Lazaro, R.
A1  - Le Bissonnais, Y.
A1  - Le Bouteiller, C.
A1  - Licciardello, F.
A1  - Lopez-Tarazon, José Andrés
A1  - Lucia, A.
A1  - Marin, C.
A1  - Marques, M. J.
A1  - Martinez-Fernandez, J.
A1  - Martinez-Mena, M.
A1  - Martinez-Murillo, J. F.
A1  - Mateos, L.
A1  - Mathys, N.
A1  - Merino-Martin, L.
A1  - Moreno-de las Heras, M.
A1  - Moustakas, N.
A1  - Nicolau, J. M.
A1  - Novara, A.
A1  - Pampalone, V
A1  - Raclot, D.
A1  - Rodriguez-Blanco, M. L.
A1  - Rodrigo-Comino, Jesús
A1  - Romero-Diaz, A.
A1  - Roose, E.
A1  - Rubio, J. L.
A1  - Ruiz-Sinoga, J. D.
A1  - Schnabel, S.
A1  - Senciales-Gonzalez, J. M.
A1  - Simonneaux, V
A1  - Sole-Benet, A.
A1  - Taguas, E.
A1  - Taboada-Castro, M. M.
A1  - Taboada-Castro, M. T.
A1  - Todisco, Francesca
A1  - Ubeda, X.
A1  - Varouchakis, E. A.
A1  - Vericat, Damia
A1  - Wittenberg, L.
A1  - Zabaleta, A.
A1  - Zorn, M.
T1  - Spatial variability of the relationships of runoff and sediment yield with weather types throughout the Mediterranean basin
JF  - Journal of hydrology
N2  - Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) W and SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures.
KW  - Synoptic weather types
KW  - Erosion
KW  - Sediment yield
KW  - Runoff
KW  - Mediterranean basin
Y1  - 2019
U6  - https://doi.org/10.1016/j.jhydrol.2019.01.059
SN  - 0022-1694
SN  - 1879-2707
VL  - 571
SP  - 390
EP  - 405
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Soliveres, Santiago
A1  - Maestre, Fernando T.
A1  - Ulrich, Werner
A1  - Manning, Peter
A1  - Boch, Steffen
A1  - Bowker, Matthew A.
A1  - Prati, Daniel
A1  - Delgado-Baquerizo, Manuel
A1  - Quero, Jose L.
A1  - Schöning, Ingo
A1  - Gallardo, Antonio
A1  - Weisser, Wolfgang W.
A1  - Müller, Jörg
A1  - Socher, Stephanie A.
A1  - Garcia-Gomez, Miguel
A1  - Ochoa, Victoria
A1  - Schulze, Ernst-Detlef
A1  - Fischer, Markus
A1  - Allan, Eric
T1  - Intransitive competition is widespread in plant communities and maintains their species richness
JF  - Ecology letters
N2  - Intransitive competition networks, those in which there is no single best competitor, may ensure species coexistence. However, their frequency and importance in maintaining diversity in real-world ecosystems remain unclear. We used two large data sets from drylands and agricultural grasslands to assess: (1) the generality of intransitive competition, (2) intransitivity-richness relationships and (3) effects of two major drivers of biodiversity loss (aridity and land-use intensification) on intransitivity and species richness. Intransitive competition occurred in >65% of sites and was associated with higher species richness. Intransitivity increased with aridity, partly buffering its negative effects on diversity, but was decreased by intensive land use, enhancing its negative effects on diversity. These contrasting responses likely arise because intransitivity is promoted by temporal heterogeneity, which is enhanced by aridity but may decline with land-use intensity. We show that intransitivity is widespread in nature and increases diversity, but it can be lost with environmental homogenisation.
KW  - Aridity
KW  - biodiversity
KW  - coexistence
KW  - drylands
KW  - land use
KW  - mesic grasslands
KW  - rock-paper-scissors game
Y1  - 2015
U6  - https://doi.org/10.1111/ele.12456
SN  - 1461-023X
SN  - 1461-0248
VL  - 18
IS  - 8
SP  - 790
EP  - 798
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Nishikawa, Ken-Ichi
A1  - Mizuno, Yosuke
A1  - Niemiec, Jacek
A1  - Kobzar, Oleh
A1  - Pohl, Martin
A1  - Gomez, Jose L.
A1  - Dutan, Ioana
A1  - Frederiksen, Jacob Trier
A1  - Nordlund, Ake
A1  - Meli, Athina
A1  - Sol, Helene
A1  - Hardee, Philip E.
A1  - Hartmann, Dieter H.
T1  - Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields
JF  - Galaxies : open access journal
N2  - In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron-proton (e(-)-p(+)) and electron-positron (e(+/-)) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of "global" jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e(-)-p(+) jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e(+/-) jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields.
KW  - relativistic jets
KW  - particle-in-cell simulations
KW  - global jets
KW  - helical magnetic fields
KW  - kinetic instabilities
KW  - kink instability
Y1  - 2016
U6  - https://doi.org/10.3390/galaxies4040038
SN  - 2075-4434
VL  - 4
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Nishikawa, Ken-Ichi
A1  - Mizuno, Yosuke
A1  - Gomez, Jose L.
A1  - Dutan, Ioana
A1  - Meli, Athina
A1  - White, Charley
A1  - Niemiec, Jacek
A1  - Kobzar, Oleh
A1  - Pohl, Martin
A1  - Frederiksen, Jacob Trier
A1  - Nordlund, Ake
A1  - Sol, Helene
A1  - Hardee, Philip E.
A1  - Hartmann, Dieter H.
T1  - Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields: Dependence on Jet Radius
JF  - Galaxies : open access journal
N2  - In this study, we investigate the interaction of jets with their environment at a microscopic level, which is a key open question in the study of relativistic jets. Using small simulation systems during past research, we initially studied the evolution of both electron-proton and electron-positron relativistic jets containing helical magnetic fields, by focusing on their interactions with an ambient plasma. Here, using larger jet radii, we have performed simulations of global jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities, such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the mushroom instability (MI). We found that the evolution of global jets strongly depends on the size of the jet radius. For example, phase bunching of jet electrons, in particular in the electron-proton jet, is mixed with a larger jet radius as a result of the more complicated structures of magnetic fields with excited kinetic instabilities. In our simulation, these kinetic instabilities led to new types of instabilities in global jets. In the electron-proton jet simulation, a modified recollimation occurred, and jet electrons were strongly perturbed. In the electron-positron jet simulation, mixed kinetic instabilities occurred early, followed by a turbulence-like structure. Simulations using much larger (and longer) systems are required in order to further thoroughly investigate the evolution of global jets containing helical magnetic fields.
KW  - relativistic jets
KW  - particle-in-cell simulations
KW  - global jets
KW  - helical magnetic fields
KW  - kinetic instabilities
KW  - kink-like instability
KW  - recollimation shocks
KW  - polarized radiation
Y1  - 2017
U6  - https://doi.org/10.3390/galaxies5040058
SN  - 2075-4434
VL  - 5
PB  - MDPI
CY  - Basel
ER  - 
TY  - GEN
A1  - Nishikawa, Ken-Ichi
A1  - Mizuno, Yosuke
A1  - Niemiec, Jacek
A1  - Kobzar, Oleh
A1  - Pohl, Martin
A1  - Gómez, Jose L.
A1  - Duţan, Ioana
A1  - Pe’er, Asaf
A1  - Frederiksen, Jacob Trier
A1  - Nordlund, Åke
A1  - Meli, Athina
A1  - Sol, Helene
A1  - Hardee, Philip E.
A1  - Hartmann, Dieter H.
T1  - Microscopic processes in global relativistic jets containing helical magnetic fields
T2  - Galaxies
N2  - In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the initial evolution of both electron-proton (e(-)-p(+)) and electron-positron (e(+/-)) relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of "global" jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). In our initial simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the e(-)-p(+) jet simulation a recollimation-like instability occurs and jet electrons are strongly perturbed. In the e(+/-) jet simulation a recollimation-like instability occurs at early times followed by a kinetic instability and the general structure is similar to a simulation without helical magnetic field. Simulations using much larger systems are required in order to thoroughly follow the evolution of global jets containing helical magnetic fields.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 446 
KW  - relativistic jets
KW  - particle-in-cell simulations
KW  - global jets
KW  - helical magnetic fields
KW  - kinetic instabilities
KW  - kink instability
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407604
ER  - 
TY  - JOUR
A1  - Nishikawa, Ken-Ichi
A1  - Mizuno, Yosuke
A1  - Gomez, Jose L.
A1  - Duţan, Ioana
A1  - Meli, Athina
A1  - Niemiec, Jacek
A1  - Kobzar, Oleh
A1  - Pohl, Martin
A1  - Sol, Hélène
A1  - MacDonald, Nicholas
A1  - Hartmann, Dieter H.
T1  - Relativistic jet simulations of the weibel instability in the slab model to cylindrical jets with helical magnetic fields
JF  - Galaxies : open access journal
N2  - The particle-in-cell (PIC) method was developed to investigate microscopic phenomena, and with the advances in computing power, newly developed codes have been used for several fields, such as astrophysical, magnetospheric, and solar plasmas. PIC applications have grown extensively, with large computing powers available on supercomputers such as Pleiades and Blue Waters in the US. For astrophysical plasma research, PIC methods have been utilized for several topics, such as reconnection, pulsar dynamics, non-relativistic shocks, relativistic shocks, and relativistic jets. PIC simulations of relativistic jets have been reviewed with emphasis placed on the physics involved in the simulations. This review summarizes PIC simulations, starting with the Weibel instability in slab models of jets, and then focuses on global jet evolution in helical magnetic field geometry. In particular, we address kinetic Kelvin-Helmholtz instabilities and mushroom instabilities.
KW  - particle-in-cell simulations
KW  - relativistic jets
KW  - the Weibel instability
KW  - kink-like instability
KW  - mushroom instability
KW  - global jets
KW  - helical magnetic fields
KW  - recollimation shocks
Y1  - 2019
U6  - https://doi.org/10.3390/galaxies7010029
SN  - 2075-4434
VL  - 7
IS  - 1
PB  - MDPI
CY  - Basel
ER  -