@misc{AbramowskiAharonianBenkhalietal.2015, author = {Abramowski, Attila and Aharonian, Felix A. and Benkhali, Faical Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Backes, Michael and Balenderan, Shangkari and Balzer, Arnim and Barnacka, Anna and Becherini, Yvonne and Tjus, Julia Becker and Berge, David and Bernhard, Sabrina and Bernl{\"o}hr, Konrad and Birsin, E. and Biteau, Jonathan and B{\"o}ttcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Bregeon, Johan and Brun, Francois and Brun, Pierre and Bryan, Mark and Bulik, Tomasz and Carrigan, Svenja and Casanova, Sabrina and Chadwick, Paula M. and Chakraborty, Nachiketa and Chalme-Calvet, R. and Chaves, Ryan C. G. and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Conrad, Jan and Couturier, Claire and Cui, Yudong and Davids, Isak Delberth and Degrange, Bernhard and Deil, Christoph and deWilt, P. and Djannati-Ata{\"i}, A. and Domainko, Wilfried and Donath, Axel and Dubus, G. and Dutson, K. and Dyks, J. and Dyrda, M. and Edwards, Tanya and Egberts, Kathrin and Eger, Peter and Espigat, P. and Farnier, C. and Fegan, Stephen and Feinstein, Fabrice and Fernandes, Milton Virgilio and Fernandez, Diane and Fiasson, A. and Fontaine, Gerard and F{\"o}rster, Andreas and Fuessling, M. and Gabici, S. and Gajdus, M. and Gallant, Yves A. and Garrigoux, Tania and Giavitto, G. and Giebels, Berrie and Glicenstein, Jean-Francois and Gottschall, Daniel and Grondin, M. -H. and Grudzinska, M. and Hadasch, Daniela and Haeffner, S. and Hahn, Joachim and Harris, Jonathan and Heinzelmann, G{\"o}tz and Henri, G. and Hermann, German and Hervet, O. and Hillert, Andreas and Hinton, James Anthony and Hofmann, Werner and Hofverberg, Petter and Holler, Markus and Horns, Dieter and Ivascenko, Alex and Jacholkowska, A. and Jahn, C. and Jamrozy, Marek and Janiak, M. and Jankowsky, F. and Jung-Richardt, I. and Kastendieck, Max Anton and Katarzynski, K. and Katz, U. and Kaufmann, S. and Khelifi, B. and Kieffer, Michel and Klepser, S. and Klochkov, Dmitry and Kluzniak, W. and Kolitzus, David and Komin, Nu and Kosack, Karl and Krakau, Steffen and Krayzel, F. and Krueger, Pat P. and Laffon, H. and Lamanna, G. and Lefaucheur, J. and Lefranc, Valentin and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Lohse, Thomas and Lopatin, A. and Lu, Chia-Chun and Marandon, Vincent and Marcowith, Alexandre and Marx, Ramin and Maurin, G. and Maxted, Nigel and Mayer, Michael and McComb, T. J. Lowry and Mehault, J. and Meintjes, P. J. and Menzler, Ulf and Meyer, M. and Mitchell, Alison M. W. and Moderski, R. and Mohamed, M. and Mora, K. and Moulin, Emmanuel and Murach, Thomas and de Naurois, Mathieu and Niemiec, J. and Nolan, Sam J. and Oakes, Louise and Odaka, Hirokazu and Ohm, S. and Optiz, Bj{\"o}rn and Ostrowski, Michal and Oya, I. and Panter, Michael and Parsons, R. Daniel and Arribas, M. Paz and Pekeur, Nikki W. and Pelletier, G. and Petrucci, P. -O. and Peyaud, B. and Pita, S. and Poon, Helen and P{\"u}hlhofer, Gerd and Punch, M. and Quirrenbach, A. and Raab, S. and Reichardt, I. and Reimer, Anita and Reimer, Olaf and Renaud, Metz and de los Reyes, Raquel and Rieger, Frank and Romoli, C. and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, Vardan and Salek, D. and Sanchez, David M. and Santangelo, Andrea and Schlickeiser, Reinhard and Schuessler, F. and Schulz, A. and Schwanke, Ullrich and Schwarzburg, S. and Schwemmer, S. and Sol, H. and Spanier, Felix and Spengler, G. and Spies, Franziska and Stawarz, Lukasz and Steenkamp, Riaan and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, Martin and Trichard, C. and Valerius, K. and van Eldik, C. and van Soelen, B. and Vasileiadis, Georges and Veh, J. and Venter, Christo and Viana, Aion and Vincent, P. and Vink, Jacco and V{\"o}lk, Heinrich J. and Volpe, Francesca and Vorster, Martine and Vuillaume, T. and Wagner, S. J. and Wagner, P. and Wagner, R. M. and Ward, Martin and Weidinger, Matthias and Weitzel, Quirin and White, R. and Wierzcholska, A. and Willmann, P. and Woernlein, A. and Wouters, D. and Yang, Ruizhi and Zabalza, Victor and Zaborov, Dmitry and Zacharias, M. and Zdziarski, A. A. and Zech, Alraune and Zechlin, Hannes -S.}, title = {H.E.S.S. detection of TeV emission from the interaction region between the supernova remnant G349.7+0.2 and a molecular cloud (vol 574, A100, 2015)}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {580}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, organization = {HESS Collaboration}, issn = {1432-0746}, doi = {10.1051/0004-6361/201425070e}, pages = {2}, year = {2015}, language = {en} } @article{NishikawaHardeeZhangetal.2013, author = {Nishikawa, Ken-Ichi and Hardee, P. and Zhang, B. and Dutan, I. and Medvedev, M. and Choi, E. J. and Min, K. W. and Niemiec, J. and Mizuno, Y. and Nordlund, Ake and Frederiksen, Jacob Trier and Sol, H. and Pohl, Martin and Hartmann, D. H.}, title = {Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability}, series = {Annales geophysicae}, volume = {31}, journal = {Annales geophysicae}, number = {9}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {0992-7689}, doi = {10.5194/angeo-31-1535-2013}, pages = {1535 -- 1541}, year = {2013}, abstract = {We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin-Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field E-z, perpendicular to the flow boundary, and the magnetic field B-y, transverse to the flow direction. After the B-y component is excited, an induced electric field E-x, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios m(i)/m(e) = 1836 and m(i)/m(e) = 20 are similar. In our simulations in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (gamma(j) = 1.5) is larger than for a relativistic jet case (gamma(j) = 15).}, language = {en} } @article{NishikawaFrederiksenNordlundetal.2016, author = {Nishikawa, Ken-Ichi and Frederiksen, J. T. and Nordlund, A. and Mizuno, Y. and Hardee, P. E. and Niemiec, J. and Gomez, J. L. and Dutan, I. and Meli, A. and Sol, H. and Pohl, Martin and Hartmann, D. H.}, title = {EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH kKHI AND THE WEIBEL INSTABILITY}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {820}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/0004-637X/820/2/94}, pages = {14}, year = {2016}, abstract = {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.}, language = {en} } @article{NishikawaHardeeDutanetal.2014, author = {Nishikawa, Ken-Ichi and Hardee, P. E. and Dutan, I. and Niemiec, J. and Medvedev, M. and Mizuno, Y. and Meli, A. and Sol, H. and Zhang, B. and Pohl, Martin and Hartmann, D. H.}, title = {Magnetic agnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {793}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/793/1/60}, pages = {16}, year = {2014}, abstract = {We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.}, language = {en} } @misc{NishikawaZhangChoietal.2012, author = {Nishikawa, K.-I. and Zhang, B. and Choi, E. J. and Min, K. W. and Niemiec, J. and Medvedev, M. and Hardee, P. and Mizuno, Y. and Nordlund, A. and Frederiksen, J. and Sol, H. and Pohl, Martin and Hartmann, D. H. and Fishman, G.J.}, title = {Radiation from accelerated particles in shocks}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {600}, issn = {1866-8372}, doi = {10.25932/publishup-41312}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-413128}, pages = {371 -- 372}, year = {2012}, abstract = {Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs in the shocked regions. Simulations show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields and for particle acceleration. These magnetic fields contribute to the electron's transverse eflection behind the shock. The "jitter" radiation from deflected electrons in turbulent magnetic fields has properties different from synchrotron radiation calculated in a uniform magnetic field. This jitter radiation may be important for understanding the complex time evolution and/or spectral structure of gamma-ray bursts, relativistic jets in general, and supernova remnants. In order to calculate radiation from first principles and go beyond the standard synchrotron model, we have used PIC simulations. We present synthetic spectra to compare with the spectra obtained from Fermi observations.}, language = {en} } @article{NishikawaMizunoGomezetal.2017, author = {Nishikawa, Ken-Ichi and Mizuno, Yosuke and Gomez, Jose L. and Dutan, Ioana and Meli, Athina and White, Charley and Niemiec, Jacek and Kobzar, Oleh and Pohl, Martin and Frederiksen, Jacob Trier and Nordlund, Ake and Sol, Helene and Hardee, Philip E. and Hartmann, Dieter H.}, title = {Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields: Dependence on Jet Radius}, series = {Galaxies : open access journal}, volume = {5}, journal = {Galaxies : open access journal}, publisher = {MDPI}, address = {Basel}, issn = {2075-4434}, doi = {10.3390/galaxies5040058}, pages = {7}, year = {2017}, abstract = {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.}, language = {en} } @article{NishikawaMizunoGomezetal.2019, author = {Nishikawa, Ken-Ichi and Mizuno, Yosuke and Gomez, Jose L. and Duţan, Ioana and Meli, Athina and Niemiec, Jacek and Kobzar, Oleh and Pohl, Martin and Sol, H{\´e}l{\`e}ne and MacDonald, Nicholas and Hartmann, Dieter H.}, title = {Relativistic jet simulations of the weibel instability in the slab model to cylindrical jets with helical magnetic fields}, series = {Galaxies : open access journal}, volume = {7}, journal = {Galaxies : open access journal}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {2075-4434}, doi = {10.3390/galaxies7010029}, pages = {20}, year = {2019}, abstract = {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.}, language = {en} } @article{NishikawaMizunoNiemiecetal.2016, author = {Nishikawa, Ken-Ichi and Mizuno, Yosuke and Niemiec, Jacek and Kobzar, Oleh and Pohl, Martin and Gomez, Jose L. and Dutan, Ioana and Frederiksen, Jacob Trier and Nordlund, Ake and Meli, Athina and Sol, Helene and Hardee, Philip E. and Hartmann, Dieter H.}, title = {Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields}, series = {Galaxies : open access journal}, volume = {4}, journal = {Galaxies : open access journal}, publisher = {MDPI}, address = {Basel}, issn = {2075-4434}, doi = {10.3390/galaxies4040038}, pages = {9}, year = {2016}, abstract = {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.}, language = {en} } @misc{NishikawaMizunoNiemiecetal.2016, author = {Nishikawa, Ken-Ichi and Mizuno, Yosuke and Niemiec, Jacek and Kobzar, Oleh and Pohl, Martin and G{\´o}mez, Jose L. and Duţan, Ioana and Pe'er, Asaf and Frederiksen, Jacob Trier and Nordlund, {\AA}ke and Meli, Athina and Sol, Helene and Hardee, Philip E. and Hartmann, Dieter H.}, title = {Microscopic processes in global relativistic jets containing helical magnetic fields}, series = {Galaxies}, journal = {Galaxies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407604}, pages = {9}, year = {2016}, abstract = {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.}, language = {en} }