Hans Laszlo Pecseli

H. L. Pécseli, Fluctuations in Physical Systems, Cambridge University Press, UK (2000) pp. 190.

H. L. Pécseli, Waves and Oscillations in Plasmas, Taylor & Francis, UK (2012) pp. 553.

H. L. Pécseli, Low Frequency Waves and Turbulence in Magnetized Laboratory Plasmas and in the Ionosphere. Institute of Physics (IOP), UK (2016). pp. 631.

• Pécseli, Hans L & Trulsen, Jan Karsten (2021). On the applicability of Taylor's hypothesis, including small sampling velocities. Journal of Fluid Mechanics. ISSN 0022-1120. 932. doi: 10.1017/jfm.2021.969. Fulltekst i vitenarkiv
• Guio, Patrick & Pécseli, Hans L (2021). The Impact of Turbulence on the Ionosphere and Magnetosphere. Frontiers in Astronomy and Space Sciences. 7. doi: 10.3389/fspas.2020.573746. Fulltekst i vitenarkiv
• Fredriksen, Åshild; Pécseli, Hans L & Trulsen, Jan Karsten (2020). Anomalous transport due to large coherent structures in a magnetized toroidal plasma. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 63(1). doi: 10.1088/1361-6587/abc518. Fulltekst i vitenarkiv
• Miyake, Yohei; Miloch, Wojciech Jacek; Høymork, Solveig Helene & Pécseli, Hans L (2020). Electron Wing-Like Structures Formed at a Negatively Charged Spacecraft Moving in a Magnetized Plasma. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 125. doi: 10.1029/2019JA027379. Fulltekst i vitenarkiv
• Pécseli, Hans L; Trulsen, Jan Karsten; Stiansen, Jan Erik & Sundby, Svein (2020). Feeding of plankton in a turbulent environment: A comparison of analytical and observational results covering also strong turbulence. Fluids. ISSN 2311-5521. 5(1). doi: 10.3390/fluids5010037. Fulltekst i vitenarkiv
• Guio, Patrick & Pécseli, Hans L (2020). Weakly nonlinear ion sound waves in gravitational systems. Physical review. E. ISSN 2470-0045. 101(4). doi: 10.1103/PhysRevE.101.043210. Fulltekst i vitenarkiv
• Pécseli, Hans L; Trulsen, Jan Karsten; Stiansen, Jan Erik; Sundby, Svein & Fossum, Petter (2019). Feeding of plankton in turbulent oceans and lakes. Limnology and Oceanography. ISSN 0024-3590. 64(3), s. 1034–1046. doi: 10.1002/lno.11094. Fulltekst i vitenarkiv
• Fredriksen, Åshild; Pecseli, Hans & Trulsen, Jan Karsten (2018). A solvable model for the basic properties of a simple magnetized plasma torus. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 60:085021(8). doi: 10.1088/1361-6587/aacd2a. Fulltekst i vitenarkiv
• Kono, Mitsuo & Pecseli, Hans (2017). Stability of electron wave spectra in weakly magnetized plasmas. Journal of Plasma Physics. ISSN 0022-3778. 83(6). doi: 10.1017/S0022377817000873.
• Kono, Mitsuo & Pecseli, Hans (2016). Parametric decay of wide band Langmuir wave-spectra. Journal of Plasma Physics. ISSN 0022-3778. 82(6). doi: 10.1017/S0022377816001070.
• Pecseli, Hans; Sortland, Daniel Selnes & Garcia, Odd Erik (2016). A solvable blob-model for magnetized plasmas. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 58(10), s. 1–8. doi: 10.1088/0741-3335/58/10/104002. Fulltekst i vitenarkiv
• Pecseli, Hans & Trulsen, Jan Karsten (2016). Plankton’s perception of signals in a turbulent environment. Advances in Physics: X. ISSN 2374-6149. 1(1), s. 20–34. doi: 10.1080/23746149.2015.1136567.
• Guio, Patrick & Pecseli, Hans (2016). Weakly nonlinear ion waves in striated electron temperatures. Physical review. E. ISSN 2470-0045. 93(4). doi: 10.1103/PhysRevE.93.043204.
• Garcia, Odd Erik; Kube, Ralph; Theodorsen, Audun & Pecseli, Hans (2016). Stochastic modelling of intermittent fluctuations in the scrape-off layer: Correlations, distributions, level crossings, and moment estimation. Physics of Plasmas. ISSN 1070-664X. 23(5), s. 1–14. doi: 10.1063/1.4951016. Fulltekst i vitenarkiv
• Pecseli, Hans (2015). Low frequency electrostatic waves propagating in plasmas with parameters varying along magnetic field lines. Plasma Sources Science & Technology. ISSN 0963-0252. 25(1). doi: 10.1088/0963-0252/25/1/015010.
• Bergsaker, Anne Schad; Fredriksen, Åshild; Pecseli, Hans & Trulsen, Jan Karsten (2015). Models for the probability densities of the turbulent plasma flux in magnetized plasmas. Physica Scripta. ISSN 0031-8949. 90(10). doi: 10.1088/0031-8949/90/10/108005.
• Pecseli, Hans (2015). Spectral properties of electrostatic drift wave turbulence in the laboratory and the ionosphere. Annales Geophysicae. ISSN 0992-7689. 33(7), s. 875–900. doi: 10.5194/angeo-33-875-2015.
• Garcia, Odd Erik; Leer, Egil; Pecseli, Hans & Trulsen, Jan Karsten (2015). Magnetic field-aligned plasma currents in gravitational fields. Annales Geophysicae. ISSN 0992-7689. 33(3), s. 257–266. doi: 10.5194/angeo-33-257-2015. Fulltekst i vitenarkiv
• Pecseli, Hans (2014). Modulational stability of electron plasma wave spectra. Journal of Plasma Physics. ISSN 0022-3778. 80(5), s. 745–769. doi: 10.1017/S002237781400035X.
• Pecseli, Hans; Trulsen, Jan Karsten & Fiksen, Øyvind (2014). Predator-prey encounter and capture rates in turbulent environments. Limnology and Oceanography. ISSN 0024-3590. 4, s. 85–105. doi: 10.1215/21573689-2768717.
• Bergsaker, Anne Schad; Fredriksen, Åshild; Pecseli, Hans & Trulsen, Jan Karsten (2014). Analytical models for skewness-kurtosis relations in turbulent transport, 41st EPS Conference on Plasma Physics. European Physical Society. ISSN 2-914771-90-8.
• Børve, Steinar; Sato, Hiroatsu; Pecseli, Hans & Trulsen, Jan Karsten (2014). Low frequency oscillations of the magnetosphere, 2014 XXXIst URSI General Assembly and Scientific Symposium (URSI GASS 2014). Curran Associates, Inc.. ISSN 978-14673-5224-6. s. 3299–3301. doi: 10.1109/URSIGASS.2014.6929936.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2013). Unstable ring-shaped ion distribution functions induced by charge–exchange collisions. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 55(12). doi: 10.1088/0741-3335/55/12/124006.
• Garcia, Odd Erik & Pecseli, Hans (2013). Models for electrostatic drift waves with density variations along magnetic field lines. Geophysical Research Letters. ISSN 0094-8276. 40(21), s. 5565–5569. doi: 10.1002/2013GL057802. Fulltekst i vitenarkiv
• Rekaa, Vegard Lundby; Pecseli, Hans & Trulsen, Jan Karsten (2013). Self-similar space-time evolution of an initial density discontinuity. Physics of Plasmas. ISSN 1070-664X. 20(7). doi: 10.1063/1.4816953. Fulltekst i vitenarkiv
• Rekaa, Vegard Lundby; Pecseli, Hans & Trulsen, Jan Karsten (2012). Numerical studies of a plasma diode with external forcing. Physics of Plasmas. ISSN 1070-664X. 19(8). doi: 10.1063/1.4747620. Fulltekst i vitenarkiv
• Pecseli, Hans; Trulsen, Jan Karsten & Fiksen, Øyvind (2012). Predator-prey encounter and capture rates for plankton in turbulent environments. Progress in Oceanography. ISSN 0079-6611. 101(1), s. 14–32. doi: 10.1016/j.pocean.2011.12.001.
• Fattorini, L.; Fredriksen, Åshild; Pecseli, Hans; Riccardi, C. & Trulsen, Jan Karsten (2012). Turbulent transport in a toroidal magnetized plasma. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 54(8). doi: 10.1088/0741-3335/54/8/085017.
• Sato, Hiroatsu; Pecseli, Hans & Trulsen, Jan Karsten (2012). Fluctuations in the direction of propagation of intermittent low-frequency ionospheric waves. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 117. doi: 10.1029/2011JA017242.
• Miloch, Wojciech Jacek; Yaroshenko, V.; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2012). Spacecraft charging in flowing plasmas; numerical simulations. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 370. doi: 10.1088/1742-6596/370/1/012004.
• Sato, Hiroatsu; Pecseli, Hans & Trulsen, Jan Karsten (2011). Fluctuations in the Direction of Propagation of Low Frequency Ionospheric Waves. I Ouwehand, L (Red.), Proceedings of the 20th ESA Symposium on European Rocket and Balloon Programmes and Related Research. ESA Communications. ISSN 978-92-9092-264-3. s. 625–628.
• Pecseli, Hans & Trulsen, Jan Karsten (2011). Encounter rates and transit time distributions for surfaces moving in turbulent flows. Journal of Physics: Conference Series (JPCS). ISSN 1742-6588. 318. doi: 10.1088/1742-6596/318/5/052034.
• Daldorff, Lars Kristen Selberg; Pecseli, Hans; Trulsen, Jan Karsten; Ulriksen, Margit Iren; Eliasson, B. & Stenflo, Lennart (2011). Nonlinear beam generated plasma waves as a source for enhanced plasma and ion acoustic lines. Physics of Plasmas. ISSN 1070-664X. 18(5). doi: 10.1063/1.3582084.
• Børve, Steinar; Sato, Hiroatsu; Pecseli, Hans & Trulsen, Jan Karsten (2011). Minute-scale period oscillations of the magnetosphere. Annales Geophysicae. ISSN 0992-7689. 29(4), s. 663–671. doi: 10.5194/angeo-29-663-2011. Fulltekst i vitenarkiv
• Jørgensen, H. E.; Mikkelsen, T. & Pecseli, Hans (2010). Concentration Fluctuations in Smoke Plumes Released Near the Ground. Boundary-Layer Meteorology. ISSN 0006-8314. 137(3), s. 345–372. doi: 10.1007/s10546-010-9532-x.
• Pecseli, Hans; Trulsen, Jan Karsten & Fiksen, Øyvind (2010). Predator-prey encounter rates in turbulent water: Analytical models and numerical tests. Progress in Oceanography. ISSN 0079-6611. 85(3-4), s. 171–179. doi: 10.1016/j.pocean.2010.01.002.
• Krane, Bård; Pecseli, Hans; Sato, Hiroatsu; Trulsen, Jan Karsten & Wernik, A. W. (2010). Low-frequency electrostatic waves in the ionospheric E region. Plasma Sources Science & Technology. ISSN 0963-0252. 19(3). doi: 10.1088/0963-0252/19/3/034007.
• Pecseli, Hans & Trulsen, Jan Karsten (2010). Transit times in turbulent flows. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 81(4). doi: 10.1103/PhysRevE.81.046310.
• Miloch, Wojciech Jacek; Rekaa, Vegard Lundby; Pecseli, Hans & Trulsen, Jan Karsten (2010). Ion acoustic double layers forming behind irradiated solid objects in streaming plasmas. Journal of Plasma Physics. ISSN 0022-3778. 76, s. 429–439. doi: 10.1017/S002237780999064X.
• Guio, Patrick & Pecseli, Hans (2010). Collisionless Plasma Shocks in Striated Electron Temperatures. Physical Review Letters. ISSN 0031-9007. 104(8). doi: 10.1103/PhysRevLett.104.085002.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2009). Interaction of two elongated dust grains in flowing plasmas studied by numerical simulations. Physics of Plasmas. ISSN 1070-664X. 16(2). doi: 10.1063/1.3077667.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2009). Charging of insulating and conducting dust grains by flowing plasma and photoemission. New Journal of Physics. ISSN 1367-2630. 11. doi: 10.1088/1367-2630/11/4/043005.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2009). Charging of Dust in the Presence of a Directed Photon Flux: Numerical Simulations. Journal of Plasma and Fusion Research Series. ISSN 1883-9630. 8, s. 265–268.
• Pecseli, Hans & Trulsen, Jan Karsten (2009). Predator-prey Encounter Rates in Turbulent Environments: Consequences of Inertia Effects and Finite Sizes. AIP Conference Proceedings. ISSN 0094-243X. 1177, s. 85–95. doi: 10.1063/1.3253968.
• Dyrud, Lars; Wilson, Derek; Børve, Steinar; Trulsen, Jan Karsten; Pecseli, Hans & Close, Sigrid [Vis alle 7 forfattere av denne artikkelen] (2008). Plasma and electromagnetic wave simulations of meteors. Advances in Space Research. ISSN 0273-1177. 42, s. 136–142. doi: 10.1016/j.asr.2007.03.048. Vis sammendrag

  Every day billions of meteoroids impact and disintegrate in the Earth’s atmosphere. Current estimates for this global meteor flux vary from 2000-200,000 tons per year, and estimates for the average velocity range between 10 km/s to 70 km/s. The basic properties of this global meteor flux, such as the average mass, velocity, and chemical composition remain poorly constrained. We believe much of the mystery surrounding the basic parameters of the interplanetary meteor flux exists for the following reason, the unknown sampling characteristics of different radar meteor observation techniques, which are used to derive or constrain most models. We believe this arises due to poorly understood radio scattering characteristics of the meteor plasma, especially in light of recent work showing that plasma turbulence and instability greatly influences meteor trail properties at every stage of evolution. We present our results on meteor plasmas simulations of head echoes using particle in cell (PIC) ions, which show that electric fields strongly influence early stage meteor plasma evolution, by accelerating ions away from the meteoroid body. We also present the results of finite difference time domain electromagnetic simulations (FDTD), which can calculate the radar cross section of the simulated meteor plasmas. These simulations have shown that the radar cross section depends in a complex manner on a number of parameters. These include the angle between radar and meteor entry, a large dependence on radar frequency, which shows that for a given meteor plasma size and density, the reflectivity as a function of probing radar frequency varies, but typically peaks below 100 MHz.

• Dyrud, Lars; Wilson, Derek; Børve, Steinar; Trulsen, Jan Karsten; Pecseli, Hans & Close, Sigrid [Vis alle 7 forfattere av denne artikkelen] (2008). Plasma and Electromagnetic Simulations of Meteor Head Echo Radar Reflections. Earth, moon, and planets. ISSN 0167-9295. 102. doi: 10.1007/s11038-007-9189-8. Vis sammendrag

  Recently, meteor head echo detections from high powered large aperture radars (HPLA) have brought new measurements to bear on the study of sporadic interplanetary meteors. These same observations have demonstrated an ability to observe smaller meteoroids without some of the geometrical restrictions of specular radar techniques. Yet incorporating data from various radar reflection types and from different radars into a single consistent model has proven challenging. We believe this arises due to poorly understood radio scattering characteristics of the meteor plasma, especially in light of recent work showing that plasma turbulence and instability greatly influences meteor trail properties at every stage of evolution. In order to overcome some of the unknown relationships between meteoroid characteristics (such as mass and velocity) and the resulting head echo radar cross-sections (RCS), we present our results on meteor plasma simulations of head echo plasmas using particle in cell (PIC) ions, which show that electric fields strongly influence early stage meteor plasma evolution, by accelerating ions away from the meteoroid body at speeds as large as several kilometers per second. We also present the results of finite difference time domain electromagnetic simulations (FDTD), which can calculate the radar cross-section of the simulated meteor plasma electron distributions. These simulations have shown that the radar cross-section depends in a complex manner on a number of parameters. In this paper we demonstrate that for a given head echo plasma the RCS as a function of radar frequency peaks at sqrt (2*peak plasma frequency) and then decays linearly on a dB scale with increasing radar frequency. We also demonstrate that for a fixed radar frequency, the RCS increases linearly on a dB scale with increasing head echo plasma frequency. These simulations and resulting characterization of the head echo radar cross-section will both help relate HPLA radar observations to meteoroid properties and aid in determining a particular radar facility’s ability to observe various meteoroid populations.

• Fredriksen, Åshild; Fredriksen, A.A.; Pecseli, Hans L. & Trulsen, Jan (2008). Crash and recovery of the potential in a toroidal plasma column, as observed by generalized conditional sampling. New Journal of Physics. ISSN 1367-2630. 10(033030). doi: 10.1088/1367-2630/10/3/033030. Fulltekst i vitenarkiv
• Miloch, Wojciech Jacek; Trulsen, Jan Karsten & Pecseli, Hans (2008). Numerical studies of ion focusing behind macroscopic obstacles in a supersonic plasma flow. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 77.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2008). Numerical simulations of potential distribution for elongated insulating dust being charged by drifting plasmas. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 78. doi: 10.1103/PhysRevE.78.036411.
• Guio, Patrick; Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2008). Patterns of sound radiation behind pointlike charged obstacles in plasma flows. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 78. doi: 10.1103/PhysRevE.78.016401.
• Guio, Patrick; Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2008). Sound Radiation from Moving Point-Like Charged Particles in Plasmas. AIP Conference Proceedings. ISSN 0094-243X. 1061, s. 142–151. doi: 10.1063/1.3013762.
• Miloch, Wojciech Jacek; Pecseli, Hans; Trulsen, Jan Karsten & Vladimirov, Sergei V. (2008). Ion focusing and interaction potential for spherical and rodlike obstacles in a supersonic plasma flow: numerical simulations. AIP Conference Proceedings. ISSN 0094-243X. 1041, s. 287–288. doi: 10.1063/1.2997133.
• Dyrud, Lars; Krane, B.; Oppenheim, Meers; Pecseli, Hans; Trulsen, Jan Karsten & Wernik, Andrzej (2008). Structure functions and intermittency in ionospheric plasma turbulence. Nonlinear processes in geophysics. ISSN 1023-5809. 15(6), s. 847–862.
• Miloch, Wojciech Jacek; Vladimirov, SV; Pecseli, Hans & Trulsen, Jan Karsten (2008). Wake behind dust grains in flowing plasmas with a directed photon flux. Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. ISSN 1539-3755. 77. doi: 10.1103/PhysRevE.77.065401.

Se alle arbeider i Cristin

• Pecseli, Hans (2016). Low Frequency Waves and Turbulence in Magnetized Laboratory Plasmas and in the Ionosphere. IOP Publishing. ISBN 978-0-7503-1252-3. 631 s.
• Pecseli, Hans (2012). Waves and Oscillations in Plasmas. Taylor & Francis. ISBN 978-1-4398-7848-4. 553 s.

Se alle arbeider i Cristin

• Pecseli, Hans (2018). Predation in a turbulent environment. Vis sammendrag

  Analytical models for the statistical distribution of the gut content of fish larvae in a turbulent ocean environment are compared to data obtained in a field experiment. The proposed model allows the nutrition state and thereby the survival probability of plankton populations to be estimated for given conditions and parameters characterizing their environment, i.e., in terms of prey concentrations and turbulence levels. These parameters were all available in the field data. The species are characterized by their capture range and fields of view together with a characteristic time for digestion of their prey. The analysis allows an estimate for the entire probability density of the gut content of plankton in terms of the number of nauplii. In particular, the analytical results give a basis for an estimate of the average gut content of a given plankton population on the basis of basic informations concerning the environment.

• Pecseli, Hans (2017). Solvable models for "blobs" in magnetized plasmas.
• Pecseli, Hans (2016). Low frequency oscillations of the Earth's magnetosphere.
• Pecseli, Hans (2016). Low frequency oscillations of the magnetosphere.
• Pecseli, Hans (2016). Linear electrostatic drift waves (3 lectures), Nonlinear electrostatic drift waves (3 lectures).
• Pecseli, Hans (2015). Excess statistics with applications to turbulence in marine environments. Vis sammendrag

  Studies of excess statistics are standard in signal analysis, addressing some basic questions like average frequencies of level crossings in a random signal, and average time durations between an up and a down crossing. Results like these have applications for many problems, noise in electric circuits, turbulent diffusion, etc. It is here argued that the results can be applied also to estimating the "noise" experienced by aquatic microorganisms in a turbulent environment. This problem has particular interest in relations to predators and prey that rely on signals transmitted through motions in the surrounding water. The joint probability densities needed in the analysis can be obtained from numerical solutions of the Navier-Stokes equation for turbulent conditions, and be given universal scaling laws. Two limiting cases need to be considered: the inertial and viscous sub-ranges of the turbulence. It is possible to give estimates for how often a predator can mistake turbulence induced noise for a signal from prey in given turbulence conditions. Such mistakes can be observed as unmotivated attack reactions. Similarly, prey can mistake noise for presence of a predator, giving rise to seemingly unmotivated escape responses. The results can be verified experimentally in a laboratory, at least in principle.

• Pecseli, Hans & Trulsen, Jan Karsten (2015). Excess statistics with applications to turbulence in marine environments.
• Pecseli, Hans (2015). Drift wave turbulence in laboratory and space plasmas.
• Pecseli, Hans (2015). Excess statistics with applications to turbulence in marine enviroments.
• Pecseli, Hans (2015). Excess statistics with applications to anomalous transport in magnetized plasmas.
• Pecseli, Hans (2015). Nonlinear waves and turbulence.
• Pecseli, Hans (2015). Weakly Nonlinear Waves in Plasmas (4 lectures).
• Pecseli, Hans (2015). Introduction to Electrostatic Drift Waves (4 lectures).
• Pecseli, Hans (2015). Anomalous transport in a magnetized toroidal plasma.
• Pecseli, Hans (2014). Excess statistics with applications to turbulence in marine environments.
• Børve, Steinar; Sato, Hiroatsu; Pecseli, Hans & Trulsen, Jan Karsten (2014). LOW FREQUENCY OSCILLATIONS OF THE MAGNETOSPHERE.
• Bergsaker, Anne Schad; Fredriksen, Åshild; Pecseli, Hans & Trulsen, Jan Karsten (2014). Analytical models for skewness-kurtosis relations in turbulent transport.
• Pecseli, Hans (2014). Predator-prey encounters in turbulent environments: life on small scales in the oceans. Vis sammendrag

  Micro-organisms in the oceans, fish larvae and similar (here called "predators"), have only little motion of their own, and it can safely be assumed that they are passively carried along by the local flow velocity, at least to a first approximation. Similarly, it can be argued that their food (micro-zooplancton, for instance, here called "prey") is also passively convected by the same flow. It is then rather evident that such micro-organisms will eventually be starving, unless motions in the water changes the predator-prey separations, and brings, at least from time to time, some prey within reach of the predators. It is then an interesting question how the known laws of turbulence are reflected in the feeding processes of micro-organisms. Fortunately, the motion of particles in turbulent flows has been investigated in great detail, in part because of the strong environmental importance of the problem. A wealth of data are available for these types of phenomena, and it will be demonstrated how some of these data can be utilized in a simple way, in order to get insight also into the present problem. The existence of seemingly universal scaling laws for the average prey flux to a selected predator can be demonstrated. These laws depend on the radius in a suitably defined "reach of interception", as well as on the intensity of the turbulence. Some of these scaling laws are in contradiction with our intuitive expectations. In a larger perspective, the results have wider application, for combustion for instance, and more generally for many problems where turbulent mixing has importance.

• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2013). Kinetic plasma instabilities due to charge exchange collisions.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2013). Numerical simulations of kinetic plasma instabilities induced by charge exchange collisions.
• Pecseli, Hans (2013). Simple models for electrostatic drift waves and their relevance for the Earth’s ionosphere. Vis sammendrag

  A simple model for electrostatic drift waves in magnetized plasmas is outlined. All the model needs is the ion continuity equation, the ExB ion drift velocity perpendicular to magnetic field lines, concluded by some reasonable assumptions concerning a quasi-stationary low frequency electron motion. This very simple model indicates that electrostatic waves can propagate along the plasma surface, but can not explain why they are spontaneously excited. There is a source of free energy in the plasma inhomogeneity (or, if you like, the diamagnetic current). An instability is excited, for instance, due to deviations of the electron dynamics from the simplified model. We can for instance have resistive drift waves or current driven drift waves. The seminar is concluded by illustrations of how a standard ionosphere can be disturbed to give conditions for excitation of electrostatic drift waves. A very simple (yet novel) idea for a battery mechanism is described, whereby magnetic field aligned currents can be generated at plasma density gradients in the direction perpendicular to magnetic field lines.

• Pecseli, Hans (2013). Unstable Ring-Shaped Ion Distributions Functions Induced by Charge-Exchange Collisions.
• Pecseli, Hans (2013). Dynamics of Collisional Plasmas in Crossed Electric and Magnetic Fields.
• Pecseli, Hans; Miloch, Wojciech Jacek & Trulsen, Jan Karsten (2013). Kinetically unstable velocity distributions formed by charge exchange collisions with drifting ions.
• Pecseli, Hans; Trulsen, Jan Karsten & Fiksen, Øyvind (2013). Predator-prey encounter and capture rates in turbulent environments.
• Sato, Hiroatsu; Pecseli, Hans; Børve, Steinar & Trulsen, Jan Karsten (2012). Dynamic models for magnetospheric oscillations on the minute scale.
• Pecseli, Hans (2012). Predator-prey encounters in turbulent environments - life on small scales in the oceans.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2012). Numerical simulations of collisional partially ionized plasmas. Vis sammendrag

  The stability of plasma can be related to the shape of its velocity distributions [1]. For instance, for ionospheric plasmas it is argued that ion velocity distributions can deviate from Maxwellian giving rise to plasma instabilities [2, 3]. In order to study the possibility for losscone instabilities in collisional plasmas with Hall currents, we have modified our particle-in-cell code to include collisional effects in a magentized plasma. We have the option of adding a DCelectric field in the direction perpendicular to the magnetic field. We present the results from the self-consistent three dimensional simulations of the plasma velocity distributions under such conditions. In this study we investigate the role of collisions with the neutral component for the evolution and stability of the velocity distributions. In the most general case, we include elastic electron-neutral collisions, as well as charge exchange and elastic ion-neutral collisions. The results will be important for a detailed understanding of low frequency ionospheric plasmas, for instance in the E-region. References [1] O. Penrose, Phys. Fluids 3, 258 (1960). [2] J.-P. St.-Maurice, E. Winkler, and A. M. Hamza, J. Geophys. Res. 99, 19527 (1994) [3] J.-P. St.-Maurice and R. W. Schunk, Planet. Space Sci. 25, 243 (1977

• Rekaa, Vegard Lundby; Pecseli, Hans & Trulsen, Jan Karsten (2012). Numerical studies of a plasma diode with external forcings. Vis sammendrag

  With reference to laboratory studies we analyze the dynamics of a plasma diode under external forcing. Assuming a strong axial magnetic field, the problem is analyzed in one spatial dimension by a Particle in Cell code. The cathode is assumed to be operated in electron rich conditions, supplying an abundance of electrons. We compare different forcing schemes with the results obtained by solving the van der Pol equation. In one method of forcing we apply an oscillation in addition to the DC end plate bias, and consider both amplitude and frequency variations. An alternative method of perturbation consists of modelling an absorbing grid at some internal position. Also in this case we can have a constant frequency with varying amplitude, or alternatively an oscillation with chirped frequency but constant amplitude. We find that the overall features of the forced van der Pol equation are recovered, but the details in the plasma response require more attention to the harmonic responses, requiring extensions of the model equation. The analysis is extended by introducing collisional effects, where we emphasize charge exchange collisions of ions, since these processes usually have the largest cross sections. Charge exchange collisions give significant modifications of the diode performance when the effects are compared with the influence of elastic electron-neutral and ion-neutral collisions with the same collisional mean free paths.

• Sato, Hiroatsu; Børve, Steinar; Pécseli, Hans & Trulsen, Jan Karsten (2012). Minute-scale period oscillations of the magnetosphere. Vis sammendrag

  Oscillations with periods on the order of 5–10 min have been observed by instrumented spacecrafts in the Earth’s magnetosphere. These oscillations often follow sudden impacts related to coronal mass ejections. It is demonstrated that a simple model is capable of explaining the basic properties of these oscillations and give scaling laws for their basic characteristics in terms of the basic parameters of the problem. The period of the oscillations and their anharmonic nature, in particular, are accounted for. The model has no free adjustable numerical parameters. We use measurable quantities as inputs (such as Solar wind momentum density), and our results can be seen as an effort to predict some dynamic properties of magnetospheres on the basis of measurable steady state characteristics. A simple test of the model is found by comparing its prediction of the Earth-Magnetopause distance with observed values. The general results agree with observations. The analysis is supported by numerical simulations solving the Magneto-Hydro-Dynamic (MHD) equations in two spatial dimensions, where we let a solar wind interact with a magnetic dipole representing a magnetized Earth. Two tilt-angles of the magnetic dipole axis were considered. We observed the formation of a magnetosheath, with the magnetopause at a distance corresponding well to the analytical results. Sudden pulses in the model solar wind sets the model magnetosphere into damped oscillatory motions and quantitatively good agreement with the analytical results is found. The models seem to be robust, and give good qualitative agreement with the numerical simulations for a range of parameters.

• Miloch, Wojciech Jacek; Yaroshenko, V.; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2011). Spacecraft charging in space and ionospheric plasma; numerical simulations.
• Pecseli, Hans (2011). Experimental studies of intermittency and turbulent transport in linear and toroidal magnetized plasmas.
• Pecseli, Hans & Trulsen, Jan Karsten (2011). Encounter rates and transit time distributions for surfacesmoving in turbulent flows. Vis sammendrag

  Reaction rates as relevant for many chemical processes as well as a number of biological applications depend on encounter rates of reacting elements and the probability of a reaction occurring given an encounter. Turbulent mixing can enhance the encounter rate, but it can also have adverse effects by reducing the reaction probability. We model the probability for a reaction by letting it depend on the time available, i.e. the time spent by of reacting particles within some given interaction volume. We study the problems by numerical simulations where we analyze the statistics of the motion of passively convected point particles in turbulent flows. The database used is obtained by direct numerical solution of the Navier-Stokes equation. We estimate the encounter rates and also the probability distribution of the transit times of particles through reference volumes with given forms and sizes. A selected position within the reference volume is moving self consistently with the local flow velocity, thus determining the motion of the entire surface. The transit time is defined as the interval between entrance and exit times of surrounding particles convected through the volume by the turbulent motions. Scale sizes in the inertial as well as in the viscous subranges of the turbulence are considered. Simple, and seemingly universal, scaling laws are obtained for the encounter rate as well as the probability density of the transit times in terms of the basic properties of the turbulent flow and the geometry. In the present formulation, the results of the analysis are relevant for chemical reactions, but also for understanding details of the feeding rate of micro-organisms in turbulent waters, for instance.

• Rekaa, Vegard Lundby; Pecseli, Hans & Trulsen, Jan Karsten (2011). Numerical simulations of anomalous resistivity in the ion acoustic and Buneman regime.
• Pecseli, Hans; Trulsen, Jan Karsten & Fiksen, Øyvind (2009). Predators in turbulent waters: an analytical model and a numerical test.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2009). Numerical studies of ion focusing in streaming plasmas; two and three dimensions.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2009). Interactions of two objects in flowing plasmas studied by numerical simulations.
• Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2009). Ion focusing behind finite size objects in flowing plasmas; numerical studies in two and three dimensions.
• Dyrud, Lars; Krane, Bård; Oppenheim, Mers; Pecseli, Hans; Trulsen, Jan Karsten & Wernik, A. W. (2008). Structure functions and intermittency in ionospheric plasma turbulence.
• Guio, Patrick; Miloch, Wojciech Jacek; Pecseli, Hans & Trulsen, Jan Karsten (2008). Ion-sound from charged obstacles in a plasma flow.
• Miloch, Wojciech Jacek; Pecseli, Hans; Trulsen, Jan Karsten & Vladimirov, Sergei V. (2008). Numerical simulations of interactions between solid surfaces (dust grains) and plasmas.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2008). The charging of dust grains and the wake formation studied by numerical simulations.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2008). Charging and wake of dust grains in supersonic plasma flows: numerical simulations.
• Miloch, Wojciech Jacek; Vladimirov, Sergei V.; Pecseli, Hans & Trulsen, Jan Karsten (2008). Numerical simulations of the charging and wake of dust grains in flowing plasmas.

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