The origin of jets emitted from black holes is not well understood, however there are two possible energy sources, the accretion disk or the rotating black hole. Magnetohydrodynamic simulations show a well-defined jet that extracts energy from a black hole. If plasma near the black hole is threaded by large-scale magnetic flux, it will rotate with respect to asymptotic infinity creating large magnetic stresses.These stresses are released as a relativistic jet at the expense of black hole rotational energy. The physics of the jet initiation in the simulations is described by the theory of black hole gravitohydromagnetics.Most quasars radiate a small fraction of their emission in the radio band (radio quiet), yet about 10% launch powerful radio jets (a highly collimated beam of energy and particles) with kinetic luminosities rivalling or sometimes exceeding the luminosity of the quasar host (radio loud).1 There is currently no clear theoretical understanding of the physics that occasionally switches on these powerful beams of energy in quasars.Powerful extragalactic radio sources tend to be associated with large elliptical galaxy host that harbour supermassive black holes (~10 9 M0). 2 The synchrotron emitting jets are clearly highly magnetized and appe ar to emanate from the environs of the central black hole, within the resolution limits of very long baseline interferometry (VLBI).Observations (see the supplementary file) indicate that jets emitted from supermassive black hole magnetospheres are likely required for any theory to be in accord with the data. 2,3,4 Previous perfect magnetohydrodynamic (MHD hereafter) simulations of entire black hole magnetospheres have shown some suggestive results. For example, the 2 simulations of [5] were the first to s how energy extraction from the black hole, but there was no outflow of plasma. Numerical models of an entire magnetosphere involve a complex set of equations that reflect the interaction of the background space-time with the plasma. In many instances, the only way to get any time evolution of the magnetosphere is to assume unphysical initial conditions. 5,6,9,10 Even so, previous simulations have not shown a black hole radiating away its potential energy into a pair of bipolar jets. 5,6,7,8,9,10 Most importantly, in previous efforts the underlying physics is masked by the complexity of the simulation. Thus, this numerical work has done little to clarify the fundamental physics that couples the jet to the black hole.We exploit the simplification that the full set of MHD equations in curved spacetime indicate that a magnetized plasma can be regarded as a fluid composed of nonlinear strings in which the strings are mathematically equivalent to thin magnetic flux tubes. 11,12 In this treatment, a flux tube is thin by definition if the pressure variations across the flux tube is negligible compared to the total external pressure (gas plus magnetic), P, that represents the effects of the enveloping magnetized plasma (the magnetosphere). By concentrating ...

[1] We study the Venus-solar wind interaction and the hemispheric asymmetries of the Venus plasma environment in the global HYB-Venus hybrid simulation. We concentrate especially on the role of the flow-aligned interplanetary magnetic field (IMF) component (i.e., the Parker spiral angle or the IMF cone angle) and analyze the dawn-dusk and E sw asymmetries between four magnetic quadrants around Venus. Using the simulation model, we study two upstream condition cases in detail: the perpendicular IMF to the solar wind flow case and the nominal Parker spiral case (dominant flow-aligned IMF component). Several differences and similarities were found in these two simulation runs. Common features of the Venus plasma environment between the two cases include asymmetric magnetic barrier and tail lobes and asymmetric planetary ion escape in the direction of the solar wind convection electric field. Further, protons of planetary origin and of solar wind origin were found to follow similar velocity patterns in the Venus plasma wake in both cases. The differences when the IMF flow-aligned component is dominating compared to the perpendicular IMF case, the so-called (magnetic) dawn-dusk asymmetries, include the parallel bow shock and the foreshock region, the asymmetric magnetic barrier, the asymmetric tail current system, and the asymmetric central tail current sheet. Further, the escaping planetary H + and O + ion fluxes are concentrated more on the hemisphere of the parallel bow shock. When interpreting in situ plasma and magnetic observations from Venus, the features of at least these two basic IMF configurations should be considered.

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[1] We study the solar wind induced escape of O + and H + ions from Venus' atmosphere in the HYB-Venus hybrid simulation. Most of the previous Venus global plasma modelling studies have concentrated only on the O + escape. According to the hybrid simulation, planetary O + and H + ions behave very differently from each other in the Venusian induced magnetosphere. Both species are asymmetrically distributed in the direction of the interplanetary electric field and in the dawn-dusk plane. The H + flow can be understood by E × B drift motion but finite Larmor radius (FLR) effects are essential to the behavior of O + ions. These differences result in different H + /O + escape ratios globally and in the plasma wake. Further, the energy ratio of the escaping planetary ions was found to be consistent with the observations made in the near Venus wake by the ASPERA-4 instrument onboard the Venus Express spacecraft. Citation: Jarvinen, R., E. Kallio, S. Dyadechkin, P. Janhunen, and I. Sillanpää (2010), Widely different characteristics of oxygen and hydrogen ion escape from Venus,

In the MHD description of plasma phenomena the concept of magnetic field lines frozen into the plasma turns out to be very useful. We present here a method of introducing Lagrangian coordinates into relativistic MHD equations in general relativity, which enables a convenient mathematical formulation for the behaviour of flux tubes. With the introduction of these Lagrangian, so-called "frozen-in" coordinates, the relativistic MHD equations reduce to a set of nonlinear 1D string equations, and the plasma may therefore be regarded as a gas of nonlinear strings corresponding to flux tubes. Numerical simulation shows that if such a tube/string falls into a Kerr black hole, then the leading portion loses angular momentum and energy as the string brakes, and to compensate for this loss, momentum and energy is radiated to infinity to conserve energy and momentum for the tube. Inside the ergosphere the energy of the leading part turns out to be negative after some time, and the rest of the tube then gets energy from the hole. In our simulations most of the compensated positive energy is also localized inside the ergosphere because 1 the inward speed of the plasma is approximately equal to the velocity of the MHD wave which transports energy outside. Therefore, an additional physical process has to be included which can remove energy from the ergophere.Magnetic reconnection seems fills this role releasing Maxwellian stresses and producing a relativistic jet.

[1] A 3-D spherical hybrid model has been developed to study how the solar wind interacts with various solar system bodies. The main advantages of the new spherical model, called the HYB-s, compared with traditional Cartesian models are that the spherical model allows significantly reduced radial cell size and, consequently, a smaller total number of cells and particles in the simulation. The high radial resolution makes it possible to use the new model for 3-D physical studies that have not been feasible before. Especially, the spherical model allows the inclusion of self-consistent ionospheric photochemistry in global hybrid simulations of the solar wind interaction with terrestrial planets Venus and Mars. In this paper we describe the main aspects of the developed spherical hybrid model. We also study the solar wind interaction with Venus in a global hybrid simulation using the spherical hybrid model and our already published Cartesian hybrid model. The comparison between the two models suggests the high potential of the developed spherical hybrid model in studies of planetary plasma interactions.Citation: Dyadechkin, S., E. Kallio, and R. Jarvinen (2013), A new 3-D spherical hybrid model for solar wind interaction studies,

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We have developed a new fully kinetic electrostatic simulation, HYBes, to study how the lunar landscape affects the electric potential and plasma distributions near the surface and the properties of lifted dust. The model embodies new techniques that can be used in various types of physical environments and situations. We demonstrate the applicability of the new model in a situation involving three charged particle species, which are solar wind electrons and protons, and lunar photoelectrons. Properties of dust are studied with test particle simulations by using the electric fields derived from the HYBes model. Simulations show the high importance of the plasma and the electric potential near the surface. For comparison, the electric potential gradients near the landscapes with feature sizes of the order of the Debye length are much larger than those near a flat surface at different solar zenith angles. Furthermore, dust test particle simulations indicate that the landscape relief influences the dust location over the surface. The study suggests that the local landscape has to be taken into account when the distributions of plasma and dust above lunar surface are studied. The HYBes model can be applied not only at the Moon but also on a wide range of airless planetary objects such as Mercury, other planetary moons, asteroids, and nonactive comets.