[en] Efect of magnetic field on the thermal instability is studied in the radiatively cooling region behind an intersteller shock of moderate propagation velocity (approx.10km/sec). It is shown that the presence of intersteller magnetic field of a few micro gauss is very effective in preventing the thermal instability from building-up density concentration. In the absence of magnetic field, the shock-induced thermal instability amplifies preshock density inhomogeneity by more than an order of magnitude. However, in the presence of magnetic field, the amplified density contrast is shown to be only a factor 2. (Author)

[en] The two possible theories of the origin of the galacic magnetic field are discussed. It is shown that the first theory, of the generation by a fast magnetic dynamo, is limited by the size field which can be generated before the back reaction of the generated field on the flow inhibits amplications. The second theory that the galactic field is a relic of a general cosmic magnetic field existing prior to formation of our galaxy is briefly discussed. It is pointed out that such a field would evolve to a field very similar to that which we see today. (author). 4 refs

[en] In the past ten years, the Vela pulsar PSR 0833-45 has undergone several large, discontinuous changes - glitches - in its pulsation period. On 24 December 1988, we were making continuous radio measurements of the Vela pulsar with a 2-min time resolution when a glitch occurred. Here we report our observations, which on the day of the glitch extend from 12 h before the event to 6 h after and represent the first time a glitch has been caught as it happened. The period decrease occurred without warning and in less than 2 min; an exponential recovery similar to previously observed post-glitch behaviour began immediately. Observations were made at 635 MHz and 950 MHz, and the lower frequency signal showed an additional delay starting at the time of the glitch and continuing for about 35 days. This behaviour is consistent with a small increase in dispersion measure or a change in the pulsar's magnetic field configuration. After the glitch, the arrival times of pulses at both frequencies differed from the smoothly predicted times according to a damped sinusoidal oscillation with a period of about 25 days. (author)

[en] We discuss the observations and simulations related to the interaction of the solar wind (SW) and local interstellar medium (LISM), and the interstellar magnetic field draping around the heliopause (HP). This Letter sheds light on some processes that are not directly seen in the Voyager data. Special attention is paid to the magnetic field behavior at the HP crossing, penetration of shocks, and compression waves across the HP, and their merging in the LISM surrounding it. Modeling identifies forward and reverse shocks propagating through the heliosheath. Voyager data shows that the magnetic field strength experiences a jump at the HP, while the elevation and azimuthal angles are continuous across it. We show that our prior numerical results are in agreement with the Voyager data, if the heliospheric magnetic field is not assumed unipolar. The simulations confirm the importance of taking into account time dependencies of the SW flow, including the presence of transient structures and magnetohydrodynamic instabilities. For the first time, we provide the heliospheric community with the Alfvén speed distribution observed by Voyagers, which shows that it is unexpectedly small and decreases with distance from the HP. This is of critical importance for the identification of physical mechanisms responsible for the Langmuir wave and radio emission generation behind the HP. The data shows that outward-propagating, subcritical shocks traversing the LISM have a rather wide dissipation structure, which raises questions about their ability to reflect electrons as collisionless shocks can do.

[en] The strength and orientation of the magnetic field in the nearby interstellar medium have remained elusive, despite continual improvements in observations and models. Data from NASA's Voyager mission and the Solar Wind ANisotropies (SWAN) experiment on board Solar and Heliospheric Observatory (SOHO) have placed observational constraints on the magnetic field, and the more recent Interstellar Boundary Explorer (IBEX) data appear to also bear an imprint of the interstellar magnetic field (ISMF). In this paper, we combine computational models of the heliosphere with data from Voyager, SOHO/SWAN, and IBEX to estimate both the strength and direction of the nearby ISMF. On the basis of our simulations, we find that a field strength of 2-3 μG pointing from ecliptic coordinates (220-224, 39-44), combined with an interstellar hydrogen density of ∼0.15 cm^-3, produces results most consistent with observations.

[en] We discuss the global modeling of the properties of the Galactic Magnetic Field (GMF). Several improvements and variations of the model of the GMF from Jansson and Farrar (2012) are investigated in an analysis constrained by all-sky rotation measures of extragalactic sources and polarized and unpolarized synchrotron emission data from WMAP and Planck. We present the impact of the investigated model variations on the propagation of ultrahigh-energy cosmic rays in the Galaxy. (authors)

No abstract available

[en] Most of the theoretical results on the kinematic amplification of small-scale magnetic fluctuations by turbulence have been confined to the model of white-noise-like (δ-correlated in time) advecting turbulent velocity field. In this work, the statistics of the passive magnetic field in the diffusion-free regime are considered for the case when the advecting flow is finite-time correlated. A new method is developed that allows one to systematically construct the correlation-time expansion for statistical characteristics of the field such as its probability density function or the complete set of its moments. The expansion is valid provided the velocity correlation time is smaller than the characteristic growth time of the magnetic fluctuations. This expansion is carried out up to first order in the general case of a d-dimensional arbitrarily compressible advecting flow. The growth rates for all moments of the magnetic-field strength are derived. The effect of the first-order corrections due to the finite correlation time is to reduce these growth rates. It is shown that introducing a finite correlation time leads to the loss of the small-scale statistical universality, which was present in the limit of the δ-correlated velocity field. Namely, the shape of the velocity time-correlation profile and the large-scale spatial structure of the flow become important. The latter is a new effect, that implies, in particular, that the approximation of a locally-linear shear flow does not fully capture the effect of nonvanishing correlation time. Physical applications of this theory include the small-scale kinematic dynamo in the interstellar medium and protogalactic plasmas

[en] A model of the heliospheric magnetic field configuration is constructed by including a uniform interstellar magnetic field to the model proposed earlier. (author)

[en] Most part of visible matter is in the form of an ionized gas, namely plasma, where radiations, magnetic fields and turbulence play an important role. An open question is to understand how the value of the interstellar magnetic field has been multiplied by a 10¹⁴ factor since the Big Bang. An explanation to this amplification was given 50 years ago and it relied on the turbulent dynamo effect that appears when plasma fluctuations are high enough to amplify small initial fluctuations of the magnetic field. In order to test this explanation, an experiment was performed with the Megajoule laser that can both generate a plasma in a turbulent regime and produce energetic protons that are deflected by the magnetic field. The deflection of the protons is linked to the intensity of the magnetic field. Preliminary results show that the magnetic field amplification is less than that predicted by the simulation of the turbulent dynamo effect. (A.C.)