L. H. S. Kadowaki

The role of magnetic reconnection on jet/accretion disk systems

Context. It was proposed earlier that the relativistic ejections observed in microquasars could be produced by violent magnetic reconnection episodes at the inner disk coronal region (de Gouveia Dal Pino & Lazarian 2005). Aims. Here we revisit this model, which employs a standard accretion disk description and fast magnetic reconnection theory, and discuss the role of magnetic reconnection and associated heating and particle acceleration in different jet/disk accretion systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs). Methods. In microquasars and AGNs, violent reconnection episodes between the magnetic field lines of the inner disk region and those that are anchored in the black hole are able to heat the coronal/disk gas and accelerate the plasma to relativistic velocities through ad iffusive first-order Fermi-like process within the reconnection site that will produce intermittent relativistic ejections or plasmons. Results. The resulting power-law electron distribution is compatible with the synchrotron radio spectrum observed during the outbursts of these sources. A diagram of the magnetic energy rate released by violent reconnection as a function of the black hole (BH) mass spanning 10 9 orders of magnitude shows that the magnetic reconnection power is more than sufficient to explain the observed radio luminosities of the outbursts from microquasars to low luminous AGNs. In addition, the magnetic reconnection events cause the heating of the coronal gas, which can be conducted back to the disk to enhance its thermal soft X-ray emission as observed during outbursts in microquasars. The decay of the hard X-ray emission right after a radio flare could also be explained in this model due to the escape of relativistic electrons with the evolving jet outburst. In the case of YSOs a similar magnetic configuration can be reached that could possibly produce observed X-ray flares in some sources and provide the heating at the jet launching base, but only if violent magnetic reconnection events occur with episodic, very short-duration accretion rates which are ∼100−1000 times larger than the typical average accretion rates expected for more evolved (T Tauri) YSOs.

THE ROLE OF FAST MAGNETIC RECONNECTION ON THE RADIO AND GAMMA-RAY EMISSION FROM THE NUCLEAR REGIONS OF MICROQUASARS AND LOW LUMINOSITY AGNS

ABSTRACTFast magnetic reconnection events can be a very powerful mechanism operating in the core region,near the jet launching area, of microquasars and AGNs. In earlier work, it has been suggested that thepower released by fast reconnection events between the magnetic field lines lifting from the inner accre-tion disk region and the lines anchored into the central black hole could accelerate relativistic particlesand produce the observed radio emission from microquasars and low luminosity AGNs (LLAGNs).Moreover, it has been proposed that the observed correlation between the radio emission and the massof these sources, spanning 10 10 orders of magnitude in mass, might be related to this process. In thepresent work, we revisit this model comparing different fast magnetic reconnection mechanisms, andapply the scenario above to a much larger sample of sources (including also blazars, and gamma-raybursts - GRBs). We find that LLAGNs and microquasars confirm the trend above, i.e., their radioemission could be due to magnetic power released by turbulent driven fast reconnection which mayaccelerate particles to relativistic velocities in the core region of these sources. The correspondinggamma-ray emission, which is believed to be produced by interactions of the accelerated particleswith the surrounding photon and density fields, seems to be also produced in the same core regionin these sources. On the other hand, the emission from blazars and GRBs does not follow the sametrend as that of the LLAGNs and microquasars, suggesting that the radio and gamma-ray emissionin these cases is produced by another population of relativistic particles, accelerated further out inthe jet, as expected.Keywords: Accretion Disks — AGNs and Microquasars — Magnetic Reconnection — Radio andGamma Emission

On the Role of Fast Magnetic Reconnection in Accreting Black Hole Sources

We attempt to explain the observed radio and gamma-ray emission produced in the surrounds of black holes by employing a magnetically-dominated accretion flow (MDAF) model and fast magnetic reconnection triggered by turbulence. In earlier work, standard disk model was used and we refine the model by focussing on the sub-Eddington regime to address the fundamental plane of black hole activity. The results do not change substantially with regard to previous work ensuring that the details of the accretion physics are not relevant in the magnetic reconnection process occurring in the corona. Rather our work puts fast magnetic reconnection events as a powerful mechanism operating in the core region, near the jet base of black hole sources on more solid ground. For microquasars and low-luminosity active galactic nuclei (LLAGNs) the observed correlation between radio emission and mass of the sources can be explained by this process. The corresponding gamma-ray emission also seems to be produced in the same core region. On the other hand, the emission from blazars and gamma-ray bursts (GRBs) cannot be correlated to core emission based on fast reconnection.

MAGNETIC FIELD EFFECTS NEAR THE LAUNCHING REGION OF ASTROPHYSICAL JETS

One of the fundamental properties of astrophysical magnetic fields is their ability to change topology through reconnection and in doing so, to release magnetic energy, sometimes violently. In this work, we review recent results on the role of magnetic reconnection and associated heating and particle acceleration in jet/accretion disk systems, namely young stellar objects (YSOs), microquasars, and active galactic nuclei (AGNs).

On the role of magnetic reconnection in jet/accretion disk systems

The most accepted model for jet production is based on the magneto-centrifugal acceleration out off an accretion disk that surrounds the central source (Blandford & Payne, 1982). This scenario, however, does not explain, e.g., the quasi-periodic ejection phenomena often observed in different astrophysical jet classes. de Gouveia Dal Pino & Lazarian (2005) (hereafter GDPL) have proposed that the large scale superluminal ejections observed in microquasars during radio flare events could be produced by violent magnetic reconnection (MR) episodes. Here, we extend this model to other accretion disk systems, namely: active galactic nuclei (AGNs) and young stellar objects (YSOs), and also discuss its hole on jet heating and particle acceleration.

Magnetic Reconnection on Jet-Accretion disk Systems

Fast Magnetic Reconnection is currently regarded as an important process also beyond the solar system, specially in magnetically dominated regions of galactic and extragalactic sources like the surrounds of black holes and relativistic jets. In this lecture we discuss briefly the theory of fast magnetic reconnection, specially when driven by turbulence which is very frequent in Astrophysical flows, and its implications for relativistic particle acceleration. Then we discuss these processes in the context of the sources above, showing recent analytical and multidimensional numerical MHD studies that indicate that fast reconnection can be a powerful process to accelerate particles to relativistic velocities, produce the associated high energy non-thermal emission, and account for efficient conversion of magnetic into kinetic energy in these flows.