Aperiodic and wave disturbances in the ionosphere: the results of vertical sounding»

The monograph presents the study results of aperiodic and quasi-periodic wave perturbations in the ionosphere during unique phenomena in geospace: partial solar eclipses, the fall of the Chelyabinsk cosmic body and during the operation of a powerful radio source – the heating stand «Sura». Experimental data obtained by the method of remote sensing are analyzed. Designed for scientists in the field of ionosphere physics, radio physics, radar, as well as for lecturers, graduate and Ph.D. students.

The Jet-Disk Coupling of Seyfert Galaxies from a Complete Hard X-ray Sample

We analyze the jet-disk coupling for different subsamples from a complete hard X-ray Seyfert sample to study the coupling indices and their relation to accretion rate. The results are: (1) the power-law coupling index ranges from nearly unity (linear correlation) for radio loud Seyferts to significantly less than unity for radio quiet ones. This decline trend of coupling index also holds from larger sources to compact ones; (2) the Seyferts with intermediate to high accretion rate (Eddington ratio λ ∼ 0.001 to 0.3) show a linear jet-disk coupling, but it shallows from near to super Eddington ( λ ∼ 0.3 to 10), and the former is more radio loud than the latter; (3) the Seyfert 1s are slightly steeper than the Seyfert 2s, in the jet-disk correlation. In the linear coupling regime, the ratio of jet efficiency to radiative efficiency ( η / ε ) is nearly invariant, but in low accretion or super accretion regime, η / ε varies with λ in our model. We note that a radio-active cycle of accretion-dominated active galactic nuclei would be: from a weaker jet-disk coupling in λ < 0 . 001 for low luminosity Seyferts, to a linear coupling in 0 . 001 < λ < 0 . 3 for radio-loud luminous Seyferts and powerful radio galaxies/quasars, and to a weaker coupling in 0 . 3 < λ < 10 ones.

“A Cold Wind A’ Blowin’ ” (1991–2019)

During the period covered at the beginning of this chapter (the early 1990s), WAMU-FM and the Birchmere both still featured bluegrass; by the chapter’s close, in the contemporary period, this powerful radio station had completely transitioned to a news and talk format and the Birchmere only occasionally booked this genre. The sheer number of bands and venues diminished noticeably as did the general interest in bluegrass. The shrinkage of bluegrass programming on WAMU-FM was gradual and deliberate, occurring over some dozen years. The local bluegrass community vehemently protest, but to no avail. However, the existence of the WAMU-FM spin-off bluegrasscountry.org and the formation of DC Bluegrass Union reflect the existence of the ongoing, though diminished, local bluegrass community.

The GLEAMing of the first supermassive black holes

We present the results of a new selection technique to identify powerful ( $L_{\rm 500\,MHz} \gt 10^{27}\,\text{WHz}^{-1}$ ) radio galaxies towards the end of the Epoch of Reionisation. Our method is based on the selection of bright radio sources showing radio spectral curvature at the lowest frequency ( ${\sim}100\,\text{MHz}$ ) combined with the traditional faintness in K-band for high-redshift galaxies. This technique is only possible, thanks to the Galactic and Extra-galactic All-sky Murchison Wide-field Array survey which provides us with 20 flux measurements across the 70– $230\,\text{MHz}$ range. For this pilot project, we focus on the GAMA 09 field to demonstrate our technique. We present the results of our follow-up campaign with the Very Large Telescope, Australian Telescope Compact Array, and the Atacama Large Millimetre Array to locate the host galaxy and to determine its redshift. Of our four candidate high-redshift sources, we find two powerful radio galaxies in the $1<z<3$ range, confirm one at $z=5.55$ , and present a very tentative $z=10.15$ candidate. Their near-infrared and radio properties show that we are preferentially selecting some of the most radio luminous objects, hosted by massive galaxies very similar to powerful radio galaxies at $1<z<5$ . Our new selection and follow-up technique for finding powerful radio galaxies at $z>5.5$ has a high 25–50% success rate.