Speaker
Description
Terrella (“little Earth” [1]) is a metalized spherical magnet with a dipolar magnetic field that can serve as a laboratory model of compact space objects with large magnetic fields (neutron stars, white dwarfs, etc.). In our case, Terrella is a spherical neodymium magnet with a diameter of $19~\mathrm{mm}$ supplied by high voltage (up to $400\,\mathrm{V}$) at a pressure between $2\,\mathrm{Pa}$ and $200\,\mathrm{Pa}$ in the environment of an inert gas (Ar). For positive polarity of applied voltage, the discharge appears mainly in the vicinity of magnetic poles, while for negative polarity, the discharge forms a disk perpendicular to the magnetic axis in the equatorial plane.
We investigated mainly the “disk” mode (negative applied voltage), where we measured electrical characteristics of the discharge, the radial distributions of Ar spectral lines by spectrograph and the radial distribution of the emitted light (integrated from all detectable wavelengths) by ICCD camera. In the selected area, the average light intensity (calculated from ICCD measurements) was determined depending on the distance from the edge of the Terrella. The resulting radial dependences were fitted by a power law in the distance of $1.1~r_{\mathrm{Terr.}} - 2.44~r_{\mathrm{Terr.}}$ from Terrella’s edge (for large “$r$”). The exponent of the power law decreased with increasing pressure, e.g., $k =-1.93~(2.1~\mathrm{Pa})$, and $k =-3.17~(200~\mathrm{Pa})$. These results fairly well overlapped with the theoretical model AGNSLIM [2], where the radial surface brightness dependence was $L(r)~\propto~r^{−2}$.
This research has been supported by Project LM2023039 funded by the Ministry of Education, Youth and Sports of the Czech Republic.
[1] Gilbert, William. De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure, 1600.
[2] Kubota, Aya and Chris Done (2019). “Modelling the spectral energy distribution of
super-Eddington quasars”. In: Monthly Notices of the Royal Astronomical Society
489.1, pp. 524–533.
