Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources

0482456 - ASÚ 2018 RIV NL eng J - Journal Article
Yasnov, L. V. - Benáček, J. - Karlický, Marian
Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources.
Solar Physics. Roč. 292, č. 11 (2017), 163/1-163/12. ISSN 0038-0938. E-ISSN 1573-093X
R&D Projects: GA ČR(CZ) GA16-13277S; GA ČR(CZ) GA17-16447S
Grant - others:GA MŠk,CERIT-SC(CZ) LM2015085; GA MŠk(CZ) LM2015042
Institutional support: RVO:67985815
Keywords : Sun corona * Su flares * radio radiation
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 2.580, year: 2017

We estimated the brightness temperature of radio zebras (zebra pattern - ZP), considering that ZPs are generated in loops having an exponential density profile in their cross section. We took into account that when in a plasma there is a source emitting in all directions, then in the escape process from the plasma the emission has a directional character nearly perpendicular to the constant-density profile. Owing to the high directivity of the plasma emission (for emission at frequencies close to the plasma frequency), the region from which the emission escapes can be very small. We estimated the brightness temperature of three observed ZPs for two values of the density scale height (1 and 0.21 Mm) and two values of the loop width (1 and 2 arcsec). In all cases, high brightness temperatures were obtained. For the higher value of the density scale height, the brightness temperature was estimated to be 1.1 x 10(15) -1.3 x 10(17) K, and for the lower value, it was 4.7 x 10(13) - 5.6 x 10(15) K. These temperatures show that the observational probability of a burst with a ZP, which is generated in the transition region with a steep gradient of the plasma density, is significantly higher than for a burst generated in a region with smoother changes of the plasma density.
Permanent Link: http://hdl.handle.net/11104/0277894