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

J 2017

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

YASNOV, Leonid V., Jan BENÁČEK and Marian KARLICKÝ

Basic information

Original name

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

Authors

YASNOV, Leonid V. (643 Russian Federation), Jan BENÁČEK (203 Czech Republic, belonging to the institution) and Marian KARLICKÝ (203 Czech Republic)

Edition

Solar Physics, DORDRECHT, NETHERLANDS, SPRINGER, 2017, 0038-0938

Other information

Language

English

Type of outcome

Článek v odborném periodiku

Field of Study

10308 Astronomy

Country of publisher

Netherlands

Confidentiality degree

není předmětem státního či obchodního tajemství

References:

URL

Impact factor

Impact factor: 2.580

RIV identification code

RIV/00216224:14310/17:00098163

Organization unit

Faculty of Science

DOI

http://dx.doi.org/10.1007/s11207-017-1174-4

UT WoS

000413851500001

Keywords in English

Sun: corona; Sun: flares; Sun: radio radiation

Abstract

V originále

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 1.3x10^17 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.We also computed the saturation energy density of the upper-hybrid waves (according to the double plasma resonance model, they are generated in the zebra source) using a 3D particle-in-cell model with a loss-cone type of distribution of hot electrons. We found that this saturated energy is proportional to the ratio of hot electron and background plasma densities. Thus, comparing the growth rate and collisional damping of the upper-hybrid waves, we estimated minimum densities of hot electrons as well as the minimum value of the saturation energy density of the upper-hybrid waves. Finally, we compared the computed energy density of the upper-hybrid waves with the energy density of the electromagnetic waves in the zebra source and thus estimated the efficiency of the wave transformation.

Citovat

YASNOV, Leonid V., Jan BENÁČEK and Marian KARLICKÝ. Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources. Solar Physics. DORDRECHT, NETHERLANDS: SPRINGER, 2017, vol. 292, No 11, p. 1-12. ISSN 0038-0938. Available from: https://dx.doi.org/10.1007/s11207-017-1174-4.

@article{1394404,
   author = {Yasnov, Leonid V. and Benáček, Jan and Karlický, Marian},
   article_location = {DORDRECHT, NETHERLANDS},
   article_number = {11},
   doi = {http://dx.doi.org/10.1007/s11207-017-1174-4},
   keywords = {Sun: corona; Sun: flares; Sun: radio radiation},
   language = {eng},
   issn = {0038-0938},
   journal = {Solar Physics},
   title = {Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources},
   url = {https://link.springer.com/article/10.1007/s11207-017-1174-4},
   volume = {292},
   year = {2017}
}

TY  - JOUR
ID  - 1394404
AU  - Yasnov, Leonid V. - Benáček, Jan - Karlický, Marian
PY  - 2017
TI  - Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources
JF  - Solar Physics
VL  - 292
IS  - 11
SP  - 1-12
EP  - 1-12
PB  - SPRINGER
SN  - 00380938
KW  - Sun: corona
KW  - Sun: flares
KW  - Sun: radio radiation
UR  - https://link.springer.com/article/10.1007/s11207-017-1174-4
L2  - https://link.springer.com/article/10.1007/s11207-017-1174-4
N2  - 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 1.3x10^17 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.We also computed the saturation energy density of the upper-hybrid waves (according to the double plasma resonance model, they are generated in the zebra source) using a 3D particle-in-cell model with a loss-cone type of distribution of hot electrons. We found that this saturated energy is proportional to the ratio of hot electron and background plasma densities. Thus, comparing the growth rate and collisional damping of the upper-hybrid waves, we estimated minimum densities of hot electrons as well as the minimum value of the saturation energy density of the upper-hybrid waves. Finally, we compared the computed energy density of the upper-hybrid waves with the energy density of the electromagnetic waves in the zebra source and thus estimated the efficiency of the wave transformation.
ER  -

YASNOV, Leonid V., Jan BENÁČEK and Marian KARLICKÝ. Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources. \textit{Solar Physics}. DORDRECHT, NETHERLANDS: SPRINGER, 2017, vol.~292, No~11, p.~1-12. ISSN~0038-0938. Available from: https://dx.doi.org/10.1007/s11207-017-1174-4.

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