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 a Marian KARLICKÝ

Základní údaje

Originální název

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

Autoři

YASNOV, Leonid V. (643 Rusko), Jan BENÁČEK (203 Česká republika, domácí) a Marian KARLICKÝ (203 Česká republika)

Vydání

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

Další údaje

Jazyk

angličtina

Typ výsledku

Článek v odborném periodiku

Obor

10308 Astronomy

Stát vydavatele

Nizozemské království

Utajení

není předmětem státního či obchodního tajemství

Odkazy

URL

Impakt faktor

Impact factor: 2.580

Kód RIV

RIV/00216224:14310/17:00098163

Organizační jednotka

Přírodovědecká fakulta

DOI

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

UT WoS

000413851500001

Klíčová slova anglicky

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

Štítky

NZ, rivok

Příznaky

Mezinárodní význam, Recenzováno

Změněno: 29. 3. 2018 14:33, Ing. Nicole Zrilić

Anotace

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 a Marian KARLICKÝ. Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources. Solar Physics. DORDRECHT, NETHERLANDS: SPRINGER, 2017, roč. 292, č. 11, s. 1-12. ISSN 0038-0938. Dostupné z: 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 a Marian KARLICKÝ. Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources. \textit{Solar Physics}. DORDRECHT, NETHERLANDS: SPRINGER, 2017, roč.~292, č.~11, s.~1-12. ISSN~0038-0938. Dostupné z: https://dx.doi.org/10.1007/s11207-017-1174-4.

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