First Observation of Lion Roar Emission in Saturn's Magnetosheath

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F18%3A10389393" target="_blank" >RIV/00216208:11320/18:10389393 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/68378289:_____/18:00487612

Výsledek na webu

<a href="https://doi.org/10.1002/2017GL075919" target="_blank" >https://doi.org/10.1002/2017GL075919</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/2017GL075919" target="_blank" >10.1002/2017GL075919</a>

Jazyk výsledku

angličtina

Název v původním jazyce

First Observation of Lion Roar Emission in Saturn's Magnetosheath

Popis výsledku v původním jazyce

We present an observation of intense emissions in Saturn&apos;s magnetosheath as detected by the Cassini spacecraft. The emissions are observed in the dawn sector (magnetic local time similar to 06:45) of the magnetosheath over a time period of 11 h before the spacecraft crossed the bow shock and entered the unshocked solar wind. They are found to be narrow-banded with a peak frequency of about 0.16 f(ce), where f(ce) is the local electron gyrofrequency. Using plane wave propagation analysis, we show that the waves are right hand circularly polarized in the spacecraft frame and propagate at small wave normal angles (&lt;10 degrees) with respect to the ambient magnetic field. Electromagnetic waves with the same properties known as &quot;lion roars&quot; have been reported by numerous missions in the terrestrial magnetosheath. Here we show the first evidence such emission outside the terrestrial environment. Our observations suggest that lion roars are a solar-system-wide phenomenon and capable of existing in a broad range of parameter space. This also includes 1 order of magnitude difference in frequencies. We anticipate our result to provide new insight into such emissions in a new parameter regime characterized by a higher plasma beta (owing to the substantially higher Mach number bow shock) compared to Earth.

Název v anglickém jazyce

First Observation of Lion Roar Emission in Saturn's Magnetosheath

Popis výsledku anglicky

We present an observation of intense emissions in Saturn&apos;s magnetosheath as detected by the Cassini spacecraft. The emissions are observed in the dawn sector (magnetic local time similar to 06:45) of the magnetosheath over a time period of 11 h before the spacecraft crossed the bow shock and entered the unshocked solar wind. They are found to be narrow-banded with a peak frequency of about 0.16 f(ce), where f(ce) is the local electron gyrofrequency. Using plane wave propagation analysis, we show that the waves are right hand circularly polarized in the spacecraft frame and propagate at small wave normal angles (&lt;10 degrees) with respect to the ambient magnetic field. Electromagnetic waves with the same properties known as &quot;lion roars&quot; have been reported by numerous missions in the terrestrial magnetosheath. Here we show the first evidence such emission outside the terrestrial environment. Our observations suggest that lion roars are a solar-system-wide phenomenon and capable of existing in a broad range of parameter space. This also includes 1 order of magnitude difference in frequencies. We anticipate our result to provide new insight into such emissions in a new parameter regime characterized by a higher plasma beta (owing to the substantially higher Mach number bow shock) compared to Earth.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10305 - Fluids and plasma physics (including surface physics)

Projekt

<a href="/cs/project/LTAUSA17070" target="_blank" >LTAUSA17070: Elektromagnetické vlny v planetárních ionosférách a magnetosférách</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)<br>I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2018

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Geophysical Research Letters

ISSN

0094-8276

e-ISSN

—

Svazek periodika

45

Číslo periodika v rámci svazku

2

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

7

Strana od-do

486-492

Kód UT WoS článku

000425514300001

EID výsledku v databázi Scopus

2-s2.0-85040713156