Localization of the Source of Quasiperiodic VLF Emissions in the Magnetosphere by Using Simultaneous Ground and Space Observations: A Case Study

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68378289%3A_____%2F20%3A00538380" target="_blank" >RIV/68378289:_____/20:00538380 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11320/20:10423192

Výsledek na webu

<a href="http://jultika.oulu.fi/files/nbnfi-fe2020052939702.pdf" target="_blank" >http://jultika.oulu.fi/files/nbnfi-fe2020052939702.pdf</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1029/2020JA027776" target="_blank" >10.1029/2020JA027776</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Localization of the Source of Quasiperiodic VLF Emissions in the Magnetosphere by Using Simultaneous Ground and Space Observations: A Case Study

Popis výsledku v původním jazyce

We study quasiperiodic very low frequency (VLF) emissions observed simultaneously by Van Allen Probes spacecraft and Kannuslehto and Lovozero ground-based stations on 25 December 2015. Both Van Allen Probes A and B detected quasiperiodic emissions, probably originated from a common source, and observed on the ground. In order to locate possible regions of wave generation, we analyze wave-normal angles with respect to the geomagnetic field, Poynting flux direction, and cyclotron instability growth rate calculated by using the measured phase space density of energetic electrons. We demonstrate that even parallel wave propagation and proper (downward) Poynting flux direction are not sufficient for claiming observations to be in the source region. Agreement between the growth rate and emission bands was obtained for a restricted part of Van Allen Probe A trajectory corresponding to localized enhancement of plasma density with scale of 700 km. We employ spacecraft density data to build a model plasma profile and to calculate ray trajectories from the point of wave detection in space to the ionosphere and examine the possibility of their propagation toward the ground. For the considered event, the wave could propagate toward the ground in the geomagnetic flux tube with enhanced plasma density, which ensured ducted propagation. The region of wave exit was confirmed by the analysis of wave propagation direction at the ground detection point.nKey PointsnComplex analysis of generation region of quasiperiodic VLF emissions were observed simultaneously by two Van Allen Probes and on the ground Wave growth rate frequency band matched the observed emission band only in a localized (similar to 0.3 Earth radii) region along Van Allen Probe A trajectory Ray tracing demonstrated the importance of a density duct for wave propagation toward the ground

Název v anglickém jazyce

Localization of the Source of Quasiperiodic VLF Emissions in the Magnetosphere by Using Simultaneous Ground and Space Observations: A Case Study

Popis výsledku anglicky

We study quasiperiodic very low frequency (VLF) emissions observed simultaneously by Van Allen Probes spacecraft and Kannuslehto and Lovozero ground-based stations on 25 December 2015. Both Van Allen Probes A and B detected quasiperiodic emissions, probably originated from a common source, and observed on the ground. In order to locate possible regions of wave generation, we analyze wave-normal angles with respect to the geomagnetic field, Poynting flux direction, and cyclotron instability growth rate calculated by using the measured phase space density of energetic electrons. We demonstrate that even parallel wave propagation and proper (downward) Poynting flux direction are not sufficient for claiming observations to be in the source region. Agreement between the growth rate and emission bands was obtained for a restricted part of Van Allen Probe A trajectory corresponding to localized enhancement of plasma density with scale of 700 km. We employ spacecraft density data to build a model plasma profile and to calculate ray trajectories from the point of wave detection in space to the ionosphere and examine the possibility of their propagation toward the ground. For the considered event, the wave could propagate toward the ground in the geomagnetic flux tube with enhanced plasma density, which ensured ducted propagation. The region of wave exit was confirmed by the analysis of wave propagation direction at the ground detection point.nKey PointsnComplex analysis of generation region of quasiperiodic VLF emissions were observed simultaneously by two Van Allen Probes and on the ground Wave growth rate frequency band matched the observed emission band only in a localized (similar to 0.3 Earth radii) region along Van Allen Probe A trajectory Ray tracing demonstrated the importance of a density duct for wave propagation toward the ground

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

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2020

Kód důvěrnosti údajů

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

Název periodika

Journal of Geophysical Research: Space Physics

ISSN

2169-9380

e-ISSN

—

Svazek periodika

125

Číslo periodika v rámci svazku

5

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

14

Strana od-do

e2020JA027776

Kód UT WoS článku

000540229100041

EID výsledku v databázi Scopus

2-s2.0-85085369827