Doppler Shifted Alpha Transmitter Signals in the Conjugate Hemisphere: DEMETER Spacecraft Observations and Raytracing Modeling

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68378289%3A_____%2F21%3A00542945" target="_blank" >RIV/68378289:_____/21:00542945 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11320/21:10439696

Výsledek na webu

<a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JA029017" target="_blank" >https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JA029017</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1029/2020JA029017" target="_blank" >10.1029/2020JA029017</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Doppler Shifted Alpha Transmitter Signals in the Conjugate Hemisphere: DEMETER Spacecraft Observations and Raytracing Modeling

Popis výsledku v původním jazyce

Alpha navigation transmitters are very low frequency (VLF) transmitters operating at mid-latitudes, which use a specific discrete radiation pattern at three distinct frequencies (11.9, 12.6, and 14.9 kHz). The transmitters are located in the northern hemisphere, but the radiated signals propagate through the magnetosphere to the conjugate hemisphere, where they are detectable by low-altitude spacecraft. We present an analysis of such signals detected by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions spacecraft at an altitude of about 660 km. It is found that, due to a Doppler shift, the observed signal frequencies can be at times rather different than the radiated frequencies. This indicates wave propagation at large wave normal angles (close to the resonance cone). Simultaneous observations of the same signal with different Doppler shifts reveal three distinct ways of signal propagation: (i) ducted propagation, (ii) unducted propagation, and (iii) propagation interpreted as only partially ducted. A raytracing analysis is employed to obtain typical wave trajectories corresponding to the individual ways of signal propagation and respective Doppler shifts. A reasonable agreement between the observed and calculated Doppler shifts is obtained. Our results demonstrate the peculiarities of VLF signal propagation throughout the magnetosphere and the possibility of using Doppler shifts to estimate wave normal angles.

Název v anglickém jazyce

Doppler Shifted Alpha Transmitter Signals in the Conjugate Hemisphere: DEMETER Spacecraft Observations and Raytracing Modeling

Popis výsledku anglicky

Alpha navigation transmitters are very low frequency (VLF) transmitters operating at mid-latitudes, which use a specific discrete radiation pattern at three distinct frequencies (11.9, 12.6, and 14.9 kHz). The transmitters are located in the northern hemisphere, but the radiated signals propagate through the magnetosphere to the conjugate hemisphere, where they are detectable by low-altitude spacecraft. We present an analysis of such signals detected by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions spacecraft at an altitude of about 660 km. It is found that, due to a Doppler shift, the observed signal frequencies can be at times rather different than the radiated frequencies. This indicates wave propagation at large wave normal angles (close to the resonance cone). Simultaneous observations of the same signal with different Doppler shifts reveal three distinct ways of signal propagation: (i) ducted propagation, (ii) unducted propagation, and (iii) propagation interpreted as only partially ducted. A raytracing analysis is employed to obtain typical wave trajectories corresponding to the individual ways of signal propagation and respective Doppler shifts. A reasonable agreement between the observed and calculated Doppler shifts is obtained. Our results demonstrate the peculiarities of VLF signal propagation throughout the magnetosphere and the possibility of using Doppler shifts to estimate wave normal angles.

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/GA21-01813S" target="_blank" >GA21-01813S: Antropogenní elektromagnetické emise a jejich vliv na vnitřní magnetosféru Země</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2021

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

2169-9402

Svazek periodika

126

Číslo periodika v rámci svazku

4

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

14

Strana od-do

e2020JA029017

Kód UT WoS článku

000645003000021

EID výsledku v databázi Scopus

2-s2.0-85104953495