Dijagnostika plazme jonosferske D oblasti elektromagnetnim VLF talasima

Abstract

U ovoj disertaciji su prikazani rezultati istraživanja plazme jonosferske Doblasti zasnovani na kontinuiranoj, simultanoj registraciji elektromagnetnih talasa vrlo niskih frekvencija emitovanih predajnicima lociranim širom sveta i registrovanih prijemnikom koji se od 2008. godine nalazi na Institutu za fiziku u Zemunu. Motivi za izradu ove studije su bili: 1. Analiza dobijene baze podataka kojom je omogu´ceno višegodišnje kontinuirano pra´cenje kako periodiˇcnih tako i neperiodiˇcnih poreme´caja plazme D-oblasti izazvanih brojnim procesima u svemiru i raznim delovima Zemlje. 2. Ispitivanje moguc´nosti detekcije dogad¯aja koji slabije perturbuju posmatranu plazmu pomo´cu eksperimentalne postavke koriš´cene u disertaciji. U okviru studije koriš´ceni su signali emitovani na razliˇcitim fiksnim frekvencijama predajnicima lociranim u Nemaˇckoj, Itaiji, Velikoj Britaniji, Islandu, Sjedinjenim Ameriˇckim Državama i Australiji. Posmatrani podaci su upotrebljeni za slede´ca istraživanja: 1. Modeliranje elektronske koncentracije tokom poreme´caja plazme D-oblasti izazvanih Sunˇcevim X-flerovima. U ovom istraživanju dobijene su prostorno-vremenske zavisnosti koncentracije elektrona koje su dalje koriš´cene u teorijskom modelu razvijenom u okviru ove studije i primenljivom tokom relaksacije plazme. Konaˇcni izrazi datog modela daju prostorno-vremenske raspodele brzina proizvodnje i gubitaka elektrona, i koeficijenta koji se odnosi na efektivne gubitke ovog konstituenta plazme. Dobijene vremenske zavisnosti teže ka vrednostima koje karakterišu neperturbovano stanje plazme na posmatranim lokacijama ˇcime se dobija prostorna raspodela posmatranih veliˇcina u mirnoj D-oblasti. 2. Detektovanje linearnih hidrodinamiˇckih talasa uzrokovanih naglim poreme´cajima u Doblasti. Analiza u ovom radu predstavlja proširenje postoje´cih istraživanja tog fenomena u višim slojevima na posmatranu oblast. Teorijska procedura je primenjena na procese izlaska i zalaska Sunca. 3. Ispitivanje mogućnosti detekcije poremećaja u D-oblasti jonosfere usled upada zračenja koje slabo jonizuje analiziranu plazmu. Konkretno, prikazana je statistička analiza uticaja bljeskova γ-zraka na D-oblast jonosfere. Pored posmatranja sumarnih rezultata za ceo uzorak od 54 registrovana događaja, ovaj uticaj je razmatran i uzimajuc´i u obzir karakteristike posmatranih γ-bljeskova, karakteristike jonosfere u periodima njihovog upada i pravce upada zraka u odnosu na putanju posmatranog signala...

This dissertation presents results of studying the ionospheric D-region plasma based on continuous, simultaneous registration of very low frequency electromagnetic waves emitted by transmitters distributed worldwide and recorded by the receiver located at the Institute of Physics in Zemun from 2008. The motives for making this study were: 1. The analysis of the obtained data base which enables perennial continuous monitoring of both periodical and non-periodical disturbances of the D-region plasma induced by numerous processes in space and various parts of the Earth. 2. Investigation of possibility to detect events that weakly perturb the considered plasmas by means of the experimental setup used in the dissertation. The performed study utilizes signals emitted at different fixed frequencies from transmitters in Germany, Italy, UK, Island, USA, and Australia. The considered data were used in the following fields of investigation: 1. Modeling of the electron concentration in perturbed plasma of the D-region induced by solar X-flares. Space-time variations of the electron concentration are obtained and further used in a theoretical model of plasma in the relaxation period that is developed in this study. The obtained final results for a given model yield space-time distributions of electron gain and loss rates, and the coefficient for the effective electron loss process. The resulting time-dependencies converge to values typical of the unperturbed plasma at considered locations which consequently reveals their spatial distribution in the unperturbed D-region plasma. 2. Detection of linear hydrodynamic waves resulting from sudden disturbances in the Dregion. The analysis developed in this work can be treated as an extension to the considered region of the existing studies at much higher altitudes. The theoretical procedure is applied to processes related to the sunrise and sunset. 3. Examining the possibilities to detect disturbances in the ionospheric D-region caused by impacts of radiation that weakly ionizes the analyzed plasma. Specifically, this includes a statistical analysis of the influence of γ-ray bursts on the ionospheric Dregion. In addition to the observation of summary results for the entire sample of 54 registered events, this influence is considered to take into account the characteristics of the observed γ-ray bursts, characteristics of the ionosphere during the periods of their impacts and directions of rays impacts in relative to the trajectory of the observed signal...