Utjecaj Sunčevih bljeskova na širenje radio valova kroz ionosferu

master's thesis

• Title (english): Influence of solar flares on radio waves propagation through the ionosphere
• Author: Silvia Štajdohar
• Mentor: Giuliana Verbanac (mentor)
• Committee member: Giuliana Verbanac (predsjednik povjerenstva)
• Committee member: Antun Marki (član povjerenstva)
• Committee member: Ivica Sović (član povjerenstva)
• Committee member: Snježana Markušić (član povjerenstva)
• Committee member: Mirko Orlić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geophysics); Zagreb
• Defense date and country: 2021-03-09, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geophysics; Other Geographic Disciplines

Abstract

Cilj ovog rada bio je proučiti utjecaj Sunčevih bljeskova na širenje radio valova kroz Zemljinu ionosferu. Ionosfera je plazma, što znači da posjeduje električni naboj koji utječe na propagaciju radio signala. Raspodjela naboja nije uniformna, već se u ionosferi formiraju slojevi različitih gustoća nabijenih čestica i ionskog sastava.
Određeni slojevi po noći nestaju ili dolazi do smanjenja gustoće, signal radio valova je manje prigušen te je izmjereni intenzitet jači. Stoga, signal radio vala propagiranog kroz ionosferu ima karakterističan oblik s većom vrijednošću noću, a manjom tijekom dana.
Sunčeva magnetska aktivnost mijenja se otprilike svakih jedanaest godina i uvelike utječe na ionizaciju i širenje radio valova kroz ionosferu. U maksimumu Sunčevog ciklusa opažamo veću učestalost Sunčevih bljeskova kojima se oslobađa visokofrekventno zračenje. Energije bljeskova su toliko visoke da u kratkom vremenu dolazi do promjene gustoće nabijenih čestica u ionosferi. Jedno takvo razdoblje (rujan 2014.-ožujak 2015.) odabrano je za analizu u ovom radu. Korišteni su intenziteti radio valova mjereni SID (Sudden Ionospheric Disturbance) monitorima na tri prijemnika. Bljesak se manifestira kao nagla i relativno kratkotrajna promjena u intenzitetu radio signala. Moguć je i porast i pad intenziteta signala, a utjecaj bljeska vidljiviji je tijekom dana kada je intenzitet signala općenito slabiji.
U promatranom vremenskom intervalu, pojedini bljeskovi najviših energija (7000 − 20000 keV) primjećeni su na sva tri prijemnika. Bljeskovi manjih energija (100 − 300 keV) detektirani su na pojedinačnim prijemnicima. Za promatrane događaje analizirana je i geomagnetska aktivnost.

Abstract (english)

The purpose of this thesis was to examine the influence of solar flares on radio waves propagation through the ionosphere. The ionosphere is made of plasma which indicates the existence of electric charge. That charge can influence radio waves propagation. Charge distribution is non-uniform, it is layered and different layers have different charged particle densities and contain different types of ions. Some layers disappear at night or the density decreases, which leads to decreased radio waves atenuation and the intensity of the radio signal increases. During the day, intensity decreases.
The magnetic activity of the Sun follows a quasy-periodic, approximately 11 years long cycle, during which the magnetic polarity reverses. The solar activity influences the state of the Earth's ionosphere. During the solar cycle maximum, solar flares occure more frequently. Each flare realeases an amount of energy, in the form of high frequency radiation, high enough to instantly cause changes in the Earth's ionosphere. In this thesis we have analised the time interval from September 2014 to March 2015, the maximum of the 24th solar cycle, by analyzing the data obtained by three SID (Sudden Ionospheric Disturbance) monitors. The solar flares can be detected on a radio signal in a form of a sudden and relatively short signal change. Both decrease and increase in the signal intensity can occure. The influence of the are is more easily seen during the day when the intensity is showing lower values. Some flares, within the highest energy range (7000−20000 keV) were detected on each of the three monitors. Lower energy flares (100 − 300 keV) were detected on a single monitor. Geomagnetic activity for each of the studied solar events was also analysed.

• Keywords: ionosfera; ionizacija; širenje radio valova; Sunčevi bljeskovi; geomagnetska aktivnost
• Keywords (english): ionosphere; ionization; radio waves propagation; Solar flares; geomagnetic activity
• Language: croatian
• URN:NBN: urn:nbn:hr:217:312184
• Study programme: Title: Graduate university study pf Physics - Geophysics; specializations in: Seismology and Physics of the Earth's Interior, Meteorology and Physical Oceanography; Course: Meteorology and Physical Oceanography; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra fizike – geofizike (magistar/magistra fizike – geofizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-03-17 08:31:35