Određivanje parametara modela geomagnetske aktivnosti primjenom nelinearne metode najmanjih kvadrata

master's thesis

• Title (english): Parameter estimation of a geomagnetic activity model using non-linear least squares method
• Author: Martina Ćorković
• Mentor: Giuliana Verbanac (mentor)
• Committee member: Giuliana Verbanac (predsjednik povjerenstva)
• Committee member: Antun Marki (član povjerenstva)
• Committee member: Ivica Sović (član povjerenstva)
• Committee member: Mirko Orlić (član povjerenstva)
• Committee member: Josip Stipčević (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geophysics); Zagreb
• Defense date and country: 2023-10-27, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geophysics; Other Geographic Disciplines

Abstract

U ovom radu ispitujemo uspješnost O’Brien-McPherronovog modela za prognozu geomagnetskih oluja na temelju poremećaja Dst indeksa za geomagnetske oluje uzrokovane koroninim izbačajima mase u razdoblju od 1996. do 2020. godine. Koronini izbačaji mase su najsnažniji izbačaji plazme sa Sunca koji mogu doći do Zemlje i uzrokovati promjene magnetskog polja unutar magnetosfere koje se mogu detektirati magnetogramima na površini Zemlje. Također, nelinearnom metodom najmanjih kvadrata tražimo nove vrijednosti parametara tog modela α, b i Vq s obzirom na četiri razine solarne aktivnosti definirane preko broja Sunčevih pjega. Isti postupak primjenjujemo i za O’Brien-McPherronov model koji uključuje Svalgaardovu popravku za utjecaj elektičnog polja međuplanetarnog magnetskog polja na magnetosferu s obzirom na nagib dipola. Rezultati su pokazali da O’Brien-McPherronov model ne može u potpunosti prognozirati magnitude maksimuma i minimuma Dst indeksa te da su odstupanja najveća za nisku i visoku razinu aktivnosti. Pokazali smo da je parametar α umjereno linearno koreliran s brojem Sunčevih pjega, a Vq slabo, dok b ne ovisi o razini aktivnosti. Konačno, pokazali smo da Svalgaardova popravka ne unosi značajno poboljšanje za analizu pojedinačnih geomagnetskih oluja.

Abstract (english)

In this study, we investigate the effectiveness of the O’Brien-McPherron model for forecasting geomagnetic storms based on disturbances in the Dst index for geomagnetic storms caused by coronal mass ejections from 1996 to 2020. Coronal mass ejections are the most powerful plasma ejections from the Sun that can reach Earth and cause changes in the magnetic field within the magnetosphere, which can be detected by magnetograms on the Earth’s surface. Additionally, we seek new values for the parameters of this model α, b and Vq based on four levels of solar activity, defined by the number of sunspots, using nonlinear least squares. We apply the same precedure to the O’Brien-McPherron model which includes Svalgaard’s correction. Svalgaard’s correction describes the influence of the interplanetary magnetic field’s electric field on the magnetosphere with respect to the dipole tilt. The results have shown that the O’Brien-McPherron model cannot fully predict the magnitudes of the maximum and the minimum of the Dst index. The deviations in predicted magnitudes are greatest for low and high activity levels. We have demonstrated that the parameter α is moderately linearly correlated with the number of sunspots, while Vq is only weakly correlated. Parameter b does not depend on the activity level. Finally, we have shown that Svalgaard’s correction does not significantly improve the analysis of individual geomagnetic storms.

• Keywords: Dst indeks; razina solarne aktivnosti; O’Brien-McPherronov model; parametri modela
• Keywords (english): Dst index; solar activity level; O’Brien-McPherron model; model parameters
• Language: croatian
• URN:NBN: urn:nbn:hr:217:856685
• 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; Embargo expiration date: 2024-10-27
• Created on: 2023-11-06 12:28:08