Physics Commons^™

Diagnostics Of Energy Release In Solar Flares With Radio Dynamic Imaging Spectroscopy, Yingjie Luo

Dissertations

Studies of the magnetic energy release and conversion process lie at the core of solar flare physics. Radio observations serve as a unique diagnostic method. In this dissertation, taking advantage of broadband radio dynamic imaging spectroscopy observations made by the Karl G. Jansky Very Large Array (VLA), studies are carried out on the flare energy release processes using different types of radio emissions.

The VLA is a general-purpose radio observatory located in New Mexico, which provides high-quality radio dynamic imaging spectroscopic observations with an ultra-fast time cadence. In the first study, stochastic decimetric radio spike bursts are observed by the …

Scaling Theory Of 3d Magnetic Reconnection X-Line Spreading, Milton Arencibia

Graduate Theses, Dissertations, and Problem Reports

Magnetic reconnection is fundamental process in plasmas that converts magnetic energy into kinetic and thermal energy via a change in magnetic topology. Magnetic reconnection is known to mediate eruptive solar flares, geomagnetic substorms that create the Northern lights, heating and particle acceleration in controlled fusion devices, and is thought to be an important process in numerous settings in high-energy astrophysics. Classical models of reconnection are two-dimensional (2D), but naturally occurring reconnection is three-dimensional (3D), and a manifestation of the 3D nature is that the x-line where the magnetic field topology changes has a finite extent in the direction normal to …

Solar Flares As Observed In The Low Frequency Microwave Gyrosynchrotron Emission, Shaheda Begum Shaik

Dissertations

Solar flares involve the sudden catastrophic release of magnetic energy stored in the Sun’s corona. This dissertation focuses on investigating the low frequency, optically-thick gyrosynchrotron emission during solar flares for its spatial and spectral dynamics, characteristics, and role in the flare process.

The first part of this dissertation first addresses the spectral dynamics and characteristics of the source morphology. The high-resolution spectra of a set of microwave bursts observed by the Expanded Owens Valley Solar Array (EOVSA) during its commissioning phase in the 2.5-18 GHz frequency range with 1-s time resolution are presented here. Out of the 12 events analyzed …

Radio Diagnostics Of Particles And Plasma In The Solar Corona, Sherry Chhabra

Dissertations

Radio diagnostics, in addition to their capabilities in exploring intense, impulsive bursts, also provide a high sensitivity to much weaker events, which may not show any substantial signature in other wavelengths.

The initial case study examines a complex event consisting of multiple radio sources/bursts associated with a fast coronal mass ejection (CME) and an M 2.1 class solar flare (SOL2015-09-20). ‘First-light’ data from the Owens Valley Radio Observatory–Long Wavelength Array is put in context with observations from Large Angle and Spectrometric Coronagraph onboard the Solar and Heliospheric Observatory, along with the WAVES radio spectrograph onboard WIND, the Expanded Owens Valley …

The Analysis And The Three-Dimensional, Forward-Fit Modeling Of The Hard X-Ray And The Microwave Emissions Of Major Solar Flares, Natsuha Kuroda

Dissertations

Solar flares are one of the most violent and energetic space weather events that are known to cause various adverse effects on the Earth. One of the major problems that must be solved to understand flares and to be able to predict their magnitudes is how the particles in the solar atmosphere are accelerated after the magnetic reconnection. One way to help solve this problem is to investigate the properties of the high energy electrons produced during the flare impulsive phase, observed in the hard X-ray (HXR) and microwave (MW). The two emissions are considered to be produced by a …

A Comprehensive Study Of Evolution Of Photospheric Magnetic Field And Flows Associated With Solar Eruptions, Shuo Wang

Dissertations

The rapid, irreversible change of the photospheric magnetic field has been recognized as an important element of the solar flare process. Recent theoretical work has shown that such a change would imply Lorentz force perturbations acting on both the outer solar atmosphere and the solar surface. This research uses vector magnetograms obtained with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory to study a number of flares, which range from GOES-class C4 to X5 and occur in four active regions. In all the events, a permanent and rapid change of photospheric magnetic field closely associated with the …

Extending F10.7'S Time Resolution To Capture Solar Flare Phenomena, Ariel O. Acebal

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Solar ultraviolet (UV) radiation ionizes the neutral components in the atmosphere, which is partly responsible for the formation of the ionosphere, and contributes to heating of the atmosphere. Solar flares change the solar spectrum at times by several orders of magnitude. These changes modify the Earth's upper atmosphere, causing problems to communication systems and space operations, such as increased satellite drag. Unfortunately, solar UV measurements are limited since they can only be observed with space-based sensors. In order to work around this limitation, the solar radio emissions at a wavelength of 10.7 cm have been used as a proxy for …

Automatic Prediction Of Solar Flares And Super Geomagnetic Storms, Hui Song

Dissertations

Space weather is the response of our space environment to the constantly changing Sun. As the new technology advances, mankind has become more and more dependent on space system, satellite-based services. A geomagnetic storm, a disturbance in Earth's magnetosphere, may produce many harmful effects on Earth. Solar flares and Coronal Mass Ejections (CMEs) are believed to be the major causes of geomagnetic storms. Thus, establishing a real time forecasting method for them is very important in space weather study.

The topics covered in this dissertation are: the relationship between magnetic gradient and magnetic shear of solar active regions; the relationship …

Prediction Of The Temporal Evolution Of Solar X-Ray Flares, Aaron J. Williams

Theses and Dissertations

A solar flare is an explosive release of stored magnetic energy on the Sun. Much of this energy is converted into x-ray photons which escape into space. As a solar flare begins, the 1-8 Å x-ray photon flux at Earth’s orbit, as measured by the GOES satellite, rapidly increases. It quickly reaches a peak and slowly decays. A plot of this flux exhibits an approximate lognormal shape. A lognormal function becomes a normal, symmetric, function when the logarithm of the independent variable is taken. Once the peak flux is reached, this symmetry is used to make a prediction of the …

An Analysis Of Changes In The Magnetic Field Of Active Region 9415 After The 2001 April 6 Solar Flare, Juli Marya Stoltz

Theses

The objective of this study was to further the current understanding of the correlation between solar flares and magnetic flux change. The average gradient of the magnetic flux around the neutral line of Active Region 9415 and the locations of the magnetic flux centers-of-mass in both polarities in AR 9415 were determined. Subsequent to the 2001 April 6 flare, there was a statistically significant mean increase of 0.00208 G/km in the average gradient. Prior to the flare, the magnetic flux centers-of-mass became increasingly sheared along the neutral line. After the flare, this shear suddenly decreased and the magnetic flux centers-of-mass …

Daytime Detection Of Space Objects, Alistair D. Funge

Theses and Dissertations

Space Situational Awareness (SSA) requires repeated object updates for orbit accuracy. Detection of unknown objects is critical. A daytime model was developed that evaluated sun flares and assessed thermal emissions from space objects. Iridium satellites generate predictable sun glints. These were used as a model baseline for daytime detections. Flares and space object thermal emissions were examined for daytime detection. A variety of geometric, material and atmospheric characteristics affected this daytime detection capability. In a photon noise limited mode, simulated Iridium flares were detected. The peak Signal-to- Noise Ratios (SNR) were 6.05e18, 9.63e5, and 1.65e7 for the nighttime, daytime and …

Statistical Study Of Solar Radio Bursts, Gelu-Marius Nita

Dissertations

The peak flux distribution of 40 years of solar radio burst data recorded by NOAA, as a function of frequency and time over a wide range of frequencies, was investigated to quantify the potential impact of radio bursts on wireless systems. Tables of fit parameters, which can be used to find burst occurrence rates in a number of frequency ranges, are presented. The typical power-law index of number density distribution, -1.8, is similar to that found in many hard X-ray studies. Significant changes were found in power-law index with frequency. The results may be useful for designers of current and …