Other 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 …

Flare Emission Observed In High Resolution And Comparison With Numerical Modeling, Nengyi Huang

Dissertations

As one of the most intense activities on the solar surface, flares have been extensively observed and studied ever since the first report. The standard model of solar flares has been established and commonly accepted. However, many limitations from the researching tools have left some of the problems unsolved or controversial. For example, the density of electrons in the corona is lower than it is required to activate the observed emission in HXR, and the mechanism that these electron beams can penetrate down to lower chromosphere is unclear. Many theoretical scenarios were suggested, and more observations had been in need. …

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 Model Of So-Called "Zebra" Emissions In Solar Flare Radio Burst Continua, R. A. Treumann, R. Nakamura, W. Baumjohann

Dartmouth Scholarship

A simple mechanism for the generation of elec- tromagnetic “Zebra” pattern emissions is proposed. “Zebra” bursts are regularly spaced narrow-band radio emissions on the otherwise broadband radio continuum emitted by the ac- tive solar corona. The mechanism is based on the generation of an ion-ring distribution in a magnetic mirror geometry in the presence of a properly directed field-aligned electric po- tential field. Such ion-rings or ion-conics are well known from magnetospheric observations. Under coronal condi- tions they may become weakly relativistic. In this case the ion-cyclotron maser generates a number of electromagnetic ion-cyclotron harmonics which modulate the electron maser …

Radio-Derived Three-Dimensional Structure Of A Solar Active Region, Samuel D. Tun

Dissertations

Solar active regions are the source of the most violent events observed on the Sun, some of which have a direct impact to modern civilization. Efforts to understand and predict such events require determination of the three-dimensional distributions of density, temperature, and magnetic fields above such active regions. This thesis presents the structure of the solar atmosphere above active region AR 10923, observed on 2006 Nov 10, as deduced from multi-wavelength studies including combined microwave observations from the Very Large Array (VLA) and the Owens Valley Solar Array (OVSA). The VLA observations provide excellent image quality at a few widely …

Long Exposure Point Spread Function Estimation From Solar Adaptive Optics Loop Data, Jose Marino

Dissertations

Adaptive optics (AG) systems provide partial correction to wavefront distortions introduced by the Earth's atmosphere. They have become an essential tool to obtain diffraction-limited observations from ground-based telescopes. However, the AG correction is only partial and post-processing with a good estimate of the point spread function (PSF) is required.

PSF estimates are impossible to measure directly during solar observations due to the lack of point sources in the field-of-view. Moreover, the highly variable day-time seeing conditions require the estimated PSF to be simultaneous with the captured image. A method is presented to estimate the long-exposure PSF of AG-corrected solar observations …

High Resolution Studies Of Complex Solar Active Regions, Na Deng

Dissertations

Flares and Coronal Mass Ejections (CMEs) are energetic events, which can even impact the near-Earth environment and are the principal source of space weather. Most of them originate in solar active regions. The most violent events are produced in sunspots with a complex magnetic field topology. Studying their morphology and dynamics is helpful in understanding the energy accumulation and release mechanisms for flares and CMEs, which are intriguing problems in solar physics.

The study of complex active regions is based on high-resolution observations from space missions and new instruments at the Big Bear Solar Observatory (BBSO). Adaptive optics (AG) in …

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 …