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Physical Sciences and Mathematics Commons™
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- Keyword
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- Solar flares (4)
- Space weather (4)
- Solar photosphere (3)
- NLFFF extrapolation (2)
- Solar corona (2)
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- Solar magnetic field (2)
- Active region (1)
- Adaptive Optics (1)
- Atmospheric Turbulence (1)
- Carrington-class coronal mass ejection (1)
- Energy flux (1)
- Optical Distortion (1)
- Optical Refraction (1)
- Optical Sensors (1)
- Refractive Error (1)
- Solar active region magnetic fields (1)
- Solar wind (1)
- Subauroral phenomenon (1)
Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Phase Error Scaling Law In Two-Wavelength Adaptive Optics, Milo W. Hyde Iv, Matthew Kalensky, Michael J. Spencer
Phase Error Scaling Law In Two-Wavelength Adaptive Optics, Milo W. Hyde Iv, Matthew Kalensky, Michael J. Spencer
Faculty Publications
We derive a simple, physical, closed-form expression for the optical-path difference (OPD) of a two-wavelength adaptive-optics (AO) system. Starting from Hogge and Butts’ classic OPD variance integral expression, we apply Mellin transform techniques to obtain series and asymptotic solutions to the integral. For realistic two-wavelength AO systems, the former converges slowly and has limited utility. The latter, on the other hand, is a simple formula in terms of the separation between the AO sensing (i.e., the beacon) and compensation (or observation) wavelengths. We validate this formula by comparing it to the OPD variances obtained from the aforementioned series and direct …
Analysis Of Modeled 3d Solar Magnetic Field During 30 X/M-Class Solar Flares, Seth H. Garland, Vasyl B. Yurchyshyn, Robert D. Loper, Benjamin F. Akers
Analysis Of Modeled 3d Solar Magnetic Field During 30 X/M-Class Solar Flares, Seth H. Garland, Vasyl B. Yurchyshyn, Robert D. Loper, Benjamin F. Akers
Faculty Publications
Using non-linear force free field (NLFFF) extrapolation, 3D magnetic fields were modeled from the 12-min cadence Solar Dynamics Observatory Helioseismic and Magnetic Imager (HMI) photospheric vector magnetograms, spanning a time period of 1 hour before through 1 hour after the start of 18 X-class and 12 M-class solar flares. Several magnetic field parameters were calculated from the modeled fields directly, as well as from the power spectrum of surface maps generated by summing the fields along the vertical axis, for two different regions: areas with photospheric |Bz|≥ 300 G (active region—AR) and areas above the photosphere with the …
Evolution Of Coronal Magnetic Field Parameters During X5.4 Solar Flare, Seth H. Garland, Benjamin F. Akers, Vasyl B. Yurchyshyn, Robert D. Loper, Daniel J. Emmons
Evolution Of Coronal Magnetic Field Parameters During X5.4 Solar Flare, Seth H. Garland, Benjamin F. Akers, Vasyl B. Yurchyshyn, Robert D. Loper, Daniel J. Emmons
Faculty Publications
The coronal magnetic field over NOAA Active Region 11,429 during a X5.4 solar flare on 7 March 2012 is modeled using optimization based Non-Linear Force-Free Field extrapolation. Specifically, 3D magnetic fields were modeled for 11 timesteps using the 12-min cadence Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager photospheric vector magnetic field data, spanning a time period of 1 hour before through 1 hour after the start of the flare. Using the modeled coronal magnetic field data, seven different magnetic field parameters were calculated for 3 separate regions: areas with surface |Bz| ≥ 300 G, areas of flare brightening seen …
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland, Daniel J. Emmons, Robert D. Loper
Studying The Conditions For Magnetic Reconnection In Solar Flares With And Without Precursor Flares, Seth H. Garland, Daniel J. Emmons, Robert D. Loper
Faculty Publications
Forecasting of solar flares remains a challenge due to the limited understanding of the triggering mechanisms associated with magnetic reconnection, the primary physical phenomenon connected to these events. Studies have indicated that changes to the photospheric magnetic fields associated with magnetic reconnection – particularly in relation to the field helicity – occur during solar flare events. This study utilized data from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) and SpaceWeather HMI Active Region Patches (SHARPs) to analyze full vector-field component data of the photospheric magnetic field during solar flare events within a near decade long HMI dataset. …
Detection Of Reconnection Signatures In Solar Flares, Taylor R. Whitney Aegerter, Daniel J. Emmons Ii, Robert D. Loper
Detection Of Reconnection Signatures In Solar Flares, Taylor R. Whitney Aegerter, Daniel J. Emmons Ii, Robert D. Loper
Faculty Publications
Solar flare forecasting is limited by the current understanding of mechanisms that govern magnetic reconnection, the main physical phenomenon associated with these events. As a result, forecasting relies mainly on climatological correlations to historical events rather than the underlying physics principles. Solar physics models place the neutral point of the reconnection event in the solar corona. Correspondingly, studies of photospheric magnetic fields indicate changes during solar flares—particularly in relation to the field helicity—on the solar surface as a result of the associated magnetic reconnection. This study utilizes data from the Solar Dynamics Observatory (SDO) Helioseismic and Magnetic Imager (HMI) and …
Carrington-Class Events As A Great Filter For Electronic Civilizations In The Drake Equation, Robert D. Loper
Carrington-Class Events As A Great Filter For Electronic Civilizations In The Drake Equation, Robert D. Loper
Faculty Publications
The Drake equation is a calculation providing an upper bound on the likely number of intelligent species in our galaxy. In order to reconcile a potentially high occurrence of intelligent extraterrestrial species with the current non-observation of them, we frequently resort to some Great Filter which represents some inevitable, cataclysmic fate (such as nuclear war, pandemic, or asteroid impact) that tends to await enough worlds to negate the expectation that the galaxy ought to be teeming with intelligent life. This paper is intended to examine one potential Great Filter for electronic-based civilizations, the impact of a Carrington-class coronal mass ejection …
A Statistical Analysis Of Steve, Bea Gallardo‐Lacourt, Y. Nishimura, E. Donovan, G. W. Gillies, W. E. Archer, Omar A. Nava, E. L. Spanswick
A Statistical Analysis Of Steve, Bea Gallardo‐Lacourt, Y. Nishimura, E. Donovan, G. W. Gillies, W. E. Archer, Omar A. Nava, E. L. Spanswick
Faculty Publications
There has been an exciting recent development in auroral research associated with the discovery of a new subauroral phenomenon called STEVE (Strong Thermal Emission Velocity Enhancement). Although STEVE has been documented by amateur night sky watchers for decades, it is as yet an unidentified upper atmosphere phenomenon. Observed first by amateur auroral photographers, STEVE appears as a narrow luminous structure across the night sky over thousands of kilometers in the east‐west direction. In this paper, we present the first statistical analysis of the properties of 28 STEVE events identified using Time History of Events and Macroscale Interactions during Substorms (THEMIS) …
Assessing Predictive Ability Of Three Auroral Precipitation Models Using Dmsp Energy Flux, Cory T. Lane, Ariel O. Acebal, Yihua Zheng
Assessing Predictive Ability Of Three Auroral Precipitation Models Using Dmsp Energy Flux, Cory T. Lane, Ariel O. Acebal, Yihua Zheng
Faculty Publications
Our study statistically compares the total energy flux outputs of Newell et al.'s (2010a) oval variation, assessment, tracking, intensity, and online nowcasting (OVATION) Prime model, Hardy et al.'s (1991) Kp‐based model, and a coupled Space Weather Modeling Framework ring current model to energy flux data obtained from 2198 Defense Meteorological Satellite Program (DMSP) satellite passes in the Northern Hemisphere. Our DMSP data set includes 28 days grouped into continuous 3 and 4 day periods between 2000 and 2008 and encompasses magnetic local times (MLTs) between 04:00 and 21:00. We obtain the most equatorward magnetic latitude coordinate, where a DMSP satellite …
Ensemble Forecasting Of Coronal Mass Ejections Using The Wsa-Enlil With Coned Model, D. Emmons, Ariel O. Acebal, A. Pulkkinen, A. Taktakishvili, Peter Macneice, D. Odstrcil
Ensemble Forecasting Of Coronal Mass Ejections Using The Wsa-Enlil With Coned Model, D. Emmons, Ariel O. Acebal, A. Pulkkinen, A. Taktakishvili, Peter Macneice, D. Odstrcil
Faculty Publications
The combination of the Wang‐Sheeley‐Arge (WSA) coronal model, ENLIL heliospherical model version 2.7, and CONED Model version 1.3 (WSA‐ENLIL with CONED Model) was employed to form ensemble forecasts for 15 halo coronal mass ejections (halo CMEs). The input parameter distributions were formed from 100 sets of CME cone parameters derived from the CONED Model. The CONED Model used image processing along with the bootstrap approach to automatically calculate cone parameter distributions from SOHO/LASCO imagery based on techniques described by Pulkkinen et al. (2010). The input parameter distributions were used as input to WSA‐ENLIL to calculate the temporal evolution of the …