Calibration of the 6302/6301 Stokes V line ratio in terms of the 5250/5247 ratio

Four decades ago the Stokes V line ratio in the Fe I 5247.06 and 5250.22 {\AA} lines was introduced as a powerful means of exploring the intrinsic field strengths at sub-pixel scales, which led to the discovery that most of the photospheric flux is in intermittent kG form. The "green" 5247-5250 line pair is unique because it allows the magnetic-field effects to be isolated from the thermodynamic effects. No other line pair with this property has since been identified. In recent years much of the magnetic-field diagnostics has been based on the "red" Fe I 6301.5 and 6302.5 {\AA} line pair, since it was chosen in the design of the Hinode space observatory. Although thermodynamic effects severely contaminate the magnetic-field signatures for this line ratio, it is still possible to use it to extract information on intrinsic magnetic fields, but only after it has been "renormalized", since otherwise it produces fictitious, superstrong fields everywhere. In the present work we explore the joint behavior of these two line ratios to determine how the "contaminated" red line ratio can be translated into the corresponding green line ratio, which then allows for a direct interpretation in terms of intrinsic magnetic fields. Our observations are mainly based on recordings with the ZIMPOL-3 spectro-polarimeter at IRSOL in Locarno, Switzerland, complemented by data from the STOP telescope at the Sayan solar observatory (Irkutsk, Russia). The IRSOL observations are unique by allowing both the green and red line pairs to be recorded simultaneously on the same CCD sensor. We show how the line ratios depend on both the measured flux densities and on the heliocentric distance (the \mu\ value on the solar disk), and finally derive the calibration function that enables the red line ratio to be translated to the green ratio for each \mu\ value

Late Quaternary tectonic activity of the Meers Fault, southwest Oklahoma

Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.The Meers fault in southwestern Oklahoma is an active fault capable of producing large, damaging earthquakes. The most recent large event is late Holocene, occurring some 1,200 - 1,300 years ago, and it was preceded by one or more earlier Quaternary events. Few faults in stable continental interior (SCI) areas are known to be active, so this fault holds many implications for seismic hazards in these poorly understood regions. Paleoseismic events probably had magnitudes of at least 6 3/4 to 7 1/4. Seismic events may be relatively larger in SCI regions and magnitudes of 7 1/2 or greater may be possible. The minimum scarp length is 37 km. Displacements have both left-lateral and high-angle reverse components. Vertical separation of the surface reaches about 5 m, while lateral separation exceeds vertical by a ratio of about 3:1 to 5:1, reaching approximately 20 m. Individual events appear to have had maximum surface displacements of several meters. This fault may be part of a larger active zone. The Washita Valley and Potter County faults also have surface expressions believed to indicate recent surface faulting. No additional active surface faults have been recognized in the Mers fault area, but activity may be concealed by poor preservation or non-brittle surface deformation. Active faults are likely to be sparse and to rupture infrequently

Center to limb observations and modeling of the Ca I 4227 A line

The observed center-to-limb variation (CLV) of the scattering polarization in different lines of the Second Solar Spectrum can be used to constrain the height variation of various atmospheric parameters, in particular the magnetic fields via the Hanle effect. Here we attempt to model non-magnetic CLV observations of the $Q/I$ profiles of the Ca I 4227 A line recorded with the ZIMPOL-3 at IRSOL. For modeling, we use the polarized radiative transfer with partial frequency redistribution with a number of realistic 1-D model atmospheres. We find that all the standard FAL model atmospheres, used by us, fail to simultaneously fit the observed ($I$, $Q/I$) at all the limb distances ($\mu$). However, an attempt is made to find a single model which can provide a fit at least to the CLV of the observed $Q/I$ instead of a simultaneous fit to the ($I$, $Q/I$) at all $\mu$. To this end we construct a new 1-D model by combining two of the standard models after modifying their temperature structures in the appropriate height ranges. This new combined model closely reproduces the observed $Q/I$ at all the $\mu$, but fails to reproduce the observed rest intensity at different $\mu$. Hence we find that no single 1-D model atmosphere succeeds in providing a good representation of the real Sun. This failure of 1-D models does not however cause an impediment to the magnetic field diagnostic potential of the Ca I 4227 A line. To demonstrate this we deduce the field strength at various $\mu$ positions without invoking the use of radiative transfer.Comment: 20 pages, 10 figures, Accepted for publication in Ap

Atmospheric fluctuations below 0.1 Hz during drift-scan solar diameter measurements

Measurements of the power spectrum of the seeing in the range 0.001-1 Hz have been performed in order to understand the criticity of the transits' method for solar diameter monitoring.Comment: 3 pages, 3 figures, proc. of the Fourth French-Chinese meeting on Solar Physics Understanding Solar Activity: Advances and Challenges, 15 - 18 November, 2011 Nice, Franc