The NSO summer student program has had another successful year. Participants included three Research Experience for Undergraduates (REU) students and two graduate students, or Senior Research Assistants (SRAs), at NSO/Sac Peak and four REUs and two SRAs at NSO/Tucson. Information about the students and the work they did is presented below. In addition to work performed at the respective NSO sites, the students exchanged site visits, which included stopovers at the White Sands National Monument in New Mexico and the Very Large Array (VLA) near Socorro, New Mexico.
Chad Bender (Illinois, Urbana-Champaign) worked with Harry Jones on the observation and analysis of He I 1083 nm imaging spectroscopy. The project was designed to explore the origins of the solar wind and involved 1083 nm data obtained with the NSO/NASA spectromagnetograph at the Kitt Peak Vacuum Telescope and the Near Infrared Magnetograph at the McMath Pierce telescope in conjunction with EUV observations from the SOHO/Coronal Diagnostics Spectrometer.
Scott Catanzariti (Indiana State) analyzed full disk Ca II spectroheliograms obtained daily at the Evans Solar Coronal Facility at NSO/SP. The project had two goals. The first was to integrate the calibrated Ca II images, which were obtained in a 0.5 Å band centered on the K3 absorption feature, to generate a disk integrated flux. This was then compared with the emission index generated from disk integrated K-line spectral scans (see http://www.sunspot.noao.edu/AF/cak.html) that are also obtained daily. The spectroheliograms were used to identify the chromospheric changes contributing to variations in the emission index. This information was then used to refine techniques for predicting variations of the solar EUV flux which effects ionization levels in the Earth's atmosphere. The second goal was to verify the capability of the disk integrated measurements to measure differential solar rotation. The latter goal is important for verifying the ability to measure stellar differential rotation. Scott's advisors were Steve Keil and Leo Milano.
Tim Donaghy (Stanford) worked with Christoph Keller and Jack Harvey in exploring very small scale features in the solar atmosphere and solar magnetic fields. Tim's first project involved using sophisticated image restoration algorithms to reconstruct diffraction-limited images using in- and slightly out-of-focus simultaneous records obtained with the Dunn Solar Telescope. The goal was to study the time evolution of tiny magnetic structures in the solar photosphere. Tim's second project was stimulated by the forthcoming SOLIS instruments. Using data from the NSO Kitt Peak Vacuum Telescope, Tim developed techniques to compare magnetic field measurements made in the photosphere and chromosphere in order to easily show their differences. He also studied a time series of magnetic field measurements made during a good-sized solar flare.
Heather Eddy (Cornell) worked with Bill Livingston on the full-disk spectrum archives. Having collected all the CaK observations from 1974 to 1999 and following a suggestion of Caty Pilachowski, Heather searched for evidence of comet infalls to the sun. From SOHO it is now known that such events are fairly common. Lloyd Wallace wrote a program that automatically put two observations on the same wavelength scale and took their ratio or difference. The expectation, based on certain stellar analogs, was that infalling material would reveal itself as a weak, narrow Ca absorption in the wing of Ca K 3933Å. Several suspicious cases were found. Confirmation involved finding an identical signal in Ca H 3967. Nothing panned out. Heather then turned to an examination of Ca 8542 for solar cycle effects. Using the same program and differencing solar minimum vs maximum, it was found that the difference signal of the line cores displays an emission feature at a constant displacement to the red of about 0.1Å (3.5 km/s). The next task, undertaken with help from Harry Jones, was to explain this signal in terms of what is known of the behavior of Ca 8542 on the resolved disk.
Robert Gutermuth (Alfred) concentrated on the analysis of large scale surface velocities in flaring and erupting filament regions as observed in chromospheric Ha images. The data were obtained with the Hilltop full-disk Ha patrol camera at NSO/SP at a 10s cadence. The surface velocities in active regions are determined from local correlation tracking of sub-images within the active region. Robert also used these surface velocities to calculate shear within the material at locations of concentrated magnetic field. Spikes in the shear of the surface material have been observed just prior to some solar flares, suggesting that this could be a valuable tool for forecasting flare events. Robert's advisors were Leo Milano, K. S. Balasubramaniam and Steve Keil.
James Hague (North Carolina) worked with Michael Sigwarth on high resolution Stokes spectra and imaging data to investigate the evolution and dynamic behavior of magnetic flux tubes of network and internetwork fields. The data were taken with the HAO/NSO Advanced Stokes Polarimeter at the Dunn Solar Telescope and consist mainly of a one-hour time sequence of a quiet sun region. Jimmy concentrated on analyzing the Stokes-V spectra to obtain information on the vertical motions within the magnetic field and to classify the significant amount of Stokes-V spectra with an unusual shape. In addition, he obtained flow maps for horizontal convective motions in the observed region to investigate the interaction of flux tubes with convective motions.
Matthew Povich (Harvard) worked with Mark Giampapa and Jeff Valenti (KPNO) on the analysis of high-resolution spectra of solar-type stars with reported planetary companions. The data were obtained with the McMath-Pierce solar-stellar spectrograph over the course of a year, under the auspices of a NASA grant from The Origins of Solar System Program. The photospheric line profiles were analyzed by Matt to discover the nature and amplitude of any variations in their line bisectors. Variations in line profile shapes, as reflected in line bisector variability, will have an effect on the accuracies that can be attained in radial velocity searches for extrasolar planets. In addition, bisector variability is of interest in the context of the study of active regions and large-scale convective patterns in solar-type stars.
Michael Gericke (Arkansas) concentrated on evaluating the suitability of surface velocities and vorticities as precursor indicators to flares and filament eruptions as observed in Ha images. The data were obtained at the Dunn Solar Telescope on 27 December 1998 over a region of about 635"2 from active region 8421. The surface velocities in active regions are determined from local correlation tracking of kernels within the active region. The results are obtained by comparing time sequences of intensities, velocity magnitudes, vorticities, and the divergence of several particularly active sub regions and determining how far their peak values precede each other. Michael also used magnetograms obtained on the same day at Kitt Peak to evaluate the correlation between the vorticities and magnetic fields in the active regions. Michael's advisors were K.S. Balasubramaniam, Leo Milano, and Steve Keil.
Oleg Ladenkov (Ulugh Bek Astronomical Institute, Tashkent, Uzbekistan) is working with Frank Hill and Doug Rabin on a study of the relationship between wave energy and cool regions in the solar chromosphere. Five data sets, from the Near-Infrared Magnetograph at the McMath-Pierce telescope, the High-Degree Helioseismometer at the Kitt Peak Vacuum telescope, and the Michelson Doppler Imager on SOHO, are being combined to study correlations between the spatial distribution of photospheric and chromospheric acoustic power, and chromospheric temperature as observed in the infrared.
K. Sankarasubramaniam (Indian Institute of Astrophysics, Bangalore) is working with Thomas Rimmele and Rich Radick (AFRL/VSBS) on spectral and imaging data taken with the NSO adaptive optics system at the Dunn Solar Telescope. Sankar is reducing time series of high resolution (0.2") spectra of the iron line FeI 5434Å with the goal of detecting high-frequency wave motion at the edge of magnetic field concentrations. He has also been working on a time sequence of vector-polarimetric data of excellent quality taken with the Advanced Stokes Polarimeter and adaptive optics in order to study the fine structure and dynamics of active regions.
1999 NSO REU and SRA Advisors