The NSO summer student program has had another successful year. Participants included four Research Experience for Undergraduates (REU) students and two graduate students, or SRAs (Senior Research Assistants), at NSO/Sac Peak and three REUs and four SRAs at NSO/Tucson. Information about the students and the work they did is presented below. In addition to work performed at each of the NSO sites, the students exchanged visits between the sites and also visited the White Sands Missile Range in New Mexico and the Very Large Array (VLA) near Socorro, New Mexico.
Brad Benson (University of Wisconsin/Madison fall senior), worked with Thomas Rimmele to pinpoint the locations on the Sun at which the five-minute oscillations are excited. The project involves reductions of high spatial and high temporal resolution data obtained at the NSO/SP Vacuum Tower Telescope. The observations were made with a new tunable narrow-band filter that consisted of dual Fabry-Perot filters and a blocker. Brad is also evaluating the performance of this filter system.
Amy Smith (Davidson College, Davidson, North Carolina), worked with John Worden and examined the SoHO CDS images to determine the plage and network intensity contrasts of the EUV emissions for He I 58.4 nm, O IV 55.4 nm, O V 62.9 nm. These contrasts can then be used for modelling solar cycle irradiance variability changes.
Jacob Taylor (Harvard third year), worked with Mark Giampapa (NSO/NOAO) and Eric Craine (Western Research) investigating the use of CCD arrays for night-to-night differential photometry at the milli-magnitude level under a variety of conditions. The subtle issues of CCD calibration were examined in detail, as were the problems of atmospheric variability and the higher order extinction effects associated with it. He prepared IRAF scripts for on-the-fly reductions accurate to 5 milli-mags, utilizing aperture photometry combined with the calibrations and extinction corrections studied. This script might allow for an observationally intensive task such as detecting planetary transits using automated telescopes, as proposed by GNAT (the Global Network of Automated Telescopes). During his summer work, Jacob obtained and analyzed CCD data from the 2.1-m and 0.9-m telescopes on Kitt Peak, as well as data from a prototype, automated 0.5-m telescope currently operated by GNAT.
Patricia (Trish) Van Lew (University of Wyoming, Laramie sophomore), worked with Christoph Keller on various aspects of the design of SOLIS. She was responsible for the photon and energy budget of the Vector-Spectromagnetograph (VSM) and the associated web page, performed grating efficiency and polarization measurements for the VSM (described in a SOLIS Instrument Memo), recorded and analyzed data from the Integrated Sunlight Spectrometer (ISS) prototype, and developed initial flat-field procedures for the ISS.
Three REU students have worked with S.L. Keil and K.S. Balasubramaniam on a project to measure and understand the evolution of active regions in the solar atmosphere prior to solar flares, filament eruptions, and coronal mass ejections. The observations they worked with were obtained simultaneously using several different instruments. Each student worked on a different aspect of the study as described below. Their results will be combined to form a complete picture of pre-activity evolution.
Jeff Clark, (University of California, Santa Cruz fall senior), reduced and analyzed polarization data made at the NSO/SP Vacuum Tower Telescope. His goal is to derive maps of the photospheric magnetic field which show the time evolution of the field prior to a solar flare. He is also collecting coronal images from several space missions (SoHO, YOHKOH, and TRACE), to investigate the overlying coronal structure.
Adam Bayliss (University of Montana fall senior), concentrated on the large-scale surface velocities in flaring and erupting filament regions as observed in chromospheric Ha images. The data were obtained with the full-disk Ha patrol camera at NSO/SP at a 10-second cadence. The surface velocities in active regions are determined from local correlation tracking of sub-images within the active region. Adam also used the full-disk Ha images and images from space to study the relationship between the flaring region and the global structures present on the Sun.
Jeremy Jones (Lehigh University fall senior), worked with high-resolution data observed at the Vacuum Tower Telescope. Simultaneous images of the structure in the photosphere (G-Band) and in the chromosphere (Ha) were obtained every 5 seconds at high spatial resolution. Jeremy will determine if flow signatures observed simultaneously at two different heights in the active region atmosphere can provide a reason for, and an early warning of, the instability leading to the observed activity.
John Barentine (University of Arizona senior) was an NSO REU student last summer (1997) and participated this summer as a Senior Research Assistant, working with Karen Harvey on analyzing the NSO/KP full-disk magnetograms to separate out different structures based on specific properties of their magnetic field distribution. He is using a set of algorithms to accomplish this task, with the product being a series of masks that specify the locations of pixels in active regions, decaying active regions, enhanced network, the quiet sun network, sunspots, and the quiet atmosphere. The objective of this project is to understand the relation between magnetic flux and spectral intensities observed in CaII K images, for example, and to determine the contributions of different magnetic structures to solar irradiance and irradiance variability. John's project, a part of this larger set of goals, is to examine various active region properties, such as the relation of magnetic flux to area, the fraction of magnetic flux in sunspots, and what happens to the magnetic flux in sunspots when they disappear.
Michele Bianda (ETH Zurich, Switzerland graduate student), worked with Don Neidig and Craig Gullixson to evaluate the performance of large-aperture (150 mm) Fabry-Perot etalons. These etalons will be part of the instrument being built by the NSO for the Air Force to replace the current instruments at the Air Force's Solar Optical Observing Network (SOON) sites. SOON consists of five sites at various locations around the Earth. Michele was also involved in the engineering of the telescopes and camera systems. In addition, Michele is working with Balasubramaniam on chromospheric structure seen in the Ca II k-line.
Scott Dahm (San Diego State University graduate student who will continue his doctoral studies at the University of Hawaii), has been working with Harrison Jones on the analysis of He I 1083 nm imaging spectroscopy. The project involves data obtained with the NSO/NASA spectromagnetograph at the Kitt Peak Vacuum Telescope and is directed towards the study of spectral asymmetry in coronal holes. The line shows an excess of blue-wing absorption in many coronal holes as compared with quiet-sun spectra, consistent with outflows which could be associated with high-speed solar wind.
Alina Donea (Astronomical Institute of the Romanian Academy graduate student), worked in local helioseismology with Drs. Charles Lindsey and Doug Braun (SPRC). She studied the temporal character of helioseismic noise created by the quiet Sun and anomalous noise emitters surrounding emerging active regions. She obtained the first helioseismic image of a solar flare whose seismic signature was discovered in the SoHO MDI observations by A.G. Kosovichev (Stanford) and V.V. Zharkova (Glasgow)
Elena Moise (MSc, Bucarest University, and works in the solar group of the Romanian Academic of Sciences), has helped Bill Livingston develop a "generic" line bisector for plage vs the quiet Sun on the solar disk. Observations were made on the FTS of 16 plage and nearby quiet regions using the 80cm image of the McMath-Pierce, 1 meter out of focus. Line bisectors are a diagnostic of granular convection, and the aim is to see how, on average, the granulation in active areas compares with non-active granulation. It is clear that in a plage convection is inhibited, but it is not certain that this localized effect is the one that dominates the Sun as a star. We hope to present our results at the Sac Peak Summer Workshop.
NSO 1998 Summer REU and SRA Advisors