The NSO summer student program had another very successful year. Participants included three Research Experience for Undergraduates (REU) students and two graduate students at NSO/Sac Peak, and five REUs and two graduate students at NSO/Tucson. Information about the students who participated in the program and the work they did is presented below. In addition to the work performed at each of the NSO sites, the students exchanged visits between the sites and also visited the Very Large Array (VLA) near Socorro, New Mexico. Recruitment for next summer's program has begun. Interested individuals can obtain information and application packets by visiting our Web-site at http://www.sunspot.noao.edu or by sending e-mail to or calling Debra Teachman at teachman@sunspot.noao.edu, (505) 434-7003. Applications are due by 31 January 1998.
John Barentine, a senior at the University of Arizona, worked with Charlie Lindsey (SPRC) on a project to explore the the diagnostic possibilities of work by Lindsey and D.C. Braun (also at SPRC) in the study of terrestrial lightning using helioseismic holography techniques. During the Tucson summer monsoons, he obtained audio recordings of thunder made from separate locations and used cross-correlation statistics to explore the prospect of acoustic reconstruction of the geometry of the lightning bolt within the thunderstorm, where it is inaccessible to visible light. His results were interesting and encouraging.
Laurel Brown, a junior at Colgate University, worked with Matt Penn on near-infrared observations from the Kitt Peak Vacuum Telescope. These spectral observations focussed on the neutral Helium line at 1083.0 nm. She worked with IDL programs to measure the spectral parameters of the Helium line and several other nearby lines; next she produced movies of these line parameters and applied spatial destretching routines to remove instrument scanning trouble and some atmospheric effects. Laurel identified and measured several moving plasma features in the data, and her measurements provide the input to a kinetic model of the events which will soon be published.
Andrea Folcik, currently a senior at the University of Florida, worked with Haosheng Lin to investigate the relationship between the size of small flux tubes and their magnetic field strength. Simultaneous observations were made in the magnetically sensitive near-infrared Fe I lines at 1564.8 nm (Landé factor, g = 3) and 1565.2 nm (g = 1.53), the Ca II K-line at 393.3 nm and the C I G-band at 430 nm. The full set of Stokes Vectors was measured in the two Fe I lines. Andrea reduced the data and looked for correlations between the various data sets, the size of features, and the measured magnetic field.
Doug Folsom, from Harvey Mudd College, worked with Harrison Jones on a long-standing project to study the surface dynamics of solar magnetic fields. He spent most of the summer comparing optical flow and correlation tracking techniques as tools for extracting solar rotation and other large-scale flow patterns from GONG magnetograms.
James Fox, currently a senior at New Mexico Institue of Mining and Technology in Socorro, New Mexico, worked with K.S. Balasubramaniam (Bala) and Richard Radick to investigate periodicities in the occurrence of solar flares. His work was presented at the 18th International NSO/Sacramento Peak Summer Workshop on Synoptic Solar Physics and will be published in the proceedings by the Astronomical Society of the Pacific. His work convincingly demonstrated that the occurrence of solar flares is sporadic. Solar flares do not exhibit any kind of sustained periodicities as previously believed.
David Harvey, an Astronomy student at the University of Arizona, designed and built a high-speed limb guider for use on the main image of the McMath-Pierce Telescope. The aim is to stabilize the extreme limb to permit observations of the infrared CO lines at 4.6 µm. David's advisor was Bill Livingston.
Edisher Kaghahsvili, a graduate student from Abastumani, Georgia, worked with Raymond Smartt to investigate the temporal behavior of coronal loop interactions. They are preparing a manuscript for publication on the "Morphology of the Cool Hydrogen-alpha Plasma Associated with Coronal loop Interaction." From this study, they are developing a model showing how MHD waves associated with coronal loops contribute to coronal heating and solar wind acceleration.
Leo Milano, a graduate student at the Instituto de Astronomia y Fisica del Espacio in Buenos Aires, Argentina worked with K.S. Balasubramaniam and Steve Keil to investigate chromospheric motions in the active region complex NOAA 8027, using the full-disk hydrogen-alpha patrol from NSO/Sacramento Peak. This active region has invoked considerable interest because of simultaneous observations from a variety of ground and space observatories. They discovered the presence of surface motions and strong vorticity signatures in this region prior to the flares and mass ejections on 6-7 April 1997. These surface velocity effects occur about 20 minutes in advance of the two-ribbon flare and the accompanying mass ejection. This work was also presented at the 18th International NSO/Sacramento Peak Summer Workshop on Synoptic Solar Physics and will be published in the proceedings by the Astronomical Society of the Pacific.
Michael Rabban, currently a senior at Cal Poly, San Luis Obispo, worked with Mark Giampapa on the analysis of high-resolution spectra of solar-type stars that have been reported to have planetary, Jupiter-like companions. Following the recent results of D. Gray, stellar convection and pulsation can give rise to variations in photospheric line bisectors. At lower resolutions these bisector variations could lead to an apparent Doppler signature that would be misinterpreted as a planetary companion. Mike reduced the data and examined solar spectra to identify additional spectral lines that could be used for line bisector measurements.
Todd Rigg, also a senior at Cal Poly San Luis Obispo, worked with John Varsik on ongoing measurements of atmospheric dust. Dust in the Earth's atmosphere limits the sensitivity of coronagraphic telescopes, such as the one proposed in the CLEAR (Coronagraphic and Low Emissivity Astronomical Reflector) feasibility study. Todd was also involved in the preparation of the CLEAR mockup telescope at NSO/Sacramento Peak, which will test methods of controlling atmospheric distortion and dust deposition in large open solar telescopes.
Dong-Xue Wang. The use of spherical harmonic functions to describe the spatial patterns of solar oscillations has the drawback that the entire solar surface needs to be observed for the functions to be orthogonal. Observations of less than the total solar surface result in "leakage" of the spatial patterns of modes with similar (l,m) values into that of the mode being measured. This leakage causes the addition of many "extra" spectral peaks in the oscillation power spectrum, many of which overlap the peaks of interest and therefore complicate the measurement process for the "target" peaks. Dong-Xue Wang, a University of Arizona graduate student who worked with Stuart Jefferies, investigated the problem of removal of the unwanted signal using sparse matrix techniques.
Bruce Wilton, currently a student at the University of Arizona, worked with Christoph Keller on obtaining the highest resolution magnetic field maps of the Sun. They consistently achieved a resolution of 0.2" and resolved many of the small magnetic elements in the quiet Sun. The results are currently written up in a paper for the Astrophysical Journal.
Steve Keil and NSO REU Advisors