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SUNSHINE, EARTHSHINE AND CLIMATE CHANGE I. ORIGIN OF, AND LIMITS ON SOLAR VARIABILITY
GOODE PHILIP R.,DZIEMBOWSKI W. A. The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.suppl1
Changes in the earth's climate depend on changes in the net sunlight reaching us. The net depends on the sun's output and earth's reflectance, or albedo. Here we develop the limits on the changes in the sun's output in historical times based on the physics of the origin of solar cycle changes. Many have suggested that the sun's output could have been $0.5\%$ less during the Maunder minimum, whereas the variation over the solar cycle is only about $0.1\%$. The frequencies of solar oscillations (f- and p-modes) evolve through the solar cycle, and provide the most exact measure of the cycle-dependent changes in the sun. But precisely what are they probing? The changes in the sun's output, structure and oscillation frequencies are driven by some combination of changes in the magnetic field, thermal structure and velocity field. It has been unclear what is the precise combination of the three. One way or another, this thorny issue rests on an understanding of the response of the solar structure to increased magnetic field, but this is complicated. Thus, we do not understand the origin of the sun's irradiance increase with increasing magnetic activity. Until recently, it seemed that an unphysically large magnetic field change was required to account for the frequency evolution during the cycle. However, the problem seems to have been solved (Dziembowski, Goode & Schou 2001) using f-mode data on size variations of the sun. From this and the work of Dziembowski & Goode (2003), we suggest that in historical times the sun couldn't be much dimmer than it is at activity minimum.
1.6 M SOLAR TELESCOPE IN BIG BEAR - THE NST
GOODE PHILIP R.,DENKER CARSTEN.J.,DIDKOVSKY LEONID I.,KUHN J. R.,WANG HAIMIN The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.suppl1
New Jersey Institute of Technology (NJIT), in collaboration with the University of Hawaii (UH), is upgrading Big Bear Solar Observatory (BBSO) by replacing its principal, 65 cm aperture telescope with a modern, off-axis 1.6 m clear aperture instrument from a 1.7 m blank. The new telescope offers a significant incremental improvement in ground-based infrared and high angular resolution capabilities, and enhances our continuing program to understand photospheric magneto-convection and chromospheric dynamics. These are the drivers for what is broadly called space weather - an important problem, which impacts human technologies and life on earth. This New Solar Telescope (NST) will use the existing BBSO pedestal, pier and observatory building, which will be modified to accept the larger open telescope structure. It will be operated together with our 10 inch (for larger field-of-view vector magnetograms, Ca II K and Ha observations) and Singer-Link (full disk H$\alpha$, Ca II K and white light) synoptic telescopes. The NST optical and software control design will be similar to the existing SOLARC (UH) and the planned Advanced Technology Solar Telescope (ATST) facility led by the National Solar Observatory (NSO) - all three are off-axis designs. The NST will be available to guest observers and will continue BBSO's open data policy. The polishing of the primary will be done in partnership with the University of Arizona Mirror Lab, where their proof-of-concept for figuring 8 m pieces of 20 m nighttime telescopes will be the NST's primary mirror. We plan for the NST's first light in late 2005. This new telescope will be the largest aperture solar telescope, and the largest aperture off-axis telescope, located in one of the best observing sites. It will enable new, cutting edge science. The scientific results will be extremely important to space weather and global climate change research.
SMALL-SCALE Hα DYNAMIC FEATURES SUPPORTED BY CHROMO SPHERIC MAGNETIC RECONNECTION
LEE SANGWOO,YUN HONG SIK,CHAE JONGCHUL,GOODE PHILIP R. The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.suppl1
In the present study, we have investigated morphology and evolution of small-scale Ha dynamic features on the quiet sun by analyzing video magnetograms and high resolution Ha images simultaneously taken for 5 hours at Big Bear Solar Observatory on April 18, 1997. From comparisons between time sequential longitudinal magnetograms and H$\alpha$ images covering $150" {\times} 150"$, several small-scale H$\alpha$ dynamic features have been observed at a site of magnetic flux cancellation. A close relationship between such features and cancelling magnetic fluxes has been revealed temporarily and spatially. Our results support that material injection by chromospheric magnetic reconnect ion may be essential in supporting numerous small-scale H$\alpha$ dynamical absorption features, being in line with recent observational studies showing that material injection by chromospheric magnetic reconnect ion is essential for the formation of solar filaments.
MAGNETIC HELICITY PUMPING BY TWISTED FLUX TUBE EXPANSION
CHAE JONGCHUL,MOON Y.-J.,RUST D. M.,WANG HAIMIN,GOODE PHILIP R. The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.1
Recent observations have shown that coronal magnetic fields in the northern (southern) hemisphere tend to have negative (positive) magnetic helicity. There has been controversy as to whether this hemispheric pattern is of surface or sub-surface origin. A number of studies have focused on clarifying the effect of the surface differential rotation on the change of magnetic helicity in the corona. Meanwhile, recent observational studies reported the existence of transient shear flows in active regions that can feed magnetic helicity to the corona at a much higher rate than the differential rotation does. Here we propose that such transient shear flows may be driven by the torque produced by either the axial or radial expansion of the coronal segment of a twisted flux tube that is rooted deeply below the surface. We have derived a simple relation between the coronal expansion parameter and the amount of helicity transferred via shear flows. To demonstrate our proposition, we have inspected Yohkoh soft X-ray images of NOAA 8668 in which strong shear flows were observed. As a result, we found that the expansion of magnetic fields really took place in the corona while transient shear flows were observed in the photosphere, and the amount of magnetic helicity change due to the transient shear flows is quantitatively consistent with the observed expansion of coronal magnetic fields. The transient shear flows hence may be understood as an observable manifestation of the pumping of magnetic helicity out of the interior portions of the field lines driven by the expansion of coronal parts as was originally proposed by Parker (1974).