SH52A-01 INVITED 10:30h
From the Inside of the Sun to its Atmosphere
Charles Greeley Abbot was correct in predicting the solar constant is decidedly inconstant. Indeed, the solar irradiance exhibits pronounced variations on nearly all currently accessible observational time scales. There is overwhelming evidence for a tight correlation between the Sun's magnetic activity cycle and broadband spectral irradiance in the sense that greater magnetic activity implies excess irradiance and vice-versa. Global dynamical and evolutionary processes determine the time-averaged solar luminosity. In this realm the variable magnetic field is of no consequence. It is therefore of interest to ask how deep within the solar envelope and interior do the irradiance fluctuations persist, and from where do they originate. Observational and theoretical evidence will be presented to suggest that an answer to this fundamental question may soon be in hand.
SH52A-02 INVITED 10:50h
Working with the photospheric magnetic field observations from Mount Wilson, Wilcox, and Kitt Solar Observatories
Routine full disk measurements of the Sun's photospheric field began at Mount Wilson Solar Observatory (MWO) in 1966, resulting in a near-continuous set of daily magnetograms over approximately the last three solar cycles. Similar measurements began both at the National Solar Observatory on Kitt Peak (NSO) and Wilcox Solar Observatory (WSO) roughly a solar cycle later in the mid-1970s. There are thus three solar observatories with near continuous daily observations of the global photospheric field that span approximately the last three decades. However, working with these data requires care and frequently a detailed understanding of important issues about the observations from each observatory. For instance, both MWO and NSO have had a number of major instrument changes over the years. MWO replaced its grating in 1982 and 1994 and NSO replaced its original magnetograph in 1992 and then again in 2003 with the recent installation of the new SOLIS instrument. At any given observatory, the data taken with new instruments are not necessarily well inter-calibrated with older ones nor is it necessarily true that all know calibration issues for a particular instrument have been fully addressed. This tends to be especially true in the older data. For example, it is well known that the observations made with the original magnetograph at NSO (i.e., pre 1992) frequently suffer from systematic biases in the zero point of the measurements [Arge et al., 2002]. In addition, the three observatories provide their line-of-sight (LOS) photospheric magnetic field observations using different file formats, spatial resolutions, and even units and frequently not with all known corrections applied to them. For example, MWO and WSO both make use of the Fe I 525.0 nm line to measure the LOS magnetic field strength. This line is well known to be especially prone to line saturation effects that require the application of an appropriate correction factor. Historically, neither observatory has routinely corrected their data for saturation effects, and in fact, each has advocated using a different correction factor for this same spectral line. In this paper, we highlight, from the perspective of someone that routinely uses them for space weather modeling purposes, some of the important issues that can make using these data less than straightforward.
SH52A-03 11:10h
The Solar Photograph Archive of the Mount Wilson Observatory - A Resource for a Century of Digital Data
The solar telescopes and spectroheliographs of the Mount Wilson Observatory were among the earliest modern facilities for the study of the solar surface. The photographic collection of the solar program at Mt. Wilson begins in 1894 and continues to the present day. A program to digitize and distribute some of the images in this collection was begun at UCLA in 2003 and is now making available the first of the catalogued and catagorized images from the Ca K sequence. Most of the instrumentation with which the images were obtained is still available although in a disassembled form. Original logbooks have been digitized and associated with the images so that a maximum of scientific return can be obtained from the data base. The present range of images available from: http://www.astro.ucla.edu/{\~}ulrich/MW{\_}SPADP/CaK{\_}fits/ extends from late 1915 to mid-1925. Each image has been digitized with 12-bit precision and represented in a 16-bit format. These images are each 13 Mbytes in size and larger than will be the final product images since not all image defects have been mitigated at this time. The radii and centers of the solar images have been determined and are included in the available data files. Optical vignetting by the system introduces an intensity gradient of known magnitude that can be used to help characterize the photograph plates. The roll angle of the images has yet to be determined.
http://www.astro.ucla.edu
SH52A-04 11:25h
Seachable Solar Feature Catalogues in EGSO
The searchable Solar Feature Catalogues (SFC) developed using automated pattern recognition techniques from digitized solar images are presented. The techniques were applied for detection of sunspots, active regions, filaments and line-on-sight magnetic neutral lines in the automatically standardized full disk solar images in Ca II K1, Ca II K3 and Ha taken at the Meudon Observatory and white light images and magnetograms from SOHO/MDI. The results of automated recognition were verified with the manual synoptic maps and available statistical data that revealed good detection accuracy. Based on the recognized parameters a structured database of the Solar Feature Catalogues was built on a mysql server for every feature and published with various pre-designed search pages on the Bradford University web site. The SFCs with 10 year coverage (1996-2005) is to be used for deeper investigation of the solar activity, activity feature classification and forecast.
http://www.cyber.brad.ac.uk/egso/
SH52A-05 INVITED 11:40h
Coronal Mass Ejections and Space Weather
Coronal mass ejections (CMEs) are a key aspect of coronal and interplanetary dynamics. They can inject large amounts of mass and magnetic fields into the heliosphere, causing major geomagnetic storms and interplanetary shocks, a key source of solar energetic particles. Studies over the past decade using the excellent data sets from the SOHO, TRACE, Yohkoh, Wind, ACE and other spacecraft and ground-based instruments have improved our knowledge of the origins and early development of CMEs at the Sun and how they affect space weather at Earth. I review some key coronal properties of CMEs, their source regions, their manifestations in the solar wind, and their geoeffectiveness. Halo-like CMEs are of special interest for space weather because they suggest the launch of a geoeffective disturbance toward Earth. However, their correspondence to geomagnetic storms varies over the solar cycle. Although CMEs are involved with the largest storms at all phases of the cycle, recurrent features such as interaction regions and high speed wind streams can also be geoeffective. I will also review some results from a new heliospheric experiment, the Solar Mass Ejection Imager, that has been observing interplanetary CMEs since Feb. 2003.
SH52A-06 INVITED 12:00h
Heliospheric energetic particle variability over the solar cycle
The energetic particle contents of the heliosphere change from solar maximum to solar minimum. The ultimate responsible for those variations is our changing Sun. Its changes are reflected in the dynamics of the large-scale structure of the heliosphere, the solar output of energetic particles, and definitively, in the origin, intensity, energy and composition of the population of energetic particles observed by spacecraft and earth-based detectors. I will describe the global changes observed over the solar cycle in both the heliospheric energetic particle contents and the large-scale structure of the 3-D heliosphere. The stable and regular pattern of recurrent energetic particle events observed in association with corotating interaction regions (CIRs) during solar minimum is replaced by the irregular and sporadic observation of solar energetic particle (SEP) events associated with the occurrence of fast coronal mass ejections (CMEs). The higher frequency of CMEs and transient events during solar maximum results in a more complex and dynamic heliosphere with important consequences for the propagation of energetic particles. Whereas the heliosphere is relatively undisturbed (CME-free) energetic particles may freely propagate throughout the heliosphere. However, the presence of multiple CMEs causes increases in the heliospheric magnetic field that may result in the confinement of energetic particles and hence the enhancement or attenuation of SEP intensities depending on the location of the observer with respect to the energetic particle confinement. I will review the occurrence frequency of the major SEP events and the effects that they had at different locations of the heliosphere.