BBSO Seminars

Seminars are to be held at 4:00pm, Back Lodge, unless noted otherwise. Speakers, please provide the title, and, if possible, abstract of your talk, when you are ready. For feedback, please direct to Vasyl Yurchyshyn (vayur bbso njit edu)

• May 9, 2014: Choudhary, Debi Prasad (CSU, Northridge) Three Dimensional Chromospheric Structure of Sunspot
We have observed sunspots using the Spectropolarimeter for infrared and optical wavelength ranges at the Dunn Solar Telescope during 29 July to 4 August 2013. The data consists of full Stokes profiles in the Ca II 854.2 nm and Fe I 1.56 micron lines. The inversion of these Stokes spectra provides the magnetic, thermal and velocity structure at photospheric and chromospheric heights of sunspots. In this contribution, we present the first results on the 3D thermal structure in the super-penumbral canopy of a well rounded sunspot, derived by a novel approach for the inversion of Ca II IR spectra. Tracing individual fibrils in the super-penumbral canopy, we find that about half of them form only short loops of a a few Mm length that return to the photosphere in the close surroundings of the sunspot instead of connecting to more remote magnetic network at the outer end of the moat flow.
• May 5, 2014: Friedrich Woeger (NSO) Adaptive Optics supported Speckle Imaging
In the recent past, two new 1.5 meter class solar telescopes were commissioned to advance our knowledge of the very details of plasma motion in the solar atmosphere: the New Solar Telescope at the Big Bear Solar Observatory, and the German GREGOR telescope located on Tenerife. In order to achieve diffraction limited performance, often post-facto image reconstruction techniques that can be combined with Adaptive Optics systems are required. In this presentation, the principles of one particular reconstruction technique are presented: adaptive optics supported speckle image reconstruction. The history and details of the method are explained, as well as its current implementation in the program package called KISIP. The future of this software will be discussed in the light of instrumentation for the Daniel K. Inouye Solar Telescope (DKIST, formerly the Advanced Technology Solar Telescope) currently under construction.
• April 17, 2014: Dr. Leif Svalgaard (Stanford) The Effects of Solar Activity on Our Earth and Our Technological Infrastructure.
The talk is focused on how the Sun's magnetic activity influences our environment, for better and for worse, how we predict and possibly mitigate those influences.
• April 16, 2014: Prof. Jan Stenflo (Institute of Astronomy, ETH, Zurich) Nature of quiet-sun magnetic fields
Since the magnetic structuring continues to scales of order 10-100 m, far smaller than can possibly be resolved, and since the polarization signals are weak on the quiet Sun, one needs to apply robust diagnostic techniques that do not get biased by measurement noise, are independent of telescope resolution, and have minimal model dependence, in order to reliably determine the intrinsic properties of quiet-sun magnetic fields. Such techniques make use of ensemble averages as the observable signatures of the spatially unresolved domain. I will outline how such concepts are applied to derive the field strengths, sizes, and angular distributions from the observed Hanle depolarization and from the symmetry properties of the transverse Zeeman effect.
• Jan 16, 2014: Prof. Jay Pasachoff,Williams College. Coronal temperature and motions from recent eclipse observations
Abstract:We have a series of images and spectra from the total solar eclipses of 2006 (Greece), 2008 (Siberia), 2009 (China), 2010 (Easter Island), 2012 (Australia), and 2013 (Gabon). They cover the solar-activity cycle from sunspot minimum through the current maximum, and our series of flash spectra show the overall change in coronal temperature through the variation of the [5303:6374 [Fe XIV]:[Fe X] line ratio. Further, our high-resolution composite imaging of coronal streamers and CMEs allows measurement of their motions over time intervals between our eclipse sites and others'. We also report on Fabry-Perot observations of motions in a coronal streamer at an eclipse. In addition, we report on our joint work with Dale Gary on Jansky Very Large Array observations of the 2012 annular eclipse. Our research on the annular and total eclipses of 2012 was supported by a grant from the Solar Terrestrial Research Program of the Atmospheric and Geospace Sciences Division of NSF, and on the 2006 eclipse from its predecessor Solar Research Program at NSF. Our research at the 2009 eclipse in China and the 2013 eclipse in Gabon was supported by a grant from the Committee for Research and Exploration of the National Geographic Society.
• July 15, 2013: Deng Yuanyong, National Astronomical Observatoires, Chinese Academy of Sciences. Observational solar physics in China: present and future
Abstract:
• Jan 8, 2013: Rajmal Jain, Physical Research Laboratory,(Dept. of Space, Govt. of India) Ahmedabad, India. Energetic relationship among geo-effective solar flares, associated CMEs and SEPs
Abstract: Firstly, I will briefly introduce our institute. Next, I will briefly discuss the Solar X-ray Spectrometer (SOXS), the first space-borne solar astronomy experiment of India. Then I will move to my main seminar topic where I present energetic relationship among flares, CMEs and SEPs. Major solar eruptions viz. flares, CMEs and SEPs, highly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood, which requires a detailed study of the energetic relationship among these eruptive phenomena. In this view, we investigate 30 flares (observed by RHESSI), followed by weak to strong geomagnetic storms. Flare spectral analysis suggests a new power-law relationship (r ~ 0:79) between the HXR spectral index (before flare-peak) and linear speed of the associated CME observed by LASCO/ SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law (r ~ 0:9) between the hardest X-ray flare spectrum and hardest SEP spectrum. Further, a strong correlation is obtained between the CME linear speed and the hardest spectrum of the corresponding SEP event (r ~ 0:96). We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help to improve our current understanding of Sun-Earth relationship, which is a major goal of research programs in Heliophysics.
• Jun 5, 2013: Udaipur Solar Observatory: An Introduction to Multi Application Solar Telescope and Research Highlights of Udaipur Solar Observatory
Abstract:
The Udaipur Solar Observatory is currently installing a state-of-the-art 50 cm aperture solar telescope with thermal control of all mirrors and backed by an adaptive optics system. I will briefly summarize the steps leading to the installation. I will then follow this with research highlights of the Udaipur Solar Observatory scientists. I will conclude with some ideas on collaboration with BBSO.
• Sept 4, 2012: Ram Ajor Maurya, Seoul National University: Chromospheric Oscillations in Sunspot Observed by NST/FISS
• Aug 29, 2012: Ram Ajor Maurya, Seoul National University: Seismology of Solar Active Regions
• May 15, 2012: W. Uddin, N. Joshi, ARIES, India: Reasearch at Aryabhatta Research Institute of Observational Sciences in India
• Apr 5, 2012: S. Goasin, NSO/SOLIS: Dissection of currents in a twisted sunspot
Abstract:
The high resolution vector magnetograms from Hinode show strong localized currents in the umbra and penumbra due to its intricate fine structure. These currents show a mixed pattern of currents specially an alternating positive and negative behavior in penumbra. This pattern of strong localized currents however masks the more general global twist in the solar magnetic structures. A decomposition of the vertical current density into the twist and shear component seems to help in isolating the broader twist component from localized current patterns. We use this decomposition method to study the currents in a unipolar twisted sunspot and the properties of twist and shear currents in a flaring region.
• Jan 23, 2012: J.P.Rozelot, Universite de Nice, France : History of solar oblatness and relationship to gravitational theories
Abstract:
Exact measurements of the shape of the Sun have a history extending back into the 19th century and dedicated observations such as those of SDT (Princeton and Mount Wilson, USA), SDS (Yale, US) or Pic du Midi (F) were playing a role in this continuing history. Previous observations are serendipitous, such as those of SOHO/MDI or RHESSI. Other space observatories are being actually designed or recently in space for determining solar global parameters, sucha s SDO, and we expect that these will make definitive oblateness measurements over the next few years. The purpose of this lecture is to show off some of the historical overview for the solar oblateness, and to remind assistance of the basic physics of the oblateness measurement. For instance, RHESSI has just completed its observations through the remarkable recent solar minimum and there is no particular reason why its data should not continue well into the operational lifetimes of SDO and latter on from Dynamiccs. We will conclude by emphasizing the rich history of solar oblateness measurements which have some profound implications touching on the determination of the planetary orbits, on the core rotation, on relativity theory or even up to shear effects in the leptocline region. The shape of the Sun is one of the ways we have now for peering into its interior and learning empirically about flows and motions there that would otherwise only be guessed from theoretical considerations.
• Jan 17, 2012: Irina Kitiashvili, Stanford Univ.: MHD Modeling of Plasma Vortices
• Nov 9, 2011: Vladimir Obridko, Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation (IZMIRAN), Russia: The unusual sunspot minimum: challenge to the solar dynamo theory
Abstract:
During the recent decades, much progress was achieved in the development of the solar dynamo theory. The beginning solar cycle 24 is the first one attempted to be predicted not only from extrapolation or precursor methods,but also based on physically consistent dynamo models. However, the predictions for the next sunspot maximum, based on virtually the same dynamo models, range from the lowest one in the last 150 years to the highest one during the whole sunspot observational period. Furthermore, the unusually low and prolonged minimum between cycles 23 and 24 was not expected, not explained, and with unclear consequences for the future solar activity. In the present talk we summarize the solar, heliospheric and geospace observations during this unusual minimum, and their implications for the solar dynamo theory.
• Sept 21, 2011: Irina Kitiashvili, Stanford Univ: MHD Modeling of Pore Formation
• June 9, 2011: Jiong Qiu, Montana SU: Heating of Flare Loops During Two-ribbon Flares
Abstract:
Many eruptive flares exhibit two extended ribbons in the lower-atmosphere outlining the feet of the post-flare coronal arcade. High-cadence and high-resolution UV observations by TRACE reveal that the flare ribbon consists of small patches sequentially brightened along the ribbon, suggesting that reconnection takes place sequentially forming individual post-flare loops along the arcade, as often seen in coronal observations in the EUV wavelengths. These reconnection events and formation of new loops continue well into the decay phase. Our recent study (Qiu et al. 2010) further shows that the spatially resolved UV brightness at the foot-points of individual loops grows rapidly on timescales of a few minutes, followed by a long decay on timescales of more than 10 minutes. The rapid rise of UV radiation is correlated with the hard X-ray light curve during the impulsive phase, hence is most likely a direct response of instantaneous heating in the reconnection formed flux tubes. In this study, we utilize the spatially resolved UV brightness time profiles to reconstruct instantaneous heating functions of individual flux tubes, and compute evolution of each flux tube using the EBTEL model (Klimchuk et al. 2008). To build the heating function, we take into account the scaling between the total UV peak count rate, the hard X-ray energy flux derived from RHESSI spectral analysis during the impulsive phase, and as well the reconnection rate that persists from the pre-impulsive phase to the decay phase. The sum of the computed coronal radiation in all the flux tubes compares favorably with the gross coronal radiation observed by GOES. This study presents the first effort to constrain heating functions of flare loops directly using all available observables, and provides a method to examine physics of heating discrete flux tubes formed by reconnection events throughout the flare.
• Nov 16, 2010: Valentyna Abramenko, BBSO: Statistical Distribution of Size and Lifetime of Bright Points Observed with the NST
Abstract:
We present results of two-hour non-interrupted observations of solar granulation obtained under excellent seeing conditions with the largest aperture ground-based solar telescope (the NST) of Big Bear Solar Observatory. Observations were performed with adaptive optics correction using a broad-band TiO filter in the 705.7 nm spectral line with a time cadence of 10 s and a pixel size of 0.0375''. Photospheric bright points (BPs) were detected and tracked. We find that the BPs detected in NST images are co-spatial with those visible in Hinode/SOT G-band images. In cases where Hinode/SOT detects one large BP, NST detects several separated BPs. Extended filigree features are clearly fragmented into separate BPs in NST images. The distribution function of BP sizes extends to the diffraction limit of NST (77 km) without saturation and corresponds to a log-normal distribution. The lifetime distribution function follows a log- normal approximation for all BPs with lifetime exceeding 100 s. A majority of BPs are transient events reflecting the strong dynamics of the quiet sun: 98.6\% of BPs live less than 120 s. The longest registered life time was 44 minutes. The size and maximum intensity of BPs were found to be proportional to their life times.
• Sept 29, 2010: Eun-Kyung Lim, Seoul National University, BBSO: Magnetic Helicity of Active Regions and Filaments
Abstract:
Magnetic helicity quantifies the self and the mutual linking of magnetic field lines. Since twisted or wound magnetic fields are often observed in associated with explosive events such as flares, coronal mass ejections, and prominence eruptions, solar activities may be better understood in terms of magnetic helicity. I will present what I have done related to magnetic helicity of an coronal active region, filaments and the formation of a helical structure called magnetic channel in an active region. Firstly, we measured the temporal variation of the coronal magnetic helicity of AR 10696 based on the linear force-free field assumption and confirmed the reliability of the linear force-free field method with an error less than 17%. Secondly, we studied the relationship between the active region helicity and the chirality of intermediate filaments. From the statistical analysis, we obtained results supporting that the chirality of intermediate filaments may originated from magnetic helicity of their associated active regions. We also studied the formation process of magnetic channel in AR 10930 by analyzing both photospheric vector magnetograms and the nonlinear force-free field reconstructed coronal magnetic fields. As a result, we obtained some observational evidence that suggests that the magnetic channel structure forms due to the emergence of the twisted flux tube.
• Aug 12, 2010: Aglae Kellerer, Institute for Astronomy, Hilo, Hawaii: Observations on Seeing
• July 20, 2010: Aaron Coulter (BBSO/NJIT): Preliminary Thermal Modeling for the NST Primary Mirror
Abstract: The New Solar Telescope (NST) was to be equipped with a forced air heat ex-changer designed to flow air, cooled slightly below ambient, across the upper and lower surfaces of the primary mirror (PM) in a closed loop, fan driven system. Production and installation issues forced the NST team to abandon plans to implement this system and all imaging, to this point, has been accomplished with no thermal control system at all. Despite general expectations and the existing conventional wisdom on large aperture solar telescope design, the NST is producing good images, even performing at the diffraction limit, with suitable real-time and post-fact image correction. Why is this the case? We will present Computational Fluid Dynamics (CFD) modeling that illustrates how this may be occurring, discuss various measurements of air flows and telescope performance related to this phenomenon, and look at CFD analysis of possible thermal control systems that could be implemented with the current NST PM cell configuration.
• July 15, 2010: Luke Johnson (UC Santa Cruz): Wind-predictive control: Applications to single and multiple conjugate adaptive optics systems
Abstract: The frozen-flow hypothesis suggests that, on short timescales, atmospheric temporal dynamics are dominated by translational shifts of a frozen Kolmogorov spatial pattern. On-sky studies have detected frozen flow in a large fraction (>90%) of datasets from Mauna Kea over varying atmospheric conditions. We propose a way to exploit frozen flow dynamics by adding a time update step to the standard adaptive optics control loop in order to estimate and predict this translational motion. I will present results from computer simulations of single-conjugate, visible-light adaptive optics systems and from the UCO/Lick Multi-Conjugate and Multi-Object Adaptive Optics testbed that quantitatively demonstrate the potential performance improvements due to wind-predictive control. I will also discuss the impact of predictive control on adaptive optics error budgets and identify next-generation systems that would reap significant benefits from incorporating predictive models into their design.
• July 6, 2010: Kenichi Otsuji (Kyoto University): "Cooperative observation between Hida observatory and Hinode/SOT"
Abstract: Cooperative observation with Hida observatory and Hinode satellite was performed in Aug. 2007. Doppler velocity of Ca II K spectra at uprising arch filament in small EFR were measured by Hida observatory Domeless Solar Telescope. There is time delay between the appearance of horizontal magnetic signal and detection of rising motion, which is indicating that the emerged flux on the solar surface stayed until the instability grew.
• Apr 22, 2010: Ali Kilcik (BBSO): "Statistical srudy of the relationship between the sunspot number, maximum of CME speeds and Ap Index"
• Mar 31, 2010: Nina Karachik (NSO) "Formation of Coronal Holes on the Ashes of Active Regions"
• Mar 16, 2010: Haisheng Ji (Purple Mountain Observatory)
• Jan 18, 2009: Vadim Uritsky (University of Calgary)
• Nov 15, 2009: Kwangsu Ahn (BBSO, KASI): PhD Thesis Presentation
• Nov 12, 2009: Zong-Jun Ning (Purple Mountain Observatory): "Prominence oscillations seen by Hinode/SOT on 2008 January 15"
• Tue., Oct 28, 2009: Yeon-Han Kim, Korea Astronomy and Space Science Institute: The small-scale X-ray/EUV jets and the evidence of propagating waves observed by Hinode
• Tue., August 11, 2009: Jiong Qiu (Montana SU): Analysis of Magnetic Reconnection Sequence: from 2D to 3D
• Wed., March 18, 2009: Kwangsu Ahn (BBSO, KASI): Fine Structures of Solar Filaments/Prominences : Their Dynamics and Magnetic Structures
• Wed., April 8, 2009: Prof. Kiyoshi Ichimoto (Kyoto Univ): Introduction to Hida Observatory; Evershed flows in sunspots as seen in Hinode data
• November 5, 2008: Alex Pevtsov (NSO): Helicity on the Sun: what is it good for anyway?
• October 30, 2008: Oskar Von Der Lühe (KIS): High resolution observations at KIS
• August 5, 2008: Friedrich Woeger (NSO): Specle Imaging and Adaptive Optics Correction
• May 7, 2008: Vadim M. Uritsky (Univ. Calgary): Spatiotemporal Event Decomposition (STED) for Solar and Magnetospheric Physics
• November 13, 2007: Franco Rappazzo and Marco Velli (Caltech): Coronal heating
• August 23, 2007: Serge Koutchmy (Institut d'Astrophysique de Paris): Chromospheric prolatenes variations, spicules, marco-spicules and SXR jets
• Apil 25, 2007: Olya Panasenco (Helioresearch): Topological analyses of eruptive filaments
• April 12, 2007: Wenda Cao (NJIT): IR Observations at BBSO
• April 11, 2007: Sridharan Rengaswamy: Crowded Field Astrometry with SIM
• February 14, 2007: Patricia Jibben: The X-ray Telescope (XRT) aboard the Hinode Observatory
• January 24, 2007: Na Deng: Spectral and Multi-wavelength Studies of Active Regions and Flares
• January 24, 2007: Haisheng Ji: The relaxation of sheared magnetic field - a process of contraction
• January 24, 2007: Chang Liu: Multiwavelength and Multiscale Study of Magnetic Fields Involved with Flares/CMEs
• January 24, 2007: Changyi Tan: Statistical Correlations between Parameters of Photospheric Magnetic Field and Coronal Soft X-ray Brightness
• January 24, 2007: Valentyna Abramenko: Solar photospheric fields and their connection with the heliosphere
• January 24, 2007: Ju Jing: Progress in Setting up Data Processing Tools for BBSO Vector Magnetogram Data
• January 24, 2007: Hui Song: Prediction of Imminent Solar Flares with Ordinal Logistic Model
• January 24, 2007: Vasyl Yurchyshyn: Observed Elongation of LASCO Halo CMEs and its Connection to the Structure of Magnetic Clouds
• January 16, 2007: Pilar Montanes-Rodriguez Earthshine applications in the search for distant worlds

• December 12, 2006: Enric Palle Bago: Ocean-cloud-albedo interactions at decadal time scales ( abstract)

• November 14, 2006: Haisheng Ji: Contracting flaring loops suggests the relaxation of sheared magnetic field (abstract)

• February 6, 2006: Jongchul Chae: The Optical Design for the Fast Imaging Solar Spectrograph

• January 28, 2006: Jongchul Chae: Study of magnetic structures of chromospheric filaments.

• January 23, 2006: Hongqi Zhang: Magnetic properties of flare-CME productive active regions

• September 13, 2004: Nancy King: Vegetation Albedoes for Life on Other Planets (abstract)

• August 2, 2004: Jongchul Chae: Fast Imaging Solar Spectrograph (FISS) for New Solar Telescope: The First Idea

• July 26, 2004: Thomas H. Zurbuchen (): The Structure and Sources of the Solar Wind During the Solar Cycle (videoconference) (abstract)

• April 15, 2004: Valentyna Abramenko: Distribution of the magnetic flux in elements of the magnetic field in an active region (abstract)

• April 5, 2004: Prof. Cheng Fang: Spectral Diagnostics Of Non-Thermal Particles In The Solar Chromosphere (abstract)

• February 10, 2004: Enric Palle Bago: A review on the Earthshine Project. Changes in the earth's reflectance over the past two decades (abstract)

• Valentyna Abramenko: Changes in the Spectral Line Profiles During a Solar Flare (abstract)

• Reiner Volkmer: Actual Status and Design of the 1.5 m Solar Telescope GREGOR

• K.D. Leka: What makes a flare? Determining the magnetic signature of a flaring photosphere. (abstract)

• Klaus Hartkorn: Application Of Adaptive Optics To The Spectroscopic Investigation Of Small-Scale Solar Structures. (abstract)

• Haisheng Ji: Report On My Work at BBSO

• Ayumi Asai: Flare Evolution and Energy Release (abstract)

• Valentyna Abramenko: Signature of Avalanche in Solar Flares as Measured by Photospheric Magnetic Fields (abstract)

• Vasyl Yurchyshyn: How Directions And Helicity Of The Magnetic Field In Erupted Solar Filaments Define Geoeffectiveness Of Coronal Mass Ejections (abstract)

• Yong-Jae Moon: Magnetic Helicity and X-Ray Fluxes of Homologous Flares (abstract)

• Martin Woodard: Seismic Imaging of Solar Convection (abstract)

• Guo Yang: The introduction to Coronal Mass Ejection and the work I am doing

• Abramenko, Magnetic Power Spectra in the Solar Photosphere Derived from Ground and Space Based Observations

• Carsten Denker, Center-to-Limb Variation of Small-Scale Magnetic Features

• Leonid Didkovsky, Proper Motion of Sunspots Observed with MDI

• Michael Steinegger, The H-alpha Network: Overview - Status - Outlook

• Louis Strous, THE DYNAMICS OF THE EXCITATION OF SOLAR OSCILLATIONS (abstract)

• Jongchul Chae, High Resolution H alpha Observations of Proper Motions in NOAA 8668: Evidence for Filament Mass Injection by Chromospheric Reconnection (abstract, H alpha movie)

• Peter Gallagher, Observing the Sun at Radio Wavelengths (abstract)

• Jung-Hoon Kim, A Rapid Magnetic Connectivity Change Observed Before a Filament Eruption

• Sangwoo Lee, Observational Evidence for Magnetic Dips in Solar Prominences

### ABSTRACTS

Title, Name
Abstract
[Top]

Topological analyses of eruptive filaments by Olya Panasenco
Erupting filaments (prominences) that we have analyzed from H" Doppler data at Helio Research and from SOHO/EIT 304 D show several different motions along the main axis and legs. Our simple geometrical analyses of these motions reveal strong coherency in some filaments between their chirality, and the direction of the vertical motions of the top of the filaments, and the directions of twisting of their legs. Viewed from the positive network side, dextral filaments develop rolling motion toward the observer along with right-hand helicity in the left leg (clockwise streaming for downward motion) and left-hand helicity in the right leg. Sinistral filaments, also viewed from the positive network field side, have the opposite pattern: rolling motion at the top away from the observer, left-hand helical twist in the left leg (counterclockwise for downward motion) and right-hand twist in the right leg. We find consistency between our analyses of these motions and forms determined from our Ha Doppler observations and twists or bending deduced from the properties of erupting filaments observed in EIT images at 304 D. We cannot reconcile these findings with filaments modeled as magnetic flux ropes that by definition only have one sign of helicity. In addition, the popular hypothetical configuration of an eruptive filament as a twisted flux rope does not account for the complete range of observed shapes in the erupting filaments. However, we find that a simple flat ribbon or sheet satisfactorily reproduces nearly all of the observed forms. The flat ribbon is the most logical beginning topology because filament spines already have this topology prior to eruption and an initial long flat sheet with parallel, non twisted threads, as a basic form, can be bent into many more and different geometrical forms than a flux rope. To date, we have been able to identify three common patterns of motion. All are consistent with the ribbon topology and characterize the helicity of many erupting filaments: (1) Roll of the top of the filament with horizontal and vertical components, (2) Twist of the legs consistent in sign with the rolling motion along the top of the filament, and (3) rotation (writhe) of the whole filament as it moves and expands outward. Considering that erupting filament dynamics have large-scale coherency and always occur beneath CMEs, we suggest that it is reasonable for the top of an erupting filament to be first in responding to relatively unknown, changing, coronal forces in its environment. For morphological analyses of eruptive filaments we used the ratio h/l, where h - is the height of filament, l - is distance between its legs, and also " - the angle in degrees of twist or roll during increments of time, t. We consider three general cases: 1) h/l - 0; 2) h/l > 1, legs close together; 3) h/l # 1, legs far apart. We also describe the relationship between the direction of twists in the legs and the roll direction at the top of the filament using the geometrical terms: l, h, and ". Starting with our finding that filaments are thin sheets after their eruption, as known before their eruption, we apply our geometrical analyses to determinate of the sign of magnetic helicity and estimate the degree of twisting or bending in different parts of the top and legs of erupting filaments.
[Top]

The X-ray Telescope (XRT) aboard the Hinode Observatory by Patricia Jibben
XRT is a high resolution grazing incidence telescope capable of observing coronal temperatures from 700,000 to 10,000,000 Kelvin. It has a 34x34 arcmin full field of view and 2" spatial resolution capable of studying global coronal structures as well as resolving active region loops. The unique combination of high spatial resolution and broad temperature range allows observations of energy buildup, storage and the release process in the corona for any transient event. XRT was launched on September 22, 2006 and has been actively observing the sun since November 2006. Recent observations include transient polar jets within polar coronal hole, C-class flares, loop evolution, and the so-called coronal 'doughnut'. A sample of these observations will be presented.
[Top]

Earthshine applications in the search for distant worlds by Pilar Montanes-Rodriguez

Since the discovery of the first planet outside the solar system, the number of planet detections is increasing exponentially. Although we have not been capable of detecting and exploring planets like our own yet, challenging space missions are already being planned for the next decades, and the discovery of earth-like planets is only a matter of time. When the time arrives, one of our main concerns will be to determine their degree of similarity with our own planet, and to answer a more intriguing question for the humankind: if there is life on them. Using real cloud cover observations from satellite, we have unequivocally detected the vegetation's signature in the Earth's globally averaged spectrum. The signature is stronger when larger vegetated regions of the Earth are seen free of clouds. Our results show that, considering the real cloud cover present in our planet, previous estimates of the vegetation signal strength were overoptimistic. Vegetation can be detected on Earth when it is observed as a distant planet, and although its signal is going to be much weaker than what we previously though, when detected, it will be an unquestionable indication of extraterrestrial complex life. Future applications of earthshine spectroscopy will also be introduced.[Top]

Ocean-cloud-albedo interactions at decadal time scales by Enric Palle Bago

Over the past century, our planet has experienced a global warming generally associated to an increase in anthropogenic greenhouse gases, superimposed to an unknown intrinsic climate variability. To understand this warming, it is essential to know the response of the climate system to external forcing, and the decadal-scale energy exchange between the oceans and the atmosphere. Presently, two of the most uncertain elements in the climate are the role of clouds and the heat storage of the Earth's oceans. Especially intriguing are the cloud feedback mechanisms, which strongly affect the ability of global circulation models to predict future climate change. Here, we compare 20 years of global ocean thermal properties and cloud amount data to derive their large-scale inter-annual relationships. Despite some restriction in our conclusions due to the nature of the datasets, we find significant correlations whose strength and sign vary with cloud type and latitude. At decadal timescales, we find an anti-correlation between the global mean cloud amount and the ocean's heat content, with the clouds leading in the correlation by about 1 year. Our results suggest that cloud changes, whether natural or anthropogenic in origin, might have a direct influence in the decadal variability of ocean temperatures and heat content.
[Top]

Contracting flaring loops suggests the relaxation of sheared magnetic field by Haisheng Ji

In recent years, a new kind of solar flare phenomenon has been discovered in many flares by different authors. That is, during the early rising phase of solar flares, hard X-ray loop top sources or radio/extreme-ultraviolet flaring loops have a shrinkage motion and, at the same time, flaring ribbons or hard X-ray footpoints have a converging motion. Only after the rising phase, there begin to appear an upward expansion for loop top sources and flaring loops and, also, an outward motion (separation motion) for flare ribbons or footpoints. So far, the shrinkage motion can not be fully explained with a 2D flare model. We propose that the new solar flare phenomenon suggests the relaxation of sheared force-free magnetic field.
[Top]

Vegetation Albedoes for Life on Other Planets by Nancy King

Scientists are fast approaching the capability to detect Earth-size planets and to resolve them spectrally. How can we tell if there is life on another planet through astronomical observations? Life abounds in extreme environments and in hidden places of the Earth and could likewise on other planets. However, on Earth, only photosynthetic organisms produce unequivocal signs of life that we can detect from space. These signs are the vegetation "red edge" (the strong contrast in absorbance by vegetation in the visible light range and high reflectance in he near-infrared) and the presence of oxygen in our atmosphere (due to water photolysis by photosynthesis). In addition, the seasonal cycles of atmospheric carbon dioxide and methane concentrations are due to the seasonal growth and respiration of the biosphere. These "biosignatures" are the result of short-term biophysical processes, which have arisen through long-term coevolution of the biosphere with the atmosphere, and perhaps due to evolutionary accidents in the origin of photosynthesis. Could photosynthesis arise on another planet, and would such organisms produce the same biosignatures as those on Earth? This talk will review the state of knowledge on the vegetation red edge and predicting plant canopy albedoes, the environmental constraints on photosynthesis, and present potential biosignatures for life around M-stars, with discussion about their detectability.
[Top]

The Structure and Sources of the Solar Wind During the Solar Cycle

The solar corona and hence the structure of the heliosphere change dramatically during the solar cycle. At solar minimum, solar wind predominantly emerges from polar coronal holes and propagates close to equatorial regions. Associated with streamers, an intermittent stream of solar wind is emerging and forming slow solar wind. As solar activity progresses, this bimodal distribution of the solar wind becomes much more complicated. Fast and slow solar wind can be found at all latitudes. We will discuss this transition from low to high solar activity focusing on solar wind composition data that provide a new way of observing the evolution of the solar corona over time. These data show interesting compositional anomalies that distinguish different sources of solar wind and mark hot ejecta in the heliosphere.
[Top]

Distribution of the magnetic flux in elements of the magnetic field in an active region by Valentyna Abramenko

Probability distribution functions (PDFs) of the unsigned magnetic flux content in flux concentrations in a mature active region NOAA 9077 were calculated by using a set of 248 high resolution SOHO/MDI magnetograms. Two independent routines to outline magnetic flux concentrations were elaborated. The analysis was performed with 4 different values of the threshold, p, of the magnetic flux density (p=25, 50, 75, 100 G). We have found that: i) the best analytical approximation of the observed PDFs in the range of low flux (F < 100 x 10^18 Mx) is a lognormal distribution, LN(m, sigma^2), with the expected value m=(0.7 to 5) x 10^18 Mx and the standard deviation sigma = (10 to 45) x 10^18 Mx. The peak of the lognormal distribution tends to shift toward the lower flux as the threshold p decreases. This tendency suggests that the real expected value may be even smaller than 0.7 x 10^18 Mx; ii) for the flux F > 100 x 10^18 Mx the observed PDFs fall off slower than the lognormal approximation predicts. In this flux range, the power law is found to be the best analytical approximation with the power law index, alpha, approximately equal to 2. The above findings are consistent with the concept of highly intermittent nature of the cluster of magnetic flux concentrations in the active region.
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Spectral Diagnostics Of Non-Thermal Particles In The Solar Chromosphere by Prof. Cheng Fang

There are at least three effects of the non-thermal particle bombardment on the solar atmosphere: (1) non-thermal ionization and excitation; (2) proton-hydrogen charge exchange; (3) impact line polarization. Due to the non-thermal ionization and excitation effects of electron bombardments in flares, H? line is widely broadened and shows a obvious central reversal. Significant enhancements at the line wings of Ly?and Ly?are also predicted. In the case of proton bombardment, less strong broadening and no large central reversal are expected. Based on theoretical calculations, we proposed a method to estimate the total flux of electron beam by the measurement of integrated flux in H? line profiles. Due to the proton-hydrogen charge exchange, the enhancements at the red wings of Ly? and especially of Ly?lines at the early impulsive phase of flares are significant. Electron beam can also in some cases produces visible and UV continuum emission in white-light flares. However, at the onset phase, a negative "black" flare may appear in several seconds, due to the increase of the H? opacity. The impact polarization of atomic lines can provide complementary information on the energetic particles, the energy transport and deposit in the solar chromosphere. New results of spectropolarimetric analysis for the major flare on are also given.
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A review on the Earthshine Project. Changes in the earth's reflectance over the past two decades by Enric Palle Bago

We correlate an overlapping period of earthshine measurements of the earth's reflectance (1999 through mid-2001) with satellite observations of global cloud properties to construct from the latter a proxy measure of the earth's global shortwave reflectance. This proxy shows a steady decrease in the earth's reflectance from 1984 to 2000, with a strong drop during the 1990's. During 2001-2003 only earthshine data are available, and they indicate a complete reversal of the decline. The radiative forcing implied by either of these decadal changes in reflectance is climatologically significant. Understanding how these changes are apportioned between natural variability, direct forcing, and feedbacks, is fundamental to confidently assessing and predicting climate change.
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Changes in the Spectral Line by Profiles During a Solar Flare by Valentyna Abramenko

The profiles of six photospheric absorption spectral lines (Fe I 5250A, Fe I 5324A, Fe I 5576A, Ca I 5590A, Ca I 6103A, and Fe I 6165A) measured in the kernel of a 2N solar flare and in a quiet-sun area, were compared. The observations were carried out with an echelle spectrograph of Crimean Astrophysical Observatory. It was shown that compared to the quiet-sun profiles, the flare profiles are shallower in the line core and are less steep in the wings. Therefore, measurements of the longitudinal magnetic field made with a magnetograph system which use the Ca 6103\AA~ spectral line, can be underestimated by 18-25\% in the areas of bright H$\alpha$ ribbons of a moderate solar flare of importance 2N. The modeling of the solar photosphere performed by using a synthesis method, showed that in a solar flare, the enhanced core emission seems to be related to heating of the photosphere by the flare, whereas the decrease of the wings slope was presumably caused by the inhomogeneity of the photospheric magnetic field.
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What makes a flare? Determining the magnetic signature of a flaring photosphere by K.D. Leka.

Big Bear Solar Observatory have searched for and in many cases, found, changes in photospheric magnetic fields associated with solar flares; this is demonstrated with the recent work of Wang et al (2002) which found variations in magnetic flux temporally associated with six X-Class solar flares. In this talk I will outline an approach we have developed to distinguish what may be unique to a flare-imminent solar atmosphere as determined by the photospheric magnetic field. Using archive data from the Imaging Vector Magnetograph from U. Hawai`i/Mees Solar Observatory, we perform statistical evaluations of the state of the photospheric magnetic field as well as on measures of the inferred coronal topological complexity (Leka & Barnes 2003; Barnes et al 2003). I will describe our method which, when applied to the minimal dataset so far acquired, has indeed been able to distinguish that atmosphere which is flare-imminent, but only by simultaneously considering six or more parameters derived from the photospheric magnetic field vector.
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Application Of Adaptive Optics To The Spectroscopic Investigation Of Small-Scale Solar Structures by Klaus Hartkorn.

We study bright points, umbral dots and the G-band using a two-dimensional spectrometer and an Adaptive Optics system, which allows us to record high-resolution dopplergrams and residual intensity images. We find evidence that bright points are smaller than 120 km in diameter. Bright points are situated exclusively in regions of enhanced G-band brightness and do not show a change in their shape or a displacement in their position of more than 120 km horizontally over a height range from 0 km to 320 km above photospheric level $\tau =1$. We do not find velocity differences of more than 100 m/s and a size of 120 km at the locations of bright points compared to the surroundings. Bright points have a higher contrast in the G-band as well as in the atomic spectral lines. We suspect the existence of two contrast enhancement mechanisms for bright points one exclusively for the G-band, one independent of specific spectral lines. We perform calculations using the results of a three-dimensional magneto-hydrodynamical model as input for a radiative transfer calculation, but find little agreement with our observations. The core intensity of the G-band CH lines is significantly influenced by the atmospheric conditions in heights of 160 km and 320 km, but not heights of 40 km. The velocity investigation of a sunspot shows that umbral dots seem to consist of two different types. The first type is the bright part of an intensity pattern of 1000-2000 km size with a corresponding negatively correlated velocity pattern which is probably related to umbral oscillations. The second type consists of localized brightening of a size of not more than 300 km that are associated with down-flowing plasma. Furthermore, we find penumbral grains that have penetrated the umbra and appear as brightenings. We study the velocity signature of penumbral grains and find strong up-flows of solar plasma associated with the inner, bright parts of penumbral grains, where as the general correlation between intensity and velocity within the penumbra is weak.
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Flare Evolution and Energy Release by Ayumi Asai.

Studies of solar flares by using optical (mainly H-alpha) data, combined with EUV (TRACE), X-rays (Yohkoh & RHESSI), and microwave (Nobeyama) data. The main results are as follows: 1) We found a good correlation between motions of H-alpha flare kernels and HXR foot point source time history. It was shown that the HXR temporal variation can be explained by a combination between the magnetic field strength and the separation speed of the H-alpha kernels. 2) Down flow motions above the EUV arcade correlate with HXR bursts in the impulsive phase.
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Signature of Avalanche in Solar Flares as Measured by Photospheric Magnetic Fields by Valentyna Abramenko.

Turbulent/fractal parameters of the longitudinal magnetic field, B_z, for four powerful solar flares were analyzed utilizing the correlation length, \lambda, of the magnetic energy dissipation field and the scaling exponent, \beta, which characterizes the measure of intermittency of the B_z structure. We select a set of four two-ribbon flares, which were followed by coronal mass ejections, for the study of magnetic structure. During the course of each flare, we found a peak in \beta which was followed by a peak in \lambda in all of the cases studied in this paper. These two peaks were separated by the time interval \tau_{\lambda} during which a rapid growth of the soft X-ray and H\alpha flux occurred. The peak in \beta was preceded by a time period \tau_{\beta} during which \beta increased gradually. For all of the flares \tau_{\beta} was longer than the time interval \tau_{\lambda}. The maximum of \lambda occurred nearly simultaneously, within an accuracy of about 2-5 minutes, with the maximum of the hard X-ray emission. For the four flares considered in this paper, we concluded that the more impulsive and/or more powerful a flare is, the shorter the \beta growth time, \tau_{\beta}, and the \lambda growth time, \tau_{\lambda}, are. In the framework of the theory of non-linear dissipative processes, these results may be interpreted as follows. Before a solar flare occurs there is a significant increase in the number of magnetic field discontinuities (\beta increasing), which is followed by an avalanche (increase of the correlation length) of magnetic energy dissipation events. The avalanche event occupies the entire active region from the corona to the photosphere. Our study indicates that the more abrupt is the avalanche, the stronger and/or more impulsive a flare is. The time profiles of an avalanche is either Gaussian, which satisfies the logistic avalanche model, or exponential with an abrupt drop, which satisfies the exponential avalanche model. The driving time, \tau_{\beta}, was longer than the avalanching time, \tau_{\lambda}, for all of the events. This qualitatively agrees with the requirements of the self-organized criticality theory.
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HOW DIRECTIONS AND HELICITY OF THE MAGNETIC FIELD IN ERUPTED SOLAR FILAMENTS DEFINE GEOEFFECTIVENESS OF CORONAL MASS EJECTIONS by Vasyl Yerchyshyn.

Coronal mass ejections (CMEs) are often associated with erupted magnetic fields or disappeared chromospheric filaments. The majority of CMEs headed directly toward the earth (halo CMEs) are observed at 1AU as magnetic clouds (MC). The 3D structure of a MC can be represented by a force-free flux rope. When CMEs reach the earth, they may or may not cause magnetic storms. The geoeffectiveness of CMEs depends on the orientation of the magnetic field in them. We show that the direction of the axial field in a MC and its helicity are consistent with the direction of the axial field and helicity of the erupted filaments. We also suggest that geoeffectiveness of a CME can be forecasted by using daily Big Bear Solar Observatory full disk H$\alpha$ and SOHO EIT 195\AA~ images and SOHO/MDI magnetograms, as well. We continue to study the orientation of magnetic fields in CMEs and its correlation with the occurrence of geomagnetic storms. Here we report on the relationship between the projected speed of CMEs, measured at 20R$_\odot$ from SOHO/LASCO images, and the hourly averaged magnitude of the southwardly directed magnetic field, B$_z$, in interplanetary ejecta, as measured by the ACE magnetometer. CMEs that origin at the central part of the solar disk ($r < 0.6R_\odot$) are the most geoeffective and the instensity of the B$_z$ is an exponential function of the CME's speeds. We propose that the strength of the southward IMF can be estimated at least one day in advance, immidiatelly after a CME started. The predicted value of the B$_z$ component can be then used to estimate the intensity of a geomagnetic storm caused by the erupteion. The prediction method is based on the correlation between the speeds of CMEs and magnitudes of the southward IMF as well as the fact that the orientaion and chirality of the erupted solar filaments correspond to the orientation and chirality of interplanetary ejecta.
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Magnetic Helicity and X-Ray Fluxes of Homologous Flares by Yong-Jae Moon
We present evidence that the occurrence of a series of homologous flares in an active region is physically related to the accumulation of magnetic helicity in the corona by shearing motion in the photosphere. We have analyzed a set of 6.5 hour 1 minute cadence magnetograms of NOAA 8100 taken by Michelson Doppler Images (MDI) on board Solar and Heliospheric Observatory (SOHO). During this period, seven homologous flares took place in the active region, but there was no remarkable change of magnetic flux. We have determined the magnetic helicity transport rate via photospheric footpoint shuffling motions, and found that magnetic helicity was significantly increasing during the observing period. It was obvious in the case of a strong M4.1 flare that magnetic helicity injection rate impulsively increased to a peak during the flaring time as the X-ray flux did. We also found that the X-ray flux of a flare integrated over the flaring time interval was strongly correlated with the magnetic helicity accumulated during the flaring time, with the integrated flux logarithmically increasing with the accumulated magnetic helicity. Our results suggest that photospheric shearing motion is an important driver of coronal activities and, hence, support Choe Cheng's homologous flare model in which flares can occur in the same plage repeatedly by continuous photospheric shearing motions.
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Seismic Imaging of Solar Convection by Martin Woodard

A new seismic technique is being developed to image inhomogeneous structure, such as subsurface convective cells, in the Sun. In the direct imaging approach, a physical model of the solar interior is inferred directly from correlations in the observed seismic wave field. A preliminary map of supergranular convection, inferred from SOHO/MDI helioseismology images, agrees reasonably well with simultaneous surface Doppler maps of supergranulation. Further development of the method is expected to improve the technique considerably.
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THE DYNAMICS OF THE EXCITATION OF SOLAR OSCILLATIONS by Louis Strous

We investigate seismic events, bursts of seismic waves that are generated locally just below the solar surface and that we detect traveling up through the photosphere. We identify a few thousand seismic events by their traveling wave character, and find that they are associated with continuum darkening and downflow, and have an extent of on average about 10 -- 15 minutes and 1 Mm. Their birth rate is about 8e-16 m^-2 s^-1. The observed upwardly traveling seismic flux in the average event (as derived from velocities in the p-mode region of k-omega space) is followed after about 3 minutes by some reflected downward flux. Only a small fraction of the energy generated in the hypocenter of the event below the surface travels straight up for us to see. The bulk of the generated energy is directed or reflected downward, and is eventually transformed into p-modes. The seismic events at the surface contain about 1.5e19 J of seismic energy each, which corresponds to an average flux level of about 8.5 kW/m^2 over the whole surface. The total energy flow is likely more than an order of magnitude greater, and is then in the same ballpark as the estimate of Libbrecht (1988) for the power required to sustain the p-mode spectrum. We find a roughly linear relation between the peak seismic flux and the peak downward convective velocity associated with each seismic event, which does not fit the highly non-linear relations found theoretically by Lighthill (1952) and Goldreich & Kumar (1990) for stochastic excitation by turbulent convection, but does fit the monopole source deduced by Nigam & Kosovichev (1999) from a study of the p-mode spectrum.
Reference: Strous, Goode, & Rimmele (2000), Ap.J. 535, 1000
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High Resolution H$\alpha$ Observations of Proper Motion in NOAA 8668: Evidence for Filament Mass Injection by Chromospheric Reconnection
by Jongchul Chae

There have been two different kinds of explanations for the source of cool material in prominences or filaments: coronal condensations from above and cool plasma injections from below. In this paper, we present observational results which support filament mass injection by chromospheric reconnection. The observations of an active filament in the active region NOAA~8668 were performed on at a wavelength of H$\alpha-0.6$ \AA\ using the 65~cm vacuum reflector, a Zeiss H$\alpha$ birefringent filter, and a 12-bit SMD digital camera of Big Bear Solar Observatory. The best image was selected every 12~s for an hour based on a frame selection algorithm. All the images were then co-aligned and corrected for local distortion due to the seeing. The time-lapse movie of the data shows that the filament was undergoing ceaseless motion. The H$\alpha$ flow field has been determined as a function of time using local correlation tracking. Time-averaged flow patterns usually trace local magnetic field lines, as inferred from H$\alpha$ fibrils and line-of-sight magnetograms. An interesting finding is a transient flow field in a system of small H$\alpha$ loops, some of which merge into the filament. The flow is associated with a cancelling magnetic feature which is located at one end of the loop system. Initially a diverging flow with speeds below 10 km s$^{-1}$ is visible at the flux cancellation site. The flow is soon directed along the loops and accelerated up to 40 km s$^{-1}$ in a few minutes. Some part of the plasma flow then merges into and moves along the filament. This kind of transient flow takes place several times during the observations. Our results clearly demonstrate that reconnection in the photosphere and chromosphere is a likely way to supply cool material to a filament, as well as re-organizing the magnetic field configuration, and, hence, is important in the formation of filaments.
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Observing the Sun at Radio Wavelengths
by Peter T. Gallagher

In this talk, I will give an introduction to observing the Sun using the Owens Valley Solar Array (OVSA). The basic elements of the radio telescopes together with the mechanisms responsible for radio emission will first be reviewed. I will then discuss the recent upgrade of OVSA, data access and analysis, and how to observe using the array. Finally, some recent scientific results from high resolution flare observations will be discussed.
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