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There are 146 abstracts


Social Media - An Interactive and Engaging Approach to Bring the Science to the People

Author(s): Romeo Durscher, Martha Wawro

Institution(s): Stanford University, NASA GSFC

Abstract:

NASA has embraced social media as a valuable tool to communicate the activities of the agency in fulfillment of its mission. Team SDO continues to be on the forefront of using social media in a very engaging and interactive way and share mission information, solar images and space weather updates via a variety of social media platforms and outlets. We will present the impact SDO’s social media strategy has made, including follower, friends and fan statistics from Twitter, Facebook, YouTube, Google+ and other outlets. We will discuss the various social media outlets and the techniques we use for reaching and engaging our audience. Effectiveness is measured through the use of various automatically gathered statistics and level of public engagement. Of key importance to effective social media use is having access to scientists who can quickly respond to questions and express their answers in meaningful ways to the public. Our presentation will highlight the importance of scientist involvement and suggest ways for encouraging more scientists to support these efforts. We will present some of the social media plans for 2012 and discuss how we can continue to educate, inform, engage and inspire.




Understanding the Dynamics of Supergranulation Using Helioseismology and Linear Acoustic Simulations

Author(s): T.L. Duvall Jr., S.M. Hanasoge

Institution(s): NASA/GSFC ; Princeton Univ.

Abstract:

Some recent work of Duvall and Hanasoge has suggested that supergranulation, on average, is shallow, with peak flows 2 Mm below the photosphere, and is quite vigorous, with peak flows (vertical 200 m/s; horizontal 700 m/s) considerably larger than the photospheric values (vertical 10 m/s; horizontal 300 m/s). This result is based on measurements of center-annulus travel time differences measured in time-distance helioseismology with larger separations (up to 24 heliocentric degrees) than previously considered and on ray theory forward modeling. This result is somewhat at odds with earlier work based on smaller separations (less than 5 heliocentric degrees). To test whether the vigorous, shallow supergranulation is viable, linear acoustic simulations were done with flow perturbations consistent with the above result. The depth of the model is 70 Mm, enabling the use of separations up to 18 deg heliocentric. The simulation has high enough horizontal resolution to study small separations (~ 1 deg) and also to examine the f mode. With this simulation then, we should be able to examine then both short and large separations and both p and f modes. By computing rays through the flow model, we can also then test the applicability of ray theory for this particular case.




Large-Scale Dynamics of the Solar Convection Zone: Puzzles, Challenges, and Insights from a Modeler's Perspective

Author(s): Featherstone, Nicholas A. (1), Miesch, Mark S. (2)

Institution(s): High Altitude Observatory, NCAR

Abstract:

Meridional circulations and rotational shear serve as a key ingredient in many models of the solar dynamo, likely playing an important role in the maintenance and timing of the solar cycle. These global-scale flows must themselves be driven by the large-scale overturning convection thought to pervade the outer layers of the Sun. As these deep interior motions are inaccessible to local helioseismic analyses in virtually all respects, global-scale numerical models have become a widely-used tool for probing their dynamics. Such models must confront a number of challenges, however, if they are to yield an accurate description of the convection zone. These difficulties stem in part from the Sun's location in parameter space being far removed from anything accessible to modern supercomputers, but also from questions concerning how to best capture the salient, but generally unresolvable, physics of the tachocline and near-photospheric layers. In recent years, global-scale models have made good contact with observations in spite of these challenges, presumably owing to their ability to accurately reflect the large-scale balances established throughout the convection zone. Due to their success in reproducing many aspects of the solar differential rotation and the solar cycle in particular, we might be encouraged to ask what insights numerical models can provide into phenomena that are much more difficult to observe directly. Of particular interest is the possibility that deep modeling efforts might provide some glimpses into the nature of the Sun's deep meridional circulation. I will describe the essential elements common amongst many global-scale models of the solar convection zone, with some discussion of the strengths and weaknesses associated with the assumptions inherent in a typical model setup. I will then present a class of solar convection models that demonstrate the existence of two distinct regimes of meridional circulation. These two regimes depend predominantly on the the vigor of the convective driving and possess, in one instance, a single monolithic cell of circulation in each hemisphere, and in the other instance, a single cell at high latitudes with multiple cells at low latitudes. The transition between these two regimes in the context of solar simulations serves to motivate the need for careful treatment of heat transport in the upper and lower convection zone. After discussing the nature of this transition, I will examine how thermal perturbations associated with the inclusion of a tachocline might alter this phenomenon. Finally, I will compare various strategies employed by different authors to address the nature of heat transport in the upper boundary layer, focusing on the implications of each approach for the resulting velocity amplitudes and the convective heat flux established throughout the bulk of the convection zone. Convective amplitudes associated with those regimes that produce a nearly solar-like differential rotation are in generally good agreement with those based on theoretical predictions, but are somewhat higher than those inferred through helioseismic analysis.




On the Effects of the SDO Orbital Motion on the HMI Vector Magnetic Field Measurements

Author(s): Fleck, B. (1), Centeno, R. (2), Cheung, M. (3), Couvidat, S. (4), Hayashi, K. (4), Rezaei, R. (5), Steiner, O. (5), Straus, T. (6)

Institution(s): (1) ESA, (2) HAO, (3) LMSAL, (4), Stanford Univ., (5) KIS, (6) INAF/OAC

Abstract:

In a previous study we have investigated the magnetic field diagnostics potential of SDO/HMI. We have used the output of high-resolution 3D, time-dependent, radiative magneto-hydrodynamics simulations to calculate Stokes profiles for the Fe I 6173 Å line. From these we constructed Stokes filtergrams using a representative set of HMI filter response functions. The magnetic field vector (x,y) and line-of-sight Doppler velocities V(x,y) were determined from these filtergrams using a simplified version of the HMI magnetic field processing pipeline, and the reconstructed magnetic field (x,y) and line-of-sight velocity V(x,y) were compared to the actual magnetic field (x,y,z) and vertical velocity V0(x,y,z) in the simulations. The present investigation expands this analysis to include the effects of the significant orbital motions of SDO, which, given the limited wavelength range of the HMI filter profiles, affects the outer wing measurements and therefore might impact the magnetic field measurements. We find that the effects of the orbital movement of SDO are noticeable, in particular for the strongest fields (B > 3 kG) and the maximum wavelength shift of 5.5 km/s (3.5 km/s orbital movement + 2 km/s solar rotation). Saturation effects for strong fields (B > 3 kG) are already visible for wavelength shifts of 3.2 km/s (orbital movement, disk center). The measurements of inclination and vertical velocity are more robust. Compared to other factors of uncertainty in the inversion of HMI Stokes measurements the orbital movement is not a major concern or source of error.




Success of Solar Dynamics Observatory (SDO) Education & Public Outreach (E/PO) in Montana

Author(s): Freed, M.S.; Lowder, S.C.; McKenzie, D.E.

Institution(s): Montana State University

Abstract:

The Space Public Outreach Team (SPOT) program at Montana State University (MSU) is the main component of SDO E/PO efforts in Montana. SPOT brings energetic presentations of recent science & NASA missions to students in primary & secondary schools. Presenters are university undergraduates that visit a diverse group of K-12 students from both rural & urban areas of Montana. This program is extremely cost effective, a valuable service-learning experience for undergraduates at MSU and has repeatedly received praise from both teachers and students. A complementary effort for training schoolteachers entitled NASA Education Activity Training (NEAT) is also employed. NEAT illustrates to teachers inexpensive and highly effective methods for demonstrating difficult science concepts to their students. We will highlight the successes and lessons learned from SPOT & NEAT, so that other E/PO programs can use it as a template to further science literacy in our nation’s schools.




MHD simulations of flux emergence in an open field region: Jet formation and explosive events.

Author(s): Klaus Galsgaard^1 & Fernando Moreno-Insertis^2

Institution(s): 1 Niels Bohr Institute, Denmark, 2 Instituto de Astrofísica de Canarias, Spain

Abstract:

The launch of Hinode in 2006 was the start of a new interest in the jet phenomena in open field regions. Since then observations by the Hinode, SDO and Stereo satellites have shown that one characteristic jet type dominates, namely the so-called Eiffeltower or inverted-Y jet. The names arise from the jet's appearance in X-ray, where they are seen having two small "legs" below a long monolith structure representing the jet. This structure is interpreted as the result of the interaction between a newly emerged bipolar field into an unipolar magnetic field region. This picture naturally leads to magnetic reconnection between the two flux regions, where two the high velocity outflows from the diffusion region forms both the long jet structure and the underlying loop structure. To investigate this scenario in detail, we have preformed new MHD experiments of the emergence of a magnetic dipole region into an uniform open field region. The new experiments represent a significant extension of both the domain size, the duration of the experiment and the details of the analysis compared to the one presented in Moreno-Insertis et al. 2008. We find the initial jet phase to last on the order of 10 minutes, showing a smoothly evolving structure which, for a part of the evolution, closely resemblance the inverted-y structure. A number of characteristic structures arises around the footpoint region of the loop that may be compared with observations. Towards the end of this "steady state" inverted-y jet phase, the amount of flux in the emerged bipolar region is being exhausted by the reconnection process and the dynamical evolution enters a new phase. In this phase we find five explosive eruption from different parts of the remaining structure. These eruptions arises from only three main areas of the emerged flux region, implying that the same physical region can host repeated instabilities in the magnetic field.




Automated Detection, Characterization and Tracking of sunspots

Author(s): Suruchi Goel, Shibu K. Mathew

Institution(s): Udaipur Solar Observatory, India

Abstract:

Sunspot identification and characterization including location, area, lifetime, brightness, and so forth are required for a quantitative study of the solar cycle. Sunspot studies are also important for the modeling of the total solar irradiance during the solar cycle. We have developed a procedure for automatic detection and characterization of sunspots from full-disk continuum intensity images applicable for high resolution images from SDO/HMI. Our procedure is based on active contour method using level set formulation. The basic idea of level-set formulation for binary image segmentation is to define a 2-D level set function such that it has opposite signs for two regions and the boundary is defined as 'zero' of level-set function. We implemented the SBGFRLS (Selective Binary and Gaussian Filtering Regularized Level Set) method for sunspot detection. It utilizes both the edge information as well as the region statistics of sunspots. This method is computationally fast and simple to implement. The algorithm is designed to run in two levels, once for umbra and then for penumbra detection with different choices of detection parameters. The proposed procedure can give all parameters of sunspots like, location; center of gravity; area, mean (/min/max) intensity of umbra/penumbra. We applied this procedure and generated the sunspots catalog with the above listed parameters from the SOHO/MDI images. We have also developed an automated procedure to extract magnetic field values from corresponding magnetograms (near in time to intensity images) for detected sunspots regions. Hence, magnetic field values are also available for the sunspots catalog. Along with the characterization of detected sunspots we have also generated the tracking report of all detected sunspots in a fully unsupervised manner. The characterization and as well as tracking report of sunspots enable us to study the evolution of sunspots parameters with the solar cycle.




Extremely Impulsive Eruption associated with an X-class Flare on 2012 October 23

Author(s): N. Gopalswamy, S. Yashiro, S. Akiyama

Institution(s): NASA Goddard Space Flight Center

Abstract:

Typically about 10% X-class solar flares are confined, i.e., they are not association with mass ejection or type II bursts in the metric and longer wavelengths. Failed eruptions are known to occur occasionally, indicating the weakness of the propelling force compared to the overlying restraining forces. Here we report an event on 2012 October 23 that is closer to an eruptive event: it was associated with a metric type II burst, EUV disturbance (SDO, STEREO) and an extremely brief CME in the STEREO coronagraphic field of view. This paper presents an analysis of the event showing that the EUV disturbance is close to a blast wave, but not quite. Model fitting indicates that the speed falls faster than that of a blast wave indicating a quick shutoff of the propelling force. We also compare this event with another eruptive event on 2012 January 27 that had a similar flare magnitude, but was accompanied by a huge CME with all the usual interplanetary disturbances.




GAIA-DEM : The Gaussian AIA DEm Maps database

Author(s): C. Guennou, F. Auchère, E. Soubrié and K. Bocchialini

Institution(s): Institut d'Astrophysique Spatiale/CNRS

Abstract:

Providing the amount of emitting material as a function of the temperature along the line-of-sight, the Differential Emisssion Measure (DEM) analysis is a widespread diagnostic tool, used for most types of coronal structures. With six available coronal bands, the AIA instrument on board the SDO satellite provides new possibilities to more reliably estimate the DEM than previous UV imagers, and over a large FOV. The purpose of this database is to provide synoptic Gaussian DEM inversions of the AIA data. Using our recent results (Guennou et al. 2012a and 2012b), these maps can be then interpreted, taking advantage of our new tools developed to facilitate the DEM interpretation. The GAIA database provides the best Gaussian DEM fit matching the observations. A Gaussian form is a good first order approximation to determine the main thermal characteristics of the coronal plasma. With generally four inversions per day, at a 6 hours cadence, this database enables the user to quickly examine the global evolution of the thermal structure of the solar corona. DEM maps are available at http://medoc-dem.ias.u-psud.fr/.




Can the Differential Emission Measure diagnostic be used to constrain the timescale of energy deposition in the corona?

Author(s): C. Guennou, F. Auchère, J. A. Klimchuk, K. Bocchialini and S. Parenti

Institution(s): Institut d'Astrophysique Spatiale/CNRS

Abstract:

Differential emission measure (DEM) analysis is a widespread tool used to diagnose the thermal properties of coronal plasmas. The slope of the DEM distribution coolward of the coronal peak (near 3-4MK in active regions) can be used to diagnose the timescale for the energy deposition repeating on a given magnetic strand. Recent AR studies suggest that some active region cores are consistent with low frequency heating mechanisms, where the plasma cools completely before being reheated, while other show consistency with high frequency energy deposition, where rapid reheating causes the temperature to fluctuate about a particular value. Distinguishing between these possibilities is important for identifying the physical mechanism of the heating. It is therefore crucial to understand the uncertainties in measurements of observed DEM slopes. In this work, based on a probabilistic approach and Monte Carlo simulations, we carefully assess the errors in the slopes determined from EIS data. We consider both the random errors due to photon counting statistics, and the systematic errors associated with uncertainties in atomic physics and instrument calibration. The technique developed provides all the solutions consistent with the data and their associated probabilities. We demonstrate how the quality and the accuracy of the inversion are affected by the presence of noises and systematic errors, and we characterise the quality of the DEM inversion and its statistical properties. From these results, estimation of the uncertainties in the reconstructed slopes can be derived, thereby allowing a proper interpretation of the degree of agreement between observations and heating model predictions.





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Last Updated on Tuesday, 29 March 2011 09:36