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Submitted Abstracts

There are 146 abstracts


Dynamic anti-parallel flows observed within an active region filament with SDO/AIA and Hi-C

Author(s): Caroline E. Alexander, Stephane Regnier, Robert W. Walsh and the Hi-C science team

Institution(s): University of Central Lancashire

Abstract:

Plasma flows within prominences/filaments have been observed for many years and hold valuable clues concerning the mass and energy balance within these structures. Previous observations of these flows primarily come from H-alpha and cool EUV lines (e.g., 304 A) where estimations of the size of the cool prominence threads has been limited by the resolution of the available instrumentation. Evidence of curious `counter-steaming' flows have previously been inferred from observations but now, for the first time, these flows have been directly imaged within the corona. In this work we present observations of an active region filament observed with SDO/AIA and Hi-C that exhibits dynamic anti-parallel flows along side-by-side threads within the structure. The ultra-high spatial resolution of Hi-C allows the individual flow velocities to be measured and complementary data from AIA provides context and allows temperature analysis to take place. Measuring the flow speeds, the spatial scale of the threads, and their emission in different temperature regimes allows us to comment on the physical mechanisms taking place and can help us to understand how these flows relate to the stability of the filament as a whole.




MEDIA : MEDoc Interface for AIA

Author(s): P. Alingery (2), E. Soubrié(1), F. Auchère(1), K. Bocchialini (1), JP. Boignard (5), E. Buchlin (1), J.C Malappert (3), S. Parenti (1, 4)

Institution(s): (1) Institut d'Astrophysique Spatiale, Bât 121 CNRS, Univ. Paris-Sud, 91405 Orsay Cedex, France (2) Exelis VIS Tour de l'Horloge, 4 place Louis Armand, 75603 PARIS Cedex 12, France (3) CNES, 8 Avenue Édouard Belin  31400 Toulouse, France (4) ROB, av. Circulaire 3 1180 Bruxelles, Belgique (5) AKKA Technologies,27 Boulevard Victor Hugo, Bât Pythagore 2 , 31770 Colomiers, France

Abstract:

MEDOC, the space solar data center at Orsay (http://www.ias.u-psud.fr/medoc) is now providing a new web access to the AIA/SDO level 1 images. This interface has the advantage of being simple, intuitive, very stable and fast. The full resolution 4k x 4k AIA level 1 images archived at MEDOC are downloaded from upstream DRMS nodes with a 1 minute cadence at all wavelengths. The dataset will be kept online on a redundant archive for the whole SDO mission duration. The FITS files are accessible via an user friendly web interface (http://medoc-sdo.ias.u-psud.fr) that allows users to request data by selecting a date range, the desired wavelengths and a sampling rate (choosing a cadence from 1 minute to 1 day). For each file, users can preview the image (using the Helioviewer tool) or display the header information before downloading the FITS files (with or without Rice-compression). This web interface was built using Sitools2, a tool developed by CNES, the French space agency, and supports most browsers. For more advanced users, a Search/Get Python module is also available at http://sdo.ias.u-psud.fr/python. The users can use it to build more complex yet more powerful queries. We encourage everyone in Europe and beyond to use these new services!




Flares, waves, and energy

Author(s): A. Andic, R.T.J. McAteer, B. McNamara

Institution(s): New Mexico State University

Abstract:

Solar energy storage and release events are interconnected. This research addresses one aspect of the interconnection of those energetic solar events. Addressed aspect emerged in recent research that showed a movement of a flux tubes generates oscillations. Analysis was performed using six C class and one M class flares during Dec. 25, 2011. Using AIA and HMI data, we investigated the connection between flare induced disturbance and changes in the flux of photospheric oscillations. Results showed significant increase of oscillatory flux following the flare itself. This increase was detected outside of flare location. Results show a need for deeper statistical analysis of the oscillatory response at flare induced disturbance. This kind of analysis might reveal energy distributions when this aspect of interconnection is in question.




Application of Bayesian Inference and Model Comparison Techniques to Solar Atmospheric Seismology

Author(s): Arregui, I. (1), Asensio Ramos, A. (1), Pascoe, D. J. (2), Diaz, A.J. (1)

Institution(s): (1) Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38205 La Laguna, Tenerife, Spain, (2) School of Mathematics and Statistics, University of St. Andrews, St. Andrews, KY16 9SS, UK

Abstract:

Wave activity is ubiquitous in the solar atmosphere. The detection and analysis of waves and oscillations is important for our understanding of solar atmospheric physics. Seismology deals with the determination of difficult to measure physical parameters by a comparison between observed and theoretical wave properties. We present recent results form the application of Bayesian inference and model comparison techniques to seismology. In the first example, quickly damped transverse coronal loop oscillation data are inverted to obtain estimates for the density contrast, the transverse inhomogeneity length scale, and the Alfvén speed in the oscillating loops. In the second example, we use the detection of multiple mode harmonic kink oscillations in coronal loops to obtain information on coronal density stratification and magnetic field expansion. The inference is based on the measurement of period ratios and their deviation due to the hypotheses of either coronal density stratification or magnetic field expansion of the wave guide. The two models are compared using a Bayesian model comparison scheme to assess how plausible each one is, given our current state of knowledge. In the last example, the spatial damping of propagating waves and the characteristic damping length scales are used to obtain estimates for the plasma density variation across the oscillating structures. This method could be applied to extended regions in the corona for obtaining information about the cross-field density structuring of the medium where these waves propagate.




Hydrodynamic Scaling Laws and Solar Flare Statistics from AIA

Author(s): Markus J.Aschwanden

Institution(s): Solar and Astrophysics Laboratory, Lockheed-Martin ATC

Abstract:

We present a statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO in all 7 coronal wavelengths (94, 131, 171, 193, 211, 304, 335 A) and investigate the wavelength-dependence of scaling laws and statistical distributions. Except for the 171 and 193 A wavelengths, which are affected by EUV dimming caused by coronal mass ejections (CMEs), we find near-identical size distributions of geometric (flare size L, area A, volume V, fractal dimension D2), temporal (flare duration D), and spatio-temporal parameters (diffusion coefficient, spreading exponent, and maximum expansion velocity) in different wavelengths, which are consistent with the universal predictions of the fractal-diffusive avalanche model of a slowly-driven self-organized criticality (FD-SOC) system, i.e., N(L) ~ L^(-3), N(A) ~ A^(-2), N(V) ~ V^(-5/3), N(D) ~ D^(-2), D2=3/2, for a Euclidean dimension d=3. We perfom also a differential emission measure (DEM) analysis in all flares to determine the flare peak emission measure EM_p, peak temperature T_p, electron density n_p, and thermal energy E_th. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T_p^2 ~ n_p L and H ~ T^(7/2) L^(-2) during the flare peak time t_p of maximum density n_p, when energy balance between the heating rate H and the conductive and radiative loss rates is achieved for a short instant, and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts powerlaw distributions for all physical parameters, which we demonstrate with numerical Monte-Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find N(H)~H^(-1.8), which is consistent with the magnetic flux distribution N(Phi)~Phi^(-1.85) observed by Parnell et al. (2009) and the heating flux scaling law F_H ~ H L ~ B/L of Schrijver et al.~(2004). The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed powerlaw distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare datasets, instruments, and detection algorithms.




FESTIVAL 5.0 - AIA and more !

Author(s): F. Auchère, E. Soubrié

Institution(s): Institut d'Astrophysique Spatiale

Abstract:

FESTIVAL is an open source IDL-based browser designed for simultaneous and dynamic compositing of multi-instrument imaging data. FESTIVAL is very flexible and works with FITS files, which allows advanced processing. It is distributed as a Solar Software package. Initially developed for SECCHI, FESTIVAL now supports most space imaging telescopes, the latest additions being AIA /SDO and SWAP / Proba2. Its native zoom/pan mouse navigation mode makes it well suited to the large format of AIA images. In additio, version 5.0 brings a variety of new features making FESTIVAL even more powerful: enhanced search options, base and N-x running differences, solar rotation compensation, remote access to the MEDOC data archive, etc.




Progress in Near-Surface Flow Determinations: Minimizing Systematics

Author(s): Charles S. Baldner (1), Sarbani Basu (2), Richard S. Bogart (1), Jesper Schou (1)

Institution(s): (1) Stanford University; (2) Yale University

Abstract:

One of the key achievements in helioseismology has been the measurement of sub-surface dynamics. Measurements of both differential rotation and meridional circulation exist from multiple instruments for more than one and a half solar cycles. The precision of flow determinations from various helioseismic techniques has been found to be greater than their accuracy. Flows have been found to depend on the disk position of the measurements, and some inconsistencies between measurements from different instruments have also been found. In this work, we report progress in understanding and correcting for these systematic errors, and present the latest ring diagram determinations of shallow subsurface flows with HMI/SDO data.




"Nanoflare heating in the solar corona -- Parker was right"

Author(s): Bingert, Sven and Peter, Hardi

Institution(s): Max Planck Institute for Solar System Research

Abstract:

We investigate the energy distribution of the heat input in a 3D MHD model of a solar active region. We find that the energy is deposited mostly in quantities around 10^17 J, which is very close to the nanoflare energy derived by Parker. For our study we employ a 3D MHD model of the solar corona to investigate the spatial and temporal evolution of the heat input based on Ohmic dissipation. The model is driven by horizontal motions shuffling around the magnetic field in the photosphere. This induces currents and their dissipation heats the coronal plasma, very similar to the field-line braiding mechanism proposed by Parker. We find a power-law behavior of the energy input due to Ohmic dissipation indicating that the system is scale invariant. However considering the coronal part of the computational box alone, we find a knee in the energy distribution and a preferred energy for the heat deposition. This energy coincides with the nanoflare energy proposed by Parker. While Parker considered a quite idealized setup, we model a realistic corona, accounting for gravity, heat conduction and radiative losses, and account for the full interaction of plasma and magnetic field. Our results are remarkable, because even in the complex and dynamic setup we find a result that basically supports Parker's original proposal. By synthesizing coronal emission from our model we can go one step further, though, and show that the resulting model corona really resembles the observed corona in structure and dynamics.




Application of Solar EUV-Spectra to the Study of Photoionization of Interstellar Neutrals in the Heliosphere (invited)

Author(s): Peter Bochsler 1), Maciej Bzowski2), Harald Kucharek1), Eberhard Möbius1), Justyna M. Sokół2)

Institution(s): 1) Space Science Center and Department of Physics, University of New Hampshire, Durham NH 03824, USA 2) Space Research Centre, Polish Academy of Sciences, 00-716 Warsaw, Poland

Abstract:

For investigations of neutral interstellar gas penetrating into the inner solar system, as well for the study of so-called pickup ions, which are produced from inflowing interstellar matter in the heliosphere, it is crucial to determine the photoionization rates of various elements by solar EUV-radiation. We routinely use the EUV-spectra from TIMED/SEE to compute the photoionization rates of H, He, O, and Ne. Since observations of interstellar neutrals and pickup ions in the heliosphere are also available for periods long before solar EUV-spectra became routinely available, it is also important to find good proxies for photoionization rates. For this purpose we have developed a linear model involving different proxies (F10.7, Mg IIc/w, Lyman alpha and SOHO/CELIAS/SEM). For the past decade, for which all proxies and the TIMED spectra are available, we typically find average deviations of the model results from the TIMED/SEE-derived values of the order of a few percent. However, this model does not include systematic errors, e.g., from calibration uncertainties. We also investigate the impact of temporal and spatial inhomogeneities on photoionization rates and on the flow of interstellar gas through the heliosphere and on the production of pickup ions.




Behavior of the vertical current during the X2 flare of 2011 February 15 observed by SDO/HMI, compared to a line-tied zero-beta resistive MHD simulation

Author(s): Veronique Bommier and Guillaume Aulanier

Institution(s): LESIA, Observatoire de Paris

Abstract:

The level-1 data of SDO/HMI have been inverted with the UNNOFIT inversion code (Bommier et al., 2007, A&A, 464, 323), which differs from VFISV about the magnetic filling factor modeling. More realistic field inclinations are obtained outside the active region. The spatial resolution seems to be also better. UNNOFIT is enabled for the taking into account of gradients of radial velocity, responsible for asymmetry of the Stokes profiles (Molodij et al., 2011, A&A, 531, A139). The ambiguity has been solved with the ME0 code of Metcalf, Leka, Barnes & Crouch. We present the movie of 4 hours of observation, the flare occurring at middle. Two current ribbons of opposite polarity are visible along the magnetic neutral line, in the vertical density current map. The negative one strengthens and radially expands from the flare center at the eruption moment. A similar current ribbon pair is visible in a 3D line-tied zero-beta resistive MHD flare simulation with the OHM code (Aulanier et al. , 2012, A&A, 543, A110). The two ribbons part from the flare center during the flare, similarly to what observed on 2011 February 15 at 02:00 with SDO/HMI.





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Last Updated on Tuesday, 29 March 2011 09:36