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There are 123 abstracts


Forward modeling of coronal polarization

Author(s): Gibson, Sarah E. (1), Casini, Roberto (1), Dove, James (2), Tomczyk Steve (1)

Institution(s): (1) HAO/NCAR, (2) Metro. State College, Denver

Abstract:

Coronal polarization measurements from the Coronal Multichannel Polarimeter (CoMP) instrument provide quantitative information about the magnetic field above the solar limb. Inversion of these measurements is difficult due to the optically thin nature of the plasma. Our forward technique can be used with both local and global models to obtain quantitative comparisons between models and observations of the coronal magnetic field. We have used the forward technique to study the magnetic nature of quiescent coronal cavities. We present results from the cavity analysis as well as ways to interpret the coronal polarization data without calculating inversions.




New insight on the coupling of the solar atmosphere from imaging spectroscopy

Author(s): K. Reardon, G. Cauzzi

Institution(s): INAF/Arcetri Astrophysical Observatory

Abstract:

We present spectrally resolved, high-resolution observations of chromospheric diagnostics obtained with IBIS covering a full active region. In particular, the data includes the first high-resolution observations of the He I D3 line (587.6 nm), a subordinate of the more famous HeI 1083.0 nm line, showing loops and other structures on the solar disk at the 150 km diffraction limit. The large FOV of our data allows a meaningfully comparison with the SDO full disk observations to investigate the coupling between different portions of the solar atmosphere and the topology of the chromospheric magnetic field. The relationship between the chromospheric signatures and the SDO 304 Å and 171 Å emission provides intriguing hints to the existence of low-lying loops at TR temperatures effectively disconnected from the corona.




Explaining observed red and blue-shifts using multi-stranded coronal loops

Author(s): S. Regnier, R. W. Walsh, J. Pearson

Institution(s): Jeremiah Horrocks Institute, University of Cental Lancashire

Abstract:

Magnetic plasma loops have been termed the building blocks of the solar atmosphere. However, it must be recognised that if the range of loop structures we can observe do consist of many ''sub-resolution'' elements, then current one-dimensional hydrodynamic models are really only applicable to an individual plasma element or strand. Thus a loop should be viewed is an amalgamation of these strands. They could operate in thermal isolation from one another with a wide range of temperatures occurring across the structural elements. This scenario could occur when the energy release mechanism consists of localised, discrete bursts of energy that are due to small scale reconnection sites within the coronal magnetic field- the nanoflare coronal heating mechanism. These energy bursts occur in a time-dependent manner, distributed along the loop/strand length, giving a heating function that depends on space and time. An important observational discovery with the Hinode/EIS spectrometer is the existence of red and blue-shifts in coronal loops depending on the location of the footpoints (inner or outer parts of the active region), and the temperature of the emission line in which the Doppler shifts are measured. Based on the multi-stranded model developed by Sarkar and Walsh (2008, ApJ, 683, 516), we show that red and blue-shifts exist in different simulated Hinode/EIS passbands: cooler lines (OV-SiVII) being dominated by red-shifts, whilst hotter lines (FeXV-CaXVII) are a combination of both. The distribution of blue-shifts depends on the energy input and not so much on the heating location. Characteristic Doppler shifts generated fit well with observed values. We also simulate the Hinode/EIS rasters to closely compare our simulation with the observations. Even if not statistically significant, loops can have footpoints with opposite Doppler shifts.




Internal vs external reconnection observed by SDO in a newly emerged active region

Author(s): S. Regnier

Institution(s): Jeremiah Horrocks Institute, University of Central Lancashire

Abstract:

The emergence of magnetic fields through the photosphere and the interaction with the coronal environment is an important process allowing the magnetic energy and magnetic helicity to be transported from the convection zone to the solar wind. SDO instruments such as AIA and HMI allow us to study in details the first steps of the emerging process and the thermal structure of the new-born active region. For this study, we combine the SDO/AIA observations at high-cadence in different temperature ranges (from photosphere to the hot corona) with potential field extrapolation of SDO/HMI line-of-sight magnetic field. In particular, we study (i) the interaction of the emerging flux with the coronal environment leading to magnetic reconnection and magnetic pressure enhancement owed to the complex topology of the magnetic field, (ii) the evidence of internal magnetic reconnection within the emerging flux tube whilst crossing the photosphere and expanding into the corona. The later is evidenced by the observation of Ellerman bombs at the chromospheric level and the structuring of the photospheric magnetic field. We thus provide a timeline of the events in the eight hours after the beginning of flux emergence.




High-resolution observations of type II spicules

Author(s): Rouppe van der Voort, Luc

Institution(s): Institute of Theoretical Astrophysics, University of Oslo, Norway

Abstract:

Type II spicules are a class of spicules that is connected with mass-loading and heating of the solar corona. Type II spicules are characterized by short lifetimes and high apparent velocities. Combined with their narrow spatial widths, type II spicules are challenging to observe. We use the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope on La Palma to observe type II spicules at the limb and their counterparts on the solar disk, the so-called "Rapid Blue-shifted Excursions" (RBEs). The combination of adaptive optics and image post-processing allows CRISP to attain high resolution simultaneously in the spatial, temporal and spectral domains. Here we present results from the analysis of several high-quality data sets which allow to constrain the physical properties of type II spicules.




Graphical introduction to chromospheric line formation

Author(s): Rob Rutten

Institution(s): Lingezicht Astrophysics and ITA, Oslo

Abstract:

The basics of chromospheric line formation theory were laid out in the 1960s and 1970s by e.g., Thomas, Avrett, Hummer, Jefferies, Mihalas, Shine, Milkey. Since then there has been a long silence, without much progress in understanding the chromosphere or its diagnostics. At present, the situation changes thanks to better ground-based observing, space-based monitoring, and increasingly realistic numerical simulations. There is a now a strong need to revamp classical one-dimensional static modeling as basis for chromospheric line interpretation into 3D dynamic understanding of the major diagnostics, including IRIS's Mg II h&k. In this introduction I aim to explain the old wisdom in tutorial fashion, using cartoons and graphs as means towards an intuitive grasp of fads and fallacies of chromospheric line formation.




Observation, inversion and numerical simulation of single-lobed Stokes V profiles in the quiet sun.

Author(s): A. Sainz Dalda, J. Martínez-Sykora, L. Bellot Rubio, A. Title

Institution(s): (1) Stanford-Lockheed Institute for Space Research, (2) Lockheed-Martin Solar and Astrophysics Laboratory, (3) Instituto de Astrofísica de Andalucía, (3) Lockheed-Martin Solar and Astrophysics Laboratory

Abstract:

We have studied characteristics and statistics of strong asymmetric profiles in Stokes V, i.e., single-lobed profiles, in quiet sun using Hinode/SOT. These profiles require the existence of a velocity gradient along the line-of-sight, possibly associated with gradients of magnetic field strength, inclination and/or azimuth. For a better understanding, observations, inversions and numerical simulations are compared. We focus our analysis of the observations on the statistical properties of the single-lobed Stokes V profiles and the results provided by the inversions using SIRJUMP, which is an LTE inversion code that can reproduce sharp discontinuities or jump in the magnetic field and line-of-sight velocity of the atmosphere model. In the quiet sun, magnetic field is continuously appearing and disappearing at small scales due to the convective motions and the input of new flux from deeper layers. From radiative MHD 3D simulations, using Bifrost code, we note that most of these small scale processes have stratifications with gradients of magnetic field strength, inclination and velocities. As result, those stratifications showing jumps in the magnetic field configuration are associated with the existence of single-lobe Stokes V profiles in the solar photosphere, as we previously assumed for the inversions. We show that most of these profiles come from emerging and disappearance magnetic flux in small scales in the simulations. Finally, we emphasize importance of the comparison between the synthetic profiles from the simulations with the observed ones and the atmospheres that produce them. This comparison will ultimately improve the realism of the simulations and quantify the emerging and disappearance flux in the quiet sun.




The IRIS Education and Public Outreach Program, an Overview

Author(s): Deborah Scherrer

Institution(s): Stanford University

Abstract:

The original IRIS Education and Public Outreach program has been recrafted to better mesh with NASA's EPO guidelines and the skill sets of our team. We will present an overview of the new plan, which includes programs in higher education, K-12, informal education (science museums, etc.), and social media support. IRIS partners are putting together such programs as an Undergraduate Student Competition, a summer research experience for undergraduates, a NASA Quest challenge geared to middle school students, addition of spectroscopy into a Challenger Center module, the distribution of punch-out spectroscopes and accompanying curricula to classrooms, and a social medium program coordinated with, and based upon, the successful SDO social media model. Partnerships abound and enthusiasm is high for our new program -- come see what we have in mind! If you are an IRIS scientist, talk with us about how you can help.




Diagnosing the Prominence-Cavity Connection

Author(s): Donald Schmit, Sarah Gibson

Institution(s): University of Colorado; High Altitude Observatory

Abstract:

Prominences are regions of cool, dense plasma which are suspended above the solar limb within the much hotter and more rarefied solar corona. The coronal environment surrounding the prominence is often observed as an elliptical region of reduced density (compared to the ambient corona) known as a cavity. The fundamental problems in prominence physics are the magnetic support of condensed plasma and the mass-source of those condensations. We use the SDO/AIA dataset to probe the correlated dynamics in between the cool prominence and the coronal cavity. These dynamics are explained through the 1D modeling of the radiative instability. The magnetic field inferred from these dynamics is also compared to the 3D MHD models of prominence support. Through this joint approach, the dynamic nature of the prominence system is brought into sharp focus for the first time.




Type-II spicules: Heating and magnetic field properties from aligned CRISP/SST and SDO observations

Author(s): Scullion, E. (1), Rouppe van der Voort, L. (1), De la Cruz Rodriguez, J. (2)

Institution(s): (1) Institute of Theoretical Astrophysics, University of Oslo, Norway (2) Department of Physics and Astronomy, University of Uppsala, Sweden

Abstract:

Over the past decade there has been a resurgence in the study of small-scale chromospheric jets known, classically, as spicules. Recent observations have lead us to conclude that there are two distinct varieties of spicule, namely, slower type-I (i.e. mottles, dynamic fibrils, H-alpha spicules etc.) and faster type-II (RBEs: Rapid Blue-shift Excursions on-disk). Such events dominate the dynamics of the chromosphere. Joint SDO (Solar Dynamics Observatory) and Hinode observations have revealed that fast spicules are the source of hot plasma channelling into the corona. Here we report on the properties of this widespread heating with observations from the high resolution CRISP (CRisp Imaging SpectroPolarimeter) instrument at the SST (1-m Swedish Solar Telescope, La Palma) and co-aligned SDO data. Furthermore, we reveal new insight into the formation of type-II spicules through considering the distribution of RBEs with respect to the photospheric magnetic field (via CRISP).





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Last Updated on Tuesday, 24 January 2012 13:45