sdo7.lws-sdo-workshops.org

  • Increase font size
  • Default font size
  • Decrease font size
Home Abstracts Submitted Abstracts

Submitted Abstracts

There are 146 abstracts


Coronal structure and dynamics above an active region - MHD model versus observation

Author(s): Bourdin, Philippe-A. (1), Bingert, Sven (1), Peter, Hardi (1)

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

Abstract:

We present a one-to-one comparison between an observed active region and a 3D MHD model including spectral synthesis. We set up the 3D MHD model from the photosphere to the corona and use the actually observed photospheric magnetograms and horizontal motions as a lower boundary condition to drive the 3D coronal model. Following Parker's model for field-line braiding this induces currents that are dissipated and heat the corona. From the 3D MHD model we synthesize emission spectra in EUV and X-rays that can be compared directly to the Hinode/EIS and XRT observation of the active region we model. We find that the hot coronal loops that form in the model occur at just the same places as they are found in the actual observations. Moreover, their spatial structure and the flows along the loops as seen in the synthesized intensity and Doppler maps compare well to the actual observations. By this we present the first coronal model driven by photospheric observations that provides a one-to-one match to the coronal structure and dynamics observed for that same active region. This shows that the distribution of the energy input in time and space through the field-line braiding is close to the real solar coronal energy deposition.




X-ray and EUV Observations of GOES C8 Solar Flare Events

Author(s): Bowen, Trevor A. (1), Testa, Paola. (2), Reeves, Katharine, K. (3)

Institution(s): Harvard Smithsonian CfA

Abstract:

We present an analysis of soft X-rays (SXR) and extreme-ultraviolet (EUV) imaging and spectral observations of solar flares with an approximate C8 GOES class. Our constraint on peak GOES SXR flux allows for the investigation of correlations between various flare parameters. We show that the the duration of the decay phase is proportional to the duration of its rise phase. Additionally, we show significant correlations between the radiation emitted in the rise and decay phases of a flare: the total radiated energy of a given flare is proportional to the energy radiated during the rise phase alone. This partitioning of radiated energy between the rise and decay phases is observed in both soft X-ray (SXR) extreme ultraviolet (EUV) wavelengths. Though observations from the EUV Variability Experiment (EVE) show significant variation in the behavior of individual EUV spectral lines during different C8 events, we show that the broadband EUV emission is well constrained. Furthermore, using GOES and AIA data, we determine several thermal parameters of these events: temperature, volume, density, and emission measure. Analysis of these parameters demonstrate that the longer duration solar flares are cooler events with larger volumes capable of emitting vast amounts of radiation. The shortest C8 flares are typically the hottest events, smaller in physical size, and have lower associated total energies. These relationships are directly comparable with several sample scaling laws and flare loop models.




The Helioseismic Search for Emerging Flux

Author(s): D.C. Braun

Institution(s): NorthWest Research Associates

Abstract:

Arguably considered the holy grail of local helioseismology is the detection of emerging flux before its appearance as a sunspot or magnetic region on the photosphere. After almost two decades of searching, this goal remains elusive and, at best, controversial. Helioseismic exploration is increasingly assisted by numerical simulations of rising flux which offer predictions of the magnitude and type of signatures, and also by computational wave propagation models which can validate and help improve the methods. We discuss some of these developments as well as results of a recent survey, carried out at NWRA, of approximately one hundred emerging active regions observed with the GONG network. A new survey, carried out in collaboration with colleagues at the Max Planck Institute for Solar System Research and made using the observations obtained by the HMI instrument on SDO is under way. This talk reviews work at NWRA which has been funded through the NASA Living with a Star program and currently though the NASA Solar and Heliospheric SR&T program (contract NNH12CF23C) and Heliophysics GI program (contract NNH12CF68C).




EUV Emission from Sungrazing Comets

Author(s): Paul Bryans, W Dean Pesnell

Institution(s): ADNET Systems, NASA GSFC

Abstract:

The EUV emission resulting from comets' passage through the solar atmosphere has opened many exciting avenues of study. The observations show the sublimated cometary material to interact with ambient magnetic field and highlight magnetic features that are not normally visible with EUV telescopes. The first step, however, is to explain why the comet produces the EUV emission. In this talk, I will outline a model that describes the interaction of the cometary atmosphere with the quiescent solar background and results in such emission. In particular, the model accurately predicts the temporal and wavelength response of the emission detected by SDO/AIA. After describing the emission process, I will go on to discuss what we can learn about the corona from these observations.




Automated detection, characterization, and tracking of filaments from SDO data

Author(s): Buchlin, E., Mercier, C., Vial, J.-C.

Institution(s): IAS, CNRS / Univ. Paris-Sud, Orsay, France

Abstract:

Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which can be associated to coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we are developing at IAS for the automated detection and tracking of filaments. Using data either from local files or from DRMS, detections are based on analysis of AIA 30.4 nm He II images and on magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as their rotate with the Sun, filament characteristics are computed. We discuss the algorithms and performances of the code, and we compare its results with the filaments detected in Halpha and already present in the HEK. We finally discuss the possibility of using this code for detecting eruptions in real time.




Progress on Reconstructing the Solar Coronal Magnetic Field above Active region at different scales

Author(s): Canou A. (1) Amari T. (2)

Institution(s): (1) Institut d'Astrophysique Spatiale, Universite Paris Sud, France (2) CNRS, Centre de Physique Theorique de l'Ecole Polytechnique, France

Abstract:

he low solar corona is dominated by the magnetic field which is created in the Sun's interior by a dynamo process and which then emerges into the atmosphere. This magnetic field plays an important role in most structures and phenomena observed at various wavelengths such as prominences, small and large scale eruptive events, and continuous heating of the plasma. It is therefore important to understand its three-dimensional properties in order to elaborate efficient theoretical models. Unfortunately, the magnetic field is difficult to measure locally in the hot and tenuous corona. But this can be done at the level of the cooler and denser photosphere, and several instruments with high resolution vector magnetographs are currently available (e.g. THEMIS/MTR, SOLIS/VSM, HINODE/SOT/SP or SDO/HMI) or will be available on future programmed missions (e.g. Solar Orbiter, ATST and EST). This has lead solar physicists to develop an approach which consists in reconstructing the coronal magnetic field from boundary data given on the photosphere.

We will present our recent progress and results to solve this problem at the active region scale or the larger one such as the full disk or synoptic one, for which the large amount of data as well as their sparsity on the solar disk, require to develop particular strategies. We will also show how this can be helpful to characterize the many aspects of active regions during their static or pre-eruptive evolution phases.




A New Observation of the Quiet Sun Soft X-ray (0.5-5 keV) Spectrum

Author(s): Caspi, Amir (1); Woods, Thomas N. (1); Stone, Jordan (2)

Institution(s): (1) Laboratory for Atmospheric and Space Physics, Univ. of Colorado, Boulder; (2) Dept. of Physics, Univ. of Arkansas, Fayetteville

Abstract:

The solar corona is the brightest source of X-rays in the solar system, and the X-ray emission is highly variable with solar activity. While this is particularly true during solar flares, when emission can be enhanced by many orders of magnitude up to gamma-ray energies, even the so-called "quiet Sun" is bright in soft X-rays (SXRs), as the ~1-2 MK ambient plasma of the corona emits significant thermal bremsstrahlung up to ~5 keV. However, the actual solar SXR (0.5-5 keV) spectrum is not well known, particularly during quiet periods, as, with few exceptions, this energy range has not been systematically studied in many years. Previous observations include ultra-high-resolution but very narrow-band spectra from crystral spectrometers (e.g. Yohkoh/BCS), or integrated broadband irradiances from photometers (e.g. GOES/XRS, TIMED/XPS, etc.) that lack detailed spectral information. In recent years, broadband measurements with fair energy resolution (~0.5-0.7 keV FWHM) were made by SphinX on CORONAS-Photon and XRS on MESSENGER, although they did not extend below ~1 keV. We present observations of the quiet Sun SXR emission obtained using a new SXR spectrometer flown on the third SDO/EVE underflight calibration rocket (NASA 36.286). The commercial off-the-shelf Amptek X123 silicon drift detector, with an 8-micron Be window and custom aperture, measured the solar SXR emission from ~0.5 to >10 keV with ~0.15 keV FWHM resolution (though, due to hardware limitations, with only ~0.12 keV binning) and 2-sec cadence over ~5 minutes on 23 June 2012. Despite the rising solar cycle, activity on 23 June 2012 was abnormally low, with no visible active regions and GOES XRS emission near 2010 levels; we measured no solar counts above ~4 keV during the observation period. We compare our X123 measurements with spectra and broadband irradiances from other instruments, including the SphinX observations during the deep solar minimum of 2009, and with upper limits of >3 keV quiet Sun emission determined from RHESSI. We discuss the possible implications for X-ray-producing physical processes in the quiescent, active-region-free corona. The X123 spectrum could potentially serve as a reference for ~0.5-4 keV quiet Sun emission, to help improve solar spectral models such as CHIANTI and XPS Level 4. Our comparisons indicate that XPS Level 4 likely requires significant revisions in the SXR range, which may have downstream implications for the Earth ionosphere models that have used XPS Level 4 as their solar input.




Exploring Thermal and Non-Thermal Flare Emission with EVE and RHESSI

Author(s): Caspi, Amir (1); McTiernan, James M. (2); Warren, Harry P. (3)

Institution(s): (1) Laboratory for Atmospheric and Space Physics, Univ. of Colorado, Boulder; (2) Space Sciences Laboratory, Univ. of Califoria, Berkeley; (3) Naval Research Laboratory

Abstract:

Solar flares accelerate electrons up to hundreds of MeV and heat plasma to tens of MK, but the physical processes behind these phenomena remain poorly understood. In intense (GOES M- and X-class) flares, in addition to the common 10-25 MK plasma thought to be the result of chromospheric evaporation, even hotter plasma (up to 50 MK) may be directly heated in the corona. While observations of hard X-ray bremmstrahlung directly probe the non-thermal electron population, for large flares, the spectra below 20-30 keV are typically dominated by this strong thermal emission. The low-energy extent of the non-thermal spectrum can be only loosely quantified, resulting in significant implications for calculating flare energy budgets and for constraining possible acceleration mechanisms. A precise characterization of the thermal electron population is imperative, and this requires an equally precise characterization of the thermal emission. Extreme ultraviolet observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO), combined with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), currently offer the most comprehensive view of the flare temperature distribution. EVE observes EUV emission lines with peak formation temperatures of 2-20 MK, while RHESSI observes the X-ray bremsstrahlung of hot, 10-50 MK plasma; combined, the two instruments cover the full range of flare plasma temperatures. Previously, we have calculated differential emission measures (DEMs) using EVE and RHESSI independently, for a small number of flares, and showed that they tend to agree well in the ~10-20 MK region, where their responses overlap, but that, as expected, they disagree significantly outside this range, where the DEM is poorly constrained by one instrument or the other, exemplifying the need for a unified solution. Recently, we have developed a technique for determining flare DEMs using both EVE and RHESSI simultaneously, with each instrument constraining the other. We apply this technique to a number of synthetic test cases to show that it robustly recovers the input test DEMs, and then show results of analyzing real data from two intense, X-class flares. Through this technique, for the first time, we can determine self-consistent DEMs over the complete flare temperature range of ~3-50 MK, and this precise determination of the thermal emission will later enable detailed studies of the non-thermal electron populations, as well.




Doppler-shifted flare emissions observed by SDO/EVE

Author(s): Phillip Chamberlin

Institution(s): NASA/GSFC

Abstract:

The EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO) has been obtaining unprecedented observations of solar variation on times scales of seconds during flares and over the rising phase of Solar Cycle 24 since its start of normal operations in May 2010. Unexpectedly, as first pointed out in Hudson et. al., Ap. J. (2011), even with EVE’s spectral resolution of 0.1 nm and ‘irradiance’ measurements, EVE has the ability to very accurately determine Doppler shifts in all emissions during solar flares and coronal mass ejections (CMEs). The technique for deriving these absolute velocities is not straightforward, as the optical and instrumental effects must first be eliminated in order to separate the absolute plasma velocities from the instrument effects. This talk will discuss these efforts to eliminate the instrumental component, as well as show some of the first results of absolute velocities of multiple emissions at a wide range of temperatures during solar flares.




FISM 2.0: Improved spectral range, resolution, and accuracy

Author(s): Phillip Chamberlin

Institution(s): NASA/GSFC

Abstract:

The Flare Irradiance Spectral Model (FISM) was first released in 2005 to provide accurate estimates of the solar VUV (0.1-190 nm) irradiance to the Space Weather community. This model was based on TIMED SEE as well as UARS and SORCE SOLSTICE measurements, and was the first model to include a 60 second temporal variation to estimate the variations due to solar flares. Along with flares, FISM also estimates the tradition solar cycle and solar rotational variations over months and decades back to 1947. This model has been highly successful in providing driving inputs to study the affect of solar irradiance variations on the Earth’s ionosphere and thermosphere, lunar dust charging, as well as the Martian ionosphere. The second version of FISM, FISM2, is currently being updated to be based on the more accurate SDO/EVE data, which will provide much more accurate estimations in the 0.1-105 nm range, as well as extending the ‘daily’ model variation up to 300 nm based on the SOLSTICE measurements. With the spectral resolution of SDO/EVE along with SOLSTICE and the TIMED and SORCE XPS ‘model’ products, the entire range from 0.1-300 nm will also be available at 0.1 nm, allowing FISM2 to be improved a similar 0.1nm spectral bins. FISM also will have a TSI component that will estimate the total radiated energy during flares based on the few TSI flares observed to date. Presented here will be initial results of the FISM2 modeling efforts, as well as some challenges that will need to be overcome in order for FISM2 to accurately model the solar variations on time scales of seconds to decades.





Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 129

Warning: Illegal string offset 'active' in /home/content/12/6998712/html/sdo7/templates/ja_purity/html/pagination.php on line 135

Last Updated on Tuesday, 29 March 2011 09:36