sdo7.lws-sdo-workshops.org

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

Submitted Abstracts

There are 146 abstracts


Time delays between radio and HXR observed during the 2011-02-15 X2.2 solar flare

Author(s): Natsuha Kuroda, Haimin Wang, and Dale Gary

Institution(s): New Jersey Institute of Technology

Abstract:

We report the second-scale delays observed between radio and HXR during the X2.2 solar flare on February 15, 2011. The delays between different energy channels from various instruments were previously reported by Dolla et al. in 2012; they reported that the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) channels in the 25-100 keV range lead all the other channels including the Nobeyama RadioPolarimeters at 9 and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). We looked at RHESSI channels in 25-250 keV and Nobeyama channels in 1-35 GHz and found that, in four data pairs that showed more than 80 % correlation, the same several RHESSI peaks lead Nobeyama peaks by few seconds. We discuss the possible physical meaning of this delay.




Probing vortical motions in the Sun with time-distance helioseismology

Author(s): Langfellner, Jan (1,2), Gizon, Laurent (2,1), Birch, Aaron (2), Schunker, Hannah (2)

Institution(s): (1) Institut für Astrophysik, Universität Göttingen, Germany, (2) Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany

Abstract:

Fluid vorticity describes fundamental aspects of the dynamics of the solar convection zone. For example, vortical flows play an important role in dynamo models and inform us about the dynamical effects of rotation on convection and active region flows. However, no specific helioseismology technique has so far been developed to infer vorticity in the solar interior. Here we propose to use a new geometrical scheme for time-distance helioseismology, which is particularly sensitive to vertical vorticity. It consists of measuring the difference in wave travel time (clockwise minus counterclockwise) around a circular array of points. We will demonstrate the capabilities of the technique using SDO/HMI observations and discuss future applications.




Living With a Star: The Van Allen Probes Mission and Space Weather

Author(s): Louis J. Lanzerotti

Institution(s): New Jersey Institute of Technology

Abstract:

Van Allen Probes, the second mission in NASA’s Living With a Star Program, is designed to answer major questions about Earth’s space environment, the Van Allen Radiation Belts. Specifically, the Probes mission will address (i) Which physical processes produce radiation belt enhancements? (ii) What are the dominant mechanisms for high-energy electron loss from the belts? (iii) What factors affect radiation belt dynamics? These questions are of more than scientific interest. Achieving understanding is also critically important for forecasting delirious effects on space technologies, for designing of space systems that can operate in harsh radiation environments, and for the secure and reliable operations of engineered space systems. Interest in this mission and its scientific and engineering objectives comes from both civilian and national security sectors. This talk will describe the Van Allen Probes mission, address solar drivers that can affect Earth’s radiation belt populations, and provide some personal views as to major issues that couple solar processes to the dynamics of Earth’s radiation belts. I will also provide a personal perspective on one or more “grand challenges” of solar predictions for space weather impacts at Earth, challenges whose solutions appear distant.




On the Modulation of the Solar Activity Cycles, and Hemispheric Asymmetry of Solar Magnetism during the Cycle 23/24 Minimum

Author(s): Leamon, Robert J. (1), McIntosh, Scott W. (2)

Institution(s): (1) Montana State Univ./NASA HQ, (2) NCAR High Altitude Observatory

Abstract:

We address the origin of the 11-year (quasi-)periodicity of the sunspot cycle by tying it to the significant temporal overlap of activity bands belonging to the 22-year magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints, and the prevalent magnetic scale on which they form, we are able to observationally demonstrate the entirety of the 22-year magnetic activity cycle. The phases of the sunspot cycle occur as landmarks in the interaction and evolution of the overlapping activity bands in each hemisphere. The unusual conditions of the recent Cycle 23/24 minimum can be directly attributed to the asymmetry (southern lag) between the two hemispheres of the sun. The work presented establishes significant observational constraints for models of the origins of solar magnetic activity and will, as a result, improve our understanding of the structure of the heliosphere and the modulation of our star's radiative and particulate output. We demonstrate how the Sun can descend into, and recover from, Grand Minima. Even if that is not where we're headed, we show why Cycle 25 is likely to be even weaker than Cycle 24.




Solar Irradiance from Days to Decades: Present, Past and Future

Author(s): Lean, Judith

Institution(s): Space Science Division, Naval Research Laboratory, Washington, DC 20375

Abstract:

The Sun’s photon output varies continuously at all wavelengths across the electromagnetic spectrum, on time scales from days to decades, and possibly longer. Reliable specification of solar irradiance is requisite for a range of geophysical applications, including space weather and space climatology, ozone and atmosphere variability, and climate change.

Continuous observations exist of total solar irradiance – the integrated emission over all wavelengths - for 33 years, but only in the last decade have space-based radiometers measured the irradiance spectrum from the shortest EUV wavelengths (TIMED/SEE and SDO/EVE) to visible and near infrared wavelengths (SORCE/SIM). Models have been developed from the observations to estimate irradiance variations during past and future epochs. The models, which estimate the irradiance changes arising from sunspots and faculae, are well constrained by observations on time scales of days to months but in some spectral regimes can differ significantly from observations over the solar cycle, possibly because of instrumental uncertainties. Reliable reconstructions of past solar irradiance do not yet exist because of incomplete understanding of solar sources of irradiance variations in addition to sunspots and faculae.

This talk summarizes evidence and mechanisms for real variations in solar irradiance on time scales for which measurements are considered reliable – in the range of days to years. Reconstructions of past irradiance variations using a variety of assumptions about plausible solar sources are compared. Projections of future solar irradiance are shown, emphasizing the need for improved forecasts of solar activity to advance these projections for terrestrial applications.




EVE/SAM: Pinhole Images to Solar Soft X-ray Irradiance

Author(s): Lin, Cissi Y. (1), Bailey, Scott M. (1), Jones, Andrew (2), Woodraska, Don (2), Woods, Thomas (2), Eparvier, Frank (2)

Institution(s): (1) Virginia Tech, (2) Laboratory for Atmospheric and Space Physics

Abstract:

The Solar Aspect Monitor (SAM) is a spare channel on EVE in which a pinhole places a solar image on unused section of one EVE detector. As the image is used for individual photon detection to resolve solar spectra from 0.1 to 7 nm, contamination from out-of-band irradiance and the photon-like energetic particles has made retrieval of the solar spectrum challenging. Techniques are developed to address these issues and determine integrated SAM irradiance in separated soft X-ray energy bands. Results under different levels of solar activity are compared with EVE ESP photodiode measurements.




Can We Predict the Geoeffectiveness of CMEs?

Author(s): Jon Linker, Roberto Lionello, Cooper Downs, Zoran Mikic, Tibor Torok, Viacheslav Titov, and Pete Riley

Institution(s): Predictive Science Inc.

Abstract:

Coronal Mass Ejections (CMEs) are immense eruptions of plasma and magnetic field that are propelled outward from the sun, sometimes with velocities greater than 2000 km/s. They are also responsible for some of the most severe space weather at Earth, including geomagnetic storms. Modeling CMEs from Sun to Earth is especially challenging, because of the enormous disparity of scales involved. At the present time, both NOAA SWPC and the CCMC use the WSA-Enlil model with "cone model" CMEs to predict the arrival of possibly geoeffective CMEs at Earth. This model has no embedded magnetic fields in the CME, and therefore does not successfully predict the magnitude and direction of Bz. In this paper, we outline a possible approach to this problem, using coupled coronal and heliospheric simulations of coronal mass ejections. Research supported by NASA, NSF, and AFOSR.




Recent Advances in Observations of Coronal EUV Waves

Author(s): Wei Liu(1), Leon Ofman(2), Markus J. Aschwanden(3), Nariaki Nitta(3), Junwei Zhao(4), Alan M. Title(3)

Institution(s): (1) Stanford-Lockheed Institute for Space Research; (2) Catholic University of America and NASA Goddard Space Flight Center; (3) Lockheed Martin Solar and Astrophysics Laboratory; (4) Stanford University.

Abstract:

MHD waves can be used as seismological tools to decipher otherwise elusive physical parameters of the solar corona, such as the magnetic field strength and plasma density. Recent high cadence, high resolution, full-disk imaging observations from SDO/AIA have opened a new chapter in understanding these waves. Various types of EUV waves associated with flares/CMEs have been discovered or observed in unprecedented detail. In this talk, we will review such new observations, focusing on the following topics and their interrelationships: (1) quasi-periodic fast waves traveling along coronal funnels within CME bubbles at speeds up to ~2000 km/s, associated with flare pulsations at similar frequencies; (2) quasi-periodic wave trains within broad, diffuse pulses of global EUV waves (so-called "EIT waves") running ahead of CME fronts; (3) interactions of global EUV waves with local coronal structures on their paths, such as flux-rope coronal cavities and their embedded filaments (kink oscillations) and coronal holes or active regions (deflections). We will discuss the implications of these observations on coronal seismology, on their roles in transporting energy through different parts of the solar atmosphere, and on understanding their associated eruptive flares/CMEs.




Magnetic Helicity in Emerging Solar Active Regions: A Statistical Study

Author(s): Y. Liu (1), J. T. Hoeksema (1), M. Bobra (1), K. Hayashi (1), P. W. Schuck (2), X. Sun (1)

Institution(s): (1) Stanford University, (2) NASA

Abstract:

Using HMI vector magnetic field data, we study magnetic helicity injection into the corona in emerging active regions and examine the hemispheric helicity sign rule. It is found that the photospheric shearing motion contributes most of the helicity accumulated in the corona. The hemisphere rule is also confirmed with the newly observed data of 28 emerging active regions observed in the early phase of Solar Cycle 24. A relationship between the size and magnetic twist of active regions is inferred in a sample of 22 emerging active regions having a bipolar magnetic field configuration. This relationship is predicted by flux emergence models.




Heating of Flare Loops During a Two-ribbon Flare on 2011 March 07 Observed by AIA and EVE

Author(s): Liu, W-J 1; O'Hara, J. 1,2; Peck, C. 1, 3; Qiu, J 1; Longcope, D. W. 1

Institution(s): 1. Department of Physics, Montana State University, Bozeman, MT 59717 2. School of Mathematics and Statistics, University of St Andrews, St Andrews, KY16 9SS,UK 3. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303

Abstract:

Recent high-resolution EUV observations have revealed that flare loops are formed and heated by reconnection events taking place successively. Our recent work shows that the rapidly rising phase of the UV emission at the foot-points of the flare loops could be used to infer the time profile of the impulsive heating rate. In this study, we analyze an M-class flare observed by AIA and EVE. We utilize the spatially resolved UV brightness time profiles to infer heating rates of a few thousand flux tubes anchored at the UV foot-points, and compute plasma evolution in each flux tube using the EBTEL model (Klimchuk et al. 2008, Cargrill et al. 2012). The coronal radiation is then calculated and compared with soft X-ray and EUV light curves observed by GOES and AIA. With a steady-state assumption, we also compute the transition-region DEM for each flux tube during its decay phase, and compare the predicted optically-thin transition-region emission in UV and EUV with AIA foot-points observations. The EUV emissions from both loops and foot points are also compared with irradiance observed by EVE. This study presents a method to infer heating functions of reconnection formed flare loops and how they affect evolution of the overlying corona as well as the lower-atmosphere dynamics coherently.





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