sdo7.lws-sdo-workshops.org

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

Submitted Abstracts

There are 146 abstracts


Active Region Emergence

Author(s): Robert Stein, Aake Nordlund

Institution(s): Michigan State University, Niels Bohr Institute

Abstract:

Neither a tachocline nor a globally coherent flux tube is necessary to form an active region. Dynamo action in the convection zone and magneto-convection together can produce active regions. We report on a small scale model of such a process. For a global scale flux tube to emerge from the tachocline and rise through the convective zone, while maintaining its coherence and emerging with the proper orientation and at the correct latitudes such coherent flux tubes must have a field strength of 40-50 kG at the base of the convection zone (Weber 2011). How they are formed with greater than equipartition field strength, stored in and released from the tachocline has long been a mystery. Recent simulations show that another scenario is possible. Global scale magnetic wreaths are produced by dynamo action inside the convection zone which reverse polarity (Nelson 2013). Both these global and also local surface simulations have shown that convective motions produce magnetic loops from these large scale wreaths which rise to the surface and produce active regions. The local simulations of magnetic flux emergence show that the field initially emerges over a confined area with horizontal fields emerging over granules with mixed polarity vertical legs at their ends in the intergranular lanes. The fields are quickly swept into the intergranular lanes and then stream into separate, opposite polarity concentrations producing pores and spots as is observed. These simulations also provide insight into the subsurface structure of spontaneously formed pores and spots.




Granules in the Quiet and Magnetic Sun

Author(s): Robert Stein, Valentyna Abramenko, Aake Nordlund

Institution(s): Michigan State University, Big Bear Solar Observatory, Niels Bohr Institute

Abstract:

High resolution magneto-convection simulations reveal that there are significant differences in granulation in quiet and magnetic regions of the Sun. In non-magnetic regions the granules have scalloped edges (not smooth intergranualr lanes) in the emergent continuum radiation and the vertical velocity at the edges of the intergranular lanes form a branching tree structure extending into the granules. In magnetic regions the intergranular lanes are smooth in both intensity and vertical velocity but with swirls (vortices) in both. These differences are borderline visible in data from the Big Bear NST.




First direct EUV observation and multi-temperature analysis of a coherent, wave-like propagating disturbance along pseudo-open field lines above a sunspot

Author(s): Stenborg, Guillermo (1), Stekel, Tardelli (1,2), Vourlidas, Angelos (3), Howard, Russell (3)

Institution(s): (1) George Mason University (GMU), Fairfax VA, USA (2) National Institute for Space Research (INPE), Sao Jose dos Campos SP, Brazil (3) Naval Research Laboratory (NRL), Washington DC, USA

Abstract:

We report the first direct observation (along with a comprehensive kinematical characterization) of a wave-like front recorded in several SDO AIA channels. The front propagates coherently along a bundle of pseudo-open field lines with origin on an active region sunspot. Wavelet-processing of AIA images makes the wave-like disturbance clearly discernible with the naked eye. The disturbance propagates with an average plane-of-sky phase velocity of ~50 km/sec in the 131 Å, 171 Å, 193 Å, 211 Å, 304 Å and 335 Å channels, exhibiting a ~3 min periodicity in all cases. Its origin could be tracked down to a higher-than-average intensity point inside the umbra of the corresponding spot (i.e., an umbral dot) observed in the 1600 Å and 1700 Å AIA channels. The intensity of the source oscillates in phase with the wave-like phenomenon observed in the other channels. We speculate on the magneto-acoustic nature of the wave.




The role of solar “tornadoes“ and vortices in filament fromation and eruption

Author(s): Yang Su, Tongjiang Wang, Astrid Veronig, Manuela Temmer, and Weiqun Gan

Institution(s): Kanzelhöhe Observatory-IGAM, Institute of Physics, University of Graz, Austria

Abstract:

Solar magnetized “tornadoes” are rotating vertical magnetic structures in the corona probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences. Detailed case studies show that these tornadoes may play a distinct role in the supply of mass and twists to filaments. The findings could lead to a new explanation of filament formation and eruption.




Direct Observations of Coronal Magnetic Reconnection

Author(s): Yang Su, Astrid Veronig, Brian R. Dennis, Gordon D. Holman, Tongjiang Wang, Manuela Temmer, Weiqun Gan

Institution(s): Kanzelhöhe Observatory-IGAM, Institute of Physics, University of Graz, Austria

Abstract:

Magnetic field reconnection is believed to play a fundamental role in magnetized plasma systems throughout the universe, but never before has it been so clearly demonstrated as in the EUV and X-ray movies of a GOES-C-class solar flare presented here. The multiwavelength EUV observations from SDO/AIA show the predicted inflowing cool loops and newly formed outflowing hot loops while simultaneous RHESSI X-ray spectra and images show the appearance of plasma heated to >10 MK at the expected locations. These two data sets provide solid visual evidence of magnetic reconnection producing a solar flare. The non-uniform, nonsteady, and asymmetric nature of the observed process, together with the measured reconnection rates, supports the so called flux-pile-up reconnection. These new features of plasma inflows should be included in reconnection and flare studies.




Hot Spine Loops and the Nature of a Late-Phase Solar Flare

Author(s): Xudong Sun, Todd Hoeksema, Yang Liu

Institution(s): Stanford University

Abstract:

The fan-spine magnetic topology is thought to be responsible for many curious emission signatures in solar explosive events. A spine field line links topologically separate flux domains and possibly their evolutionary trends, but direct observational evidence of such structure has been rare. Here we report a unique event observed by the Solar Dynamic Observatory (SDO) where a set of hot coronal loops (over 10 MK) that developed during the rising phase of the flare connected to a quasi-circular chromospheric ribbon at one end and a remote brightening at the other. Magnetic field extrapolation suggest these loops are tracers of the spine field line. The sequential brightening of the ribbon and the increasing number of hot loops suggest that continuous slipping and null-point type reconnection were at work, transferring flux from below the fan dome to the exterior. This event also features an extreme-ultraviolet (EUV) late phase – a second emission peak observed in the warm EUV lines (2–7 MK) hours after the flare. Observations indicate that the initially confined process transitioned to a fluxrope eruption near the flare peak. The eruption opened the overlying field and drastically accelerated the energy release. Slow cooling of the large post-flare arcades naturally explains the sequential delay of the late-phase peak in increasingly cooler EUV lines. Our result demonstrates the crucial nature of magnetic coupling between systems of different sizes – a minor topological change may lead to violent eruptions on a much larger scale.




Multi--instrument estimation of the non--flaring heating and reconnection rates of an emerging active region: NOAA AR11112

Author(s): Lucas A. Tarr, Dr. Dana W. Longcope, and Dr. Keiji Yoshimura

Institution(s): Montana State University

Abstract:

In NOAA Active Region 11112, a small bipole emerges into an area of preexisting, unipolar flux. When overlaid on HMI magnetograms, the bright, low lying kernel of loops above the emerging field, observed with AIA and XRT, originally show magnetic connectivity only between regions of newly emerged flux. Over the course of several days, this bright kernel advances into the preexisting flux. The advancement of this easily visible boundary into the old flux regions over time provides a quantifiable rate of reconnection between old and new magnetic domains. We compare the reconnection rate to the inferred heating of the coronal plasma. To our knowledge, this is the first measurement of steady, quiescent heating related to reconnection. While AR11112 does produce an M3.0 flare on Oct 16th, 2010, the implied reconnection we focus on here predates the flare by several days, and does not result in any observable flaring active of its own, such as increases in the GOES light curve, chromospheric flare ribbons, or post--flare loops.




CME propagation analysis using remote and in-situ observations

Author(s): Teresa Nieves-Chinchilla(1), Guillermo Stenborg(2), Angelos Vourlidas(3), Neel P. Savani(3), Miguel A. Hidalgo(4), Luis A. Vena(4), Adam Szabo(5), Robin C Colaninno(3)

Institution(s): (1) IACS/CUA-GSFC/NASA, Greenbelt, MD (2) George Mason University, Fairfax, VA (3) NRL, Washington, DC (4) UAH, Alcala de Henares, Spain (5) GSFC/NASA, Greenbelt, MD

Abstract:

Coronal mass ejections (CMEs) are the main drivers of Space Weather. Accurate forecasting of their likely geo-effectiveness requires accurate tracking of their morphological and kinematical evolution throughout the interplanetary medium. However, single view-point observations depend on strong assumptions to model the development of the CME; the most common hypotheses are those of radial propagation and self-similar expansion. The use of different view-points show that, at least for some cases, those assumptions may not be valid. Analyses of remote sensing and in-situ data show signatures of strong deflection, over-expansion and/or large deformation. These behaviors could hide effects as rotation, deviation from radial propagation, or interaction with other magnetic obstacles. Understanding the 3D development and evolution of CME features is therefore of utmost importance to help establish the connection between remote and in-situ observations, and hence improve forecasting of Space Weather. In this work, we present the analysis of a set of selected events exhibiting clear signatures of deflection. With the help of remote imaging observations provided by the SOHO, STEREO and SDO missions, and in-situ measurements recorded by Wind, ACE, and Messenger. We show that such signatures are evidence of hidden effects such as rotation, changes in the direction of propagation, and/or interaction with other magnetic obstacles.




Global oscillations and small scale dynamics of a filament

Author(s): Hui Tian (1), Leon Ofman (2,3), Tongjiang Wang (2,3)

Institution(s): (1) Harvard-Smithsonian Center for Astrophysics; (2) Catholic University of America; (3) NASA Goddard Space Flight Center

Abstract:

Using AIA data, we observed global oscillatory motions along the axis of a filament with detailed small scale dynamics. The global oscillation lasted for more than two days before the eruption of the filament. Both magnetic tension and gravity are likely to be involved in the global oscillation, as predicted by theoretical models. A closer look of the detailed dynamics within the filament suggests that torsional motions around the prominence axis are also present. Torsional motions around the two legs of the filament resemble the so-called "solar tornadoes" observed at limb by AIA. Variable counter-streaming flows in the prominence body were detected as well before the filament eruption. The HMI magnetic field data and multi-line diagnostics are used to investigate possible mechanisms responsible for the different types of oscillations and flows before the eventual eruption of the filament.




Formation of a hot plasma blob: observations of AIA, CoMP and MK4

Author(s): Hui Tian (1), Sarah Gibson (2)

Institution(s): (1) Harvard-Smithsonian Center for Astrophysics; (2) High Altitude Observatory, National Center for Atmospheric Research

Abstract:

Using AIA observations, we found that a hot blob of plasma formed as a trans-equatorial loop system rose and opened up. The hot blob was most clearly seen in the AIA 94 passband and not obvious in any other passbands. A cusp-like structure quickly developed below the hot blob when the blob left the FOV of AIA 1.5 hours after its formation. This event was also observed by the CoMP and MK4 instruments in Mauna Loa Solar Observatory. The CoMP observation reveals a clear "bunny ear" pattern suggestive of a magnetic flux rope around the AIA blob. The hot blob observed by AIA seems to coincide with the region of enhanced linear polarization between the two dark ears. A comparison between these observations with MHD simulations of flux rope eruption suggest that the hot blob might be the lower part of, or just below, the erupted flux rope. In the MK4 data we see a clear three-part CME propagating outward.





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