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Solar Tornado Prominences: Plasma Motions Along Filament Barbs

Author(s): Panasenco, Olga (1), Velli, Marco (2), Martin, Sara F. (1), Rappazzo, Franco (3)

Institution(s): (1) Helio Research, La Crescenta, CA, (2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, (3) Bartol Research Institute, University of Delaware, USA

Abstract:

Recent high-resolution observations from the Solar Dynamic Observatory (SDO) have reawakened interest in the old and fascinating phenomenon of solar tornado prominences. This class of prominences was first introduced by E. Pettit in 1932, who studied them over many years up to 1950. High resolution and high cadence multi-wavelength data obtained by SDO reveal that the tornado-like properties of these prominences are mainly an illusion due to projection effects. We show that counterstreaming plasma motions with projected velocities up to +/- 45 km/sec along the prominence spine and barbs create a tornado-like impression when viewed at the limb. We demonstrate that barbs are often rooted at the intersection between 4-5 supergranular cells. We discuss the observed oscillations along the vertical parts of barbs and whether they may be related to vortex flows coming from the convection downdrafts at the intersection of supergranules (and possibly smaller convective cells) in the photosphere and their entrained magnetic field. The unwinding of magnetic threads near the photosphere via reconnection might be a source of the waves which are observed as oscillations in prominence barbs.




Formation of the Coronal Cloud Prominences Inside Magnetic Funnels

Author(s): Panasenco, Olga (1), Velli, Marco (2), Martin, Sara F. (1)

Institution(s): (1) Helio Research, La Crescenta, CA, (2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA

Abstract:

We describe observations of coronal cloud prominences with the Solar Dynamics Observatory and STEREO. Observations of this phenomenon during the month of September 2012, in similar locations but over widely separated periods, are used to investigate the reasons for the appearance of coronal cloud prominces at different times in the same location. In particular, we focus on the large scale structure of the background magnetic field. Using a potential field source-surface extrapolation to compute the coronal field from photospheric maps, we find that coronal cloud prominences always form after filament eruptions and CMEs have occurred nearby. The location of the cloud prominence coincides with a magnetic field region which appears to be open but rapidly expanding, an open field with a funnel structure. Part of the plasma from the neighboring eruption falling back towards the sun is captured and accumulates in these field regions of strong expansion of the field. The plasma suspension at heights of 0.3 Rs, coinciding with the largest gradients in the field naturally lead to a diamagnetic hypothesis for the force counteracting gravity. We study the evolution of the funnel-like open fields during several solar rotations and find a direct relation between funnels and the presence of coronal clouds at great heights in the solar corona.




Rotating sunspots and their role in the activity of solar active region NOAA 11158

Author(s): P. Vemareddy (1), A. Ambastha (1), R. A. Maurya (2)

Institution(s): (1) Physical Research laboratory, (2) Seoul National University

Abstract:

We study the role of rotating sunspots in relation to the evolution of various physical parameters characterizing the non-potentiality of the active region (AR) NOAA 11158 and its eruptive events using the magnetic field data from the Helioseismic and Magnetic Imager (HMI) and multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. From the evolutionary study of HMI intensity and AIA channels, it is observed that the AR consists of two major rotating sunspots, one connected to a flare-prone region and another with coronal mass ejection (CME). The constructed space-time intensity maps reveal that the sunspots exhibited peak rotation rates coinciding with the occurrence of major eruptive events. Further, temporal profiles of twist parameters, namely, average shear angle, α_{av}, α_{best}, derived from HMI vector magnetograms, and the rate of helicity injection, obtained from the horizontal flux motions of HMI line-of-sight magnetograms, correspond well with the rotational profile of the sunspot in the CME-prone region, giving predominant evidence of rotational motion causing magnetic non-potentiality. Moreover, the mean value of free energy from the virial theorem calculated at the photospheric level shows a clear step-down decrease at the onset time of the flares revealing unambiguous evidence of energy release intermittently that is stored by flux emergence and/or motions in pre-flare phases. Additionally, distribution of helicity injection is homogeneous in the CME-prone region while in the flare-prone region it is not and often changes sign. This study provides a clear picture that both proper and rotational motions of the observed fluxes played significant roles in enhancing the magnetic non-potentiality of the AR by injecting helicity, twisting the magnetic fields and thereby increasing the free energy, leading to favorable conditions for the observed transient activity.




The Importance of Priors in Bayesian Reconstruction of Emission Measure Distributions

Author(s): Joseph Plowman, Charles Kankelborg

Institution(s): Montana State University

Abstract:

Bayesian methods such as MCMC are popular tools for reconstruction of differential emission measures (DEMs) from coronal observations, but the careful choice of prior probability distributions for these reconstructions has received relatively little consideration. The choice of prior is especially important for DEM reconstructions due to their ill-posed nature; aspects of the reconstruction which are ill-posed (i.e., not constrained by the data) will be determined exclusively by the prior. We illustrate the effect of various choice of prior on the reconstruction of example DEMs and outline some considerations for choosing more physical priors. We also show results from application of the MultiNest Bayesian inference tool to DEM reconstruction, and compare with the results of the popular PINTofALE MCMC package.




UV and EUV Emissions at the Flare Foot-points Observed by AIA

Author(s): Qiu, J., Sturrock, Z.

Institution(s): Montana State University

Abstract:

A solar flare is composed of impulsive energy release events by magnetic reconnection, which forms and heats flare loops. Recent studies have revealed a {\em two-phase} evolution pattern of UV 1600\AA\ emission at the feet of these flare loops: a rapid rise lasting for a few minutes, followed by a gradual decay on timescales of a few tens of minutes. These signatures are indicative of instantaneous lower-atmosphere response to impulsive energy deposition, and the subsequent plasma evolution in the overlying corona that is heated and then cools down. Multiple band EUV observations by AIA further reveal very similar signatures at the foot-points of flare loops. We report the coordinated and spatially resolved observations of UV and EUV emissions at the foot-points of a C3.2 thermal flare, and discuss the governing mechanism of the two-phase evolution of the flare foot-point emissions with a simple conductive heating model.




Small-scale heating events at the footpoints of coronal loops observed by Hi-C and SDO/AIA

Author(s): S. Regnier, C. E. Alexander, R. W. Walsh, and the Hi-C science team

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

Abstract:

Hi-C was sounding rocket dedicated to the observation of the hot EUV corona at high spatial resolution (0.2 arcsec) and high time cadence (5s). The Hi-C instrument flew on July 11, 2012 and provided observations in the 193A channel of a large complex of active regions (NOAA 11519-21). We have discovered small-scale (0.74 Mm) and short duration (25s) brightenings, called EUV bright dots (EBDs) at the edge of the active regions. The comparison with SDO/AIA observations in the 193A channel shows that EBDs can also be observed at the very limit of the noise level. EBDs also exist in the 171A, 211A and 335A channels, and have a small contribution in the 304A channel. This strongly suggests that EBDs are transition region and/or coronal transient features. By comparing with SDO/HMI magnetograms and with the support a potential field extrapolation, the observed EBDs are located in unipolar regions at the foot-points of large-scale trans-equatorial loops. We discuss the viable mechanisms that can produce such a short burst/release of energy by comparing the different time scales of the plasma evolution.




Structure and evolution of a unipolar streamer observed by SDO/AIA

Author(s): S. Regnier

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

Abstract:

We report on the observation of unipolar streamer in different wavelength ranges by the SDO/AIA instrument (171A, 193A, 211A, 304A and 335A) observed on July 11, 2012 between 21:30 UT and 23:59 UT. Surrounded by field lines originating in the same polarity, the streamer contains a double-arcade structure, both filled by a prominence with clear evidence of the prominence material sitting in the corona and a cavity. This unipolar streamer is similar to the magnetic field structure described by Torok et al. (ApJ, 2011, 739, L63) for a sympathetic eruption of filaments. The streamer also evidences a pressure build-up on the equatorial side as suggested by the modelling of Riley and Luhmann (Solar Physics, 2012, 277, 355).




The solar dynamo -- where do we stand, where do we go?

Author(s): Matthias Rempel

Institution(s): HAO/NCAR

Abstract:

Understanding the origin of the large scale solar magnetic field and its temporal evolution is one of the still unsolved key questions in solar physics. While large scale dynamos are understood on a fundamental level for more than 5 decades, the details of how the solar dynamo operates are still heavily debated. In this talk I will review the various approaches taken in the past (mean field models vs. 3D numerical simulations) and discuss their intrinsic strengths and weaknesses. I will present a collection of recent modeling results including cyclic behavior in 3D numerical simulations, the connection between dynamo action and torsional oscillations, the role of flux transport and near surface field evolution (Babcock-Leighton alpha-effects) as well as flux emergence and sunspot formation. I will close the talk with an outlook on future developments.




Observational Calculation of Flare Filling Factors Using GOES/XRS, SDO/EVE and SDO/AIA

Author(s): Daniel F. Ryan, Trevor A. Bowen, Philip C. Chamberlin, Ryan O. Milligan, Peter T. Gallagher

Institution(s): Trinity College Dublin, NASA/GSFC, Harvard-Smithsonian Center for Astrophysics, Queen's University Belfast

Abstract:

A solar flare’s filling factor is the fraction of its total volume which is occupied by high density emitting plasma. This is a completely unknown factor and a major source of uncertainty in many studies requiring density calculations. While the filling factor is usually assumed to be unity, tentative observational evidence suggests it may be orders of magnitude less than that. This would have significant consequences on past and future flare density and emission measure analyses. In this poster we examine several C-class events and present the first observational calculations of flare filling factors using GOES/XRS, SDO/EVE and SDO/AIA. We find that filling factors are indeed orders of magnitude less than unity. The sample in this study ranges from 10-1 – 10-6, with a mean of 10-2.4 and a median of 10-3.4.




TEBBS: A New Automatic Method for Calculating Background-Subtracted Thermal Flare Properties Using GOES/XRS

Author(s): Daniel F. Ryan, Ryan O. Milligan, Peter T. Gallagher, Brian R. Dennis, A. Kim Tolbert, Richard A. Schwartz, C. Alex Young

Institution(s): Trinity College Dublin, NASA/GSFC, Catholic University of America, Wyle Information Systems, ADNET System Inc.

Abstract:

The GOES/XRS has become a “standard candle” by which flare observations from other satellites are compared. It is increasingly being used alongside SDO to help us better understand solar flares. In addition, the longevity of GOES makes it uniquely suited to the study of large numbers of flares over multiple solar cycles. However, in order to use the GOES/XRS to accurately derive flare thermal properties, it is essential to adequately subtract emission from non-flaring plasma. To date, the potential of the GOES/XRS has been limited by the lack of standard background subtraction method, capable of being quickly and automatically applied to any number of flares. In this poster we present just such a method, the Temperature and Emission measure-Based Background Subtraction (TEBBS; Ryan et al. 2012). This method calculates a flare’s thermal properties (temperature, emission measure etc.) by first automatically determining a suitable background subtraction based on the physical credibility of the results it produces. This method increases the GOES/XRS’s potential both as a stand-alone instrument as well as in complimenting observations made by SDO and other solar observatories.





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Last Updated on Tuesday, 29 March 2011 09:36