Submitted Abstracts

There are 131 abstracts


Ellerman Bombs and IRIS Bombs; In the photosphere and above

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Presentation Type: No Preference

Session: Session 2: Motions Near and Above the Solar Surface

Abstract:

The lower Solar atmosphere, consisting of the photosphere and chromosphere, can occasionally show violent activity more often associated with the magnetically dominated outer layers of the Sun; the upper chromosphere, transition region and corona. However, in regions of strong flux emergence, where Solar active regions are being formed, one can see evidence of photospheric reconnection as the field struggles to emerge through the non-buoyant photosphere and expand into the atmosphere above. Ellerman bombs, short lived, brightness enhancements in the outer wings of strong optical lines are thought to be a result of such reconnection. Observations made with the NASA’s Interface Region Imaging Spectrograph, showed similar ‘UV bursts’ in lines usually associated with the outer Solar atmosphere, while at the same time clearly being situated below much cooler gas. We here present a numerical model of flux emergence in which both Ellerman bombs and perhaps IRIS bombs (UV bursts) are naturally and copiously produced.




Unraveling the Complexity of the Evolution of the Sun’s Photospheric Magnetic Field

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Presentation Type: Oral

Session: Session 3: Solar Magnetic Variability and the Solar Cycle

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Given the emergence of tilted, bipolar active regions, surface flux transport has been shown to reproduce much of the complex evolution of the Sun’s photospheric magnetic field. Surface flux is transported by flows in the surface shear layer – the axisymmetric differential rotation and meridional flow and the non-axisymmetric convective motions (granules, supergranules, and giant cells). We have measured these flows by correlation tracking of the magnetic elements themselves, correlation tracking of the Doppler features (supergranules), and by direct Doppler measurements using SDO/HMI data. These measurements fully constrain (with no free parameters) the flows used in our surface flux transport code – the Advective Flux Transport or AFT code. Here we show the up-to-date evolution of these flows, their impact on the detailed evolution of the Sun’s photospheric magnetic field, and predictions for what the polar fields will be at the next minimum in 2020.




Comparing Time-Distance Results within a Coronal Hole to the Quiet Sun

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Presentation Type: Poster

Session: Session 1: Motions Inside the Sun

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Time-distance helioseismology studies perturbations in solar wave modes. We use these techniques with SDO/HMI time-distance velocity-tracked dopplergram data to investigate differences between f -mode wave propagation within a coronal hole feature and without. We use symmetry arguments to enhance the signal-to-noise ratio of the cross-correlation results. We then look for phase and amplitude discrepancies between the coronal hole and quiet sun by comparing statistically significant differences between the regions.




Towards a Physics-Based Flare Irradiance Model

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Presentation Type: Oral

Session: Session 5: Studies of Solar Eruptive Events (SEEs)

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The Extreme UltraViolet (EUV) irradiance from solar flares is a critical driver of short term variability in the Earth’s upper atmosphere. The EUV Variability Experiment (EVE) onboard NASA’s Solar Dynamics Observatory (SDO) has been making moderate spectral resolution (0.1 nm), high time cadence (10 s) measurements of the solar EUV irradiance (5-105 nm) since 2010. A key observation from EVE is that flares of the same magnitude at one wavelength (e.g. GOES XRS) have different peak intensities and time profiles in other wavelengths. As it is impractical to measure the entire EUV spectrum with sufficient spectral resolution and temporal cadence to capture these differences for space weather operations, the next generation of flare irradiance models must be able to capture these variations. We have developed a framework for a physics-based flare irradiance model based on the EBTEL model. At present, this Multi-Strand Flare Irradiance Model (MS-FIM) is able to predict EUV lightcurves over a range of coronal temperatures given the lightcurves from two EVE lines as inputs. In this paper, we present an overview of the Multi-Strand Flare Irradiance Model as well as initial results showing its ability to predict the irradiances for a diverse range of flares, including EUV late phase flares. We also describe preliminary efforts to drive the model with parameters derived from images of the flaring region instead of EUV lightcurves.




Vector Magnetic Field Synoptic Maps from HMI

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Presentation Type: No Preference

Session: Session 3: Solar Magnetic Variability and the Solar Cycle

Abstract:

The Helioseismic and Magnetic Imager (HMI) project has made full-disk vector magnetograms every 12 minutes since beginning of regular operation in May 2010. Synoptic maps of the vector magnetic field that cover most of Solar Cycle 24 have now been created. Like previously created line-of-sight synoptic maps, the size in longitude and sine-latitude is 3600 x 1440. Maps of radial and horizontal field components are created from near-central-meridian observations that combine data from 20 full-disk magnetograms. We compare the affects on synoptic maps of using different methods for determining the disambiguation in weak-field regions – annealing, random, radial acute, and potential field. Data in the polar regions is of high quality. We compare these new maps with standard line-of-sight synoptic maps. Next steps include generation of more frequent vector-field synchronic frames.




On-orbit Performance and Calibration of the HMI Instrument

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Presentation Type: Poster

Session: Session 3: Solar Magnetic Variability and the Solar Cycle

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The Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory (SDO) has observed the Sun almost continuously since the completion of commissioning in May 2010, returning more than 100,000,000 filtergrams from geosynchronous orbit. Diligent and exhaustive monitoring of the instrument’s performance ensures that HMI functions properly and allows proper calibration of the full-disk images and processing of the HMI observables. We constantly monitor trends in temperature, pointing, mechanism behavior, and software errors. Cosmic ray contamination is detected and bad pixels are removed from each image. Routine calibration sequences and occasional special observing programs are used to measure the instrument focus, distortion, scattered light, filter profiles, throughput, and detector characteristics. That information is used to optimize instrument performance and adjust calibration of filtergrams and observables.




Project for Solar-Terrestrial Environment Prediction (PSTEP): Towards Predicting Next Solar Cycle

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Presentation Type: Poster

Session: Session 3: Solar Magnetic Variability and the Solar Cycle

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It is believed that the longer-term variations of the solar activity can affect the Earth’s climate. Therefore, predicting the next solar cycle is crucial for the forecast of the “solar-terrestrial environment”. To build prediction schemes for the activity level of the next solar cycle is a key for the long-term space weather study. Although three-years prediction can be almost achieved, the prediction of next solar cycle is very limited, so far. We are developing a five-years prediction scheme by combining the Surface Flux Transport (SFT) model and the most accurate measurements of solar magnetic fields as a part of the PSTEP (Project for Solar-Terrestrial Environment Prediction),. We estimate the meridional flow, differential rotation, and turbulent diffusivity from recent modern observations (Hinode and Solar Dynamics Observatory). These parameters are used in the SFT models to predict the polar magnetic fields strength at the solar minimum. In this presentation, we will explain the outline of our strategy to predict the next solar cycle. We also report the present status and the future perspective of our project.




Variations in the Geometry of the Sun Observed with HMI/SDO during Cycle 24

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Presentation Type: Poster

Session: Session 3: Solar Magnetic Variability and the Solar Cycle

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Geometry of the Sun and its temporal variations observed with ground-based instruments are still subject to questioning. The geometry, which inform us on the interior of the Sun, is achieved by high resolution measurements of the radius, oblateness and gravitational moments c2 and c4. Several space missions were developed these last decades to validate or refute its observed variations with ground experiments and the link with solar activity. High angular resolution of solar radius measurements and its long term trend is however a challenge in Space. The first attempts with MDI (Soho) then SODISM (PICARD) and HMI (SDO) revealed the difficulties of such measures due to hostile environment which introduces thermal variations of the instruments along the satellite orbit. These variations have non negligible impacts on optical properties of onboard telescopes and therefore on images and parameters extracted, such as the solar radius. We need to take into account the thermal behavior (housekeeping data) recorded together with the science data to correct them. Solar oblateness and gravitational moments ask for both special spacecraft operations and appropriate processing methods to obtain the needed accuracy for their measurements. We present here some results on the solar radius and oblateness obtained with HMI data. Images analysed cover six years since May 1, 2010 (beginning of Cycle 24), until now. Results show that the geometry of the Sun presents some temporal variations related to solar activity. In particular we evidence a Quasi-Biennale Oscillation (QBO) correlated with the solar cycle, as was observed with ground observations.




What would you like to see next from the Helioviewer Project?

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Presentation Type: Poster

Session: Session 7: Space Weather at the Earth and other Planets

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This year saw the release of major new upgrades to the capabilities of helioviewer.org and JHelioviewer. We review the new features of this software and report our latest usage statistics. We will also be soliciting bug reports, requests for new features and comments on the effectiveness of helioviewer.org and JHelioviewer. What would you like to see next from the Helioviewer Project?




AWARE - The Automated EUV Wave Analysis and REduction algorithm

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Presentation Type: Poster

Session: Session 2: Motions Near and Above the Solar Surface

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Extreme ultraviolet (EUV) waves are large-scale propagating disturbances observed in the solar corona, frequently associated with coronal mass ejections and flares. Since their discovery over two hundred papers discussing their properties, causes and physics have been published. However, their fundamental nature and the physics of their interactions with other solar phenomena are still not understood. To further the understanding of EUV waves, and their relation to other solar phenomena, we have constructed the Automated Wave Analysis and REduction (AWARE) algorithm for the detection of EUV waves over the full Sun. The AWARE algorithm is based on a novel image processing approach to isolating the bright wavefront of the EUV as it propagates across the corona. AWARE detects the presence of a wavefront, and measures the distance, velocity and acceleration of that wavefront across the Sun. Results from AWARE are compared to results from other algorithms for some well known EUV wave events. Suggestions are also give for further refinements to the basic algorithm presented here.