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There are 146 abstracts


An Examination of Flare Cooling Using SDO/EVE

Author(s): Daniel F. Ryan, Phil C. Chamberlin, Peter T. Gallagher, Ryan O. Milligan

Institution(s): Trinity College Dublin, NASA/GSFC, Catholic University of America, Queen's University Belfast

Abstract:

The processes by which solar flares cool have been modeled many times using magnetohydrodynamic simulations. However, few studies have tried to compare the results of such models to observations of large numbers of flares. A better observational understanding of flare cooling would help us to better constrain initial flare energy inputs and better understand how potentially harmful radiation is released into the solar system. The advent of SDO/EVE allows us to observe flare cooling more directly than before while making fewer assumptions (e.g. the isothermal assumption). This is done by charting the temporal evolution from several temperature sensitive lines within the EVE spectral range. In this poster we have used SDO/EVE and GOES/XRS to calculate flare cooling profiles of 72 M- and X-class flares. The observed cooling times have been compared to those predicted by the simple and highly idealized Cargill et al. (1995) model. We find that although the model does not accurately fit the distribution, the agreement is still better than expected, particularly at shorter cooling times.




Differences between the vector magnetic field provided by the SDO/HMI and Hinode-SOT/SP databases.

Author(s): A. Sainz Dalda

Institution(s): Stanford-Lockheed Institute for Space Research

Abstract:

Since April 7, 2010, SDO/HMI has been observing the photosphere of the full solar disk with almost continuous coverage. Because of its high temporal cadence, SDO/HMI data are especially useful to study those dynamic phenomena that involve the vector magnetic field and its derived quantities, e.g.: electric current density or helicity. Hinode-SOT/SP has a better spectral and spatial resolution, but a worse temporal sampling than SDO/HMI. Hinode SOT/SP takes about 0.5-1h to scan a typical AR. We can overcome both instruments' disadvantages by combining their data. We compare the vector magnetic field of NOAA AR 11410, obtained from inversions of data from both instruments. We found that the magnetic field observed by both instruments is mainly the same for the umbra and penumbra, but it is slightly different for the plage. The most important difference is due to the spectral sampling. However, the spatial sampling also plays an important role in the derived quantities, i.e. those that require calculating derivatives on the spatial coordinates. While we cannot validate which inversion code or instrument gives 'better' estimates of the vector magnetic field, we can provide a conversion between SDO/HMI and Hinode-SOT/SP data.




Using Solar Dynamics Observatory Data in the Classroom to Do Real Science - A Community College Astronomy Laboratory Class Investigation

Author(s): Scott Hildreth, Shannon Lee, Timothy Dave, Deborah Scherrer, Philip Scherrer

Institution(s): Chabot Community College, Stanford University

Abstract:

The incredible accessibility of extremely high spatial and temporal resolution data from the Solar Dynamics Observatory creates an opportunity for students to do near real-time solar investigations in an astronomy lab environment. We are developing a short series of laboratory exercises using SDO (AIA, HMI) data, targeted for Community College students in an introductory astronomy lab class, extendable to high school and university students. The labs initially lead students to explore what SDO can do, online, through existing SDO video clips taken on specific dates. Students then investigate solar events using the Heliophysics Events Knowledgebase (HEK), and make their own online movies of events, to discuss and share with classmates. Finally, students can investigate specific events and areas, selecting specific dates, locations, wavelength regions, and time cadences to create and gather their own SDO datasets for more detailed investigation. In exploring the Sun using actual data, students actually do real science. We are in the process of beta testing the sequence of labs, and are seeking interested community college, university, and high school astronomy lab teachers who might consider trying the labs themselves.




HMI Status and Highlights

Author(s): P.H. Scherrer

Institution(s): Stanford University

Abstract:

Calibrated HMI basic observable quantities have been available for almost 2.5 years. Higher level standard HMI data products for magnetic fields and helioseismic derived parameters have been available for about a year. This talk will give a brief status update on the standard products and describe a few findings based on these products.




SDO/AIA Prominence physical conditions

Author(s): Schmieder, B.(1), Parenti, S.(2), Dudik, J.(1) (3), Aulanier, G.(1), Heinzel, P.(4), Zapior, M. (5), Golub, L. (6)

Institution(s): (1) Observatoire de Paris, France, (2) Observatoire Royal de Belgique, Belgium, (3) University of Bratislava, Slovakia, (4) Astrophysical Institute of Ondrejov, Czech, (5) Poland, (5) SAO, Cambridge, US

Abstract:

SDO/AIA has carried out continuous observations of prominences in multiple wavelengths, with high spatial and temporal resolution. These data provide us an opportunity to understand the physical conditions and dynamics of prominences. The surprising brightness of prominences in some coronal lines has been well explained by the presence of transition region lines in the bandpass of the filters (171 A, 131 A), a result that leads us to revise our model of the transition region of prominences and to consider a relatively dense transition region in some prominence evolutionary phases or in some viewing orientation. An additional aspect of prominence dynamics will be presented with a new quasi-static MHD model proposed for bubbles and plumes. We propose an alternative to the interpretation that thermal instabilities are responsible for the formation of bubbles. The bubbles are found to correspond to magnetic separatrices formed by emerging magnetic field close to prominence footpoints.




Using Distortion of Global Mode Eigenfunctions to Estimate Large Scale Flows

Author(s): Schou, J. (1), Woodard, M. F. (2), Baldner, C. S. (1), Larson, T. P. (1)

Institution(s): (1) Stanford University, Stanford, CA, USA, (2) NWRA/CORA, Boulder, CO, USA

Abstract:

The accurate measurement of large scale flows, such as differential rotation and meridional flow, throughout the solar interior is important for understanding the solar interior and the processes relevant for the solar dynamo. Ordinarily normal modes would be expected to give more accurate measurement of large scale flows than local helioseismic techniques. Unfortunately, mode frequencies are not sensitive to the meridional flow and so traditional methods do not work. Here we describe our progress on using the distortion of the eigenfunctions to measure flows. In particular on identifying the source of the large systematic errors previously reported and determining the effect of light travel time, center to limb phase variations and other physical effects.




Role of 3D-Dispersive Alfven Waves in Coronal Heating and Solar Wind

Author(s): Sharma, R.P.(1),Yadav, N.(2)

Institution(s): Centre for Energy Studies, Indian Institute of Technology Delhi-110016, India

Abstract:

Dispersive Alfven waves (DAWs) play a very important role in the acceleration and heating of plasma particles in space as well in laboratory plasmas. DAWs may be Kinetic Alfven waves (KAW) or Inertial Alfven waves (IAW) depending upon the plasma beta (here beta is ratio of the plasma thermal pressure and magnetic pressure). Using two-fluid model of plasma DAWs have been studied extensively in literature but to explain the dynamics of Alfvén vortices one has to study the three dimensional (3D) propagation of these waves rather than 2D- propagation. 3D- DAW itself propagates in magnetized plasma in the form of a vortex beam which is manifestation of orbital angular momentum. These magnetic flux ropes or Alfvén vortices trap charged plasma particles and energize and transport them from one place to another. Thus these Alfvén vortices can also be an alternative mechanism to explain the energy transport in space plasmas. Coronal heating is one of the unresolved problems in solar physics. A number of theories have been given to explain the mystery behind coronal heating but no satisfactory solution has been found yet. We propose to study the nonlinear interaction between 3D-DAW and Ion acoustic wave as a mechanism in solar environment to generate the 3D- DAW localized structures. In the absence of ponderomotive non-linearity we get Laguerre Gauss (LG) polynomials as solutions of paraxial wave equation governing propagation of 3D-KAW. These LG modes are characterized by spiral phase front and concentric rings as intensity pattern. The relevance of this nonlinear process to coronal heating and solar wind turbulence has been pointed out. For this we have developed a (numerical) code based on pseudo-spectral technique and simulate this nonlinear interaction.




Non-Equilibrium Ionization Modeling of the Current Sheet in a Simulated Solar Eruption

Author(s): C. Shen, K. K. Reeves, J. C. Raymond, N. A. Murphy, Y-K. Ko, J. Lin, Z. Mikić

Institution(s): Smithsonian Astrophysical Observatory

Abstract:

The current sheet that extends from the top of flare loops to an associated flux rope is a common structure in models of coronal mass ejections (CMEs). To understand the observational properties of CME current sheets, we generate predictions from flare/CME models to be compared with observations. We use a simulation of a large-scale CME current sheet previously reported by Reeves et al. (2010). This simulation includes Ohmic and coronal heating, thermal conduction, and radiative cooling in the energy equation. Using the results of this simulation, we perform time-dependent ionization calculations of the flow in a CME current sheet and construct two-dimensional spatial distributions of ionic charge states for multiple chemical elements. We use the filter responses from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory and the predicted intensities of emission lines to compute the count rates for each of the AIA bands. The results show differences in the emission line intensities between equilibrium and non-equilibrium ionization. The current sheet plasma is underionized at low heights and overionized at large heights. At low heights in the current sheet, the intensities of the AIA 94Å and 131Å channels are lower for non-equilibrium ionization than for equilibrium ionization; and at large heights, these intensities are higher for non-equilibrium ionization than for equilibrium ionization. We also calculated the intensity of ultraviolet lines and predicted emission features that could be compared with those events observed by the Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory, including a low intensity region around the sheet present in the model.




Abstract Title: LONG TERM VARIATIONS IN THE SOLAR CHROMOSPHERE-CA K LINE PROFILES

Author(s): Sindhuja, G.

Institution(s): Indian Institute of Astrophysics

Abstract:

The previous studies show that there is a lack of information on the variation of network flux with solar cycle phase and also the center of solar disc was found to show no variation with solar cycle phase(white and Livingston 1978). A study on solar variability model(Skumanich et al 1984) shows that there is an excess component during the solar maximum phase. Therefore the above mentioned studies, forms the basis for the development of new program(Jagdev singh 1989) at kodaikanal tower telescope since 1986 to monitor Ca K line profiles as a function of latitude and integrated over the visible 180o longitude. The huge database is being used to study the various parameters of the Ca K line and to study the variation of chromospheric flux as a function of solar latitude with solar cycle phase. Activity related with sunspots has been studied widely but variations in the polar regions have not been observed systematically. Our data permits to study the changes in polar regions systematically and its implications to the magnetic cycle of the Sun. Here we shall discuss the results about the variation in the chromospheric flux in terms of CaK plages, network and background flux. These variations have long and short term implications on the climatic modeling.




EVE and the E-Layer

Author(s): J. J. Sojka, J. B. Jensen, M. David, R. W. Schunk, T. N. Woods and F. G. Eparvier

Institution(s): Utah State University and LASP/University of Colorado

Abstract:

The ionosphere is arguably the most extensively observed region in the Living With a Star (LWS) environment. Even so, it is only now with the availability of the SDO EVE solar irradiance observations that the connection between the ionospheric layers and their production by the solar irradiance can be fully explored. This is because the EVE measurements have unique cadence (at least 10 seconds), irradiance spectral coverage, and adequate wavelength resolution to constrain the ionosphere photoionization response in both altitude and time. This presentation will discuss how the EVE 10-second cadence is a crucial new observation attribute and how this relates to an altitude dependence in the ionosphere’s response. Problems related to how energetic photons create photoelectrons with sufficient energy to produce additional ionization will be revisited. The ionospheric modelers procedures for handling this process are at best antiquated. Present-day ionospheric models are only now becoming sensitive enough that improved handling of these photoelectrons is needed. This arises because for the first time EVE is able to provide high time resolution of the short wavelength irradiance photons responsible for this process. Another aspect of how important the absolute calibration of the irradiance is to the ionosphere will be explored by contrasting conventional irradiance representations with that observed by EVE. In this case, differences of irradiances over narrow wavelength regions are found to create or not create key ionospheric features such as the E-layer.





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Last Updated on Tuesday, 29 March 2011 09:36