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There are 123 abstracts


Opportunities and challenges in determining the chromospheric magnetic field

Author(s): J. Harvey

Institution(s): NSO

Abstract:

While some progress has been made inferring the chromospheric magnetic field from intensity-only images and field extrapolations from the photosphere, this has to be followed by actual measurements. Great interest in measuring the magnetic field in the chromosphere is indicated by ~20 instruments currently operational and ~17 under development or planned. The instrumentation falls into two distinct and complementary classes with advocates for both approaches. A challenge is to find enough clever people to effectively use all of these chromospheric polarimetric facilities. A major impediment is converting the polarization signals into magnetic field patterns in the highly structured and dynamic chromospheric atmosphere. Several physical processes compete to produce spectral line polarization. Ranging from simple bisector and center-of-gravity to forward modeling and several inversion methods, the analysis of chromospheric polarization observations is a messy problem with many opportunities for vigorous discussions.




The synoptic maps of Br from HMI observations

Author(s): Hayashi, Keiji (1), Hoeksema, J. Todd (1), Liu, Yang (1) Sun, Xudong (1), Centeno, Rebecca (2), Leka, K.D. (3), Barnes, Graham (3)

Institution(s): (1) Stanford University, (2) HAO, (3) NWRA/CoRA

Abstract:

The vector magnetic field measurement can, in principal, give the “true” radial component of the magnetic field. We prepare 4 types of synoptic maps of the radial photospheric magnetic field, from the vector magnetic field data disambiguated by means of the minimum energy method developed at NWRA/CoRA, the vector data determined under the potential-field acute assumption, and the vector data determined under the radial-acute assumption, and the standard line-of-sight magnetogram. The models of the global corona, the MHD and the PFSS, are applied to different types of maps. Although the three-dimensional structures of the global coronal magnetic field with different maps are similar and overall agreeing well the AIA full-disk images, noticeable differences among the model outputs are found especially in the high latitude regions. We will show details of these test maps and discuss the issues in determining the radial component of the photospheric magnetic field near the poles and limb.




Formation of MgII lines in solar prominences

Author(s): Petr Heinzel

Institution(s): Astronomical Institute, Academy of Sciences, Czech Republic

Abstract:

Solar prominences have been observed in MgII h and k lines, both from space (OSO-8) or from stratospheric balloons. Non-LTE modeling of these resonance lines was then performed and the results have been compared to available observations. We briefly review this past effort and present new transfer computations which take into account all details of the MgII line formation under realistic prominence conditions. We estimate the role of MgII lines in radiation cooling of prominence plasmas and show how they affect the radiative relaxation in these structures. Finally, we also demonstrate the diagnostic capabilities of these lines useful for thermodynamic and velocity measurements.




The nature of hydrogen and helium continua in SDO/EVE spectra of solar flares

Author(s): P. Heinzel, E. H. Avrett

Institution(s): Astronomical Institute, Academy of Sciences, Czech Republic; Center for Astrophysics, Cambridge, USA

Abstract:

For selected flare events we present the SDO/EVE spectra of hydrogen and helium resonance continua and compare them with the results of the non-LTE transfer computations based on semi-empirical flare models. We discuss the formation of these continua and their diagnostic potential for determination of the temperature structure of the flaring atmosphere. Non-thermal processes are also considered. As a benchmark we present our comparison of the quiet-Sun EVE spectra with the flux synthesized from the model C6 of Avrett and Loeser (2008).




HMI Magnetic Field Observations

Author(s): J.T. Hoeksema & the HMI Magnetic Field Team

Institution(s): Stanford University

Abstract:

SDO/HMI produces a wide array of full-disk photospheric magnetic field observations on a regular cadence. The current status and procedures to access the line-of-sight, vector, synoptic, synchronic, space weather, and other magnetic images, movies, and data products are described.




What is there before a flare?

Author(s): Hugh S. Hudson

Institution(s): SSL/UC Berkeley

Abstract:

The physical parameters in a region about to flare (or to make a micro-event of any sort) should be of interest to many people, and should be a suitable topic for (serendipitous) IRIS observations. Flaring is associated generally with magnetic fields, but apparently only infrequently with pre-existing coronal structures at high temperatures. This poster reviews what is known and aims at eliciting discussion of what could be observed with IRIS.




Observations and modeling of magnetic reconnection in the coupled solar atmosphere

Author(s): Hiroaki Isobe

Institution(s): Kyoto University

Abstract:

The plasma parameters in the solar atmosphere varies drastically with height. The corona is fully ionized and almost collisionless, the photosphere and chromosphere is partially ionized and fully collisional, and the transition region is a marginal region in terms of collisionality and ionization. These very different regions are dynamically coupled by magnetic fields and waves. It is also interesting that, similarly to terrestrial ionosphere, the ratio of ion-cyclotron frequency and ion-neutral collisional frequency varies with height, giving rise to differnt effects by neutrals such as ambipolar diffusion and Hall effect. Recent observations have shown that magnetic reconnection occurs throughout the solar atmosphere, not only in the fully ionized and collisionless corona but also in the partially ionized and fully collisinal lower atmosphere, in similar mophologies but different scales. Therefore the solar atmosphere can be considered as an unique laboratory for magnetic reconnection in various plasma parameters. In this talk I will review the recent observations and the advances in theoretical modelings of magnetic reconnection in different part of the solar atmosphere.




A preliminary study of the HOP-187 jet analysis

Author(s): Jackson, B. (1), Yu, H.-S. (1), Buffington, A. (1), Clover, J. (1), Shimojo, M. (2), Sako, N. (3)

Institution(s): (1) University of California, San Diego, CA, USA, (2) Nobeyama Solar Radio Observatory, NAOJ, NINS, Japan, (3) Department of Astronomical Science, Sokendai, NAOJ, Japan

Abstract:

The Hinode Observing Proposal (HOP)-187, “Tracking X-ray Jets from the Solar Surface to Interplanetary Space” (Jackson and Shimojo, 2011) was carried out successfully during the summer of 2011. On two occasions (00-06 UT 17 June, 2011, and 00-08 UT 22 August 2011) XRT observations were run at a higher cadence over the south polar region in conjunction with LASCO C2 observations that also provided an enhanced 5-minute cadence and 100-sec exposures from this instrument. This campaign effort was joined by the NASA SDO AIA, the Solar TErrestrial RElations Observatory (STEREO) Coronagraph (COR II) and Heliospheric Imagers (HI’s), ground-based interplanetary scintillation (IPS) observations from the Solar Terrestrial Environment Laboratory (STELab) and Ootacamund (Ooty), India, and finally data from the Solar Mass Ejection Imager (SMEI). In this data analysis, as in previous campaign-mode operations of the Hinode XRT instrument, we find a positive correlation between the brightest of the polar jets and a high-speed response traced into the interplanetary medium. Here, we report on the preliminary measurements of the jet responses that were observed during this successful HOP-187 campaign.




Non-Stationary Deconvolution for the IRIS NUV Slit-Jaw Imager

Author(s): Sarah A. Jaeggli, Charles C. Kankelborg, & The IRIS Team

Institution(s): Montana State University

Abstract:

High spatial resolution context imaging is essential to linking spatial structures with spectral signatures in the chromosphere, a critical part of the science requirements for IRIS (Interface Region Imaging Spectrograph).  Measurements of the optical figure of the Solc filter indicate that the NUV slit-jaw imager on IRIS will have a somewhat broader PSF than the other instrument channels.  We have developed an advanced deconvolution technique which combines measured PSFs sampled over the image plane to achieve the best correction for each pixel.  We have conducted an analysis of this technique on synthetic data, and we assess the quality of the resulting images containing a variety of simulated effects, including cosmic ray hits, photon counting noise, discrete energetic solar events (flares), and saturation and overflow artifacts.




Diffusivity of Isolated Internetwork Ca II H Bright Points Observed by SuFI/SUNRISE

Author(s): Jafarzadeh, S. (1), Solanki, S. K. (1), Cameron, R. H. (1), Feller A. (1), Pietarila, A. (2), Lagg, A. (1), Barthol, P. (1), Berkefeld, T. (3), Gandorfer, A. (1), Knoelker, M. (4), Martinez Pillet, V. (5), Schmidt, W. (3), and Title, A. (6)

Institution(s): (1) Max-Planck-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg- Lindau, Germany, (2) National Solar Observatory, 950 N. Cherry Avenue, Tucson, Az 85719, USA, (3) Kiepenheuer-Institut fuer Sonnenphysik, Schoeneckstr. 6, 79104 Freiburg, Germany, (4) High Altitude Observatory, NCAR, 3080 Center Green, Boulder, CO 80301, USA, (5) Instituto de Astrofisica de Canarias, C/Via L tea, s/n 38205, La Laguna, E-38200 Tenerife, Spain, (6) Lockheed-Martin Solar and Astrophysics Lab., 3251 Hanover St., Palo Alto, CA 94304, USA

Abstract:

We analyze trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to obtain their diffusivity behaviors. We use high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager (SuFI) on board the SUNRISE balloon-borne solar observatory. In order to avoid misidentification, the BPs are semi-manually selected and then automatically tracked. The trajectory of each BP is then calculated and its diffusion index is described by a power law exponent, using which we classify the BPs' trajectories into sub-, normal and super- diffusive. In addition, the corresponding diffusion coefficients (D) based on the observed displacements are consequently computed. We find a strong super-diffusivity at a height sampled by the SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to the temperature minimum). We find that 74% of the identified tiny BPs are super-diffusive, 18% move randomly (i.e. their motion corresponds to normal diffusion) and only 8% belong to the sub-diffusion regime. In addition, we find that 53% of the super-diffusion regime (i.e. 39% of all BPs) have the diffusivity index of 2 which are termed as "Ballistic BPs". Finally, we explore the distribution of diffusion index with the help of a simple simulation. The results suggest that the BPs are random walkers superposed by a systematic (background) velocity in which the magnitude of each component (and hence their ratio) depends on the time and spatial scales. We further discuss a simple sketch to explain the diffusivity of observed BPs while they migrate within a supergranule (i.e. internetwork areas) or close to the network regions.





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Last Updated on Tuesday, 24 January 2012 13:45