Author name code: meyer-karen ADS astronomy entries on 2022-09-14 author:"Meyer, Karen A." ------------------------------------------------------------------------ Title: Defining the Middle Corona Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.; Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski, Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.; Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee, Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs, Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason, Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler, Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina; Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2022arXiv220804485W Altcode: The middle corona, the region roughly spanning heliocentric altitudes from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. Eruptions that could disrupt the near-Earth environment propagate through it. Importantly, it modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, this region is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the middle corona has been poorly studied by major solar remote sensing missions and instruments, extending back to the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions it covers, and the underlying physics believed to be encapsulated by the region. This paper aims to define the middle corona and give an overview of the processes that occur there. Title: The Effect of Internal Gravity Waves on Cloud Evolution in Substellar Atmospheres Authors: Parent, Amy; Falconer, Ruth E.; Meyer, Karen A.; Stark, Craig R. Bibcode: 2021csss.confE.147P Altcode: Substellar objects exhibit photometric variability which is believed to be caused by a number of processes such as magnetically-driven spots or inhomogeneous cloud coverage. Recent substellar models have shown that turbulent flows and waves, including internal gravity waves, may play an important role in dust cloud evolution. The aim of this paper is to investigate the effect of internal gravity waves on dust cloud nucleation and dust growth, and whether observations of the resulting cloud structures could be used to recover atmospheric density information. For a simplified atmosphere in two dimensions, we numerically solve the governing fluid equations to simulate the effect on dust nucleation and mantle growth as a result of the passage of an internal gravity wave. Furthermore, we derive an expression that relates the properties of the wave-induced cloud structures to observable parameters in order to deduce the atmosphere density. Numerical simulations show that the density, pressure and temperature variations caused by gravity waves lead to an up to 20-fold increase of the dust nucleation rate and an up to 80% increase of the dust growth rate in the linear regime. These variations lead to banded areas in which dust formation is much more pronounced. We show that internal gravity waves in substellar atmospheres lead to banded cloud structures similar to those observed on Earth. Using the proposed method, potential observations of banded clouds could be used to estimate the atmospheric density of substellar objects. Title: Investigation of the Middle Corona with SWAP and a Data-Driven Non-Potential Coronal Magnetic Field Model Authors: Meyer, Karen A.; Mackay, Duncan H.; Talpeanu, Dana-Camelia; Upton, Lisa A.; West, Matthew J. Bibcode: 2020SoPh..295..101M Altcode: 2020arXiv200702668M The large field-of-view of the Sun Watcher using Active Pixel System detector and Image Processing (SWAP) instrument onboard the PRoject for Onboard Autonomy 2 (PROBA2) spacecraft provides a unique opportunity to study extended coronal structures observed in the EUV in conjunction with global coronal magnetic field simulations. A global non-potential magnetic field model is used to simulate the evolution of the global corona from 1 September 2014 to 31 March 2015, driven by newly emerging bipolar active regions determined from Helioseismic and Magnetic Imager (HMI) magnetograms. We compare the large-scale structure of the simulated magnetic field with structures seen off-limb in SWAP EUV observations. In particular, we investigate how successful the model is in reproducing regions of closed and open structures, the scale of structures, and compare the evolution of a coronal fan observed over several rotations. The model is found to accurately reproduce observed large-scale, off-limb structures. When discrepancies do arise they mainly occur off the east solar limb due to active regions emerging on the far side of the Sun, which cannot be incorporated into the model until they are observed on the Earth-facing side. When such "late" active region emergences are incorporated into the model, we find that the simulated corona self-corrects within a few days, so that simulated structures off the west limb more closely match what is observed. Where the model is less successful, we consider how this may be addressed, through model developments or additional observational products. Title: The effect of internal gravity waves on cloud evolution in sub-stellar atmospheres Authors: Parent, A.; Falconer, R. E.; Lee, E. K. H.; Meyer, K. A.; Stark, C. R. Bibcode: 2020A&A...635A.159P Altcode: 2020arXiv200210379P Context. Sub-stellar objects exhibit photometric variability, which is believed to be caused by a number of processes, such as magnetically-driven spots or inhomogeneous cloud coverage. Recent sub-stellar models have shown that turbulent flows and waves, including internal gravity waves, may play an important role in cloud evolution.
Aims: The aim of this paper is to investigate the effect of internal gravity waves on dust nucleation and dust growth, and whether observations of the resulting cloud structures could be used to recover atmospheric density information.
Methods: For a simplified atmosphere in two dimensions, we numerically solved the governing fluid equations to simulate the effect on dust nucleation and mantle growth as a result of the passage of an internal gravity wave. Furthermore, we derived an expression that relates the properties of the wave-induced cloud structures to observable parameters in order to deduce the atmospheric density.
Results: Numerical simulations show that the density, pressure, and temperature variations caused by gravity waves lead to an increase of the dust nucleation rate by up to a factor 20, and an increase of the dust mantle growth rate by up to a factor 1.6, compared to their equilibrium values. Through an exploration of the wider sub-stellar parameter space, we show that in absolute terms, the increase in dust nucleation due to internal gravity waves is stronger in cooler (T dwarfs) and TiO2-rich sub-stellar atmospheres. The relative increase, however, is greater in warm (L dwarf) and TiO2-poor atmospheres due to conditions that are less suited for efficient nucleation at equilibrium. These variations lead to banded areas in which dust formation is much more pronounced, similar to the cloud structures observed on Earth.
Conclusions: We show that internal gravity waves propagating in the atmosphere of sub-stellar objects can produce banded clouds structures similar to that observed on Earth. We propose a method with which potential observations of banded clouds could be used to estimate the atmospheric density of sub-stellar objects. Title: The effect of internal gravity waves on cloud evolution in sub-stellar atmospheres Authors: Parent, Amy; Falconer, Ruth; Meyer, Karen; Stark, Craig R. Bibcode: 2019ESS.....432910P Altcode: Substellar objects exhibit photometric variability which is believed to be caused by a number of processes such as magnetically-driven spots or inhomogeneous cloud coverage. Recent substellar models have shown that turbulent flows and waves, including internal gravity waves, may play an important role in dust cloud evolution. The aim of this paper is to investigate the effect of internal gravity waves on dust cloud nucleation and dust growth, and whether observations of the resulting cloud structures could be used to recover atmospheric density information. For a simplified atmosphere in two dimensions, we numerically solve the governing fluid equations to simulate the effect on dust nucleation and mantle growth as a result of the passage of an internal gravity wave. Furthermore, we derive an expression that relates the properties of the wave-induced cloud structures to observable parameters in order to deduce the atmosphere density. Numerical simulations show that the density, pressure and temperature variations caused by gravity waves lead to an up to 600-fold increase of the dust nucleation rate and an up to 80% increase of the dust growth rate in the linear regime. These variations lead to banded areas in which dust formation is much more pronounced. We show that internal gravity waves in substellar atmospheres lead to banded cloud structures similar to those observed on Earth. Using the proposed method, potential observations of banded clouds could be used to estimate the atmospheric density of substellar objects. Title: Nonlinear Force-free Field Modeling of Solar Coronal Jets in Theoretical Configurations Authors: Meyer, K. A.; Savcheva, A. S.; Mackay, D. H.; DeLuca, E. E. Bibcode: 2019ApJ...880...62M Altcode: Coronal jets occur frequently on the Sun, and may contribute significantly to the solar wind. With the suite of instruments available now, we can observe these phenomena in greater detail than ever before. Modeling and simulations can assist further with understanding the dynamic processes involved, but previous studies tended to consider only one mechanism (e.g., emergence or rotation) for the origin of the jet. In this study we model a series of idealized archetypal jet configurations and follow the evolution of the coronal magnetic field. This is a step toward understanding these idealized situations before considering their observational counterparts. Several simple situations are set up for the evolution of the photospheric magnetic field: a single parasitic polarity rotating or moving in a circular path; as well as opposite polarity pairs involved in flyby (shearing), cancellation or emergence; all in the presence of a uniform, open background magnetic field. The coronal magnetic field is evolved in time using a magnetofrictional relaxation method. While magnetofriction cannot accurately reproduce the dynamics of an eruptive phase, the structure of the coronal magnetic field, as well as the buildup of electric currents and free magnetic energy are instructive. Certain configurations and motions produce a flux rope and allow the significant buildup of free energy, reminiscent of the progenitors of so-called blowout jets, whereas other, simpler configurations are more comparable to the standard jet model. The next stage is a comparison with observed coronal jet structures and their corresponding photospheric evolution. Title: The Role of Small-Scale Processes in Solar Active Region Decay Authors: Meyer, Karen; Mackay, Duncan Bibcode: 2017SPD....4810106M Altcode: Active regions are locations of intense magnetic activity on the Sun, whose evolution can result in highly energetic eruptive phenomena such as solar flares and coronal mass ejections (CMEs). Therefore, fast and accurate simulation of their evolution and decay is essential in the prediction of Space Weather events. In this talk we present initial results from our new model for the photospheric evolution of active region magnetic fields. Observations show that small-scale processes appear to play a role in the dispersal and decay of solar active regions, for example through cancellation at the boundary of sunspot outflows and erosion of flux by surrounding convective cells. Our active region model is coupled to our existing model for the evolution of small-scale photospheric magnetic features. Focusing first on the active region decay phase, we consider the evolution of its magnetic field due to both large-scale (e.g. differential rotation) and small-scale processes, such as its interaction with surrounding small-scale magnetic features and convective flows.This project is funded by The Carnegie Trust for the Universities of Scotland, through their Research Incentives Grant scheme. Title: Solar Coronal Jets: Observations, Theory, and Modeling Authors: Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.; Meyer, K.; Dalmasse, K.; Matsui, Y. Bibcode: 2016SSRv..201....1R Altcode: 2016arXiv160702108R; 2016SSRv..tmp...31R Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of "nominal" solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broad range of solar-heliospheric problems. Title: Modeling the Sun’s Small-scale Global Photospheric Magnetic Field Authors: Meyer, K. A.; Mackay, D. H. Bibcode: 2016ApJ...830..160M Altcode: We present a new model for the Sun’s global photospheric magnetic field during a deep minimum of activity, in which no active regions emerge. The emergence and subsequent evolution of small-scale magnetic features across the full solar surface is simulated, subject to the influence of a global supergranular flow pattern. Visually, the resulting simulated magnetograms reproduce the typical structure and scale observed in quiet Sun magnetograms. Quantitatively, the simulation quickly reaches a steady state, resulting in a mean field and flux distribution that are in good agreement with those determined from observations. A potential coronal magnetic field is extrapolated from the simulated full Sun magnetograms to consider the implications of such a quiet photospheric magnetic field on the corona and inner heliosphere. The bulk of the coronal magnetic field closes very low down, in short connections between small-scale features in the simulated magnetic network. Just 0.1% of the photospheric magnetic flux is found to be open at 2.5 R ⊙, around 10-100 times less than that determined for typical Helioseismic and Magnetic Imager synoptic map observations. If such conditions were to exist on the Sun, this would lead to a significantly weaker interplanetary magnetic field than is currently observed, and hence a much higher cosmic ray flux at Earth. Title: The Sun's Magnetic Field During a Grand Minimum of Activity Authors: Meyer, Karen; Mackay, Duncan Bibcode: 2014AAS...22411205M Altcode: During a grand minimum of solar activity, no sunspots are observed on the photosphere, but what might the Sun's magnetic field look like? One possibility is that there would be no active regions or larger scale magnetic activity. We have extended our photospheric model for small-scale magnetic flux evolution to cover the full Sun. As an initial study, we consider how the surface magnetic field of the Sun would look if only smaller-scale magnetic features were allowed to emerge. We also consider the resultant coronal and inner heliospheric magnetic fields, and discuss potential consequences of such fields for Earth. Title: Analyzing an IRIS Blowout jet via Magnetofrictional Simulation Authors: Savcheva, Antonia; Tian, Hui; Meyer, Karen Bibcode: 2014AAS...22432310S Altcode: The imaging spectrograph, IRIS, offers unprecedented spatial and temporal resolution of small-scale phenomena, which allows the study of their spectral properties in the chromosphere and transition region. This study present IRIS observations of a blowout coronal jet, demonstrating the ability of IRIS to detect reconnection effects in the low atmosphere in the available suite of spectral lines. We present Doppler velocity and non-thermal width (NTW) maps of the jet and their evolution in time. We interpret the results using MHD simulations of jets. In addition, we present a data-driven magnetofrictional simulation of the same jet and match the magnetic and current structure of the jet to the observed NTW maps. We infer the height of the null point and the extent of the region showing reconnection effects. We discuss the implications of understanding reconnection effects in conjunction with NTW maps. Title: Data-constrained Magnetofrcitional Simulation of a Flux Rope Build-up in a Sigmoidal Active Region Authors: Savcheva, Antonia Stefanova; Mackay, D.; Meyer, K.; Gibb, G.; DeLuca, E. Bibcode: 2014shin.confE...3S Altcode: We present a data-constrained magnetofrictional (MF) simulation of the evolution over two days of the sigmoidal active region from 6-7 Dec 2007. The lower boundary condition is supplied by a series of line-of-sight (LoS) namgnetograms from MDI, but for the first time the initial condition is taken from a data-constrained non-linear force-free (NLFFF) model of the active region early on Dec 6. The NLFFF model is produced with the flux rope insertion method and is constrained by a LoS magnetogram, filament path from STEREO, and coronal loops from XRT. The initial condition is that of a sheared arcade and as time progresses the photospheric evolution builds a flux rope, which becomes unstable a few hours before the actual observed eruption. We show field lines and current density distributions over time and compare them to XRT images. We present the evolution of the free and potential energy and relative helicity in the region. We compare our results to a previous a simulation starting from a potential field as initial condition. Title: Simulating the Formation of a Sigmoidal Flux Rope in AR10977 from SOHO/MDI Magnetograms Authors: Gibb, G. P. S.; Mackay, D. H.; Green, L. M.; Meyer, K. A. Bibcode: 2014ApJ...782...71G Altcode: The modeling technique of Mackay et al. is applied to simulate the coronal magnetic field of NOAA active region AR10977 over a seven day period (2007 December 2-10). The simulation is driven with a sequence of line-of-sight component magnetograms from SOHO/MDI and evolves the coronal magnetic field though a continuous series of non-linear force-free states. Upon comparison with Hinode/XRT observations, results show that the simulation reproduces many features of the active region's evolution. In particular, it describes the formation of a flux rope across the polarity inversion line during flux cancellation. The flux rope forms at the same location as an observed X-ray sigmoid. After five days of evolution, the free magnetic energy contained within the flux rope was found to be 3.9 × 1030 erg. This value is more than sufficient to account for the B1.4 GOES flare observed from the active region on 2007 December 7. At the time of the observed eruption, the flux rope was found to contain 20% of the active region flux. We conclude that the modeling technique proposed in Mackay et al.—which directly uses observed magnetograms to energize the coronal field—is a viable method to simulate the evolution of the coronal magnetic field. Title: Solar Magnetic Carpet III: Coronal Modelling of Synthetic Magnetograms Authors: Meyer, K. A.; Mackay, D. H.; van Ballegooijen, A. A.; Parnell, C. E. Bibcode: 2013SoPh..286..357M Altcode: 2013arXiv1303.1342M This article is the third in a series working towards the construction of a realistic, evolving, non-linear force-free coronal-field model for the solar magnetic carpet. Here, we present preliminary results of 3D time-dependent simulations of the small-scale coronal field of the magnetic carpet. Four simulations are considered, each with the same evolving photospheric boundary condition: a 48-hour time series of synthetic magnetograms produced from the model of Meyer et al. (Solar Phys.272, 29, 2011). Three simulations include a uniform, overlying coronal magnetic field of differing strength, the fourth simulation includes no overlying field. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. In particular, we study their dependence upon the evolution of the photospheric magnetic field and the strength of the overlying coronal field. We also consider where energy is stored and dissipated within the coronal field. The free magnetic energy built up is found to be more than sufficient to power small-scale, transient phenomena such as nanoflares and X-ray bright points, with the bulk of the free energy found to be stored low down, between 0.5 - 0.8 Mm. The energy dissipated is currently found to be too small to account for the heating of the entire quiet-Sun corona. However, the form and location of energy-dissipation regions qualitatively agree with what is observed on small scales on the Sun. Future MHD modelling using the same synthetic magnetograms may lead to a higher energy release. Title: A Non-Linear Force-Free Field Model for the Solar Magnetic Carpet Authors: Meyer, Karen; Mackay, D.; van Ballegooijen, A.; Parnell, C. Bibcode: 2013SPD....4430201M Altcode: The magnetic carpet is defined to be the small-scale photospheric magnetic field of the quiet-Sun. Recent high resolution, high cadence observations have shown that although small-scale, the magnetic carpet is far from 'quiet', it is continually evolving in a complex and dynamic manner. I will present a two-component model for the dynamic evolution of the Sun's magnetic carpet. The first component is a 2D model for the photospheric evolution of the small-scale solar magnetic field, that reproduces many observed parameters. The basic evolution of magnetic elements within the model is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. The synthetic magnetograms produced by the 2D model are then applied as photospheric boundary data to drive the continuous evolution of a 3D non-linear force-free coronal field. We studied the resultant complex, small-scale coronal magnetic field, in particular the energetics of the field. Title: The Storage and Dissipation of Magnetic Energy in the Quiet Sun Corona Determined from SDO/HMI Magnetograms Authors: Meyer, K. A.; Sabol, J.; Mackay, D. H.; van Ballegooijen, A. A. Bibcode: 2013ApJ...770L..18M Altcode: In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona. Title: High-resolution wide-band fast Fourier transform spectrometers Authors: Klein, B.; Hochgürtel, S.; Krämer, I.; Bell, A.; Meyer, K.; Güsten, R. Bibcode: 2012A&A...542L...3K Altcode: 2012arXiv1203.3972K We describe the performance of our latest generations of sensitive wide-band high-resolution digital fast Fourier transform spectrometer (FFTS). Their design, optimized for a wide range of radio astronomical applications, is presented. Developed for operation with the GREAT far infrared heterodyne spectrometer on-board SOFIA, the eXtended bandwidth FFTS (XFFTS) offers a high instantaneous bandwidth of 2.5 GHz with 88.5 kHz spectral resolution and has been in routine operation during SOFIA's Basic Science since July 2011. We discuss the advanced field programmable gate array (FPGA) signal processing pipeline, with an optimized multi-tap polyphase filter bank algorithm that provides a nearly loss-less time-to-frequency data conversion with significantly reduced frequency scallop and fast sidelobe fall-off. Our digital spectrometers have been proven to be extremely reliable and robust, even under the harsh environmental conditions of an airborne observatory, with Allan-variance stability times of several 1000 s. An enhancement of the present 2.5 GHz XFFTS will duplicate the number of spectral channels (64k), offering spectroscopy with even better resolution during Cycle 1 observations. Title: Solar Magnetic Carpet II: Coronal Interactions of Small-Scale Magnetic Fields Authors: Meyer, K. A.; Mackay, D. H.; van Ballegooijen, A. A. Bibcode: 2012SoPh..278..149M Altcode: 2012arXiv1211.3924M This paper is the second in a series of studies working towards constructing a realistic, evolving, non-potential coronal model for the solar magnetic carpet. In the present study, the interaction of two magnetic elements is considered. Our objectives are to study magnetic energy build-up, storage and dissipation as a result of emergence, cancellation, and flyby of these magnetic elements. In the future these interactions will be the basic building blocks of more complicated simulations involving hundreds of elements. Each interaction is simulated in the presence of an overlying uniform magnetic field, which lies at various orientations with respect to the evolving magnetic elements. For these three small-scale interactions, the free energy stored in the field at the end of the simulation ranges from 0.2 - 2.1×1026 ergs, whilst the total energy dissipated ranges from 1.3 - 6.3×1026 ergs. For all cases, a stronger overlying field results in higher energy storage and dissipation. For the cancellation and emergence simulations, motion perpendicular to the overlying field results in the highest values. For the flyby simulations, motion parallel to the overlying field gives the highest values. In all cases, the free energy built up is sufficient to explain small-scale phenomena such as X-ray bright points or nanoflares. In addition, if scaled for the correct number of magnetic elements for the volume considered, the energy continually dissipated provides a significant fraction of the quiet Sun coronal heating budget. Title: A non-linear force-free field model for the solar magnetic carpet Authors: Meyer, Karen A. Bibcode: 2012PhDT.......460M Altcode: The magnetic carpet is defined to be the small-scale photospheric magnetic field of the quiet Sun. Observations of the magnetic carpet show it to be highly dynamic, where the time taken for all flux within the magnetic carpet to be replaced is on the order of just a few hours. The magnetic carpet is continually evolving due to the Sun's underlying convection and the interaction of small-scale magnetic features with one another. Due to this, the small-scale coronal field of the magnetic carpet is also expected to be highly dynamic and complex. Previous modelling has shown that much of the flux from the magnetic carpet is stored along low-lying closed connections between magnetic features. This indicates that significant coronal heating could occur low down in the small-scale corona. In this thesis, a new two-component magnetic field model is developed for the evolution of the magnetic carpet. A 2D model is constructed to realistically simulate the evolution of the photospheric field of the magnetic carpet, where many of the parameters for the model are taken from observational studies. The photospheric model contains a granular and supergranular flow profile to describe the motion of the small-scale magnetic features, and includes the processes of flux emergence, cancellation, coalescence and fragmentation. This 2D model then couples to a 3D model as the lower boundary condition, which drives the evolution of the coronal field through a series of non-linear force-free states, via a magnetofrictional relaxation technique. We first apply the magnetofrictional technique to consider the coronal evolution of three basic small-scale photospheric processes: emergence, cancellation and flyby. We consider the interaction of the magnetic features with an overlying coronal magnetic field, and quantify magnetic energy build-up, storage and dissipation. The magnetofrictional technique is then applied to synthetic magnetograms produced from the 2D model, to simulate the evolution of the coronal field in a situation involving many hundreds of magnetic features. We conduct a preliminary analysis of the resultant 3D simulations, considering the magnetic energy stored and dissipated, as well as regions of enhanced velocity and electric current density within the coronal volume. The simulations show that the so-called 'quiet Sun' is not quiet and a significant amount of complex interactions take place. Title: A non-linear force-free field model for the solar magnetic carpet Authors: Meyer, Karen Alison Bibcode: 2012PhDT.......542M Altcode: No abstract at ADS Title: Solar Magnetic Carpet I: Simulation of Synthetic Magnetograms Authors: Meyer, K. A.; Mackay, D. H.; van Ballegooijen, A. A.; Parnell, C. E. Bibcode: 2011SoPh..272...29M Altcode: 2011SoPh..tmp..294M; 2011SoPh..tmp..198M; 2011SoPh..tmp..319M; 2011SoPh..tmp..267M; 2011arXiv1108.1080M This paper describes a new 2D model for the photospheric evolution of the magnetic carpet. It is the first in a series of papers working towards constructing a realistic 3D non-potential model for the interaction of small-scale solar magnetic fields. In the model, the basic evolution of the magnetic elements is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. Model parameters for the emergence of bipoles are based upon the results of observational studies. Using this model, several simulations are considered, where the range of flux with which bipoles may emerge is varied. In all cases the model quickly reaches a steady state where the rates of emergence and cancellation balance. Analysis of the resulting magnetic field shows that we reproduce observed quantities such as the flux distribution, mean field, cancellation rates, photospheric recycle time and a magnetic network. As expected, the simulation matches observations more closely when a larger, and consequently more realistic, range of emerging flux values is allowed (4×1016 - 1019 Mx). The model best reproduces the current observed properties of the magnetic carpet when we take the minimum absolute flux for emerging bipoles to be 4×1016 Mx. In future, this 2D model will be used as an evolving photospheric boundary condition for 3D non-potential modeling. Title: Fast Fourier Transform Spectrometer Authors: Klein, B.; Krämer, I.; Hochgürtel, S.; Güsten, R.; Bell, A.; Meyer, K.; Chetik, V. Bibcode: 2009stt..conf..199K Altcode: No abstract at ADS Title: Submillimeter heterodyne arrays for APEX Authors: Güsten, R.; Baryshev, A.; Bell, A.; Belloche, A.; Graf, U.; Hafok, H.; Heyminck, S.; Hochgürtel, S.; Honingh, C. E.; Jacobs, K.; Kasemann, C.; Klein, B.; Klein, T.; Korn, A.; Krämer, I.; Leinz, C.; Lundgren, A.; Menten, K. M.; Meyer, K.; Muders, D.; Pacek, F.; Rabanus, D.; Schäfer, F.; Schilke, P.; Schneider, G.; Stutzki, J.; Wieching, G.; Wunsch, A.; Wyrowski, F. Bibcode: 2008SPIE.7020E..10G Altcode: We report on developments of submillimeter heterodyne arrays for high resolution spectroscopy with APEX. Shortly, we will operate state-of-the-art instruments in all major atmospheric windows accessible from Llano de Chajnantor. CHAMP+, a dual-color 2×7 element heterodyne array for operation in the 450 μm and 350 μm atmospheric windows is in operation since late 2007. With its state-of-the-art SIS detectors and wide tunable local oscillators, its cold optics with single sideband filters and with 3 GHz of processed IF bandwidth per pixel, CHAMP+ does provide outstanding observing capabilities. The Large APEX sub-Millimeter Array (LAsMA) is in the final design phase, with an installation goal in 2009. The receiver will operate 7 and 19 pixels in the lower submillimeter windows, 285-375 GHz and 385-520 GHz, respectively. The front-ends are served by an array of digital wideband Fast Fourier Transform spectrometers currently processing up to 32×1.5 (optionally 1.8) GHz of bandwidth. For CHAMP+, we process 2.8 GHz of instantaneous bandwidth (in 16.4 k channels) for each of the 14 pixels. Title: CHAMP: A powerful submm Heterodyne Array Authors: Kasemann, C.; Heyminck, S.; Bell, A.; Belloche, A.; Castenholz, C.; Güsten, R.; Hafok, H.; Henseler, A.; Hochgürtel, S.; Klein, B.; Klein, T.; Krämer, I.; Korn, A.; Meyer, K.; Muders, D.; Pacek, F.; Schäafer, F.; Schneider, G.; Wieching, G.; Baryshev, A.; Hesper, R.; Zijlstra, T.; Lodewijk, C. F. J.; Klapwijk, T. M. Bibcode: 2008stt..conf..166K Altcode: No abstract at ADS Title: Minor Planet Observations [671 Stony Ridge] Authors: Brewster, S. C.; Hoff, J. M.; Sable, P. K.; Hadlen, D.; Martin, S.; Meyer, K.; Sable, P.; Sloman, C.; Sousa, J.; Sousa, L. Bibcode: 2004MPC..52895...6B Altcode: No abstract at ADS Title: Sun-Earth Day 2004: Venus Transit Authors: Thieman, J. R.; Odenwald, S.; Cline, T.; Lewis, E.; Mayo, L.; Ng, C.; Meyer, K. Bibcode: 2003AGUFMED12E..02T Altcode: The NASA Sun-Earth Connection Education Forum annually promotes an event called Sun-Earth Day. For Sun-Earth Day 2004 SECEF has selected the transit of Venus as the theme. Opportunities are available to prepare for the viewing of this event. The event last occurred in 1882, so no one alive today has ever witnessed the transit of Venus. Through parallax measurements, it allowed astronomers to define, for the first time, a fairly accurate number for the A.U. and therefore, the distance to all the other known planets. The website http://sunearth.gsfc.nasa.gov/sunearthday has been developed to provide the necessary resources and opportunities for participation in Sun-Earth Day. This is the fourth year that we offer new and exciting space science. This year in particular the content area crosses all of space sciences offering activities and resources for every classroom and museum event. The goal is to involve as much of the student population and the public in this event as possible and to help them understand the immense importance and excitement surrounding this and previous transits. Through engaging activities focused on US and world history, technology, math, and astronomy, classrooms and museums can create their own event or participate in one of the opportunities we make available. Comparisons of Venus with the Earth and Mars, calculations of the distances to nearby stars, and the use of transits to identify extra-solar planets will all add to the excitement of this cosmic occurrence. Title: Space Science Education Resource Directory Authors: Betrue, R.; Miner, E.; Lowes, L.; Meyer, K.; Rosendhal, J.; Morrow, C. Bibcode: 2000DPS....32.6541B Altcode: 2000BAAS...32.1647B One of the more difficult tasks facing educators (and others involved in education and public outreach) is that of identifying, finding, and accessing existing NASA science resources that meet their specific needs. NASA's OSS EPO Support Network has assembled a NASA Space Science Education resource Directory to assist interested individuals (including planetary scientists) to identify and download desired electronic products funded by NASA. This presentation will describe and demonstrate the system, which was unveiled in early October 2000 through a NASA Press Release; the Resource Directory is located at URL http://teachspacescience.stsci.edu. We are investigating solutions to the difficult issue of efficient distribution of hard copy resources. We hope to have a live computer demonstration of the Directory at the NASA Space Science EPO booth at the Conference. Comments and feedback on the Directory structure and contents will be solicited and welcome. Title: The Sun-Earth Connection Education Forum -Helping NASA Missions and Scientists Participate in Education and Public Outreach Authors: Hawkins, I.; Vondrak, R.; Meyer, K.; Thieman, J. Bibcode: 1999AAS...194.7021H Altcode: 1999BAAS...31..941H The Sun-Earth Connection Education Forum (SECEF) is one of four national centers of space science education and outreach funded by NASA's Office of Space Science (OSS). SECEF acts as a central clearinghouse of information and coordination, facilitating the effective archiving and dissemination of education and public outreach materials from NASA SEC missions and scientists. SECEF also helps coordinate participation of SEC missions at national education conferences, such as the National Science Teachers Association and the Association of Science and Technology Centers. SECEF is working with the other three OSS theme Education Forums (Solar System Exploration, Origins, and Structure and Evolution of the Universe) to develop an on-line resource directory for EPO products for teachers and the general public. SECEF is also leveraging high visibility public events, such as the 1998 Total Solar Eclpise Webcast in partnership with the Exploratorium museum, to highlight SEC research and the people responsible for the science discoveries. Our poster will describe in more detail how SECEF can serve the NASA SEC community in the context of EPO, show a short video of the Eclipse '98 Webcast, and describe how scientists can become involved in the upcoming Eclipse '99 Webcast from the Black Sea and Turkey. This will be the best looking poster at the meeting - don't miss it! Title: CHAMP: the Carbon Heterodyne Array of the MPIfR Authors: Guesten, Rolf; Ediss, Geoffrey A.; Gueth, F.; Gundlach, K. H.; Hauschildt, H.; Kasemann, Christoph; Klein, Thomas; Kooi, Jacob W.; Korn, A.; Kramer, I.; Leduc, Henry G.; Mattes, H.; Meyer, K.; Perchtold, E.; Pilz, M. Bibcode: 1998SPIE.3357..167G Altcode: A 16-element SIS heterodyne array for operation in the 625 micrometer atmospheric window is under development at the MPIfR. The array consists of 2 X 8 elements with closest feasible spacing of the pixels on the sky ((root)2 (DOT) (Theta) (subscript mb)). The L.O. tuning range covers the astronomically important CI and the CO(4-3) transitions, and an IF bandwidth of 2 GHz (1200 kms(superscript -1)) will permit mapping of extragalactic systems. For best system sensitivity the design allows for cold optics ( 15K) and single-sideband operation. The frontend will be linked to a flexible autocorrelator, with a maximum bandwidth of 2 GHz (2048 channels) for each of the 16 modules. In the high-resolution mode, 500 MHz of bandwidth can be operated with 8192 channels of 61 kHz spectral resolution. System components are currently undergoing final integration and critical evaluation in our laboratories. First astronomical commissioning is scheduled for later this year. The sensitivity expected with CHAMP, for e.g. carbon studies, will be unparalleled. With the full array in SSB operation the mapping speed will be enhanced by a factor of 50 - 100 compared to current single-pixel detectors. Title: Molecular gas in the Galactic center region. I. Data from a large scale C18O(J = 1-->0) survey Authors: Dahmen, G.; Huettemeister, S.; Wilson, T. L.; Mauersberger, R.; Linhart, A.; Bronfman, L.; Tieftrunk, A. R.; Meyer, K.; Wiedenhoever, W.; Dame, T. M.; Palmer, E. S.; May, J.; Aparici, J.; Mac-Auliffe, F. Bibcode: 1997A&AS..126..197D Altcode: 1997A&AS..125....1D A large scale survey of the Galactic center region in the C18O(J = 1 --> 0) transition is presented. This survey was obtained with the 1.2m Southern Millimeter-Wave Telescope (SMWT) at the Cerro Tololo Interamerican Observatory (CTIO) near La Serena, Chile. It covers the region -1.05d <= l <= +3.6d and -0.9d <= b <= +0.75d with a grid spacing of 9', i.e. the sampling is at full FWHP beamwidth. 357 positions were in total observed. After reviewing the instrumentation of the 1.2m SMWT, the observing techniques, and the methods used in the data reduction, the data of the survey are presented and morphologically described. In addition, data of the HNCO(5_{0,5}-4_{0,4}) line are presented, which was also included in the large bandwidth of the spectrometer. 12CO(1-0) measurements performed for comparison purposes are presented and compared with other 12CO results. The maps of the C18O(1-0) survey demonstrate that there are great differences between the distribution of the optically thin C18O(1-0) emission and the usually optically thick 12CO(1-0) emission. Title: The Molecular Gas in the Galactic Center Region based on C-18 O Measurements Authors: Dahmen, C.; Huttemeister, S.; Wilson, T. L.; Mauersberger, R.; Linhart, A.; Bronfman, L.; Tieftrunk, A. R.; Meyer, K.; Wiedenhover, W.; Dame, T. M.; Palmer, E. S.; May, J.; Aparici, J.; Macauliffe, F. Bibcode: 1996ASPC..102...54D Altcode: 1996gace.conf...54D No abstract at ADS Title: An Innovative Concept for Secondary Batteries Applicable Particularly to Small Satellites Authors: Meyer, K.; Mickan, J.; Kieb, K. Bibcode: 1995ESASP.369..623M Altcode: 1995esp..conf..623M No abstract at ADS Title: A C18O survey of the Galactic center. Authors: Dahmen, G.; Henkel, C.; Hüttemeister, S.; Lemme, C.; Linhart, A.; Mauersberger, R.; Meyer, K.; Tieftrunk, A.; Wiedenhöver, W.; Wilson, T. L.; Aparici, J.; Bronfman, L.; May, J.; Dame, T.; Palmer, S. Bibcode: 1993AGAb....9..162D Altcode: No abstract at ADS Title: A 1 GHz bandwidth acousto-optical spectrometer for airborne submillimetre astronomy Authors: Schwaab, G. W.; Meyer, K.; Roeser, H. P.; van der Wal, P.; Wattenbach, R.; Wiedenhoever, W. Bibcode: 1989JPhE...22..510S Altcode: A modular easily transportable acoustooptical spectrometer (AOS) designed for airborne submillimeter astronomical observations is described. The large bandwidth (992 MHz) of the AOS, combined with high resolution (1.7 MHz), make it possible to observe astronomical transitions within a wide variety of spectral widths. The AOS provides its own data acquisition and handling system, enabling on-line data reduction and a high degree of flexibility. The AOS was flown aboard the Kuiper Airborne Observatory in September 1988. Even in the noisy, shaky, and thermally unstable environment encountered by the AOS its performance was comparable to that in the laboratory. A diagram of the electrooptical part of the AOS is included. Title: Infrared detector arrays with multiplexing cryogenic read-out electronics for ISOPHOT. Authors: Engemann, D.; Faymonville, R.; Felten, R.; Frenzl, O.; Meyer, K.; Sohn, A.; Dierickx, B.; Vermeiren, J. Bibcode: 1989InfPh..29..235E Altcode: Cryogenic Read out Electronic circuits (CRE) are developed in a CMOS technology for the multiplexing operation at temperatures around 4K and below of extrinsic photoconducting detectors and detector arrays of Ge and Si in the Infrared Space Observatory (ISO) instrument ISOPHOT covering a wavelength region between 10-200 μm. Measurements on the 66 elements spectroscopic array ISOPHOT S2 show performance data of an NEP around 4×10-17W/√Hz and a voltage responsivity of 1014V/Ws at low background operation. Title: Tests of low background Si:Ga-Infrared-Detector-Arrays with Cold Multiplexer Readout Circuits Authors: Weitzel, L.; Wolf, J.; Grözinger, U.; Lemke, D.; Raymonville, R.; Frenzl, O.; Meyer, K.; Dierickx, B.; Vermeiren, J. Bibcode: 1989AGAb....3..129W Altcode: No abstract at ADS Title: 2.5. Discussions at the Weil der Stadt symposium Authors: Krafft, F.; Meyer, K.; Sticker, B. Bibcode: 1975VA.....18...53K Altcode: No abstract at ADS Title: Discussion at the Weil der Stadt Symposium. Authors: Krafft, F.; Meyer, K.; Sticker, B. Bibcode: 1975kfhy.conf...53K Altcode: No abstract at ADS Title: Object Lowell Observatory Authors: Esclangon, M. E.; de Grandchamp; Canavaggia; Mineur; Barbier; Baade, W.; Shapley, H.; Leuschner, A. O.; Bower, E. C.; Whipple, F. L.; Meyer Bibcode: 1930IAUC..268....1E Altcode: Observations. In Circulaire No. 8 D (Service des informations rapides) M. E. Esclangon, Director of the observatory Paris, publishes the following observations made at Paris observatory (Equatorial of the Carte du Ciel; observers: de Grandchamp, Canavaggia, Mineur, Barbier; computers: Mineur, Canavaggia, Barbier): 1930 U.T. R.A. (1930.0) Decl. March 26 21h32m5 7 15 31.17 +22 8 17.8 27 21 35.0 7 15 31.09 +22 8 24.4 28 21 44.0 7 15 30.63 +22 8 26.4 31 21 7.0 7 15 30.21 +22 8 40.7 April 3 20 7.0 7 15 30.77 +22 8 50.2 Dr. W. Baade at the observatory Bergedorf sends the following positions: 1930 U.T. R.A. (1930.0) Decl. March 30 19h47m 4s 7 15 30.23 +22 8 33.6 April 3 23 6 20 7 15 30.84 +22 8 48.8 We have received the following telegram from Prof. Shapley: "Leuschner telegraphs preliminary investigation Lowell observatory object by Bower and Whipple results in group of solutions giving approximate present distance forty one astronomical units inclination 17 deg. longitude node 109 deg. Observations chiefly by Meyer Lick Observatory March 16th to April 4th are accurately represented by orbits varying from near circle to parabola with perihelion distance 17 astronomical units." An Observation Circular from the Lowell Observatory of 1930 March 13 gives details about the search for a transneptunian planet, the discovery of the new object on plates of 1930 Jan. 21, 23 and 29 and about the observations since that time.