Search Publications
Ring-diagram parameter comparisons for GONG, MDI and HMI
Howe, R.; Komm, R.; Hill, F. +4 more
We examine the differences between ring-diagram mode frequency estimates from samples of Global Oscillation Network Group [GONG], Michelson Doppler Imager [MDI] and Helioseismic and Magnetic Imager [HMI] data, and find that different instruments and analysis pipelines do result in small systematic differences which may not be uniform across the so…
Effect of heavy ions on coupling between density structures and electromagnetic waves in the auroral zone
Streltsov, A. V.
This paper presents the results from a numerical study of the effects of multiple ion species on the development of small-scale, intense electromagnetic waves and density structures that are frequently observed in the auroral ionosphere in the vicinity of discrete auroral arcs. The study is based on a multifluid MHD model describing nonlinear coup…
THEMIS observations of double-onset substorms and their association with IMF variations
Russell, C. T.; Glassmeier, K. -H.; Baumjohann, W. +3 more
On 16 July 2008, two pairs of consecutive bursts of Pi2 pulsations were recorded simultaneously across the THEMIS ground-based observatory system. Wavelet transformation reveals that for each high-latitude pair, the dominant frequency of the first burst is higher than that of the second. But at low latitudes, the dominant frequency does not change…
Integrating advanced visualization technology into the planetary Geoscience workflow
Dickson, James; Huffman, John; Forsberg, Andrew +3 more
Recent advances in computer visualization have allowed us to develop new tools for analyzing the data gathered during planetary missions, which is important, since these data sets have grown exponentially in recent years to tens of terabytes in size. As part of the Advanced Visualization in Solar System Exploration and Research (ADVISER) project, …
Mid-infrared lightcurve of Vesta
Sykes, M. V.; Tedesco, E. F.; Chamberlain, M. A.
We present a thermal mid-infrared lightcurve of Asteroid 4 Vesta and use this to infer variations in thermophysical properties over the surface. Vesta was observed over three nights during the May 2007 opposition with the Infrared Telescope Facility on Mauna Kea. Mid-infrared observations are compared to a model based on the Standard Thermal Model…
Regular Versus Diffusive Photospheric Flux Cancellation
Litvinenko, Yuri E.
Observations of photospheric flux cancellation on the Sun imply that cancellation can be a diffusive rather than regular process. A criterion is derived, which quantifies the parameter range in which diffusive photospheric cancellation should occur. Numerical estimates show that regular cancellation models should be expected to give a quantitative…
Whistler-Langmuir oscillitons and their relation to auroral hiss
Sauer, K.; Sydora, R. D.
A new type of oscilliton (soliton with superimposed spatial oscillations) is described which arises in plasmas if the electron cyclotron frequency Ωe is larger than the electron plasma frequency ωe, which is a typical situation for auroral regions in planetary magnetospheres. Both high-frequency modes of concern, the Langmuir…
Corrections to the Magnitude of Cross-Correlation Functions for Dispersion of Solar Acoustic Waves
Zhao, Hui; Liang, Zhi-Chao; Chou, Dean-Yi +2 more
The cross-correlation function is a useful tool in helioseismology. The magnitude of the cross-correlation function has been used to represent the power of wave packets. Dispersion causes a decrease in amplitude and an increase in width of wave packets. This leads to a decrease in magnitude and an increase in width of cross-correlation functions. …
Does NGC 5408 X-1 really contain an intermediate-mass black hole?
Done, C.; Roberts, T. P.; Middleton, M. J. +1 more
NGC 5408 X-1 is one of only a handful of ultraluminous X-ray sources (ULXs) to demonstrate a strong quasi-periodic oscillation (QPO) in its lightcurve. This has been interpreted as being analogous to the type C low-frequency QPO seen in black hole binaries (BHBs) when accreting at sub-Eddington rates, implying an intermediate-mass black hole (IMBH…
Contemporaneous XMM-Newton Investigation of a Giant X-ray Flare and Quiescent State from a Cool M-Class Dwarf in the Local Cavity
Gupta, A.; Williams, B.; Galeazzi, M.
We report the serendipitous detection of a giant X-ray flare from the source 2XMM J043527.2-144301 during an XMM-Newton observation of the high latitude molecular cloud MBM20. The source has not been previously studied at any wavelength. The X-ray flux increases by a factor of more than 52 from quiescent state to peak of flare. A 2MASS counterpart…