Search Publications
Application of Mutual Information Methods in Time-Distance Helioseismology
Pevtsov, Alexei A.; Kholikov, Shukur; Keys, Dustin
We apply a new technique, the mutual information (MI) from information theory, to time-distance helioseismology, and demonstrate that it can successfully reproduce several classic results based on the widely used cross-covariance method. MI quantifies the deviation of two random variables from complete independence and represents a more general me…
The Balmer Lines of He II in the Blue Wing of the Hydrogen Lyman α Line Observed in a Quiescent Prominence
Vial, J. -C.; Curdt, W.; Eurin, G.
We revisit the prominence observations in the Lyman α line of Curdt et al. (Astron. Astrophys.511, L4, 2010) and focus on the bump in the blue wing of the line, which we identify with He II Balmer lines. We determine the transition candidates, derive an upper limit for the width of the profile and an associated non-thermal velocity close to 0 km s…
Hinode SOT Plate Scale Reinvestigated by G-Band Images on the 2012 Transit of Venus
Shimizu, T.; Imamura, T.; Nakamura, M. +1 more
The Hinode Solar Optical Telescope (SOT) successfully observed the transit of Venus with an unprecedented high spatial resolution on 5 - 6 June 2012, providing images of the aureole refracted by the atmosphere of Venus and the dark Venus disk against the bright solar surface. The transit of Venus provided a unique opportunity for calibrating the p…
The Interface Region Imaging Spectrograph (IRIS)
Weber, M.; Scherrer, P. H.; Larsen, S. +85 more
The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 - 0.4 arcsec spatial resolution, two-second temporal resolution, and 1 km s−1 velocity resolution over a field-of-view of up to 175 arcsec × 175 arc…
The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance
Liu, Yang; Leka, K. D.; Hayashi, Keiji +9 more
The Helioseismic and Magnetic Imager (HMI) began near-continuous full-disk solar measurements on 1 May 2010 from the Solar Dynamics Observatory (SDO). An automated processing pipeline keeps pace with observations to produce observable quantities, including the photospheric vector magnetic field, from sequences of filtergrams. The basic vector-fiel…
> 25 MeV Proton Events Observed by the High Energy Telescopes on the STEREO A and B Spacecraft and/or at Earth During the First ∼ Seven Years of the STEREO Mission
Christian, E. R.; Leske, R. A.; Labrador, A. W. +7 more
Using observations from the High Energy Telescopes (HETs) on the STEREO A and B spacecraft and similar observations from near-Earth spacecraft, we summarize the properties of more than 200 individual > 25 MeV solar proton events, some detected by multiple spacecraft, that occurred from the beginning of the STEREO mission in October 2006 to Dece…
Multi-Scale Gaussian Normalization for Solar Image Processing
Morgan, Huw; Druckmüller, Miloslav
Extreme ultra-violet images of the corona contain information over a wide range of spatial scales, and different structures such as active regions, quiet Sun, and filament channels contain information at very different brightness regimes. Processing of these images is important to reveal information, often hidden within the data, without introduci…
A Multi-Observatory Inter-Comparison of Line-of-Sight Synoptic Solar Magnetograms
Liu, Y.; Riley, P.; Hoeksema, T. +7 more
The observed photospheric magnetic field is a crucial parameter for understanding a range of fundamental solar and heliospheric phenomena. Synoptic maps, in particular, which are derived from the observed line-of-sight photospheric magnetic field and built up over a period of 27 days, are the main driver for global numerical models of the solar co…
Three-Dimensional Evolution of Flux-Rope CMEs and Its Relation to the Local Orientation of the Heliospheric Current Sheet
Kilpua, E. K. J.; Vourlidas, A.; Isavnin, A.
Flux ropes ejected from the Sun may change their geometrical orientation during their evolution, which directly affects their geoeffectiveness. Therefore, it is crucial to understand how solar flux ropes evolve in the heliosphere to improve our space-weather forecasting tools. We present a follow-up study of the concepts described by Isavnin, Vour…
Photometric and Thermal Cross-calibration of Solar EUV Instruments
Schrijver, C. J.; Testa, P.; Warren, H. +2 more
We present an assessment of the accuracy of the calibration measurements and atomic physics models that go into calculating the SDO/AIA response as a function of wavelength and temperature. The wavelength response is tested by convolving SDO/EVE and Hinode/EIS spectral data with the AIA effective area functions and by comparing the predictions wit…