Search Publications
MAG4 versus alternative techniques for forecasting active region flare productivity
Moore, Ronald L.; Falconer, David A.; Barghouty, Abdulnasser F. +1 more
MAG4 is a technique of forecasting an active region's rate of production of major flares in the coming few days from a free magnetic energy proxy. We present a statistical method of measuring the difference in performance between MAG4 and comparable alternative techniques that forecast an active region's major-flare productivity from alternative o…
Interaction of magnetic reconnection and Kelvin-Helmholtz modes for large magnetic shear: 2. Reconnection trigger
Ma, Xuanye; Otto, Antonius; Delamere, Peter A.
A typical property of magnetopause reconnection is a significant perpendicular shear flow due to the fast streaming magnetosheath plasma. Therefore, the magnetopause represents a large magnetic and flow shear boundary during periods of southward interplanetary magnetic field, which can be unstable to Kelvin-Helmholtz (KH) modes and to magnetic rec…
Properties of Kelvin-Helmholtz waves at the magnetopause under northward interplanetary magnetic field: Statistical study
Wang, Chi; Li, Wenya; Tang, Binbin +3 more
We search the plasma and magnetic field data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes B and C during 2008 and 2009 for observation evidences of the Kelvin-Helmholtz instability (KHI). Fourteen KHI events with rolled-up vortices are identified under the northward interplanetary magnetic field (IMF) …
Abundance stratification in Type Ia supernovae - IV. The luminous, peculiar SN 1991T
Pian, E.; Cappellaro, E.; Benetti, S. +4 more
The abundance distribution of the elements in the ejecta of the peculiar, luminous Type Ia supernova (SN Ia) 1991T is obtained modelling spectra from before maximum light until a year after the explosion, with the method of `Abundance Tomography'. SN 1991T is different from other slowly declining SNe Ia (e.g. SN 1999ee) in having a weaker Si II 63…
Herschel/HIFI observations of ionised carbon in the β Pictoris debris disk
Fridlund, M.; Olofsson, G.; Liseau, R. +9 more
Context. The dusty debris disk around the ~20 Myr old main-sequence A-star β Pictoris is known to contain gas. Evidence points towards a secondary origin of the gas as opposed to being a direct remnant from the initial protoplanetary disk, although the dominant gas production mechanism is so far not identified. The origin of the observed overabund…
Blowing in the wind: The dust wave around σ Orionis AB
Kaper, L.; Tielens, A. G. G. M.; Berné, O. +5 more
Observations obtained with the Spitzer Space Telescope and the WISE satellite have revealed a prominent arc-like structure at 50'' (≃0.1 pc) from the O9.5V/B0.5V system σ Ori AB. We measure a total dust mass of 2.3 ± 1.5 × 10-5 M⊙. The derived dust-to-gas mass ratio is ≃0.29 ± 0.20. We attribute this dust structure to the int…
Mars Express investigations of Phobos and Deimos
Bibring, J. -P.; Gondet, B.; Barabash, S. +39 more
The Mars Express mission was launched in June 2003 and was inserted into orbit around Mars in December 2003. Its main objective is to study the Mars' subsurface, surface, atmosphere and interaction with the solar wind. A secondary objective is to study the martian moons, in particular the largest one Phobos, thanks to a near polar and elliptical o…
The solar meridional circulation and sunspot cycle variability
Hathaway, D. H.; Upton, L.
We have measured the meridional motions of the magnetic elements in the Sun's surface layers since 1996 and find systematic and substantial variations. In general the meridional flow speed is fast at cycle minima and slow at cycle maxima. We find that these systematic variations are characterized by a weakening of the meridional flow on the polewa…
Ultraviolet Observations of Super-Chandrasekhar Mass Type Ia Supernova Candidates with Swift UVOT
Wang, Lifan; Krisciunas, Kevin; Milne, Peter +6 more
Among Type Ia supernovae (SNe Ia), a class of overluminous objects exist whose ejecta mass is inferred to be larger than the canonical Chandrasekhar mass. We present and discuss the UV/optical photometric light curves, colors, absolute magnitudes, and spectra of three candidate Super-Chandrasekhar mass SNe—2009dc, 2011aa, and 2012dn—observed with …
Measurements of EUV Coronal Holes and Open Magnetic Flux
Liu, Y.; Qiu, J.; Lowder, C. +1 more
Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in th…