Search Publications
The Solar Energetic Particle Event of 14 December 2006
Leske, R. A.; Wiedenbeck, M. E.; Cohen, C. M. S. +6 more
The solar energetic particle event on 14 December 2006 was observed by several near-Earth spacecraft including the Advanced Composition Explorer (ACE), STEREO A and B, SOHO and Wind. An interesting feature of this event is a series of unusual fluctuations in the particle intensity that occurred during the first few hours. These fluctuations were o…
The Apparent Layered Structure of the Heliospheric Current Sheet: Multi-Spacecraft Observations
Sauvaud, J. -A.; Luhmann, J. G.; Lavraud, B. +9 more
Multiple current sheet crossings are ubiquitous features of the solar wind associated with high-beta plasma sheets, notably during the passage of the heliospheric current sheet (HCS). As the HCS is being convected past near-Earth, we attempt to resolve spatial scales and temporal variations of the apparent layered structure of the HCS, including a…
Contrast of Coronal Holes and Parameters of Associated Solar Wind Streams
Obridko, V. N.; Shelting, B. D.; Livshits, I. M. +1 more
It is shown that the contrast of coronal holes, just as their size, determines the velocity of the solar wind streams. Fully calibrated EIT images of the Sun have been used. About 450 measurements in 284 Å have been analyzed. The time interval under examination covers about 1500 days in the declining phase of cycle 23. All coronal holes recorded f…
Formation, Interaction and Merger of an Active Region and a Quiescent Filament Prior to Their Eruption on 19 May 2007
van Driel-Gesztelyi, L.; Bone, L. A.; Culhane, J. L. +2 more
We report observations of the formation of two filaments - one active and one quiescent, and their subsequent interactions prior to eruption. The active region filament appeared on 17 May 2007, followed by the quiescent filament about 24 hours later. In the 26 hour interval preceding the eruption, which occurred at around 12:50 UT on 19 May 2007, …
Expansion Speed of Coronal Mass Ejections
Gopalswamy, N.; Michalek, G.; Yashiro, S.
A large set of limb coronal mass ejections (CMEs) are used to determine the accurate relationship between radial (Vrad) and expansion (Vexp) speeds of CMEs. It is demonstrated that this relation is exceptionally well described by the function f(w)=1/2(1+cot w), representing a full cone model for the CME with a half-width, w. …
High-Energy Emission from a Solar Flare in Hard X-rays and Microwaves
Kundu, M. R.; White, S. M.; Grechnev, V. V. +3 more
We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) at hard X-rays. This flare is one of the few in which emission up to en…
Spectro-Polarimetric Observations of Solar Magnetic Fields and the SOHO/MDI Calibration Issue
Balthasar, H.; Demidov, M. L.
Comparisons of solar magnetic-field measurements made in different spectral lines are very important, especially in those lines in which observations have a long history or (and) specific diagnostic significance. The spectral lines Fe I 523.3 nm and Fe I 525.0 nm belong to this class. Therefore, this study is devoted to a comprehensive analysis us…
Surface-Focused Seismic Holography of Sunspots: II. Expectations from Numerical Simulations Using Sound-Speed Perturbations
Birch, A. C.; Braun, D. C.; Hanasoge, S. M. +1 more
Helioseismic observations of sunspots show that wave travel times, at fixed horizontal phase speed, depend on the temporal frequency of the waves employed in the data analysis. This frequency variation has been suggested to be consistent with near-surface (vertical length scales of order one Mm or smaller) changes in wave propagation properties re…
Relative Kinematics of the Leading Edge and the Prominence in Coronal Mass Ejections
Vršnak, Bojan; Maričić, Darije; Roša, Dragan
We present a statistical analysis of the relationship between the kinematics of the leading edge and the eruptive prominence in coronal mass ejections (CMEs). We study the acceleration phase of 18 CMEs in which kinematics was measured from the pre-eruption stage up to the post-acceleration phase. In all CMEs, the three part structure (the leading …
Transient Magnetic and Doppler Features Related to the White-Light Flares in NOAA 10486
Maurya, R. A.; Ambastha, A.
Rapidly moving transient features have been detected in magnetic and Doppler images of super-active region NOAA 10486 during the X17/4B flare of 28 October 2003 and the X10/2B flare of 29 October 2003. Both these flares were extremely energetic white-light events. The transient features appeared during impulsive phases of the flares and moved with…