Search Publications
Composition of the Solar Corona, Solar Wind, and Solar Energetic Particles
Schmelz, J. T.; Reames, D. V.; von Steiger, R. +1 more
Along with temperature and density, the elemental abundance is a basic parameter required by astronomers to understand and model any physical system. The abundances of the solar corona are known to differ from those of the solar photosphere via a mechanism related to the first ionization potential of the element, but the normalization of these val…
The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging
Cohen, C. M. S.; Mewaldt, R. A.; Mason, G. M. +10 more
We use combined high-cadence, high-resolution, and multi-point imaging by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory to investigate the hour-long eruption of a fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin STEREO spacecraft were located beyond the solar limbs. We analy…
Observing the Fine Structure of Loops through High-resolution Spectroscopic Observations of Coronal Rain with the CRISP Instrument at the Swedish Solar Telescope
Rouppe van der Voort, L.; Antolin, P.
Observed in cool chromospheric lines, such as Hα or Ca II H, coronal rain corresponds to cool and dense plasma falling from coronal heights. Considered as a peculiar sporadic phenomenon of active regions, it has not received much attention since its discovery more than 40 years ago. Yet, it has been shown recently that a close relationship exists …
The Deflection of the Two Interacting Coronal Mass Ejections of 2010 May 23-24 as Revealed by Combined in Situ Measurements and Heliospheric Imaging
Möstl, C.; Farrugia, C. J.; Temmer, M. +4 more
In 2010 May 23-24, Solar Dynamics Observatory (SDO) observed the launch of two successive coronal mass ejections (CMEs), which were subsequently tracked by the SECCHI suite on board STEREO. Using the COR2 coronagraphs and the heliospheric imagers (HIs), the initial direction of both CMEs is determined to be slightly west of the Sun-Earth line. We …
Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set
Kosovichev, A. G.; Stenflo, J. O.
The magnetic flux that is generated by dynamo processes inside the Sun emerges in the form of bipolar magnetic regions. The properties of these directly observable signatures of the dynamo can be extracted from full-disk solar magnetograms. The most homogeneous, high-quality synoptic data set of solar magnetograms has been obtained with the Michel…
Solar Magnetic Field Reversals and the Role of Dynamo Families
Hoeksema, J. T.; Brun, A. S.; DeRosa, M. L.
The variable magnetic field of the solar photosphere exhibits periodic reversals as a result of dynamo activity occurring within the solar interior. We decompose the surface field as observed by both the Wilcox Solar Observatory and the Michelson Doppler Imager into its harmonic constituents, and present the time evolution of the mode coefficients…
Sigmoidal Active Region on the Sun: Comparison of a Magnetohydrodynamical Simulation and a Nonlinear Force-free Field Model
Aulanier, G.; Pariat, E.; Savcheva, A. +2 more
In this paper we show that when accurate nonlinear force-free field (NLFFF) models are analyzed together with high-resolution magnetohydrodynamic (MHD) simulations, we can determine the physical causes for the coronal mass ejection (CME) eruption on 2007 February 12. We compare the geometrical and topological properties of the three-dimensional ma…
The Role of Streamers in the Deflection of Coronal Mass Ejections: Comparison between STEREO Three-dimensional Reconstructions and Numerical Simulations
Mierla, M.; Poedts, S.; Bemporad, A. +3 more
On 2009 September 21, a filament eruption and the associated coronal mass ejection (CME) were observed by the Solar Terrestrial Relations Observatory (STEREO) spacecraft. The CME originated from the southern hemisphere and showed a deflection of about 15° toward the heliospheric current sheet (HCS) during the propagation in the COR1 field of view.…
Calibrating 100 Years of Polar Faculae Measurements: Implications for the Evolution of the Heliospheric Magnetic Field
DeLuca, Edward E.; Zhang, Jie; Muñoz-Jaramillo, Andrés +1 more
Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11 year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar field measurements spans relatively few sunspot cycles. In this paper, we address this deficiency by consolidating Mou…
Coronal Magnetic Field Measurement from EUV Images Made by the Solar Dynamics Observatory
Gopalswamy, Nat; Akiyama, Sachiko; Yashiro, Seiji +2 more
By measuring the geometrical properties of the coronal mass ejection (CME) flux rope and the leading shock observed on 2010 June 13 by the Solar Dynamics Observatory (SDO) mission's Atmospheric Imaging Assembly we determine the Alfvén speed and the magnetic field strength in the inner corona at a heliocentric distance of ~1.4 Rs. The basic measure…