Search Publications
The Evolution of Sunspot Magnetic Fields Associated with a Solar Flare
Gallagher, Peter T.; Murray, Sophie A.; Bloomfield, D. Shaun
Solar flares occur due to the sudden release of energy stored in active-region magnetic fields. To date, the precursors to flaring are still not fully understood, although there is evidence that flaring is related to changes in the topology or complexity of an active-region's magnetic field. Here, the evolution of the magnetic field in active regi…
Long-Term Variation of the Corona in Quiet Regions
Mariska, J. T.; Kamio, S.
Using Hinode EUV Imaging Spectrometer (EIS) spectra recorded daily at Sun center from the end of 2006 to early 2011, we studied the long-term evolution of the quiet corona. The light curves of the higher temperature emission lines exhibit larger variations in sync with the solar activity cycle while the cooler lines show reduced modulation. Our st…
Connecting Coronal Mass Ejections and Magnetic Clouds: A Case Study Using an Event from 22 June 2009
Möstl, C.; Marubashi, K.; Howard, R. A. +5 more
On 27 June 2009 the Wind and Advanced Composition Explorer (ACE) spacecraft near Earth detected a magnetic cloud (MC). The MC can be traced back to a slow coronal mass ejection (CME) launched from the Sun on 22 June 2009 but this connection relies entirely on heliospheric imaging of the Sun-Earth line from the two STEREO spacecraft, illustrating t…
Solar Intranetwork Magnetic Elements: Intrinsically Weak or Strong?
Wang, J. X.; Xie, Z. X.; Jin, C. L.
The high spatial resolution observation of a quiet region taken with the Solar Optical Telescope/Spectro-Polarimeter aboard the Hinode spacecraft is analyzed. Based on the Milne-Eddington atmospheric model, the vector magnetic field of the quiet region is derived by fitting the full Stokes profiles of the Fe I 630 nm line pair. We extract intranet…
Study of an Extended EUV Filament Using SoHO/SUMER Observations of the Hydrogen Lyman Lines. II. Lyman α Line Observed During a Multi-wavelength Campaign
Heinzel, P.; Schmieder, B.; Schwartz, P. +1 more
A filament and its channel close to the solar disk were observed in the complete hydrogen Lyman spectrum, and in several EUV lines by the SUMER (Solar Ultraviolet Measurement of Emitted Radiation) and CDS (Coronal Diagnostic Spectrometer) spectrographs on the SoHO satellite, and in Hα by ground-based telescopes during a multi-instrument campaign i…
Multi-spacecraft Study of the 8 November 2000 SEP Event: Electron Injection Histories 100° Apart
Lario, D.; Vainio, R.; Kilpua, E. +3 more
We present the analysis of a large solar near-relativistic electron event observed by the Ulysses and the ACE spacecraft on 8 November 2000, when Ulysses was located at a heliocentric distance of 2.4 AU and at a heliographic latitude of ∼80° S. We use a particle propagation model to infer the local interplanetary transport conditions and the injec…
Study of Differences Between Sunspot and White Light Facular Area Data Determined from SDO/HMI and SOHO/MDI Observations
Győri, L.
Sunspot and white light facular areas are important data for solar activity and are used, for example, in the study of the evolution of sunspots and their effect on solar irradiance. Solar Dynamic Observatory's Helioseismic and Magnetic Imager (SDO/HMI) solar images have much higher resolution (∼0.5'' pixel−1) than Solar and Heliospheri…
Effects of Hysteresis Between Maximum CME Speed Index and Typical Solar Activity Indicators During Cycle 23
Özgüç, A.; Kilcik, A.; Rozelot, J. P.
Using the smoothed time series of maximum CME speed index for solar cycle 23, it is found that this index, analyzed jointly with six other solar activity indicators, shows a hysteresis phenomenon. The total solar irradiance, coronal index, solar radio flux (10.7 cm), Mg II core-to-wing ratio, sunspot area, and Hα flare index follow different paths…
Solar Stereoscopy with STEREO/EUVI A and B Spacecraft from Small (6∘) to Large (170∘) Spacecraft Separation Angles
Aschwanden, Markus J.; Nitta, Nariaki; Lemen, James +1 more
We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles (αsep≈6∘,43∘,89∘,127∘,and 170∘). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar…
Recent Developments of NEMO: Detection of EUV Wave Characteristics
Podladchikova, O.; Van der Linden, R. A. M.; Vuets, A. +1 more
Recent developments in space instrumentation for solar observations and increased telemetry have necessitated the creation of advanced pattern recognition tools for different classes of solar events. The Extreme Ultraviolet Imaging Telescope (EIT) onboard the SOHO spacecraft has uncovered a new class of eruptive events on the solar disk, which are…