Search Publications
Oscillations in Active Region Fan Loops: Observations from EIS/ Hinode and AIA/SDO
Banerjee, D.; Krishna Prasad, S.; Singh, Jagdev
Active region fan loops in AR 11076 were studied, in search of oscillations, using high cadence spectroscopic observations from Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode combined with imaging sequences from the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO). Spectra from EIS were analyzed in two s…
Coronal Mass Ejections from Magnetic Systems Encompassing Filament Channels Without Filaments
Pevtsov, Alexei A.; Panasenco, Olga; Martin, Sara F.
Well-developed filament channels may be present in the solar atmosphere even when there is no trace of filament material inside them. Such magnetic systems with filament channels without filaments can result in coronal mass ejections that might appear to have no corresponding solar surface source regions. In this case study, we analyze CMEs on 9 A…
Uncovering the Birth of a Coronal Mass Ejection from Two-Viewpoint SECCHI Observations
Tsinganos, K.; Vourlidas, A.; Syntelis, P.
We investigate the initiation and formation of Coronal Mass Ejections (CMEs) via a detailed two-viewpoint analysis of low corona observations of a relatively fast CME acquired by the SECCHI instruments aboard the STEREO mission. The event which occurred on 2 January 2008, was chosen because of several unique characteristics. It shows upward motion…
The Creation of Outflowing Plasma in the Corona at Emerging Flux Regions: Comparing Observations and Simulations
van Driel-Gesztelyi, L.; Harra, L. K.; Hood, A. W. +3 more
In this paper we analyse the flux emergence that occurred in the following polarity area of an active region on 1 - 2 December 2006. Observations have revealed the existence of fast outflows at the edge of the emerging flux region. We have performed 3-D numerical simulations to study the mechanisms responsible for these flows. The results indicate…
The Free Energy of NOAA Solar Active Region AR 11029
Leka, K. D.; Wheatland, M. S.; Gilchrist, S. A.
The NOAA active region (AR) 11029 was a small but highly active sunspot region which produced 73 GOES soft X-ray flares during its transit of the disk in late October 2009. The flares appear to show a departure from the well-known power law frequency-size distribution. Specifically, too few GOES C-class and no M-class flares were observed by compa…
On Signatures of Twisted Magnetic Flux Tube Emergence
van Driel-Gesztelyi, L.; Vargas Domínguez, S.; MacTaggart, D. +2 more
Recent studies of NOAA active region 10953, by Okamoto et al. (Astrophys. J. Lett.673, 215, 2008; Astrophys. J.697, 913, 2009), have interpreted photospheric observations of changing widths of the polarities and reversal of the horizontal magnetic field component as signatures of the emergence of a twisted flux tube within the active region and al…
Scientific Analysis within SEPServer - New Perspectives in Solar Energetic Particle Research: The Case Study of the 13 July 2005 Event
Vainio, R.; Valtonen, E.; Riihonen, E. +19 more
Solar energetic particle (SEP) events are a key ingredient of solar-terrestrial physics both for fundamental research and space weather applications. Multi-satellite observations are an important and incompletely exploited tool for studying the acceleration and the coronal and interplanetary propagation of the particles. While STEREO uses for this…
Modeling and Interpreting the Effects of Spatial Resolution on Solar Magnetic Field Maps
Leka, K. D.; Barnes, G.
Different methods for simulating the effects of spatial resolution on magnetic field maps are compared, including those commonly used for inter-instrument comparisons. The investigation first uses synthetic data, and the results are confirmed with Hinode/SpectroPolarimeter data. Four methods are examined, one which manipulates the Stokes spectra t…
Coronal Density Structures and CMEs: Superior Solar Conjunctions of Mars Express, Venus Express, and Rosetta: 2004, 2006, and 2008
Tellmann, Silvia; Tyler, G. Leonard; Tsurutani, Bruce T. +5 more
Coronal radio-sounding experiments were carried out using the S-band (2.3 GHz) and X-band (8.4 GHz) signals of the ESA Mars Express, Venus Express, and Rosetta spacecraft during five superior conjunctions occurring in 2004, 2006 (3×), and 2008/2009. Differential frequency and propagation delay (ranging) observations were recorded during these oppo…
A New Look at Solar Irradiance Variation
Foukal, Peter
We compare total solar irradiance (TSI) and ultraviolet (Fuv) irradiance variation reconstructed using Ca K facular areas since 1915, with previous values based on less direct proxies. Our annual means for 1925 - 1945 reach values 30 - 50 % higher than those presently used in IPCC climate studies. A high facula/sunspot area ratio in spo…