Search Publications
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…
Clear Detection of Chromospheric Evaporation Upflows with High Spatial/Temporal Resolution by Hinode XRT
Yamamoto, T. T.; Imada, S.; Nitta, S.
We find clear evidence for typical chromospheric evaporation associated with small transient brightenings, using the data from the X-ray Telescope (XRT) onboard Hinode. We found 13 events, each having a pair of evaporation upflows arising almost symmetrically from both foot points of a magnetic loop. These facts strongly support the standard flare…
A Simultaneous Forbush Decrease Associated with an Earthward Coronal Mass Ejection Observed by STEREO
Yi, Y.; Oh, S. Y.
The intensity-time profile of Forbush decrease (FD) events observed by neutron monitors (NMs) looks like that of a geomagnetic storm as defined by the Dst index. Oh, Yi, and Kim (J. Geophys. Res. 113, A01103, 2008) and Oh and Yi (J. Geophys. Res. 114, A11102, 2009) classified FD events based on the amount of overlap and simultaneity of their main …
Forecasting a CME by Spectroscopic Precursor?
van Driel-Gesztelyi, L.; Baker, D.; Green, L. M.
Multi-temperature plasma flows resulting from the interaction between a mature active region (AR) inside an equatorial coronal hole (CH) are investigated. Outflow velocities observed by Hinode EIS ranged from a few to 13 km s−1 for three days at the AR's eastern and western edges. However, on the fourth day, velocities intensified up to…
A Fast Model for the Reconstruction of Spectral Solar Irradiance in the Near- and Mid-Ultraviolet
Charbonneau, P.; Crouch, A. D.; Bolduc, C. +2 more
We present a model for the reconstruction of spectral solar irradiance between 200 and 400 nm. This model is an extension of the total solar irradiance (TSI) model of Crouch et al. (Astrophys. J.677, 723, 2008) which is based on a data-driven Monte Carlo simulation of sunspot emergence, fragmentation, and erosion. The resulting time-evolving daily…
On Magnetic Fields of Active Regions at Coronal Heights
Bogod, V. M.; Stupishin, A. G.; Yasnov, L. V.
This paper analyzes the magnetic field structure of active regions at coronal heights determined by means of multi-wavelength observations of polarized radio emission in the microwave range, and compares it with the force-free magnetic field extrapolation into the corona from the photospheric magnetograms. Our method of one-dimensional radio stere…
A Unified and Very Fast Way for Computing the Global Potential and Linear Force-Free Fields
Feng, Xueshang; Jiang, Chaowei
We present a fast solver for computing potential and linear force-free fields (LFFF) above the full solar disk with a synoptic magnetic map as input. The global potential field and the LFFF are dealt with in a unified way by solving a three-dimensional Helmholtz equation in a spherical shell and a two-dimensional Poisson equation on the solar surf…
Solar Intranetwork Magnetic Elements: Bipolar Flux Appearance
Wang, Jingxiu; Li, Hui; Jin, Chunlan +1 more
This study aims to quantify characteristic features of the bipolar flux appearance of solar intranetwork (IN) magnetic elements. To attack this problem, we use the Narrowband Filter Imager (NFI) magnetograms from the Solar Optical Telescope (SOT) on board Hinode; these data are from quiet and enhanced network areas. Cluster emergence of mixed pola…
Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
Hill, F.; González Hernández, I.; Komm, R. W. +2 more
The temporal variation of the horizontal velocity in sub-surface layers beneath three different types of active region is studied using the technique of ring diagrams. In this study, we select active regions (ARs) 10923, 10930, 10935 from three consecutive Carrington rotations: AR 10930 contains a fast-rotating sunspot in a strong emerging active …