Search Publications
Dynamics of Intense Currents in the Solar Wind
Zelenyi, Lev M.; Angelopoulos, Vassilis; Artemyev, Anton V. +3 more
Transient currents in the solar wind are carried by various magnetic field discontinuities that contribute significantly to the magnetic field fluctuation spectrum. Internal instabilities and dynamics of these discontinuities are believed to be responsible for magnetic field energy dissipation and corresponding charged particle acceleration and he…
Understanding the HMI Pseudocontinuum in White-light Solar Flares
Kleint, Lucia; Kašparová, Jana; Jurčák, Jan +1 more
We analyze observations of the X9.3 solar flare (SOL2017-09-06T11:53) observed by SDO/HMI and Hinode/Solar Optical Telescope. Our aim is to learn about the nature of the HMI pseudocontinuum I c used as a proxy for the white-light continuum. From model atmospheres retrieved by an inversion code applied to the Stokes profiles observed by …
In Search of Recent Disruption of (3200) Phaethon: Model Implication and Hubble Space Telescope Search
Ye, Quanzhi; Hui, Man-To; Wiegert, Paul A.
Near-Earth asteroid (3200) Phaethon is notable for its association with a strong annual meteor shower, the Geminids, indicative of one or more episodes of mass ejection in the past. The mechanism of Phaethon’s past activity is not yet understood. Here, we present a Hubble Space Telescope (HST) search of meter-sized fragments in the vicinity of Pha…
Connections between Star Cluster Populations and Their Host Galaxy Nuclear Rings
Ho, Luis C.; de Grijs, Richard; Ma, Chao
Nuclear rings are excellent laboratories for probing diverse phenomena such as the formation and evolution of young massive star clusters and nuclear starbursts, as well as the secular evolution and dynamics of their host galaxies. We have compiled a sample of 17 galaxies with nuclear rings, which are well resolved by high-resolution Hubble and Sp…
Spitzer Infrared Spectrograph Observations of the Galactic Center: Quantifying the Extreme Ultraviolet/Soft X-ray Fluxes
Simpson, Janet P.
It has long been shown that the extreme ultraviolet spectrum of the ionizing stars of H II regions can be estimated by comparing the observed line emission to detailed models. In the Galactic Center (GC), however, previous observations have shown that the ionizing spectral energy distribution (SED) of the local photon field is strange, producing b…
North-South Asymmetry of the Rotation of the Solar Magnetic Field
Qu, Zhining; Xie, Jinglan; Shi, Xiangjun
Using the rotation rates of the solar magnetic field during solar cycles 21 to 23 obtained by Chu et al. by analyzing the synoptic magnetic maps produced by the NSO/Kitt Peak and SOHO/MDI during the years 1975 to 2008, the temporal variation of the equatorial rotation rate (A) and the latitude gradient of rotation (B) in the northern and southern …
Spots, Flares, Accretion, and Obscuration in the Pre-main-sequence Binary DQ Tau
Pál, A.; Ábrahám, P.; Kóspál, Á. +4 more
DQ Tau is a young low-mass spectroscopic binary, consisting of two almost equal-mass stars on a 15.8 day period surrounded by a circumbinary disk. Here, we analyze DQ Tau’s light curves obtained by Kepler K2, the Spitzer Space Telescope, and ground-based facilities. We observed variability phenomena, including rotational modulation by stellar spot…
Bridging the Gap: Capturing the Lyα Counterpart of a Type-II Spicule and Its Heating Evolution with VAULT2.0 and IRIS Observations
Vourlidas, Angelos; Martínez-Sykora, Juan; De Pontieu, Bart +3 more
We present results from an observing campaign in support of the VAULT2.0 sounding rocket launch on 2014 September 30. VAULT2.0 is a Lyα (1216 Å) spectroheliograph capable of providing spectroheliograms at high cadence. Lyα observations are highly complementary to the IRIS observations of the upper chromosphere and the low transition region (TR) bu…
The Evolution of the Warm Absorber Reveals a Shocked Outflow in the Narrow Line Seyfert 1 Galaxy IRAS 17020+4544
Guainazzi, Matteo; Krongold, Yair; Panessa, Francesca +2 more
We present the analysis of grating spectra of the Narrow Line Seyfert 1 Galaxy IRAS 17020+4544 observed by XMM-Newton in 2004 and 2014. In a previous work on these data, we reported the discovery of a multicomponent ultra-fast outflow that is capable of producing feedback in the host galaxy. We also reported the presence of a slow, multiphase warm…
Solar-cycle Variations of Meridional Flows in the Solar Convection Zone Using Helioseismic Methods
Chou, Dean-Yi; Lin, Chia-Hsien
The solar meridional flow is an axisymmetric flow in solar meridional planes, extending through the convection zone. Here we study its solar-cycle variations in the convection zone using SOHO/MDI helioseismic data from 1996 to 2010, including two solar minima and one maximum. The travel-time difference between northward and southward acoustic wave…