Search Publications
Multiscale Edge Detection in the Corona
Gallagher, Peter T.; Young, C. Alex
Coronal Mass Ejections (CMEs) are challenging objects to detect using automated techniques, due to their high velocity and diffuse, irregular morphology. A necessary step to automating the detection process is to first remove the subjectivity introduced by the observer used in the current, standard, CME detection and tracking method. Here we descr…
Solar Radio Spikes in 2.6 - 3.8 GHz during the 13 December 2006 Event
Zhang, Y.; Yan, Y. H.; Liu, Y. Y. +3 more
On 13 December 2006, some unusual radio bursts in the range 2.6 - 3.8 GHz were observed during an X3.4 flare/CME event from 02:30 to 04:30 UT in active region NOAA 10930 (S06W27) with the digital spectrometers of the National Astronomical Observatories of China (NAOC). During this event many spikes were detected with the high temporal resolution o…
Time Distance Analysis of the Emerging Active Region NOAA 10790
Thompson, M. J.; Zharkov, S.
We investigate the emergence of Active Region NOAA 10790 by means of time - distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the…
Multiresolution Analysis of Active Region Magnetic Structure and its Correlation with the Mount Wilson Classification and Flaring Activity
Gallagher, P. T.; Young, C. A.; McAteer, R. T. J. +3 more
Two different multiresolution analyses are used to decompose the structure of active-region magnetic flux into concentrations of different size scales. Lines separating these opposite polarity regions of flux at each size scale are found. These lines are used as a mask on a map of the magnetic field gradient to sample the local gradient between op…
Perspectives in Global Helioseismology and the Road Ahead
Chaplin, William J.; Basu, Sarbani
We review the impact of global helioseismology on key questions concerning the internal structure and dynamics of the Sun and consider the exciting challenges the field faces as it enters a fourth decade of science exploitation. We do so with an eye on the past, looking at the perspectives global helioseismology offered in its earlier phases, in p…
Relationship between Powerful Flares and Dynamic Evolution of the Magnetic Field at the Solar Surface
Zhang, Hongqi; Liu, Jihong; Zhang, Yin
Powerful flares are closely related to the evolution of the complex magnetic field configuration at the solar surface. The strength of the magnetic field and speed of its evolution are two vital parameters in the study of the change of magnetic field in the solar atmosphere. We propose a dynamic and quantitative depiction of the changes in complex…
Analysis of MDI High-Degree Mode Frequencies and their Rotational Splittings
Schou, J.; Korzennik, S. G.; Rabello-Soares, M. C.
We present a detailed analysis of solar acoustic mode frequencies and their rotational splittings for modes with degree up to 900. They were obtained by applying spherical harmonic decomposition to full-disk solar images observed by the Michelson Doppler Imager onboard the Solar and Heliospheric Observatory spacecraft. Global helioseismology analy…
Recent Developments in Local Helioseismology
Thompson, M. J.; Zharkov, S.
Local helioseismology is providing new views of subphotospheric flows from supergranulation to global-scale meridional circulation and for studying structures and dynamics in the quiet Sun and active regions. In this short review we focus on recent developments, and in particular on a number of current issues, including the sensitivity of differen…
A Time-Evolving 3D Method Dedicated to the Reconstruction of Solar Plumes and Results Using Extreme Ultraviolet Data
Auchère, Frédéric; Vial, Jean-Claude; Barbey, Nicolas +1 more
An important issue in the tomographic reconstruction of the solar poles is the relatively rapid evolution of the polar plumes. We demonstrate that it is possible to take into account this temporal evolution in the reconstruction. The difficulty of this problem comes from the fact that we want a four-dimensional reconstruction (three spatial dimens…
Physical Properties of Wave Motion in Inclined Magnetic Fields within Sunspot Penumbrae
Braun, D. C.; Cally, P. S.; Lindsey, C. +1 more
At the surface of the Sun, acoustic waves appear to be affected by the presence of strong magnetic fields in active regions. We explore the possibility that the inclined magnetic field in sunspot penumbrae may convert primarily vertically-propagating acoustic waves into elliptical motion. We use helioseismic holography to measure the modulus and p…