Search Publications
Surface-Focused Seismic Holography of Sunspots: I. Observations
Birch, A. C.; Braun, D. C.
We present a comprehensive set of observations of the interaction of p-mode oscillations with sunspots using surface-focused seismic holography. Maps of travel-time shifts, relative to quiet-Sun travel times, are shown for incoming and outgoing p modes as well as their mean and difference. We compare results using phase-speed filters with results …
Multifractal Properties of Evolving Active Regions
Maguire, K.; Gallagher, P. T.; Young, C. A. +5 more
Magnetohydrodynamic turbulence is thought to be responsible for producing complex, multiscale magnetic field distributions in solar active regions. Here we explore the multiscale properties of a number of evolving active regions using magnetograms from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The multifr…
Stream Interactions and Interplanetary Coronal Mass Ejections at 5.3 AU near the Solar Ecliptic Plane
Luhmann, J. G.; Russell, C. T.; Jian, L. K. +2 more
We have performed a survey of the characteristics of two types of large spatial-scale solar-wind structures, stream interaction regions (SIRs), and interplanetary coronal mass ejections (ICMEs), near 5.3 AU, using solar-wind observations from Ulysses. Our study is confined to the three aphelion passes of Ulysses, and also within ± 10° of the solar…
Influence of Low-Degree High-Order p-Mode Splittings on the Solar Rotation Profile
Eff-Darwich, A.; Korzennik, S. G.; Jiménez-Reyes, S. J. +3 more
The solar rotation profile is well constrained down to about 0.25R⊙ thanks to the study of acoustic modes. Since the radius of the inner turning point of a resonant acoustic mode is inversely proportional to the ratio of its frequency to its degree, only the low-degree p modes reach the core. The higher the order of these modes, the dee…
Absorption Phenomena and a Probable Blast Wave in the 13 July 2004 Eruptive Event
Shibasaki, K.; Grechnev, V. V.; Chertok, I. M. +3 more
We present a case study of the 13 July 2004 solar event, in which disturbances caused by eruption of a filament from an active region embraced a quarter of the visible solar surface. Remarkable are the absorption phenomena observed in the SOHO/EIT 304 Å channel, which were also visible in the EIT 195 Å channel, in the Hα line, and even in total ra…
Structure and Evolution of Supergranulation from Local Helioseismology
Hirzberger, Johann; Solanki, Sami K.; Gizon, Laurent +1 more
Supergranulation is visible at the solar surface as a cellular pattern of horizontal outflows. Although it does not show a distinct intensity pattern, it manifests itself indirectly in, for example, the chromospheric network. Previous studies have reported significant differences in the inferred basic parameters of the supergranulation phenomenon.…
MHD Modeling of Coronal Large-Amplitude Waves Related to CME Lift-off
Vainio, R.; Pomoell, J.; Kissmann, R.
We have employed a two-dimensional magnetohydrodynamic simulation code to study mass motions and large-amplitude coronal waves related to the lift-off of a coronal mass ejection (CME). The eruption of the filament is achieved by an artificial force acting on the plasma inside the flux rope. By varying the magnitude of this force, the reaction of t…
High-Resolution Mapping of Flows in the Solar Interior: Fully Consistent OLA Inversion of Helioseismic Travel Times
Birch, A. C.; Gizon, L.; Jackiewicz, J.
To recover the flow information encoded in travel-time data of time - distance helioseismology, accurate forward modeling and a robust inversion of the travel times are required. We accomplish this using three-dimensional finite-frequency travel-time sensitivity kernels for flows along with a (2+1)-dimensional (2+1D) optimally localized averaging …
Magnetic Causes of the Eruption of a Quiescent Filament
Golub, L.; Bommier, V.; Schmieder, B. +5 more
During the JOP178 campaign in August 2006, we observed the disappearance of our target, a large quiescent filament located at S25°, after an observation time of three days (24 August to 26 August). Multi-wavelength instruments were operating: THEMIS/MTR ("MulTi-Raies") vector magnetograph, TRACE ("Transition Region and Coronal Explorer") at 171 Å …
Dynamics of Sunspot Light Bridges as Revealed by High-Resolution Images from Hinode
Venkatakrishnan, P.; Mathew, Shibu K.; Louis, Rohan E. +1 more
We present G-band and Ca II H filtergrams of two sunspot light bridges in NOAA AR 10953 taken from the 50-cm Solar Optical Telescope onboard the Japanese space satellite Hinode on 1 May 2007. The two light bridges differ in structure, with one of them resembling the filamentary penumbra and the other possessing a dark central lane running along th…