Category Archives: Helioseismology

122. Simultaneous Inversions for Vector Flows and Sound-Speed Perturbations

Contributed by Michal Švanda. Posted on March 6, 2019

To minimize cross-talk effect from vertical flows and sound-speed perturbations, a new inversion code is developed to invert for flows and sound-speed perturbations simultaneously from time-distance travel-time measurements. The code is validated using numerical simulation data.

120. Magnetic Fields and the Supply of Low-Frequency Acoustic Waves to the Solar Chromosphere

Contributed by S. P. Rajaguru. Posted on February 27, 2019

Through analyzing simultaneous HMI’s visible-light observations and AIA’s ultraviolet observations, the authors show that a significant amount of acoustic waves with frequencies lower than the theoretical cutoff frequency can channel up along less inclined magnetic field from the photosphere to the chromosphere.

110. Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017

Contributed by Alexander Kosovichev. Posted on September 17, 2018

Analysis of HMI and KONUS/WIND data shows that photospheric and helioseismic flare impacts started to develop in compact regions in close vicinity of the magnetic polarity inversion line in the pre-impulsive phase before detection of hard X-ray emission.

107. Cyclic Variations of the Sun’s Seismic Radius

Contributed by Alexander Kosovichev. Posted on July 30, 2018

The Sun’s seismic radius, measured from the frequencies of f modes, is determined using both MDI and HMI data, covering a total of 21 years. It is found that the seismic radius is reduced by 1-2 km during the maxima, but the largest change of the radius happens at about 5 Mm beneath the surface.

105. Waves of Magnetic-field Variations Observed in a Flare-excited Sunquake Event

Contributed by Junwei Zhao. Posted on July 13, 2018

Waves of magnetic-field variations were observed associated with the sunquake waves that were excited by the X9.3 flare on 2017 September 6. The nature and cause of the magnetic waves are discussed after the phase relations and power distributions of the magnetic waves and Doppler-observed sunquake waves are investigated.

98. Solar-Cycle Variations of Meridional Flows in the Solar Convection Zone with Helioseismic Methods

Contributed by Chia-Hsien Lin. Posted on May 18, 2018

Meridional flows during the solar minimum and maximum years are derived using 14 years of SOHO/MDI data. The flows changed significantly from the minimum to the maximum, and major changes were associated with the active latitudes.

91. On The Origin of the Double-Cell Meridional Circulation in the Solar Convection Zone

Contributed by Valery Pipin. Posted on March 19, 2018

It is demonstrated that when taking into account of the radial inhomogeneity of the Coriolis number, the solar-like differential rotation and the double-cell meridional circulation can both be reproduced by the mean-field model.