Category Archives: Helioseismology

150. Photospheric Oscillations in and around Active Region 11158, including the Polarity Inversion Line

Contributed by Aimee Norton. Posted on January 20, 2021

To search for signatures of Alfvénic waves in the solar photosphere, the authors analyze the oscillation amplitudes, phases and time-distance behavior between different observables in a sunspot umbra, its polarity inversion line, and surrounding area.

133. Hemispherical Asymmetry in the Solar Meridional Flow

Contributed by B. Lekshmi. Posted on October 28, 2019

Subsurface meridional flows from ring-diagram analysis showed a clear hemispheric asymmetry in last 18 years. Interestingly, this flow asymmetry leads the magnetic flux and sunspot number asymmetry by 3.1 – 3.6 years.

129. A Chromospheric Response to the Sunquake generated by the X9.3 Flare of 6 September 2017

Contributed by Sean Quinn. Posted on August 29, 2019

A number of sunquake events were detected in the photosphere after the X9.3 flare of 6 September 2017. This analysis reported the first detection of the chromspheric response to the sunquake events using CaII and Hα observations made by the Swedish 1-meter Solar Telescope.

126. Solar Oblateness and Its Variations in Phase with the 22-yr Magnetic Cycle

Contributed by Abdanour Irbah. Posted on June 18, 2019

The Sun’s oblateness shows a variation with solar cycles, in phase with the solar activity level in Cycle 23 but in anti-phase with the activity level in Cycle 24. Such a trend of in-phase during odd cycles and anti-phase during even cycles is confirmed after examining past observations.

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.