Tag Archives: sunspots

125. Solar Farside Magnetograms from Deep Learning Analysis of STEREO/EUVI Data

Contributed by Yong-Jae Moon. Posted on April 29, 2019

A deep learning code is trained using the Sun’s front-side observations, HMI’s magnetograms and AIA’s 304Å EUV images, to establish a relation between magnetic field and EUV flux. Then the code is applied on the STEREO/EUVI 304Å data to obtain the Sun’s far-side magnetic field.

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.

114. What We Learned from a Long-term Study of Sunspot Physical Parameters

Contributed by Jing Li. Posted on November 20, 2018

Physical parameters, including sunspots tilt angles, total magnetic flux, polarity pole separations, and magnetic areas, are measured for most sunspot groups in solar cycles 23 and 24. Differences between Hale and anti-Hale sunspots in separate hemispheres and cycles are studied statistically.

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.

97. Successive X-class Flares and Coronal Mass Ejections Driven by Shearing Motion and Sunspot Rotation in Active Region NOAA 12673

Contributed by Xiaoli Yan. Posted on April 26, 2018

Shearing motions and sunspot rotations found in NOAA AR 12673 are believed to lead the free energy buildup and flux rope formation, which are responsible for the two successive X-class flares.

93. Formation of Penumbra in A Sample of Active Regions Observed by the SDO Satellite

Contributed by Mariarita Murabito. Posted on March 29, 2018

Where does a sunspot’s penumbra start to form, on the same side or the opposite side of its opposite-polarity sunspot? When does Evershed flow start to appear, before or after the penumbral formation? These questions are answered through analyzing selected samples observed by the HMI.

90. A Comparative Study of the Eruptive and Non-Eruptive Flares Produced by the Largest Active Region of Solar Cycle 24

Contributed by Ranadeep Sarkar. Posted on March 18, 2018

AR12192, the largest active region in Solar Cycle 24, produced 6 X-class flares, but none of them were associated with a CME. However, a much weaker flare, of M4.0-class, was associated with a CME. Magnetic field and morphological changes are analyzed during these flares to understand why this is the case.