Twelve years of HMI Dopplergram and magnetogram data have been used to uncover the solar cycle dependence of the magnetically quietest regions on the Sun and to reveal an enigmatic behavior of the surface-gravity wave energy contained in those regions.
This study reveals that a significant number of coronal-hole field lines extend beyond the coronal-hole boundaries and that many coronal-holes contain no open magnetic field lines.
Compactness is one geometric property of a sunspot group that has not yet been systematically quantified. We calculate the compactness of a small sample of δ-spots and β-spots using a minimum bounding circle. On average, the δ-spots are found to be more than twice as compact as the β-spots.
Analysis on high-spectral resolution data shows that oscillations in the higher atmosphere lead those in the lower atmosphere by an order of 1 s when their frequencies are below about 3.0 mHz, and lags behind by about 1 s when their frequencies are above 3.0 mHz. These phase shifts in the evanescent waves pose great challenges to the interpretation of some local helioseismic measurements that involve data acquired at different atmospheric heights.
Inverse Evershed flow is derived from chromospheric observations. Coupling these flow with the non force-free model, the authors find that the flow is driven along magnetic field lines connecting network elements with the outer penumbra by a gas pressure difference.
High-frequency inertial waves were detected inside the Sun, propagating retrograde relative to the solar rotation with a phase speed faster than equatorial Rossby waves. How these waves are generated is discussed but remains unclear.
Briefly shown here are some results from a new global coronal MHD simulation model, with a new method to use the three-component vector HMI synoptic maps as time-dependent boundary values.
Another white-light flare was captured by HMI off the solar limb, this time with materials seen ejected from the Sun. A fraction of the ejecta was seen falling back to the Sun.
A new model, which explores the polar field build-up rate and the amplitude of the following cycle, predicts a slightly stronger Cycle 25 than previously thought.
A statistical study of emerging active regions demonstrates that these ARs tend to produce CMEs when they accumulate significant budgets of both magnetic helicity and energy.