National Solar Observatory

Empirical flare energy limits for the largest historical sunspots

Extreme solar particle events (ESPEs) reveal that the Sun can occasionally produce eruptions significantly more energetic than those observed in the modern era. These events are thought to originate from powerful coronal mass ejections (CMEs), typically associated with large sola...

Tension in the solar energetic proton paradigm for historical cosmogenic nuclide events

'Miyake events' are exceptional increases in atmospheric 14C recorded in tree rings that, if confirmed, are accompanied by simultaneous 10Be and 36Cl enhancements in ice cores. During the last 15 000 years, six such events have been confirmed. They are generally thought to origin...

International Intercomparison of Primary Photovoltaic Reference Cell Calibrations With Excellent Agreement

This study presents the results of an international intercomparison of primary calibration methods for photovoltaic (PV) reference devices according to IEC 60904‐4. The comparison involves three leading calibration laboratories—PTB, NLR, and AIST—representing independent traceabi...

The origin of dark lane on sunspot’s light bridge

Light bridges (LBs), embedded in sunspots, appear as elongated narrow bright features, in contrast to the surrounding dark sunspot umbra or penumbra. Under high-resolution observations, dark lanes were reported along the spine of LBs. Although numerical modeling explains the basi...