Solid evidence of magnetic reconnection is rarely reported within sunspots, the darkest regions with the strongest magnetic fields and lowest temperatures in the solar atmosphere. Using the world's largest solar telescope, the 1.6-meter Goode Solar Telescope, we detect prevalent reconnection through frequently occurring fine-scale jets in the Hα line wings at light bridges, the bright lanes that may divide the dark sunspot core into multiple parts. Many jets have an inverted Y-shape, shown by models to be typical of reconnection in a unipolar field environment. Simultaneous spectral imaging data from the Interface Region Imaging Spectrograph show that the reconnection drives bidirectional flows up to 200 km s −1 , and that the weakly ionized plasma is heated by at least an order of magnitude up to ∼80,000 K. Such highly dynamic reconnection jets and efficient heating should be properly accounted for in future modeling efforts of sunspots. Our observations also reveal that the surge-like activity previously reported above light bridges in some chromospheric passbands such as the Hα core has two components: the ever-present short surges likely to be related to the upward leakage of magnetoacoustic waves from the photosphere, and the occasionally occurring long and fast surges that are obviously caused by the intermittent reconnection jets.

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Climatic time series from historical documents and instrumental records from China showed temporal and regional patterns in the last two to three centuries, including two multidecadal oscillations at quasi-20-year and quasi-70-year timescales revealed by signal analysis from wavelet transform. Climatic anomalous events on the decadal timescale were identified based on the two oscillations when their positive (or negative) phases coincide with each other to amplify amplitude. The coldest event occurred in the decade of 1965-1975 in eastern China, while the periods of

Observations from the Interface Region Imaging Spectrograph (IRIS) often reveal significantly broadened and non-reversed profiles of the Mg II h, k and triplet lines at flare ribbons. To understand the formation of these optically thick Mg II lines, we perform plane parallel radiative hydrodynamics modeling with the RADYN code, and then recalculate the Mg II line profiles from RADYN atmosphere snapshots using the radiative transfer code RH. We find that the current RH code significantly underestimates the Mg II h & k Stark widths. By implementing semi-classical perturbation approximation results of quadratic Stark broadening from the STARK-B database in the RH code, the Stark broadenings are found to be one order of magnitude larger than those calculated from the current RH code. However, the improved Stark widths are still too small, and another factor of 30 has to be multiplied to reproduce the significantly broadened lines and adjacent continuum seen in observations. Non-thermal electrons, magnetic fields, three-dimensional effects or electron density effect may account for this factor. Without modifying the RADYN atmosphere, we have also reproduced non-reversed Mg II h & k profiles, which appear when the electron beam energy flux is decreasing. These profiles are formed at an electron density of ∼ 8 × 10 14 cm −3 and a temperature of ∼ 1.4 × 10 4 K, where the source function slightly deviates from the Planck function. Our investigation also demonstrates that at flare ribbons the triplet lines are formed in the upper chromosphere, close to the formation heights of the h & k lines.

Historical annual dry-wet index for 1470-2003 combined with instrumental precipitation since 1951 were used to identify extremely dry years and events near the northern fringe of the East Asian summer monsoon in China-the Great Bend of the Yellow River (GBYR) region. In total, 49 drought years, of which 26 were severe, were identified. Composites of the dry-wet index under the drought years show an opposite wet pattern over the Southeast China. The longest drought event lasted for 6 years (1528-1533), the second longest one 4 years (1637-1640). The most severe 2-year-long drought occurred in 1928-1929, and the two driest single years were 1900 and 1965. These persistent and extreme drought events caused severe famines and huge losses of human lives. Wavelet transform applied to the dry-wet index indicates that the severe drought years are nested in several significant drywet variations across multiple timescales, i.e., the 65-85 year timescale during 1600-