We study the sunspot activity in relation to spotless days(SLDs)during the descending phase of solar cycles 11-24 to predict the amplitude of sunspot cycle 25.For this purpose,in addition to SLD,we also consider the g...We study the sunspot activity in relation to spotless days(SLDs)during the descending phase of solar cycles 11-24 to predict the amplitude of sunspot cycle 25.For this purpose,in addition to SLD,we also consider the geomagnetic activity(aa index)during the descending phase of a given cycle.A very strong correlation of the SLD(0.68)and aa index(0.86)during the descending phase of a given cycle with the maximum amplitude of next solar cycle has been estimated.The empirical relationship led us to deduce the amplitude of cycle 25 to be 99.13±14.97 and 104.23±17.35 using SLD and aa index,respectively as predictors.Both the predictors provide comparable amplitude for solar cycle 25 and reveal that solar cycle 25 will be weaker than cycle 24.Further,we predict that the maximum of cycle 25 is likely to occur between February and March 2024.While the aa index has been utilized extensively in the past,this work establishes SLDs as another potential candidate for predicting the characteristics of the next cycle.展开更多
A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their so...A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century.The small scale features are classified into three distinct categories:enhanced network,active network and quiet network.All these features show that their areas vary according to the11 yr solar cycle.The relative amplitude of the Ca-K network variations agrees with that of the sunspot cycle.The total area of these small-scale features varies from about 5%during the minimum phase of the solar cycle to about20%during its maximum phase.展开更多
Polarimetry plays an important role in the measurement of solar magnetic fields. We devel- oped a high-sensitivity and high-accuracy polarimeter （HHP） based on nematic liquid crystal variable retarders （LCVRs）, wh...Polarimetry plays an important role in the measurement of solar magnetic fields. We devel- oped a high-sensitivity and high-accuracy polarimeter （HHP） based on nematic liquid crystal variable retarders （LCVRs）, which has a compact setup and no mechanical moving parts. The system design and calibration methods are discussed in detail. The azimuth error of the transmission axis of the polarizer as well as the fast axes of the two LCVRs and the quarter-wave plate were determined using dedicated procedures. Linearly and circularly polarized light were employed to evaluate the performance of the HHP. The experimental results indicate that a polarimetric sensitivity of better than 5.7 × 10-3 can be achieved by using a single short-exposure image, while an accuracy on the order of 10-5 can be reached by using a large number of short-exposure images. This makes the HHP a high-performance system that can be used with a ground-based solar telescope for high-precision solar magnetic field investigations.展开更多
基金funding support from NSFC-11950410498KLSA-202010 grants。
文摘We study the sunspot activity in relation to spotless days(SLDs)during the descending phase of solar cycles 11-24 to predict the amplitude of sunspot cycle 25.For this purpose,in addition to SLD,we also consider the geomagnetic activity(aa index)during the descending phase of a given cycle.A very strong correlation of the SLD(0.68)and aa index(0.86)during the descending phase of a given cycle with the maximum amplitude of next solar cycle has been estimated.The empirical relationship led us to deduce the amplitude of cycle 25 to be 99.13±14.97 and 104.23±17.35 using SLD and aa index,respectively as predictors.Both the predictors provide comparable amplitude for solar cycle 25 and reveal that solar cycle 25 will be weaker than cycle 24.Further,we predict that the maximum of cycle 25 is likely to occur between February and March 2024.While the aa index has been utilized extensively in the past,this work establishes SLDs as another potential candidate for predicting the characteristics of the next cycle.
基金supported by the International Space Science Institute (ISSI),Bern,Switzerland and ISSI-Beijing,China。
文摘A combined uniform and long-time series of Ca-K images from the Kodaikanal Observatory,Mount Wilson Observatory and Mauna Loa Solar Observatory was used to identify and study the Ca-K small-scale features and their solar cycle variations over a century.The small scale features are classified into three distinct categories:enhanced network,active network and quiet network.All these features show that their areas vary according to the11 yr solar cycle.The relative amplitude of the Ca-K network variations agrees with that of the sunspot cycle.The total area of these small-scale features varies from about 5%during the minimum phase of the solar cycle to about20%during its maximum phase.
基金funded by the National Natural Science Foundation of China(NSFC,Grant Nos.11661161011,11433007,11220101001,11328302,11373005 and 11303064)the Opening Project of Key Laboratory of Astronomical Optics&Technology,Nanjing Institute of Astronomical Optics&Technology,Chinese Academy of Sciences(CASKLAOT-KF201606)+4 种基金the“Strategic Priority Research Program”of the Chinese Academy of Sciences(Grant No.XDA04075200)the special fund for astronomy of CAS(2015–2016)the special funding for Young Researcher of Nanjing Institute of Astronomical Optics&Technologythe International Partnership Program of the Chinese Academy of Sciences(Grant No.114A32KYSB20160018)the Mt.Cuba Astronomical Foundation
文摘Polarimetry plays an important role in the measurement of solar magnetic fields. We devel- oped a high-sensitivity and high-accuracy polarimeter （HHP） based on nematic liquid crystal variable retarders （LCVRs）, which has a compact setup and no mechanical moving parts. The system design and calibration methods are discussed in detail. The azimuth error of the transmission axis of the polarizer as well as the fast axes of the two LCVRs and the quarter-wave plate were determined using dedicated procedures. Linearly and circularly polarized light were employed to evaluate the performance of the HHP. The experimental results indicate that a polarimetric sensitivity of better than 5.7 × 10-3 can be achieved by using a single short-exposure image, while an accuracy on the order of 10-5 can be reached by using a large number of short-exposure images. This makes the HHP a high-performance system that can be used with a ground-based solar telescope for high-precision solar magnetic field investigations.
