We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dyna...We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,the 5 minutes decayless kink oscillations of coronal loops were detected and they are independent of the solar flare.Based on the observed oscillations and seismological diagnostics,we estimate that the Alfvén speed and magnetic field in these coronal loops are around 466 kms^(-1) sand 7.6 G,respectively.Additionally,the flare-related jet shows its plasmoids with 1 minute periodicity same as the intensity fluctuation of nearby flare ribbon.The correlation between the intensity fluctuation of jet and that of flare ribbon indicates that their 1 minute oscillations should originate from the same reconnection process.展开更多
Using observations from the Michelson Doppler Imager（MDI） onboard Solar and Heliospheric Observatory（SOHO）, we develop a computational algorithm to automatically identify bipolar magnetic regions（BMRs） in active...Using observations from the Michelson Doppler Imager（MDI） onboard Solar and Heliospheric Observatory（SOHO）, we develop a computational algorithm to automatically identify bipolar magnetic regions（BMRs） in active regions（ARs）, and then study their statistical properties.The individual magnetic（positive or negative） pole of a BMR is determined from the region with an absolute strength above 55 G and with an area larger than 250 pixel^2（~495 Mm^2）, while a BMR is identified as a pair of positive and negative poles with the shortest area-weight distance between them.Based on this method, 2234 BMRs are identified from MDI synoptic magnetograms between Carrington Rotations 1909（1996 May 06） and 2104（2010 December 10）. 1005 of them are located in the northern hemisphere, while the other 1229 are in the southern hemisphere. We find that the BMR parameters（e.g., latitude, separation, fragment number and strength） are similar to those of ARs. Moreover, based on the maximum likelihood estimation（MLE） method, the frequency distributions representing the occurrence of these BMRs as functions of area and magnetic flux exhibit a power-law behavior, i.e.,dN/dx ∝ x^（-αx）, with indices of α_A = 1.98 ± 0.06 and α_F = 1.93 ± 0.05 respectively. We also find that their orientation angles（θ） follow ＂Hale＇s Polarity Law＂ and deviate slightly toward the direction of the solar equator. Consistent with previous findings, we obtain the dependence of orientation angles on latitudes for normal BMRs during the 23 rd solar cycle. The north-south asymmetry of these BMRs is also detected here.展开更多
基金funded by NSFC under Grant Nos.12073081,11973092 and 11790302CAS Strategic Pioneer Program on Space Science under Grant Nos.XDA15052200 and XDA15320301supported by Surface Project of Jiangsu No.BK20211402。
文摘We investigate the oscillations in active region(AR)NOAA 12891,which produces a C2.0 three-ribbon flare accompanying a jet on 2021 November 2.Using the data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,the 5 minutes decayless kink oscillations of coronal loops were detected and they are independent of the solar flare.Based on the observed oscillations and seismological diagnostics,we estimate that the Alfvén speed and magnetic field in these coronal loops are around 466 kms^(-1) sand 7.6 G,respectively.Additionally,the flare-related jet shows its plasmoids with 1 minute periodicity same as the intensity fluctuation of nearby flare ribbon.The correlation between the intensity fluctuation of jet and that of flare ribbon indicates that their 1 minute oscillations should originate from the same reconnection process.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11603077, 11573072 and 11333009)the Youth Fund of Jiangsu (No. BK20161095)the Laboratory (No. 2010DP173032)
文摘Using observations from the Michelson Doppler Imager（MDI） onboard Solar and Heliospheric Observatory（SOHO）, we develop a computational algorithm to automatically identify bipolar magnetic regions（BMRs） in active regions（ARs）, and then study their statistical properties.The individual magnetic（positive or negative） pole of a BMR is determined from the region with an absolute strength above 55 G and with an area larger than 250 pixel^2（~495 Mm^2）, while a BMR is identified as a pair of positive and negative poles with the shortest area-weight distance between them.Based on this method, 2234 BMRs are identified from MDI synoptic magnetograms between Carrington Rotations 1909（1996 May 06） and 2104（2010 December 10）. 1005 of them are located in the northern hemisphere, while the other 1229 are in the southern hemisphere. We find that the BMR parameters（e.g., latitude, separation, fragment number and strength） are similar to those of ARs. Moreover, based on the maximum likelihood estimation（MLE） method, the frequency distributions representing the occurrence of these BMRs as functions of area and magnetic flux exhibit a power-law behavior, i.e.,dN/dx ∝ x^（-αx）, with indices of α_A = 1.98 ± 0.06 and α_F = 1.93 ± 0.05 respectively. We also find that their orientation angles（θ） follow ＂Hale＇s Polarity Law＂ and deviate slightly toward the direction of the solar equator. Consistent with previous findings, we obtain the dependence of orientation angles on latitudes for normal BMRs during the 23 rd solar cycle. The north-south asymmetry of these BMRs is also detected here.
