A geomagnetic storm is a global disturbance of Earth?s magnetosphere,occurring as a result of the interaction with magnetic plasma ejected from the Sun.Despite considerable research,a comprehensive classification of s...A geomagnetic storm is a global disturbance of Earth?s magnetosphere,occurring as a result of the interaction with magnetic plasma ejected from the Sun.Despite considerable research,a comprehensive classification of storms for a complete solar cycle has not yet been fully developed,as most previous studies have been limited to specific storm types.This study,therefore,attempted to present complete statistics for solar cycle 24,detailing the occurrence of geomagnetic storm events and classifying them by type of intensity(moderate,intense,and severe),type of complete interval(normal or complex),duration of the recovery phase(rapid or long),and the number of steps in the storm?s development.The analysis was applied to data from ground-based magnetometers,which measured the Dst index as provided by the World Data Center for Geomagnetism,Kyoto,Japan.This study identified 211 storm events,comprising moderate(177 events),intense(33 events),and severe(1 event)types.About 36%of ICMEs and 23%of CIRs are found to be geoeffective,which caused geomagnetic storms.Up to four-step development of geomagnetic storms was exhibited during the main phase for this solar cycle.Analysis showed the geomagnetic storms developed one or more steps in the main phase,which were probably related to the driver that triggered the geomagnetic storms.A case study was additionally conducted to observe the variations of the ionospheric disturbance dynamo(Ddyn)phenomenon that resulted from the geomagnetic storm event of 2015July 13.The attenuation of the Ddyn in the equatorial region was analyzed using the H component of geomagnetic field data from stations in the Asian sector(Malaysia and India).The variations in the Ddyn signatures were observed at both stations,with the TIR station(India)showing higher intensity than the LKW station(Malaysia).展开更多
Among electromagnetic methods of short-term earthquake prediction,an approach is being actively developed based on the phenomenon of magnetic ultra-low-frequency(ULF)power depression occurring a few days before an ear...Among electromagnetic methods of short-term earthquake prediction,an approach is being actively developed based on the phenomenon of magnetic ultra-low-frequency(ULF)power depression occurring a few days before an earthquake.In particular,a nighttime geomagnetic power depression in the band 0.03-0.05 Hz was observed approximately 5 days before the catastrophic Tohoku 2011 earthquake.To verify the reliability of this method,we performed an extended analysis using data from magnetometer arrays JMA,MAGDAS,PWING,and INTERMAGNET.The selected stations included sites close to the epicenter(<300 km)and remote points(~10000 km).The band-integrated spectral power of nighttime magnetic noise decreased significantly from March 6-9,several days before the earthquake.However,such variations occur simultaneously not only at nearby stations but also at distant stations.During this event,the ULF power depression was caused by low global geomagnetic activity,as evidenced by the planetary index SME.Thus,the depression of geomagnetic ULF noise cannot be considered a reliable short-term precursor.展开更多
Radiative transfer models(RTMs) have been used to estimate grain size of amorphous and crystalline water(H_(2)O)ice in the outer solar system from near-infrared(NIR) wavelengths. We use radiative scattering models to ...Radiative transfer models(RTMs) have been used to estimate grain size of amorphous and crystalline water(H_(2)O)ice in the outer solar system from near-infrared(NIR) wavelengths. We use radiative scattering models to assess the discrepancy in grain size estimation of H_(2)O ice at a temperature of 15, 40, 60, and 80 K(amorphous) and 20,40, 60, and 80 K(crystalline)—relevant to the outer solar system. We compare the single scattering albedos of H_(2)O ice phases using the Mie theory and Hapke approximation models from the optical constant at NIR wavelengths(1–5 μm). This study reveals that Hapke approximation models—Hapke slab and internal scattering model(ISM)—predict grain size of crystalline phase slightly closer to Mie model than amorphous phase at temperatures of 15–80 K. However, the Hapke slab model predicts, in general, grain sizes much closer to those of the Mie model’s estimations while ISM predicted grain sizes exhibit a higher uncertainty. We recommend using the Mie model for unknown spectra of outer solar system bodies to estimate H_(2)O ice grain sizes. While choosing the approximation model for employing RTMs, we recommend using a Hapke slab approximation model over the ISM.展开更多
基金funding by Fundamental Research Grant Scheme(FRGS)under Ministry of Higher Education(KPT)Malaysia with the grant No.FRGS/1/2023/STG07/UKM/02/1supported by Universiti Sains Malaysia through Short-Term Grant with project No.304/PFIZIK/6315730supported by JSPS KAKENHI grant Nos.JP20H01961,JP22K03707,JP21H04518,JP22K21345。
文摘A geomagnetic storm is a global disturbance of Earth?s magnetosphere,occurring as a result of the interaction with magnetic plasma ejected from the Sun.Despite considerable research,a comprehensive classification of storms for a complete solar cycle has not yet been fully developed,as most previous studies have been limited to specific storm types.This study,therefore,attempted to present complete statistics for solar cycle 24,detailing the occurrence of geomagnetic storm events and classifying them by type of intensity(moderate,intense,and severe),type of complete interval(normal or complex),duration of the recovery phase(rapid or long),and the number of steps in the storm?s development.The analysis was applied to data from ground-based magnetometers,which measured the Dst index as provided by the World Data Center for Geomagnetism,Kyoto,Japan.This study identified 211 storm events,comprising moderate(177 events),intense(33 events),and severe(1 event)types.About 36%of ICMEs and 23%of CIRs are found to be geoeffective,which caused geomagnetic storms.Up to four-step development of geomagnetic storms was exhibited during the main phase for this solar cycle.Analysis showed the geomagnetic storms developed one or more steps in the main phase,which were probably related to the driver that triggered the geomagnetic storms.A case study was additionally conducted to observe the variations of the ionospheric disturbance dynamo(Ddyn)phenomenon that resulted from the geomagnetic storm event of 2015July 13.The attenuation of the Ddyn in the equatorial region was analyzed using the H component of geomagnetic field data from stations in the Asian sector(Malaysia and India).The variations in the Ddyn signatures were observed at both stations,with the TIR station(India)showing higher intensity than the LKW station(Malaysia).
基金supported by Grant 22-17-00125 from the Russian Science Foundation.
文摘Among electromagnetic methods of short-term earthquake prediction,an approach is being actively developed based on the phenomenon of magnetic ultra-low-frequency(ULF)power depression occurring a few days before an earthquake.In particular,a nighttime geomagnetic power depression in the band 0.03-0.05 Hz was observed approximately 5 days before the catastrophic Tohoku 2011 earthquake.To verify the reliability of this method,we performed an extended analysis using data from magnetometer arrays JMA,MAGDAS,PWING,and INTERMAGNET.The selected stations included sites close to the epicenter(<300 km)and remote points(~10000 km).The band-integrated spectral power of nighttime magnetic noise decreased significantly from March 6-9,several days before the earthquake.However,such variations occur simultaneously not only at nearby stations but also at distant stations.During this event,the ULF power depression was caused by low global geomagnetic activity,as evidenced by the planetary index SME.Thus,the depression of geomagnetic ULF noise cannot be considered a reliable short-term precursor.
基金国家自然科学基金项目(40773013)教育部博士点新教师基金项目(20070491518)+2 种基金GPMR开放基金项目(GPMR0742)美国National Science Foundation(EAR-0838227)阿肯色州Arkansas Space Grant Consortium(SW19002)联合资助
文摘Radiative transfer models(RTMs) have been used to estimate grain size of amorphous and crystalline water(H_(2)O)ice in the outer solar system from near-infrared(NIR) wavelengths. We use radiative scattering models to assess the discrepancy in grain size estimation of H_(2)O ice at a temperature of 15, 40, 60, and 80 K(amorphous) and 20,40, 60, and 80 K(crystalline)—relevant to the outer solar system. We compare the single scattering albedos of H_(2)O ice phases using the Mie theory and Hapke approximation models from the optical constant at NIR wavelengths(1–5 μm). This study reveals that Hapke approximation models—Hapke slab and internal scattering model(ISM)—predict grain size of crystalline phase slightly closer to Mie model than amorphous phase at temperatures of 15–80 K. However, the Hapke slab model predicts, in general, grain sizes much closer to those of the Mie model’s estimations while ISM predicted grain sizes exhibit a higher uncertainty. We recommend using the Mie model for unknown spectra of outer solar system bodies to estimate H_(2)O ice grain sizes. While choosing the approximation model for employing RTMs, we recommend using a Hapke slab approximation model over the ISM.
