We report on the characteristics of nighttime medium-scale traveling ionospheric disturbances （MSTIDs） propagating northward observed with the SuperDARN Hokkaido HF radar, which has a field of view to the north of J...We report on the characteristics of nighttime medium-scale traveling ionospheric disturbances （MSTIDs） propagating northward observed with the SuperDARN Hokkaido HF radar, which has a field of view to the north of Japan, and occasionally with the GNSS Earth Observation NETwork （GEONET）, which provides total electron content （TEC） data over Japan. From statis- tical analysis of MSTIDs observed with the Hokkaido radar during nighttime （1700-0700 LT） from January 2007 to July 2009, we find that these MSTIDs traveling northward, although rare in comparison with those traveling southwestward, have a relatively high occurrence rate after sunset and around midnight in May and August, which is partly consistent with the occurrence rate of MSTIDs over Japan observed with GEONET in 2002, when the MSTID event database is available. We also use the data from simultaneous observation of nightside MSTIDs by the Hokkaido radar and GEONET to find that when the HF radar observed northward-propagating MSTIDs, GEONET did not always observe such MSTIDs with the same propagation direction. Judging from this result and considering the HF radar field of view located to the north of the GEONET coverage area, we speculate that some physical parameters of the ionosphere/thermosphere over Japan differ from those to the north of Japan, which may result in the inconsistency of MSTID propagation direction. The present results provide new knowledge of MSTIDs propagating northward using the Hokkaido radar, whose field of view was not covered by GEONET.展开更多
OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over ...OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.展开更多
Data analysis method (CRA, hereafter) to correlate multiple TEC anomaly signals has detected pre-seismic anomalies before the 2011 Tohoku-Oki earthquake (Iwata & Umeno 2016), the 2016 Kumamoto earthquake (Iwata &a...Data analysis method (CRA, hereafter) to correlate multiple TEC anomaly signals has detected pre-seismic anomalies before the 2011 Tohoku-Oki earthquake (Iwata & Umeno 2016), the 2016 Kumamoto earthquake (Iwata & Umeno 2017) and the 2016 Tainan earthquake (Goto <i><span style="font-family:Verdana;">et al</span></i><span style="font-family:Verdana;">. 2019). However, a critical argument said that those anomalies detected by CRA would not </span><span style="font-family:Verdana;">be pre-seismic anomalies published by Journal of Geophysical Re</span><span style="font-family:Verdana;">search-Space Physics (126), 2021 (JGR-SP (126), hereafter). In this paper, we would point out its incorrect use of statistical anomalies in evaluating CRA as the following points: CRA is shown to increase the signal-to-noise ratio (SNR) to amplify pre-seismic TEC’s small anomaly signals with synchronizing and correlating multiple GNSS receivers’ data. We proved again that pre-seismic anomalies certainly exist before the 2011 Tohoku-Oki earthquake and the 2016 Kumamoto earthquake with additional data analysis. In particular, </span><span style="font-family:Verdana;">a</span><span style="font-family:Verdana;">s </span><span style="font-family:Verdana;">a</span><span style="font-family:Verdana;"> temporal anomaly, deceleration at propagation velocities of medium-scale traveling ionospheric disturbances (MSTID, hereafter) before the 2016 Kumamoto earthquake captured by CRA (Iwata & Umeno 2017) is elucidated as pre-seismic anomalies. Furthermore, we proposed a physical model to predict that 35 m/s change at MSTID propagation velocities estimated by TEC’s CRA requires 0.58</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;"><span style="white-space:nowrap;">-</span>3</span></sup><span style="font-family:Verdana;"> V/m electric field in the F Layer ionosphere. Contrary to the claim with the incorrect use of statistical anomalies in JGR-SP (126), TEC’s correlation anomalies detected by CRA (Iwata & Umeno 2016 and Iwata & Umeno 2017) clearly provided supporting evidence that physical pre-seismic anomalies really exist.</span>展开更多
基金supported by a Grant-in-Aid for Scientific Research of the Ministry of Education,Culture,Sports,Science and Technology of Japan(Grant no.19340141)by Special Funds for Education and Research(Energy Transport Processes in Geospace) of the Ministry of Education,Culture,Sports,Science and Technology of Japan
文摘We report on the characteristics of nighttime medium-scale traveling ionospheric disturbances （MSTIDs） propagating northward observed with the SuperDARN Hokkaido HF radar, which has a field of view to the north of Japan, and occasionally with the GNSS Earth Observation NETwork （GEONET）, which provides total electron content （TEC） data over Japan. From statis- tical analysis of MSTIDs observed with the Hokkaido radar during nighttime （1700-0700 LT） from January 2007 to July 2009, we find that these MSTIDs traveling northward, although rare in comparison with those traveling southwestward, have a relatively high occurrence rate after sunset and around midnight in May and August, which is partly consistent with the occurrence rate of MSTIDs over Japan observed with GEONET in 2002, when the MSTID event database is available. We also use the data from simultaneous observation of nightside MSTIDs by the Hokkaido radar and GEONET to find that when the HF radar observed northward-propagating MSTIDs, GEONET did not always observe such MSTIDs with the same propagation direction. Judging from this result and considering the HF radar field of view located to the north of the GEONET coverage area, we speculate that some physical parameters of the ionosphere/thermosphere over Japan differ from those to the north of Japan, which may result in the inconsistency of MSTID propagation direction. The present results provide new knowledge of MSTIDs propagating northward using the Hokkaido radar, whose field of view was not covered by GEONET.
基金supported by Coordenacao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq),under the processes 470589/2012-4,305461/2015-0,303511/2017-6,307653/2017-0,and 169815/2017-0the Fundacao de AmparoàPesquisa do Estado de Sao Paulo(FAPESP)under the process 2018/09066-8。
文摘OI 630.0 nm airglow observations,from a new observatory at Bom Jesus de Lapa,were used to study the interaction between EPBs(Equatorial Plasma Bubbles)and the MSTID(Medium-Scale Traveling Ionospheric Disturbance)over the Northeast region in Brazil.On the night of September 16 to 17,2020,an EPB was observed propagating eastward,in an apparent fossil stage,until it interacted with a dark band electrified MSTID(e MSTID).After the interaction,four EPBs merged,followed by an abrupt southward development and bifurcations.Analysis of the data suggests that an eastward polarization electric field,induced by the dark band e MSTID,forced the EPB into an upward drift,growing latitudinally along the magnetic field lines and then bifurcating.
文摘Data analysis method (CRA, hereafter) to correlate multiple TEC anomaly signals has detected pre-seismic anomalies before the 2011 Tohoku-Oki earthquake (Iwata & Umeno 2016), the 2016 Kumamoto earthquake (Iwata & Umeno 2017) and the 2016 Tainan earthquake (Goto <i><span style="font-family:Verdana;">et al</span></i><span style="font-family:Verdana;">. 2019). However, a critical argument said that those anomalies detected by CRA would not </span><span style="font-family:Verdana;">be pre-seismic anomalies published by Journal of Geophysical Re</span><span style="font-family:Verdana;">search-Space Physics (126), 2021 (JGR-SP (126), hereafter). In this paper, we would point out its incorrect use of statistical anomalies in evaluating CRA as the following points: CRA is shown to increase the signal-to-noise ratio (SNR) to amplify pre-seismic TEC’s small anomaly signals with synchronizing and correlating multiple GNSS receivers’ data. We proved again that pre-seismic anomalies certainly exist before the 2011 Tohoku-Oki earthquake and the 2016 Kumamoto earthquake with additional data analysis. In particular, </span><span style="font-family:Verdana;">a</span><span style="font-family:Verdana;">s </span><span style="font-family:Verdana;">a</span><span style="font-family:Verdana;"> temporal anomaly, deceleration at propagation velocities of medium-scale traveling ionospheric disturbances (MSTID, hereafter) before the 2016 Kumamoto earthquake captured by CRA (Iwata & Umeno 2017) is elucidated as pre-seismic anomalies. Furthermore, we proposed a physical model to predict that 35 m/s change at MSTID propagation velocities estimated by TEC’s CRA requires 0.58</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;"><span style="white-space:nowrap;">-</span>3</span></sup><span style="font-family:Verdana;"> V/m electric field in the F Layer ionosphere. Contrary to the claim with the incorrect use of statistical anomalies in JGR-SP (126), TEC’s correlation anomalies detected by CRA (Iwata & Umeno 2016 and Iwata & Umeno 2017) clearly provided supporting evidence that physical pre-seismic anomalies really exist.</span>
