The CIR characteristic features exhibit no clear solar-cycle phase dependence. CIRs are characterized by average (median) plasma density of \(\approx 29\) cm −3 ( \(\approx 26\) cm −3), ram pressure of \(\approx 11\) nPa ( \(\approx 9\) nPa), temperature of \(\approx 5\times 10^\) K), and magnetic-field magnitude of \(\approx 15\) nT ( \(\approx 14\) nT). At 1 AU, CIRs are found to be large-scale interplanetary structures with an average (median) duration of \(\approx 26\) hours ( \(\approx 24\) hours) and radial extent of \(\approx 0.31\) AU ( \(\approx 0.27\) AU). The occurrence rate is the maximum during the solar-cycle descending phase ( \(\approx 33\) year −1), followed by occurrences during solar minimum ( \(\approx 24\) year −1), the ascending phase ( \(\approx 22\) year −1), and solar maximum ( \(\approx 11\) year −1). Using solar-wind measurements upstream of Earth, we identified 290 CIRs encountered by Earth during January 2008 through December 2019 (Solar Cycle 24). 2a–c) shows the electron fluxes near/at 6.6 R E as observed by ERG, GOES-15 and GOES-13, respectively.Corotating interaction regions (CIRs) form in the interaction region between the solar-wind high-speed streams and slow streams, leading to compressed plasma and magnetic fields. Considering 90° local pitch angle electrons, Fig. HEP is equipped with two types of telescope, HEP-L (70 keV ~ 1 MeV) and HEP-H (0.7 ~ 2 MeV) (Mitani et al. 1h) of ERG, which was orbiting near the magnetic equator at radial distances shorter than GEO. At ~ 22:30 UT, significant enhancement of electron differential fluxes was observed by the High-energy Electron exPeriments (HEP) (Fig. The gradual dipolarization signatures and duration were similar to the second substorm injection in Gkioulidou et al. ERG observed a nearly dispersionless, namely not perfectly dispersionless, injection accompanied by a gradual increase of B z instead of a sharp dipolarization. The apogee and perigee altitudes of ERG orbit were \(\sim6 R_\) components observed at ERG positions. The magnetospheric spacecraft, ERG, was successfully launched by the Epsilon launch vehicle from the JAXA Uchinoura Space Center on December 20, 2016. But the Exploration of energization and Radiation in Geospace (ERG, nicknamed Arase) spacecraft also observed a substorm injection event at radial distances shorter than GEO during a special period of the mission. Particle injections associated with substorms were usually studied based on observations at the geosynchronous orbit (GEO). The substorm injection expanding earthward farther than GEO was observed by ERG, and the event can be better simulated by the further-developed model shown in this work. Despite possible deviation of the model magnetic fields from reality, the relativistic computations still show dominant effect on the drift echoes periods. Our work shows that the main features of the substorm injection event are successfully reproduced with the drift echoes periods showing a better fit to the observations of this event when relativistic effects are considered. Since the electron energies of interest are comparable to the rest mass energy, our work further provides the relativistic form of the previous model and employs a semiempirical model as background field instead of a dipole-based one in the previous study. ERG and GOES spacecraft measured tens to a few hundred keV electrons injected during the substorm, providing important seed population for ring current and radiation belts. To study the substorm injection event and produce drift echoes with better periods, we modify an existing model in the literature. So far such models showed good results of dispersionless features compared to spacecraft observations, but could only produce drift echoes with periods somewhat different from geosynchronous observations. Models built on an impulsive earthward-propagating electromagnetic field have been proposed to simulate substorm injections. The observations provided constraints to study the event and opportunities to make adjustments to the previous substorm injection models. The GOES-15 and GOES-13 measured the drift echoes of the event as well. ERG successfully observed a clear and sufficient extent of manifestations of the dispersionless injection and the successive drift echoes at radial distances shorter than geosynchronous orbit (GEO) during a unique period of the satellite mission. 5, 2017, was observed by the ERG (Arase), GOES-15 and GOES-13 spacecraft. Substorm-associated electron injection, starting on Apr.
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