Interstellar Boundary Explorer (IBEX) may have recorded a cross-tail current disruption event of the substorm

The spatial and temporal variations of satellite measurements correspond to different physical connotations. ENA imaging is an effective method to avoid the confusion of spatial and temporal variations of plasma space distribution in remote sensing region. However, for the neutral atom imager with scanning sampling, if the sampling time is too long (such as exceeding the evolution period of related physical events), it is still necessary to carefully analyze the time change factors of the space environment during the sampling period. Our re-certi ﬁ cation of ENA scanning images of the IBEX-Hi’s “terrestrial plasma sheet disconnection” revealed that a magnetospheric substorm occurred during sampling, most likely due to the pitch angle diffusion of energetic ions in the ring current to create the so-called “plasma sheet disconnection” illusion. The observation of ENA imaging re ﬂ ects the motion pattern of its parent ions, which have a certain distance from space plasma visualization. The dynamic evolution of ring current energetic ion diffusion has inspired us to create a new macroscopic model of substorms that can be visually monitored in the ecliptic plane using ENA imaging

The American Interstellar Boundary Explorer (IBEX) team published their fi rst ENA image of the terrestrial plasma sheet in 2011 [1].One of the images shows a possible disconnection event of the plasma sheet (Figure S1) and identifi es the red area with high fl ux on the right of Figure S1 as a plasmoid.This image has appeared several times in recent ENA exploration project proposals.In fact, it has the worst spatiotemporal resolution of any previous ENA imaging measurements (a spatial resolution of about 6 R E and a temporal resolution of 40 hours).However, it appears near the inner boundary of the plasma sheet at a distance of -10 R E of the magnetotail, providing imagination space for the visualization of space plasma.As a symbol of space plasma visualization, it has substantially affected the positioning of scientifi c objectives, making many ENA imaging proposals aim at the distant magnetotail lobe reconnection.However, neutral atom imaging measurements are remote sensing of parent energetic ions via ENA tracer particles.The ring current ion fl ux and plasma sheet ion density distributed in the magnetotail corresponds to different ion motion patterns and the ENA tracking particles produced by them also have different propagation characteristics.Is the above ENA image a disconnection event of the plasma sheet or a current disruption of the substorm?We need to verify whether the ENA image records spatial or temporal changes during IBEX-Hi scanning.
The raw data in the same literature (Figure S2) indicate that the so-called plasmoid signal stopped abruptly in the afternoon of the 29th.The ENA fl ux recorded before and after the valley value of the measured data on the 28th is of the same magnitude, which should belong to the same generation mechanism.After the 29th, IBEX-Hi continued to aim at the plasma sheet, but the measurement results were only equivalent to the background intensity.It was not until November 2 that IBEX-Hi entered the plasma sheet to obtain measurements of a full fi eld of view.This shows that the ENA tracer particles produced by thermally moving ions in the plasma sheet propagate omnidirectional, and the fl ux decay is inversely proportional to the square of the distance, and soon decays to be indistinguishable from the background.
During the geomagnetic quiet period, the pitch angle of energetic ions in the ring current is mostly 90°.The ENAs they produce propagate only within the equatorial plane, the fl ux decay is inversely proportional to the distance, and the relative decay is slow so that the fl ux of such particles can still be telemetered near the orbit of the moon.
During the substorm, the pitch angle of energetic ions in Citation: Lu L (2023) Interstellar Boundary Explorer (IBEX) may have recorded a cross-tail current disruption event of the substorm.J Civil Eng Environ Sci 9(2): 065-067.DOI: https://dx.doi.org/10.17352/2455-488X.000070 the ring current diffused, resulting in a decrease in the ENA fl ux propagated in the ecliptic plane, and consequently the observational illusion of the plasma sheet disconnection.Before midnight on the 28th, the geomagnetic activity returned to quiet, and the scanning fi eld of view of IBEX-Hi could still cover the ring current at the far end of the magnetotail, and the ENA fl ux enhancement signal was measured.That is, the ENA fl ux with a gap recorded by IBEX-Hi in orbit 51 is generated by the parent energetic ions of the ring current.Therefore, we conclude that IBEX-Hi in orbit 51 recorded a cross-tail current disruption event of the substorm.Inspired by the measurement result, we created a substorm macro model, this model can use ENA panoramic imaging technology for dynamic monitoring, recently published in MDPI astronomy [2].We simulate the dynamic evolution of ring current during substorms through the pitch angle diffusion of energetic ions (Figure 2) and propose to establish a lunar base ENA imaging monitoring station with a stable observation fi eld.

Figure 1 :
Figure 1: Substorm index curves, where the red and gray areas represent AU and AL, respectively, and two vertical dashed lines represent the ENA image scanning period of IBEX-Hi.

Figure 2 :
Figure 2: The sequence diagram (A-D) shows the dynamic evolution of ring current during the growth phase of substorm simulated by ENA imaging at the fi rst quarter of moon orbit.