We simulated the Nov 4, 2021 geomagnetic storm event penetrating electric field using the Multiscale Atmosphere-Geospace Environment (MAGE) and compared with the NASA ICON observation. The ICON observation showed enhancement of the vertical ion drift when the penetrating electric field arrived at the equatorial region. The simulated vertical ion drifts are consistent with ICON observation. Hence, we are able to verify the MAGE simulation with ICON observation. On the dusk side, the MAGE simulation showed strong pre-reversal enhancement (PRE), whereas the ICON observation did not display any sign of the PRE. The MAGE simulation did show that PRE amplitude decreases as altitude increase. Because the ICON orbital height is above the model upper boundary, it could be a factor for the discrepancy. Instrumental issue cannot be ruled out at this moment. GOLD UV image at the same time exhibits multiple plasma bubbles, which seem to suggest the existence of the PRE.

Ionospheric convection patterns from the Super Dual Auroral Radar Network are used to determine the trajectories, transit times and decay rates of three polar cap patches from their creation in the dayside polar cap ionosphere to their end of life on the nightside. The first two polar cap patches were created within 12 minutes of each other and travelled through the dayside convection throat, before entering the nightside auroral oval after 104 and 92 minutes, respectively. When the patches approached the nightside auroral oval, an intensification in the poleward auroral boundary occurred close to their exit point, followed by a decrease in the transit velocity. The airglow decay rates of patches 1 and 2 were found to be ≈0.6% and ≈0.9% per minute, respectively. The third patch decayed completely within the polar cap and had a lifetime of only 78 minutes. After a change in drift direction, patch 3 had a radar backscatter power half-life of 4.23 minutes, which reduced to 1.80 minutes after a stagnation, indicating a variable decay rate. 28 minutes after the change in direction, and 16 minutes after stagnation, patch 3 completely disintegrated. We relate this rapid decay to increased frictional heating, which speeds up the recombination rate. Therefore, we suggest that the stagnation of a polar cap patch is a main determinant to whether or not a polar cap patch can exit through the nightside auroral oval.

Solar eruptions cause geomagnetic storms in the near-Earth environment, creating spectacular aurorae visible to the human eye and invisible dynamic changes permeating all of geospace. Just equatorward of the aurora, radars and satellites often observe intense westward plasma flows called subauroral polarization streams (SAPS) in the dusk-to-midnight ionosphere. SAPS occur across a narrow latitudinal range and lead to intense frictional heating of the ionospheric plasma and atmospheric neutral gas. SAPS also generate small-scale plasma waves and density irregularities that interfere with radio communications. As opposed to the commonly observed duskside SAPS, intense eastward subauroral plasma flows in the morning sector were recently discovered to have occurred during a super storm on 20 November 2003. However, the origin of these flows termed “dawnside SAPS” could not be explained by the same mechanism that causes SAPS on the duskside and has remained a mystery. Through real-event global geospace simulations, here we demonstrate that dawnside SAPS can only occur during major storm conditions. During these times the magnetospheric plasma convection is so strong as to effectively transport ions to the dawnside, whereas they are typically deflected to the dusk by the energy-dependent drifts. Ring current pressure then builds up on the dawnside and drives field-aligned currents that connect to the subauroral ionosphere, where eastward SAPS are generated. The origin of dawnside SAPS explicated in this study advances our understanding of how the geospace system responds to strongly disturbed solar wind driving conditions that can have severe detrimental impacts on human society and infrastructure.

We propose a ‘system-of-systems’—an integrated web of SpWx stations and state-of-the-art modeling facilities to enable a transformative advance in Space Weather nowcasting and forecasting. The Space Weather Aggregated Network of Systems (SWANS) will enable space situational awareness for end-users invested in spaceflight operations, infrastructure risk mitigation, and future human endeavors in space exploration while profoundly transforming Heliophysics research by 2050 or earlier.

Using the newly developed, Multiscale Atmosphere-Geospace Environment (MAGE) model, we simulated the penetrating electric field in the equatorial region under different interplanetary magnetic field (IMF) Bz conditions during September 2020. Two intervals were selected for detailed analysis with the vertical ion drift data from the NASA ICON. The MAGE simulations show that in southward IMF (S-IMF) cases, the dawn-dusk electric potential drop at the equator is about 14% of the cross polar cap potential difference. The dawn-dusk potential drop at the equator varies instantaneously with the changes in the IMF Bz or interplanetary electric field, which in turn alters the vertical ion drift. The daytime changes of the equatorial vertical ion drift in response to the penetrating electric field related to the IMF Bz are only half of that during the nighttime, due mostly to the E-region dynamo. MAGE simulation shows pre-reversal enhancement (PRE) during southward IMF cases, but the PRE was absent in the ICON IVM observations. Further observations and modeling are needed to resolve this discrepancy.

Strong subauroral plasma flows were observed in the dawnside ionosphere during the 20 November 2003 super geomagnetic storm. They are identified as dawnside subauroral polarization streams (SAPS) in which plasma drift direction is eastward and opposite to the westward SAPS typically found in the dusk sector. Both dawnside and duskside SAPS are driven by the enhanced meridional electric field in the low latitude portion of Region-2 field-aligned currents (FACs) in the subauroral region where ionospheric conductance is relatively low. However, dawnside eastward SAPS were only observed in the main and recovery phases while duskside westward SAPS were found much earlier before the sudden storm commencement. Simulations with the Multiscale Atmosphere-Geospace Environment (MAGE) model demonstrate that the eastward SAPS are associated with dawnside ring current build-up. Unlike the duskside where ring current build-up and SAPS formation can occur under moderate driving conditions, strong magnetospheric convection is required for plasmasheet ions to overcome their energy-dependent drifts to effectively build up the dawnside ring current and upward Region-2 FACs. We further used test particle simulations to show the characteristic drift pattern of energetic protons under strong convection conditions and how they are related to the dawnside SAPS occurrence. This study demonstrates the connection between the level of solar wind driving condition and a rare ionospheric structure, eastward SAPS on the dawnside, which only occur under strong convection typically associated with intense or super storms. Dawnside SAPS are suggested as a unique feature of major geomagnetic storms.

The equatorial ionosopheric anomalies (EIA) at night are the slowly recombining remnants of the dayside ionosphere, and charged particle densities slowly decay during the course of the night. Thus the electron density in ionosphere in the early morning (0300-0400 Local time) is usually very low and the ionospheric UV 135.6 nm O+ recombination emission is rarely detectable from current UV remote sensing instruments. However, there are times when the EIA have unusually high density even during these morning times and are observable by the DMSP/SSUSI and TIMED/GUVI instruments. By using other UV ‘colors’ - 130.4 nm (from monatomic Oxygen) and N2 Lyman Birge Hopfield bands - we can establish that this emission is definitely from the ionosphere recombination emission. We will show examples of this phenomenon, and correlate these occurrences to geomagnetic storm events. We estimate the electron density in the early morning EIA and compare with other ionosphere observations and climatological models. In the figure below, we show the 135.6 nm radiance seen by DMSP F16 SSUSI as it crosses the equator around 210 degrees longitude (over the Pacific Ocean) at 03:45 local time. The equatorial anomaly peaks are clearly visible in the SSUSI data. These radiances are background subtracted, which is not perfect and introduces a small (-1 Rayleigh) bias to the resulting radiances. DMSP = Defense Meteorological Satellite Program, SSUSI = Special Sensor Ultraviolet Spectrographic Imager; TIMED = Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics, GUVI = Global UltraViolet Imager