Global simulations predict that the low‐latitude mantle may be an important pathway for the solar wind entry into the tail magnetosphere close to the current sheet when interplanetary magnetic field (IMF)
We have developed a new global magnetohydrodynamic (MHD) model for Jupiter's magnetosphere based on the BATSRUS code and an ionospheric electrodynamics solver. Our model includes the Io plasma torus at its appropriate location and couples the global magnetosphere with the planetary ionosphere through field‐aligned currents. Through comparisons with available particle and field observations as well as empirical models, we show that the model captures the overall configuration of the magnetosphere reasonably well. In order to understand how the magnetosphere responds to different solar wind drivers, we have carried out time‐dependent simulations using various kinds of upstream conditions, such as a forward shock and a rotation in the interplanetary magnetic field (IMF). Our model predicts that compression of the magnetosphere by a forward shock of typical strength generally weakens the corotation enforcement currents on the dayside and produces an enhancement on the nightside. However, the global response varies depending on the IMF orientation. A forward shock with a typical Parker‐spiral IMF configuration has a larger impact on the magnetospheric configuration and large‐scale current systems than with a parallel IMF configuration. Plasmoids are found to form in the simulation due to tail reconnection and have complex magnetic topology, as they evolve and propagate down tail. For a fixed mass input rate in the Io plasma torus, the frequency of plasmoid occurrence in our simulation is found to vary depending on the upstream solar wind driving.
more » « less- NSF-PAR ID:
- 10375390
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 124
- Issue:
- 7
- ISSN:
- 2169-9380
- Page Range / eLocation ID:
- p. 5317-5341
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract B y dominates over IMFB z . To evaluate this entry mechanism in the near‐Earth tail (X ∼ −10–−20R E ), we investigate the predictions from 3D global hybrid simulations as well as in situ observations by magnetospheric multiscale (MMS) spacecraft. The simulations predict that the low‐latitude mantle plasma can appear in the near‐Earth tail lobe extending inward approximately 5R E from the flank magnetopause. The low‐latitude mantle plasma appears in the dawnside northern lobe and duskside southern lobe during positive IMFB y , while the opposite asymmetry is seen during negative IMFB y . After a change in the IMFB y direction arriving at the bow shock nose, it takes another ∼15–30 min for the asymmetry to completely reverse to the opposite sense in the near‐Earth tail. We present six MMS events in the tail lobe showing that the existence and absence of the low‐latitude mantle plasma is consistent with the predicted asymmetries. Statistical analysis of 5 years of MMS observations shows that the dependencies of the magnitudes of the lobe densities and tailward field‐aligned flow speeds on the IMFB y directions are consistent with the predicted contributions from the low‐latitude mantle plasma in the expected lobe regions. -
more » « less
Abstract The existence of Birkeland magnetic field‐aligned current (FAC) system was proposed more than a century ago, and it has been of immense interest for investigating the nature of solar wind‐magnetosphere‐ionosphere coupling ever since. In this paper, we present the first application of deep learning architecture for modeling the Birkeland currents using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The model uses a 1‐hr time history of several different parameters such as interplanetary magnetic field (IMF), solar wind, and geomagnetic and solar indices as inputs to determine the global distribution of Birkeland currents in the Northern Hemisphere. We present a comparison between our model and bin‐averaged statistical patterns under steady IMF conditions and also when the IMF is variable. Our deep learning model shows good agreement with the bin‐averaged patterns, capturing several prominent large‐scale features such as the Regions 1 and 2 FACs, the NBZ current system, and the cusp currents along with their seasonal variations. However, when IMF and solar wind conditions are not stable, our model provides a more accurate view of the time‐dependent evolution of Birkeland currents. The reconfiguration of the FACs following an abrupt change in IMF orientation can be traced in its details. The magnitude of FACs is found to evolve with e‐folding times that vary with season and MLT. When IMF Bz turns southward after a prolonged northward orientation, NBZ currents decay exponentially with an e‐folding time of
∼ 25 min, whereas Region 1 currents grow with an e‐folding time of 6–20 min depending on the MLT. -
more » « less
Abstract We present examples of high‐latitude field‐aligned current (FAC) and toroidal magnetic potential patterns in both hemispheres reconstructed at a 2‐min cadence using an updated optimal interpolation (OI) method that ingests magnetic perturbation data provided by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) program. A solstice and an equinoctial event are studied to demonstrate the reconstructed patterns and to provide scientific insights into FAC response to different solar wind drivers. For the 14 June 2011 high‐speed stream event with mostly northward
B z B x changes is identified. For the 17–18 March 2013 period, we provide global snapshots of rapid FAC changes related to an interplanetary shock passage. We further present comparisons between instantaneous and mean behaviors of FAC for the solar wind sheath passage and interplanetary coronal mass ejection southwardB z B z B z B z -
more » « less
Abstract We propose a mechanism for the formation of the horse‐collar auroral configuration during periods of strongly northward interplanetary magnetic field (IMF), invoking the action of dual‐lobe reconnection (DLR). Auroral observations are provided by the Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP). We also use ionospheric flow measurements from DMSP and polar maps of field‐aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Sunward convection is observed within the dark polar cap, with antisunward flows within the horse‐collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR. We suggest that newly closed flux is transported antisunward and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes. Horse‐collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northward IMF. The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low‐latitude boundary layer and cold, dense plasma sheet. We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse‐collar auroras being an intermediate step.
-
On the bow shock in front of Earth’s magnetosphere flows a current due to the curl of the interplanetary magnetic field across the shock. The closure of this current remains uncertain; it is unknown whether the bow shock current closes with the Chapman-Ferraro current system on the magnetopause, along magnetic field lines into the ionosphere, through the magnetosheath, or some combination thereof. We present simultaneous observations from Magnetosphere Multiscale (MMS), AMPERE, and Defense Meteorological Satellite Program (DMSP) during a period of strong B y , weakly negative B z , and very small B x . This IMF orientation should lead to a bow shock current flowing mostly south to north on the shock. AMPERE shows a current poleward of the Region 1 and Region 2 Birkeland currents flowing into the northern polar cap and out of the south, the correct polarity for bow shock current to be closing along open field lines. A southern Defense Meteorological Satellite Program F18 flyover confirms that this current is poleward of the convection reversal boundary. Additionally, we investigate the bow shock current closure for the above-mentioned solar wind conditions using an MHD simulation of the event. We compare the magnitude of the modeled bow shock current due to the IMF B y component to the magnitude of the modeled high-latitude current that corresponds to the real current observed in AMPERE and by Defense Meteorological Satellite Program. In the simulation, the current poleward of the Region 1 currents is about 37% as large as the bow shock I z in the northern ionosphere and 60% in the south. We conclude that the evidence points to at least a partial closure of the bow shock current through the ionosphere.more » « less
