Comprehensive Ring Current Model Research Articles

Two-Dimensional Phenomenological Model of Ring Current Dynamics in the Earth’s Magnetosphere

The dynamics of ring current protons with variable boundary conditions in the inner magnetosphere during a magnetic storm has been studied. The spatial and temporal evolution of differential fluxes of protons in the dipole magnetic field has been calculated. The calculations have been performed with the two-dimensional Phenomenological Model of the Ring Current (PheMRC 2-D) offered by the author, which examines the radial and pitch angle diffusions with consideration of losses due to wave–particle interactions. The simulation begins with the distribution of magnetically quiet time. The model has been tested via comparison of the calculated proton fluxes with values measured on the Polar/MICS satellite during the magnetic storm on October 21–22, 1999. The calculated pitch angle distribution is quite consistent (well) with the experimental data. The model has been compared with the other ring current model (Extended Comprehensive Ring Current Model, ECRCM) (Ebihara et al., 2008). PheMRC 2-D is more accurate than ECRCM in describing the experimental data. The offered model can be used to simulate the dynamics of charged particles in the Jovian and Saturn magnetospheres.

A scheme for forecasting severe space weather

AbstractA scheme is suggested and tested for forecasting severe space weather (SvSW) using solar wind velocity (V) and the north‐south component (Bz) of the interplanetary magnetic field (IMF) measured using the ACE (Advanced Composition Explorer) satellite from 1998 to 2016. SvSW has caused all known electric power outages and telegraph system failures. Earlier SvSW events such as the Carrington event of 1859, Quebec event of 1989 and an event in 1958 are included with information from the literature. Dst storms are used as references to identify 89 major space weather events (DstMin ≤ −100 nT) in 1998–2016. The coincidence of high coronal mass ejection (CME) front (or CME shock) velocity ΔV (sudden increase in V over the background by over 275 km/s) and sufficiently large Bz southward at the time of the ΔV increase is associated with SvSW; and their product (ΔV × Bz) is found to exhibit a large negative spike at the speed increase. Such a product (ΔV × Bz) exceeding a threshold seems suitable for forecasting SvSW. However, the coincidence of high V (not containing ΔV) and large Bz southward does not correspond to SvSW, indicating the importance of the impulsive action of large Bz southward and high ΔV coming through when they coincide. The need for the coincidence is verified using the CRCM (Comprehensive Ring Current Model), which produces extreme Dst storms (<DstMP> < −250 nT) characterizing SvSW when there is coincidence.

The Comprehensive Inner Magnetosphere‐Ionosphere Model

AbstractSimulation studies of the Earth's radiation belts and ring current are very useful in understanding the acceleration, transport, and loss of energetic particles. Recently, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model were merged to form a Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model. CIMI solves for many essential quantities in the inner magnetosphere, including ion and electron distributions in the ring current and radiation belts, plasmaspheric density, Region 2 currents, convection potential, and precipitation in the ionosphere. It incorporates whistler mode chorus and hiss wave diffusion of energetic electrons in energy, pitch angle, and cross terms. CIMI thus represents a comprehensive model that considers the effects of the ring current and plasmasphere on the radiation belts. We have performed a CIMI simulation for the storm on 5–9 April 2010 and then compared our results with data from the Two Wide‐angle Imaging Neutral‐atom Spectrometers and Akebono satellites. We identify the dominant energization and loss processes for the ring current and radiation belts. We find that the interactions with the whistler mode chorus waves are the main cause of the flux increase of MeV electrons during the recovery phase of this particular storm. When a self‐consistent electric field from the CRCM is used, the enhancement of MeV electrons is higher than when an empirical convection model is applied. We also demonstrate how CIMI can be a powerful tool for analyzing and interpreting data from the new Van Allen Probes mission.

First results using TWINS‐derived ion temperature boundary conditions in CRCM

AbstractWe have integrated dynamic, spatiotemporally resolved ion temperature boundary conditions into the Comprehensive Ring Current Model (CRCM), which are based on 2‐D equatorial maps derived from the Two Wide‐Angle Imaging Neutral‐Atom Spectrometers (TWINS) energetic neutral atom (ENA) data. The high‐speed stream‐driven event on 22 July 2009 is simulated and compared against an identical simulation using a statistically derived boundary condition model. ENA‐derived temperatures allow users to include event‐specific observations associated with a dynamic plasma sheet. This method also provides temperatures in the important region between geosynchronous orbit and the plasma sheet, a region which existing empirical models exclude. We find that the spatial and energy distributions of ring current flux and pressure have sensitive dependence on boundary conditions during this event. The coupling of boundary conditions to the time history of the convection field strength also plays an important role by throttling the influence of the boundary plasma on the inner magnetosphere. Simulated moments and spectra from our simulations are compared with remotely imaged ion temperatures from TWINS and also in situ energy spectra and temperature moments from Time History of Events and Macroscale Interactions during Substorms‐D. Storm time dusk‐dawn asymmetries consistent with observational data, such as Zhang et al. (2006), are reproduced well when CRCM is provided with the event‐specific boundary model. A hot localized structure observed by TWINS at geosynchronous midnight during a strong northward interplanetary magnetic field interval is also reproduced with this boundary model, whereas the empirical boundary model fails to yield this feature.

Pressure anisotropy in global magnetospheric simulations: Coupling with ring current models

We have recently extended the global magnetohydrodynamic (MHD) model BATS‐R‐US to account for pressure anisotropy. Since the inner magnetosphere dynamics cannot be fully described even by anisotropic MHD, we coupled our anisotropic MHD model with two inner magnetospheric models: the Rice Convection Model (RCM) and the Comprehensive Ring Current Model (CRCM). The coupled models provide better representations of the near‐Earth plasma, especially during geomagnetic storms. In this paper, we present the two‐way coupling algorithms with both ring current models. The major difference between these two couplings is that the RCM assumes isotropic and constant pressures along closed field lines, while the CRCM resolves pitch angle anisotropy. For model validation, we report global magnetosphere simulations performed by the coupled models. The simulation results are compared to the results given by the coupled isotropic MHD and ring current models. We find that in the global MHD simulations coupled with ring current models, pressure anisotropy results in a thinner magnetosheath, a shorter tail, a much smaller Earthward plasma jet from the tail reconnection site, and is also important in controlling the magnetic field configuration. The comparisons with satellite data for the magnetospheric event simulations show improvements on reproducing the measured tail magnetic field and inner magnetospheric flow velocity when including pressure anisotropy in the ring current model coupled global MHD model.

Superposed epoch analyses of ion temperatures during CME- and CIR/HSS-driven storms

Coronal mass ejections (CMEs) and corotating interaction regions associated with high speed solar wind streams (CIR/HSSs) drive geomagnetic storms in the terrestrial magnetosphere. Each type of storm driver yields different dynamics of storm evolution. We present results from comparative superposed epoch analyses of global ion temperatures calculated from TWINS energetic neutral atom (ENA) data and simulations using the comprehensive ring current model (CRCM). During the June 2008–April 2012 timeframe, 48 geomagnetic storms (minimum Dst≤−40nT) occurred. Of these, 21 storms were CME-driven and 15 were driven by CIR/HSSs. Superposed epoch analysis results demonstrate that ion temperatures increase during the recovery phase of CIR/HSS-driven storms, while ions are rapidly heated at the commencement of CME-driven storms then cool over the main phase, particularly for intense (minimum Dst≤−78nT) CME-driven storms. Higher energy ions are convected to lower L-shells during CME-driven storms, while CIR/HSS-driven storms tend to have average ion temperatures that are higher on the dayside than nightside.

Simulated ring current response during periods of dawn‐dusk oriented interplanetary magnetic field (B y )

[1] Ring current formation is mainly attributed to enhanced global magnetospheric convection and particle injection. One of the indicators of enhanced global magnetospheric convection is the transpolar potential. The transpolar potential has been shown to respond to dawn-dusk oriented interplanetary magnetic field (IMF), enhancing as the IMF magnitude grows. This suggests that the ring current should respond to dawn-dusk oriented IMF. This work examines the ring current response during periods of dawn-dusk oriented IMF using the Lyon-Fedder-Mobarry and Comprehensive Ring Current Model simulations. Exploring three hypotheses, this work shows through simulation results that the ring current does respond during periods of dawn-dusk oriented IMF, that the inner magnetospheric response is different for periods of dawn-dusk oriented IMF than for periods of southward IMF, and that these differences are attributed to both lower magnetospheric convection on closed field lines and the location of the reconnection region on the nightside. Specifically, the simulation results show that as the magnitude of the dawn-dusk oriented IMF increases, producing a corresponding increase in the transpolar potential, the ring current response increases. The response is always much less than a comparable southward IMF would produce. This lower response is due to both magnetospheric convection on closed field lines, which builds the ring current but at a slower rate, and flank reconnection, which allows energy to flow through the inner magnetosphere without building the ring current plasma population (as a conduit).

CRCM + BATS‒R‒US two‒way coupling

We present the coupling methodology and validation of a fully coupled inner and global magnetosphere code using the infrastructure provided by the Space Weather Modeling Framework (SWMF). In this model, the Comprehensive Ring Current Model (CRCM) represents the inner magnetosphere, while the Block‒Adaptive‒Tree Solar‒Wind Roe‒Type Upwind Scheme (BATS‒R‒US) represents the global magnetosphere. The combined model is a global magnetospheric code with a realistic ring current and consistent electric and magnetic fields. The computational performance of the model was improved to surpass real‒time execution by the use of the Message Passing Interface (MPI) to parallelize the CRCM. Initial simulations under steady driving found that the coupled model resulted in a higher pressure in the inner magnetosphere and an inflated closed field‒line region as compared to simulations without inner‒magnetosphere coupling. Our validation effort was split into two studies. The first study examined the ability of the model to reproduce Dst for a range of events from the Geospace Environment Modeling (GEM) Dst Challenge. It also investigated the possibility of a baseline shift and compared two approaches to calculating Dst from the model. We found that the model did a reasonable job predicting Dst and Sym‒H according to our two metrics of prediction efficiency and predicted yield. The second study focused on the specific case of the 22 July 2009 moderate geomagnetic storm. In this study, we directly compare model predictions and observations for Dst, THEMIS energy spectragrams, TWINS ENA images, and GOES 11 and 12 magnetometer data. The model did an adequate job reproducing trends in the data. Moreover, we found that composition can have a large effect on the result.

Effects of different geomagnetic storm drivers on the ring current: CRCM results

The storm‐time magnetic disturbance at the Earth's equator, as commonly measured by the Dst index, is induced by currents in the near‐Earth magnetosphere. The ring current is generally considered the most important contributor, but other magnetospheric currents have also been found to have significant effects. Of the two main types of solar geomagnetic storm drivers, Coronal Mass Ejections (CMEs) tend to have a much greater impact on Dst than Corotating Interaction Regions (CIRs). Ring current models have been found to underestimate Dst, particularly during storms driven by CIRs. One possible explanation is that the models neglect to handle some aspect of ring current physics that is particularly important for CIRs. This study uses the Comprehensive Ring Current Model (CRCM) to estimate the ring current contribution to Dst for a selection of storms of various strengths and different drivers (CMEs and CIRs) that have solar wind parameters that fit a typical profile. The model boundary is set to 10 RE at the equator, encompassing the entire ring current region. The magnetic field is held fixed, based on average storm parameters, which limits our model results to the effects of convection and plasma sheet density at the model boundary. Our model results generally show good agreement with the size and timing of fluctuations in Dst, which indicates that convection and boundary conditions play an important role in shaping Dst. We also find excellent agreement with the magnitude of Dst for CME‐driven storms. For CIR‐driven storms, however, the magnitude at the peak of the storm frequently deviates from actual Dst. In general, we agree with the results of previous research that CIR‐driven storms are more underpredicted. However, this study includes some weaker CIR‐driven storms for which Dst is actually overpredicted. Overall, when examining the dependence of modeled Dst* on actual Dst* at storm peak, we find that there is a statistically significant difference between CME‐ and CIR‐driven storms. We also find that approximately half of the total ring current energy lies beyond an L‐value of 6.6. However, this figure could be overestimated due to the use of a static magnetic field, which limits radial transport.

Ring current dynamics in moderate and strong storms: Comparative analysis of TWINS and IMAGE/HENA data with the Comprehensive Ring Current Model

We present a comparative study of ring current dynamics during strong and moderate storms. The ring current during the strong storm is studied with IMAGE/HENA data near the solar cycle maximum in 2000. The ring current during the moderate storm is studied using energetic neutral atom (ENA) data from the Two Wide‐Angle Imaging Neutral‐Atom Spectrometers (TWINS) mission during the solar minimum in 2008. For both storms, the local time distributions of ENA emissions show signatures of postmidnight enhancement (PME) during the main phases. To model the ring current and ENA emissions, we use the Comprehensive Ring Current Model (CRCM). CRCM results show that the main‐phase ring current pressure peaks in the premidnight‐dusk sector, while the most intense CRCM‐simulated ENA emissions show PME signatures. We analyze two factors to explain this difference: the dependence of charge‐exchange cross section on energy and pitch angle distributions of ring current. We find that the IMF By effect (twisting of the convection pattern due to By) is not needed to form the PME. Additionally, the PME is more pronounced for the strong storm, although relative shielding and hence electric field skewing is well developed for both events.

Simulation and TWINS observations of the 22 July 2009 storm

TWINS is the first mission to perform stereo imaging of the Earth's ring current. The magnetic storm on 22 July 2009 was at the time the largest storm observed since TWINS began routine stereo imaging in June 2008. On 22 July 2009, the Dst dropped to nearly −80 nT at 0700 and 1000 UT. During the main phase, and at the peak of the storm, TWINS 1 and 2 were near apogee and moving between predawn and postdawn local time. The energetic neutral atom (ENA) imagers on the two spacecraft captured the storm intensification and the formation of the partial ring current. The peak of the high‐altitude ENA emissions was seen in the midnight‐to‐dawn local time sector. The development of this storm has been simulated using the comprehensive ring current model (CRCM) to understand and interpret the observed signatures. We perform CRCM runs with constant and time‐varying magnetic field. The model calculations are validated by comparing the simulated ENA and ion flux intensities with TWINS ENA images and in situ ion data from a THEMIS satellite. Simulation with a static magnetic field produces a strong shielding electric field that skews the ion drift trajectories toward dawn. The model's corresponding peak ENA emissions are always more eastward than those in the observed TWINS images. On the other hand, the simulation with a dynamic magnetic field gives better spatial agreement with both ENA and in situ particle data, suggesting that temporal variations of the geomagnetic field exert a significant influence upon global ring current ion dynamics.

Global response to local ionospheric mass ejection

We revisit a reported “Ionospheric Mass Ejection” using prior event observations to guide a global simulation of local ionospheric outflows, global magnetospheric circulation, and plasma sheet pressurization, and comparing our results with the observed global response. Our simulation framework is based on test particle motions in the Lyon‐Fedder‐Mobarry (LFM) global circulation model electromagnetic fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere, and includes an embedded plasmaspheric simulation. Global circulation is stimulated using the observed solar wind conditions for the period 24–25 September 1998. This period begins with the arrival of a Coronal Mass Ejection, initially with northward, but later with southward interplanetary magnetic field. Test particles are launched from the ionosphere with fluxes specified by local empirical relationships of outflow to electrodynamic and particle precipitation imposed by the MHD simulation. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the full equations of motion. Results are compared with the observed ring current and a simulation of polar and auroral wind outflows driven globally by solar wind dynamic pressure. We find good quantitative agreement with the observed ring current, and reasonable qualitative agreement with earlier simulation results, suggesting that the solar wind driven global simulation generates realistic energy dissipation in the ionosphere and that the Strangeway relations provide a realistic local outflow description.

Penetration of the convection and overshielding electric fields to the equatorial ionosphere during a quasiperiodic DP 2 geomagnetic fluctuation event

The convection electric field penetrates to the equatorial ionosphere with no significant shielding during DP 2 fluctuation events with periods of 30–60 min (Nishida, 1968) and even during the main phase of a storm that continues over several hours (Huang et al., 2007). On the other hand, shielding becomes effective in 20 min during the substorm growth phase (Somayajulu et al., 1987), and in 1 h during the main phase of a storm (Kikuchi et al., 2008a). To clarify the relative contributions of the convection and shielding electric fields at middle to equatorial latitudes, we analyzed an equatorial DP 2 fluctuation event of 30 min duration, using magnetometer data, Super Dual Auroral Radar Network (SuperDARN) convection maps, and electric potentials calculated with the comprehensive ring current model (CRCM). The equatorial DP 2 fluctuations were found to be caused by alternating eastward electrojets (e‐EJ) and westward electrojets (w‐EJ) in the equatorial ionosphere, which were caused by the southward and northward interplanetary magnetic field, respectively. Using the SuperDARN convection map, we further show that the e‐EJ is associated with large‐scale two‐cell convection vortices, while the w‐EJ accompanies reverse flow vortices equatorward of the two‐cell vortices. With the aid of the CRCM, we suggest that the reverse flow vortices were associated with the region 2 field‐aligned currents (R2 FACs) that caused overshielding at the equator. We think it reasonable that the overshielding electric field could appear at middle to equatorial latitudes irrespective of the period of fluctuations as the region 1 FACs decrease their intensity. This scenario well explains both DP 2 fluctuations with periods of 30–60 min and continuous penetration for several hours during the main phase of storms.

Dynamics of ring current and electric fields in the inner magnetosphere during disturbed periods: CRCM–BATS‐R‐US coupled model

We present simulation results from a one‐way coupled global MHD model (Block‐Adaptive‐Tree Solar‐Wind Roe‐Type Upwind Scheme, BATS‐R‐US) and kinetic ring current models (Comprehensive Ring Current Model, CRCM, and Fok Ring Current, FokRC). The BATS‐R‐US provides the CRCM/FokRC with magnetic field information and plasma density/temperature at the polar CRCM/FokRC boundary. The CRCM uses an electric potential from the BATS‐R‐US ionospheric solver at the polar CRCM boundary in order to calculate the electric field pattern consistent with the CRCM pressure distribution. The FokRC electric field potential is taken from BATS‐R‐US ionospheric solver everywhere in the modeled region, and the effect of Region II currents is neglected. We show that for an idealized case with southward‐northward‐southward Bz IMF turning, CRCM–BATS‐R‐US reproduces well known features of inner magnetosphere electrodynamics: strong/weak convection under the southward/northward Bz; electric field shielding/overshielding/penetration effects; an injection during the substorm development; Subauroral Ion Drift or Polarization Jet (SAID/PJ) signature in the dusk sector. Furthermore, we find for the idealized case that SAID/PJ forms during the substorm growth phase, and that substorm injection has its own structure of field‐aligned currents which resembles a substorm current wedge. For an actual event (12 August 2000 storm), we calculate ENA emissions and compare with Imager for Magnetopause‐to‐Aurora Global Exploration/High Energy Neutral Atom data. The CRCM–BATS‐R‐US reproduces both the global morphology of ring current and the fine structure of ring current injection. The FokRC‐BATS‐R‐US shows the effect of a realistic description of Region II currents in ring current–MHD coupled models.

Subauroral polarization streams: observations with the Hokkaido and King Salmon SuperDARN radars and modeling

Abstract. The newly installed SuperDARN Hokkaido HF radar monitors ionospheric plasma flow between magnetic latitudes of 45° and 65° and thus has a great potential for studies of subauroral polarization streams (SAPS) in combination with another SuperDARN radar located at King Salmon, Alaska as well as the DMSP satellites and ground-based instruments in the Alaskan sector of the Arctic. Preliminary survey shows that although SAPS are often detected with the Hokkaido radar, their velocities are rather low, to the order of 150 m/s in its most suitable central beams. In this study, observations of unusually fast Hokkaido flows of up to 800 m/s are presented. The event of 1 April 2007 is investigated in detail. It is shown that high-velocity echoes appear after substorm onsets over North America with a delay of ~30 min. In terms of latitude, the velocity peaks just outside the auroral oval; signatures of a detached polarization jet are occasional and not pronounced. The King Salmon radar operating concurrently detects SAPS signatures as well but at different times and locations. Simulation with the Comprehensive Ring Current Model for the 1 April event reasonably identifies the period of fast flow occurrence but the velocity is underestimated. The event studied suggests that substorm-injected particle populations may intensify the pre-existing SAPS flow and lead to a mismatch of the predictions and observations.

Viewing perspective in energetic neutral atom intensity

Through interspacecraft comparison of energetic neutral oxygen (ENO) intensity from two different vantage points provided by IMAGE and Geotail, Lui et al. (2005) showed that viewing perspective plays a very important role in the observed ENO intensity level during a magnetic storm period. Motivated by the findings of Lui et al. (2005), we investigate how viewing perspective influences energetic neutral atom emissions from a modeling perspective. The main results of this paper are that (1) our simulation results, based upon O+ ion fluxes from the Comprehensive Ring Current Model and the subsequent ENO calculation, reproduce the total differential ENO intensity obtained from two spacecraft to a reasonable degree and (2) further analysis of our results indicates that pitch angle anisotropy in ring current ion flux, a crucial physical quantity in ring current dynamics, is one major contributor to the difference in energetic neutral atom intensity from different viewing perspectives.

Generation of plasmaspheric undulations

We have modeled the plasmaspheric plume region using the Comprehensive Ring Current model (CRCM) and the Dynamical Global Core Plasma model (DGCPM), for an event that exhibited substantial undulations or ripples as observed by the IMAGE EUV imager during 17 April 2002. We drove the simulated electric field using the Weimer cross polar cap potential. We specified the magnetic field to vary in response to solar wind conditions according to the T96 model. As a control, we performed a run with a fixed magnetic field and a run with a low ring current pressure. The results show that particle injections into the inner magnetosphere and ring current–ionosphere–plasmasphere interaction are an essential part of the undulation response. We also conclude that the undulations are stronger in the case of magnetic field variations because associated induction electric field causes more pronounced injections.

Plasma plume circulation and impact in an MHD substorm

We investigate the fate of a plasmaspheric plume generated by a discrete period of southward interplanetary magnetic field (IMF) to assess its contribution to plasma sheet and ring current pressure and compare with that for other sources. We use test particle motions in Lyon‐Fedder‐Mobarry (LFM) global circulation model fields. The inner magnetosphere is simulated with the Comprehensive Ring Current Model (CRCM) model of Fok and Wolf, driven by the transpolar potential developed by the LFM magnetosphere. A variant of the Ober plasmasphere model is embedded within the models and driven by them. Global circulation is stimulated by a period of southward IMF embedded within a long interval of northward IMF. This leads to the production of a well‐defined plasmaspheric plume, enhancing the plasma density sunward of the plasmasphere. Test particles are launched with the properties of plasmaspheric ions on the L = 6.6 RE shell and weighted with densities as specified by the Ober model, as it responds to convection imposed by CRCM. Particles are tracked until they are lost from the system downstream or into the atmosphere, using the Delcourt full equations of motion, implemented for finite element fields. Results are compared with earlier computations of polar and auroral wind outflows. The plume produces an enhanced flow of plasma ∼10 times the normal polar wind global fluence. However, we find that most of the “plasmaspheric wind” is lost from the magnetosphere such that its contribution to the ring current energy density is comparable to that of the normal polar wind for this type of event.

A comparison of Neutral Atom Detector Unit neutral atom image inversion with a comprehensive ring current model

We present energetic neutral atom (ENA) images in the energy range 45 to 50 keV for H and 92 to 138 keV for O measured by the Neutral Atom Detector Unit (NUADU) onboard Double Star TC‐2 during a geomagnetic storm on 8 May 2005. We compare the ion fluxes deduced from inversion of the NUADU image with those calculated using the Comprehensive Ring Current Model (CRCM). This comparison shows that the two approaches are consistent when used to derive the configuration of the corresponding global ion distribution and the peak ion fluxes. The deduced peak ion flux is located in the premidnight sector at 1540 UT, while the deduced ion peak flux is located in the midnight sector at 1610 UT. There are strong ion fluxes in the region between L = 2 and L = 4 which form a closed loop configuration. The ion peak flux is about 2.2 × 106/cm2/sr/keV/s. The deduced ion distribution agrees well with the NUADU measurement. The agreement between the inverted ion distributions and the CRCM results give us confidence in applying our ENA imaging and modeling techniques to the study of the evolution of the inner magnetosphere plasma distribution and the global dynamics of the ring current during magnetic storms.

On ionospheric trough conductance and subauroral polarization streams: Simulation results

Subauroral polarization streams (SAPS) are usually associated with geomagnetically disturbed times and considered a manifestation of magnetosphere and ionosphere coupling. Previous research results using radar and satellite measurements have revealed many features of the SAPS events. In this paper we focus on the effects of subauroral trough conductance on the attributes of SAPS and the evolution of the coupled magnetosphere and ionosphere system through the comprehensive ring current model, which includes the coupled electrodynamics of the inner magnetosphere and ionosphere with a self‐consistent description of the electric field. Our numerical analysis indicates that low conductance at the subauroral latitudes (due to midlatitude trough) is critical to the large amplitude of SAPS. The model results are generally in good agreement with common characteristics of SAPS and are consistent with their existing generation mechanism.