LANL Satellites Research Articles

Statistical Model of the Relationship of Electron Fluxes in Geostationary Orbit with Solar Wind Parameters and Geomagnetic Activity Based on Multivariate Correlation Analysis

On the basis of multivariate correlation analysis, a statistical model of the relationship of energetic electron fluxes on a geostationary orbit with solar wind parameters and geomagnetic activity indices for 22 and 23 cycles of solar activity is constructed. Energetic electron data obtained with the help of GOES satellite instruments and LANL satellites were used. A cross-correlation analysis of the relationship of logarithms of energetic electron fluxes with solar wind parameters and geomagnetic activity indices was carried out. The maximum correlation coefficient of the crosscorrelation function was taken as the value of the communication efficiency (Ref).

Worst‐Case Severe Environments for Surface Charging Observed at LANL Satellites as Dependent on Solar Wind and Geomagnetic Conditions

AbstractThe 400 worst‐case severe environments for surface charging detected at Los Alamos National Laboratory satellites during the years of 1990–2005 as binned by the definitions of four criteria developed by Matéo‐Vélez et al. (2018,https://doi.org/10.1002/2017sw001689) and the solar wind and Interplanetary Magnetic Field (IMF) parameters and geomagnetic activity indices are analyzed. The conducted analysis shows that only Auroral Electrojet/Auroral Lower index determines the highest risk for severe environments for surface charging to happen. The presence of a substorm with the southward turning pattern in IMFindicates that the environment can be severe for surface charging to occur but this environment will not depend on whether a substorm was moderate or intense. No clear dependence on IMFis found for risk to a severe environment to occur. Appearances of severe environments for surface charging do not necessarily require high values ofKp(Planetarische Kennziffer) and no storm is needed for such an event to be detected. Among solar wind parameters, solar wind velocityis directly related to the highest risk of severe environments, dependent on thevalue; and number densityis of no importance. Two criteria for severe environment events based on the enhancements of low energy particle fluxes exhibit clearer dependencies on the solar wind and IMF parameters and geomagnetic activity indices with more distinct patterns in their time history.

Dynamic Properties of Particle Injections Inside Geosynchronous Orbit: A Multisatellite Case Study.

Four closely located satellites at and inside geosynchronous orbit (GEO) provided a great opportunity to study the dynamical evolution and spatial scale of premidnight energetic particle injections inside GEO during a moderate substorm on 23 December 2016. Just following the substorm onset, the four spacecraft, a LANL satellite at GEO, the two Van Allen Probes (also called “RBSP”) at ~5.8 R E, and a THEMIS satellite at ~5.3 R E, observed substorm‐related particle injections and local dipolarizations near the central meridian (~22 MLT) of a wedge‐like current system. The large‐scale evolution of the electron and ion (H, He, and O) injections was almost identical at the two RBSP spacecraft with ~0.5 R E apart. However, the initial short‐timescale particle injections exhibited a striking difference between RBSP‐A and ‐B: RBSP‐B observed an energy dispersionless injection which occurred concurrently with a transient, strong dipolarization front (DF) with a peak‐to‐peak amplitude of ~25 nT over ~25 s; RBSP‐A measured a dispersed/weaker injection with no corresponding DF. The spatiotemporally localized DF was accompanied by an impulsive, westward electric field (~20 mV m−1). The fast, impulsive E × B drift caused the radial transport of the electron and ion injection regions from GEO to ~5.8 R E. The penetrating DF fields significantly altered the rapid energy‐ and pitch angle‐dependent flux changes of the electrons and the H and He ions inside GEO. Such flux distributions could reflect the transient DF‐related particle acceleration and/or transport processes occurring inside GEO. In contrast, O ions were little affected by the DF fields.

Evidence for injection of relativistic electrons into the Earth's outer radiation belt via intense substorm electric fields

Observation and model results accumulated in the last decade indicate that substorms can promptly inject relativistic ‘killer’ electrons (≥MeV) in addition to 10–100 keV subrelativistic populations. Using measurements from Cluster, Polar, LANL, and GOES satellites near the midnight sector, we show in two events that intense electric fields, as large as 20 mV/m, associated with substorm dipolarization are associated with injections of relativistic electrons into the outer radiation belt. Enhancements of hundreds of keV electrons at dipolarization in the magnetotail can account for the injected MeV electrons through earthward transport. These observations provide evidence that substorm electric fields inject relativistic electrons by transporting magnetotail electrons into the outer radiation belt. In these two events, injected relativistic electrons dominated the substorm timescale enhancement of MeV electrons as observed at geosynchronous orbit.

Responses of geostationary orbit energetic electron fluxes to chorus waves under different geomagnetic conditions

We investigate the flux evolution of geostationary orbit energetic electrons during a strong storm on 24 August 2005 (event A, the storm index Dst -50 nT, average AE=320 nT). Data collected by LANL and GOES-12 satellites show that energetic electron fluxes increase by a factor of 10 during the recovery phase compared to the prestorm level for both events A and B. As the substorm continued, the Cluster C4 satellite observed strong whistler-mode chorus waves (with spectral density approaching 10−5 nT2/Hz). The wave amplitude correlates with the substorm AE index, but is less correlated with the storm Dst index. Using a Gaussian distribution fitting method, we solve the Fokker-Planck diffusion equation governing the wave-particle interaction. Numerical results demonstrate that chorus waves efficiently accelerate ∼1 MeV energetic electrons, particularly at high pitch angles. The calculated acceleration time scale and amplitude are comparable to observations. Our results provide new observational support for chorus-driven acceleration of radiation belt energetic electrons.

Spectral characteristics of the plasma dispersionless injection during the storm recovery phase on 11 March 1998

A substorm dispersionless injection event observed during the storm recovery phase on 11 March 1998 at geosynchronous orbit is carefully studied. The event shows the notable characteristics that for energetic ions the flux enhancement ratio before and after injection increases and remains elevated with increasing energy, while for energetic electrons it tends to decrease with increasing energy. In order to explain the unique injection feature, the authors propose a possible mechanism that velocity space diffusion in common to electric acceleration adjusts the particle injection state. Spectral characteristics of four different phases (pregrowth phase, the growth phase, the substorm expansion phase, and the recovery phase) have been investigated. The differential fluxes of electrons from 50 keV to 1.5 Mev and ions from 50 keV to 1.2 MeV measured by Synchronous Orbit Plasma Analyzer (SOPA) instrument onboard LANL satellite 1991–080 are found to be best fitted with the three‐parameter kappa distribution function (f ∼ A0 · E[1 + E / (κE0)]−κ−1) by Levenberg‐Marquardt and Universal Global Optimization methods. The evolutions of the three parameters in the above kappa distribution in different substorm phases have been depicted for both electrons and ions. In each phase, E0 and κ show an approximately linear relationship κ(E0) = κ0 + ηE0. This linear relationship can be obtained by solving the velocity space diffusion equation with an initial superthermal kappa distribution. Ion and electron are found to have opposite trend of parameters κ0 and η in each phase, which indicates that the different species of particles exert different velocity space diffusion processes so that their flux enhancement ratios before and after injection are rather different. This implies that not only electric field acceleration, but also velocity space diffusion plays a very important role in the particle injection.

Magnetospheric disturbances associated with the 13 December 2006 solar flare and their ionospheric effects over North-East Asia

We present an observational study of magnetospheric and ionospheric disturbances during the December 2006 intense magnetic storm associated with the 4В/Х3.4 class solar flare. To perform the study we utilize the ground data from North–East Asian ionospheric and magnetic observatories (60–72°N, 88–152°E) and in situ measurements from LANL, GOES, Geotail and ACE satellites. The comparative analysis of ionospheric, magnetospheric and heliospheric disturbances shows that the interaction of the magnetosphere with heavily compressed solar wind and interplanetary magnetic field caused the initial phase of the magnetic storm. It was accompanied by the intense sporadic E and F2 layers and the total black-out in the nocturnal subauroral ionosphere. During the storm main phase, LANL-97A, LANL 1994_084, LANL 1989-046 and GOES_11 satellites registered a compression of the dayside magnetosphere up to their orbits. In the morning–noon sector the compression was accompanied by an absence of reflections from ionosphere over subauroral ionospheric station Zhigansk (66.8°N, 123.3°E), and a drastic decrease in the F2 layer critical frequency (foF2) up to 54% of the quite one over subauroral Yakutsk station (62°N, 129.7°E). At the end of the main phase, these stations registered a sharp foF2 increase in the afternoon sector. At Yakutsk the peak foF2 was 1.9 time higher than the undisturbed one. The mentioned ionospheric disturbances occurred simultaneously with changes in the temperature, density and temperature anisotropy of particles at geosynchronous orbit, registered by the LANL-97A satellite nearby the meridian of ionospheric and magnetic measurements. The whole complex of disturbances may be caused by radial displacement of the main magnetospheric domains (magnetopause, cusp/cleft, plasma sheet) with respect to the observation points, caused by changes in the solar wind dynamic pressure, the field of magnetospheric convection, and rotation of the Earth.

SAPS intensification during substorm recovery: A multi-instrument case study

[1] A case of the major intensification of the subauroral polarization stream (SAPS) during the substorm recovery phase is presented. The continuous high-time-resolution Doppler velocity measurements in the subauroral and auroral regions were conducted with the Unwin HF radar, and these are analyzed in the context of the simultaneous and coincident measurements of the auroral luminosity and the total electron content (TEC) by the IMAGE and GPS satellites. Additional information was provided by other SuperDARN radars, DMSP F15 satellite crossing the fully-developed SAPS region, ground-based measurements near the location of the substorm onset, and GOES and LANL satellites in the inner magnetosphere. The association between the SAPS and TEC trough is further substantiated at short timescales and TEC is shown to exhibit two distinct types of responses to substorm onset poleward of and within SAPS, with no evidence of a TEC decrease during SAPS intensification. It is argued that the positive feedback between the electric fields and electron densities was probably not responsible for the observed SAPS intensification. Moreover, it is proposed that the strong and steady plasma acceleration within SAPS may be triggered by a burst of auroral activity, rather than accompanied by a similarly steady variation in other observed parameters either in the ionosphere or in the inner magnetosphere. It is also argued that the SAPS intensification occurring during the recovery phase is not necessarily expected from the current models of the SAPS formation and evolution, but is consistent with the observationally-based view of a fully-developed SAPS as a substorm recovery phenomenon.

Spatial structure and temporal evolution of a dayside poloidal ULF wave event

[1] We investigate a strong poloidal ultralow frequency wave event in the noon sector observed by THEMIS and LANL satellites on 29 May 2007. From 07:00 to 10:00 UT, the five THEMIS satellites that were lined up in similar outbound orbits consecutively observed narrow-band poloidal pulsations from 10 to 4 mHz. The wave activity covered a broad region from 09:00 to 13:30 LT azimuthally and 5 to 9.5 RE radially. The radial extent and power of the wave decreased with time from 07:00 to 08:30 UT, suggesting a decay process with a time scale of hours. In the region outside the plasmapause, the wave power was observed to decrease then increase from 08:00 to 09:00 UT with a rapid temporal variation. The decrease in wave power, which suggests fast decay (within one hour), might be related to the evolution of the plasmasphere. The subsequent increase could possibly be related to a regeneration process by a surface wave at the plasmapause. We suggest that a coupling between the surface wave and the resonance of the field line around the plasmapause takes place when the density inside the plasmapause is twice the density outside the plasmapause.

Characteristics of Magnetic Variations and Current Wedge in the Sawtooth Event on 30 September 2000

AbstractThe purpose of this paper is to study the response of auroral electrojets during the sawtooth event observed by LANL satellites on 30 September 2000. Firstly, we establish a method to determine large‐scale 2‐dimensional ionospheric equivalent current systems in the high‐latitude ionosphere using the spherical elementary current system method. Then we apply this method and magnetic data of high‐latitude magnetometers in the Northern Hemisphere to study the variations of auroral electrojets during the sawtooth event. By comparing characteristics of enhancements of nightside ionospheric westward electrojets with those of positive magnetic bays of H components in the middle/low‐latitude ground magnetic field after each sawtooth injection, it is demonstrated that there are current wedges formed during this sawtooth event. The local time width of current wedges suggested by the two observations are both around 11 hours (MLT). In addition, time durations of middle/low‐latitude magnetic bays to reach maximum variations were generally longer than those for high‐latitude electrojets, implying that source currents for middle/low‐latitude magnetic bays are multiple.

Response of the magnetic field and plasmas at the geosynchronous orbit to interplanetary shock

Interplanetary shock can greatly disturb the Earth’s magnetosphere and ionosphere, causing the temporal and spatial changes of the magnetic field and plasmas at the geosynchronous orbit. In this paper, we use the magnetic field data of GOES satellites from 1997 to 2007 and the plasma data of MPA on the LANL satellites from 1997 to 2004 to study the properties of magnetic field and plasma (0.03–45 keV) at the geosynchronous orbit (6.6 RE) within 3 hours before and after the arrival of shock front at the geosynchronous orbit through both case study and superposed epoch analysis. It is found that following the arrival of shock front at the geosynchronous orbit, the magnetic field magnitude, as well as GSM BZ component increases significantly on the dayside (8–16 LT), while the BY component has almost no change before and after shock impacts. In response to the interplanetary shock, the proton becomes much denser with a peak number density of 1.2 cm−3, compared to the typical number density of 0.7 cm−3. The proton temperature increases sharply, predominantly on the dusk and night side. The electron, density increases dramatically on the night side with a peak number density of 2.0 cm−3. The inferred ionospheric O+ density after the interplanetary shock impact reaches the maximum value of 1.2 cm−3 on the dusk side and exhibits the clear dawn-dusk asymmetry. The peak of the anisotropy of proton’s temperature is located at the noon sector, and the anisotropy decreases towards the dawn and dusk side. The minimum of temperature anisotropy is on the night side. It is suggested that the electromagnetic ion cyclotron (EMIC) wave and whistler wave can be stimulated by the proton and electron temperature anisotropy respectively. The computed electromagnetic ion cyclotron wave (EMIC) intense on the day side (8–16 LT) with a frequency value of 0.8 Hz, and the wave intensity decreases towards the dawn and dusk side, the minimum value can be found on the night side. The computed electron whistler wave locates on the day side (8–16 LT) with a value of 2 kHz.

Responses of properties in the plasma sheet and at the geosynchronous orbit to interplanetary shock

On July 22, 2004, the WIND spacecraft detected a typical interplanetary shock. There was sustaining weak southward magnetic field in the preshock region and the southward field was suddenly enhanced across the shock front (i.e., southward turning). When the shock impinged on the magnetosphere, the magnetospheric plasma convection was abruptly enhanced in the central plasma sheet, which was directly observed by both the TC-1 and Cluster spacecraft located in different regions. Simultaneously, the Cluster spacecraft observed that the dawn-to-dusk electric field was abruptly enhanced. The variations of the magnetic field observed by TC-1, Cluster, GOES-10 and GOES-12 that were distributed in different regions in the plasma sheet and at the geosynchronous orbit are obviously distinct. TC-1 observations showed that the magnetic intensity kept almost unchanged and the elevation angle decreased, but the Cluster spacecraft, which was also in the plasma sheet and was further from the equator, observed that the magnetic field was obviously enhanced. Simultaneously, GOES-12 located near the midnight observed that the magnetic intensity sharply increased and the elevation angle decreased, but GOES-10 located in the dawn side observed that the magnetic field was merely compressed with its three components all sharply increasing. Furthermore, the energetic proton and electron fluxes at nearly all channels observed by five LANL satellites located at different magnetic local times (MLTs) all showed impulsive enhancements due to the compression of the shock. The responses of the energetic particles were much evident on the dayside than those on the nightside. Especially the responses near the midnight were rather weak. In this paper, the possible reasonable physical explanation to above observations is also discussed. All the shock-induced responses are the joint effects of the solar wind dynamic pressure pulse and the magnetic field southward turning.

Pc5 waves generated by substorm injection: a case study

Abstract. We analyzed the spectral-polarized characteristics of Pc5 ULF waves observed on 17 September 2000 after the 03:20:25 UT substorm onset with the satellites GOES 8 and 10 located east and west of the onset location. In the course of the event, the wave polarization changed from mixed (between toroidal and poloidal) to poloidal, and then to mixed again. The hodogram of magnetic field oscillations rotated counterclockwise at GOES 8, and clockwise at GOES 10. It is suggested that the satellites detected the waves generated by the substorm injected clouds of the charged particles drifting in the magnetosphere in the opposite azimuthal directions: GOES 8 (located east of the substorm onset) detected the wave generated by an electron cloud, and GOES 10 (west of the onset) detected the wave generated by a positive ion cloud. This interpretation is confirmed by the energetic particles data recorded by LANL satellites.

Multispacecraft and ground‐based observations of substorm timing and activations: Two case studies

Two case studies are performed to investigate substorm timing and activations based on Double Star TC1, Cluster, Polar, IMAGE, LANL geostationary satellites and ground‐based geomagnetic field measurements. In both events, an earthward flow associated with plasma sheet thinning is measured by Cluster 8–10 min ahead of the auroral breakup. A couple of minutes after the breakup, either TC1 at ∼X‐10 RE first detects plasma sheet expansion and then the LANL satellites near the midnight measure energetic electron injections at geostationary orbit or the LANL satellites first measure the electron injections and then TC1 detects the plasma sheet expansion. More than about 20 min later, Cluster at X∼16 RE and Polar (at higher latitude) successively observe plasma sheet expansion. The open magnetic flux of the polar cap, Ψ, is found to continually increase during the early substorm phase and then to rapidly fall when the IMF turns northward. When Ψ reaches its minimum value, bright and broad auroral activities start to decrease. Tailward progression of the magnetic dipolarization and a poleward expansion of auroral bulges are shown to closely map to one another. These results suggest that substorm activations start in the midtail before ground onset and then move earthward, which leads to an expansion onset in the near‐Earth tail around X∼ ‐(8–9) RE. After onset, the activations progress both earthward and tailward. Substorm onset is possibly related to plasma sheet reconnection of close field lines, while tail lobe reconnection of open field lines release more energy to support the full expansion of the substorm. In a fully developed expansion phase, an initial dipolarization in the near‐Earth may eventually evolve to enable disruption of the cross‐tail current over a wide region of the magnetotail.

Metrics analysis of the coupled Block Adaptive‐Tree Solar Wind Roe‐Type Upwind Scheme and Fok ring current model performance

Modeling is an important tool in understanding physical processes in the solar system. Metrics analysis evaluates model performance by comparing model output to a measurable parameter of interest. In this paper we studied the performance of the coupled Block Adaptive‐Tree Solar Wind Roe‐Type Upwind Scheme (BATSRUS) global magnetosphere MHD code and the Fok ring current model (FRC) by examining in detail the geosynchronous proton fluxes during the injection event on 21–22 January 2005. The output of BATSRUS code, calculated ionospheric potential and magnetic field, as well as proton temperature and density distribution, is used as an input boundary condition for the FRC model. We also discuss another event, on 10–11 August 2000, and speculate about the reasons of an apparent difference in the performance of the coupled models for these two events. The results of the simulation are compared with two LANL satellite observations, LANL‐97A and 1994‐084. The comparison of the simulation results for strongly varying solar wind and for prolonged interval of steady solar wind with southward IMF Bz, demonstrates that coupled BATSRUS and FRC models perform fairly for the magnetosphere driven by strong solar wind disturbances and probably are missing some internal magnetosphere dynamics in the second case.

Data assimilation of LANL satellite data into the Salammbô electron code over a complete solar cycle by direct insertion

Past work of data reanalysis using the Salammbô three‐dimensional code and LANL satellite data was done on a magnetic storm timescale. Here, we focus on the solar cycle timescale reanalysis. We study the accuracy of the reconstitution of the electron radiation belts from 1990 to 2005 using data from Los Alamos instruments on GPS and GEO spacecrafts. First, we simulate the 9 October 1990 storm. By predicting fluxes at CRRES orbit, we estimate a confidence level and propose quantitative limitations on the current state of the art for chorus wave‐particle interaction modeling. By performing a run covering 15 a, we have been able to distinguish dynamics of different timescales and compare and validate our results with the statistical radiation belt models AE‐8 and CRRESELE. The main conclusion is that the history of the radiation belts is of prime importance in order to best fit their real state. Data reanalysis is a new and valuable way to describe them.

Modeling the electromagnetic ion cyclotron wave‐induced formation of detached subauroral proton arcs

Detached dayside proton arcs have been recently observed at Earth with the IMAGE FUV instrument as subauroral arcs separated from the main oval and extending over several hours of local time in the afternoon sector. We investigate the mechanisms causing the proton precipitation during two subauroral arc events that occurred on 23 January 2001 and 18 June 2001. We employ our kinetic physics‐based model coupled with a dynamic plasmasphere model and calculate the growth rate of electromagnetic ion cyclotron (EMIC) waves self‐consistently with the evolving ring current H+, O+, and He+ ion distributions. Modeled plasmaspheric densities agree well with in situ observations from geosynchronous LANL satellites and duskside plasmapause observations from IMAGE EUV but overestimate the drainage plume extent toward noon on 18 June. Global images of precipitating H+ ions are obtained and compared with IMAGE observations of proton arcs. We find that EMIC waves are preferentially excited, and proton precipitation maximizes, within regions of spatial overlap of energetic ring current protons and dayside plasmaspheric plumes and along steep density gradients at the plasmapause. The model matches very well the temporal and spatial evolution of FUV observations on 23 January. The predicted location of the proton precipitation on 18 June extends a few hours westward of the observations, and an offset of 2 hours in the convection electric field is needed to reproduce well the evolution of the proton arc. This study indicates that cyclotron resonant wave‐particle interactions are a viable mechanism for the generation of subauroral proton arcs.

STUDY ON THE PARTICLE INJECTIONS DURING HILDCAA INTERVALS

The relation between substorm occurrences and HILDCAA events has been an issue. We have studied the association of particle injections with substorm onsets during HILDCAA intervals for the first half of year 2003. The examination of aurora images observed by IMAGE spacecraft and electron flux data measured by LANL satellites exhibits a close association of repetitive particle injections with substorm activity. We also find that HILDCAA events can occur equally frequently during slow speed solar wind streams as long as the interplanetary magnetic field exhibits Alfvenic wave feature.

Prompt response of SAPS to stormtime substorms

We report on satellite, incoherent scatter radar, and ground magnetometer observations of the development of SAPS during a stormtime substorm event on 25 September 1998. The substorm onset was determined from the data of the ground magnetometer array and LANL satellites. The radar and Defense Meteorological Satellite Program (DMSP) satellites identified the SAPS region. The pre-existing SAPS in the afternoon sector moved equatorward and intensified within ∼ 10 min after the substorm onset. It is shown that this transition began when the westward traveling surge (WTS) arrived at the adjacent auroral region. The observations indicate that the stormtime ring current responds to the substorm expansion on a rapid timescale, characteristic for the dipolarization pulse and WTS development. A scenario for the generation of the post-onset SAPS-wave structures is proposed.

Kinetic simulations of ring current evolution during the Geospace Environment Modeling challenge events

We investigate the temporal and spatial evolution of the ring current during two storms selected for study by the Geospace Environment Modeling (GEM) program using our kinetic drift‐loss model coupled with a time‐dependent plasmasphere model. We use geosynchronous data from LANL satellites to model the inflow of plasma from the magnetotail. We compare results from simulations using either Volland‐Stern (VS) or Weimer (W01) model of the convection electric field and investigate the relative effect of magnetospheric convection and radial diffusion on the storm‐time injection and trapping of energetic particles and ring current asymmetry. Model comparisons with in situ Cluster, NOAA, and Polar energetic particle observations show overall better agreement with W01 than with VS model. On the other hand, VS model reproduced better the evolution of the plasmapause as observed by IMAGE. Additional ring current ion injections caused by radial diffusion near Dst minima improved the agreement with observations. Radial diffusion did not affect much ring current buildup during the main phase of the storms and the ring current fluxes remained asymmetric, in good agreement with NOAA data. We calculated the excitation of electromagnetic ion cyclotron (EMIC) waves self‐consistently with the evolving plasma populations, and the resulting precipitating fluxes of resonant protons. These fluxes increased significantly within regions of enhanced plasma wave excitation near the plasmapause or inside plasmaspheric plumes and reduced the total H+ energy by ∼10% during the storm recovery phase. Initial results from self‐consistent magnetic field calculations are presented as well. We found that while the magnitude of the ring current fluxes was reduced when adiabatic drifts in a self‐consistent magnetic field were calculated, their morphology was not affected significantly and the local time of the equatorial flux peaks remained almost unchanged.