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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Radial deformation of the solar current sheet as a cause of geomagnetic storms

It is suggested that the solar current sheet, extending from a coronal streamer, develops a large-scale radial deformation, at times with a very steep gradient at the earth's distance. The associated magnetic field lines (namely, the interplanetary magnetic field (IMF) lines) are expected to have also a large gradient in the vicinity of the current sheet. It is also suggested that some of the major geomagnetic storms occur when the earth is located in the region where IMF field lines have a large dip angle with respect to the ecliptic plane for an extended period (6-48 h), as a result of a steep radial deformation of the current sheet.

Akasofu, S.-I.↗
DOE OSTI2024

The Impact of the 8–10 March 2012 Geomagnetic Storm on Inner Zone Protons as Measured by Van Allen Probes

The Relativistic Electron Proton Telescope (REPT) instrument on the Van Allen Probes observed a double-peaked inner zone proton population throughout the 7 year lifetime of the mission. M. Hudson et al. (2023) showed that a strong SEP event accompanied by a CME-shock in early March 2012 provided the Solar Energetic Proton (SEP) source for the higher L trapped proton population, which then diffused radially inward to be observed by REPT at L = 2. The study followed trajectories of SEP protons launched isotropically from a sphere at 7 Re for 2.5 hr in fields calculated by the LFM-RCM global MHD model, which includes electric fields needed to model the transport and trapping of the protons by the shock, and then a radial diffusion simulation was run for 2 years using the result from the test-particle simulation as the initial condition. The simulation result was compared with REPT measurement in November 2013 and showed reasonable agreement. However, the simulation overestimated the Phase Space Density by a factor of four due to lack of field line curvature scattering during the storm in the model. In this study, a test-particle simulation is performed for 2 days following the injection and trapping of protons in March 2012 using TS05 fields to simulate the field line curvature scattering of the trapped SEP due to the buildup of the ring current during the geomagnetic storm. The resulting sample distribution was then weighted using the flux at the end of the two-hour MHD-test particle simulation. A radial diffusion simulation is then run using the initial profile that included the loss effect, with improved comparison with REPT measurements after 2 years.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2023

Comparing Magnetopause Predictions From Two MHD Models During A Geomagnetic Storm and A Quiet Period

Magnetopause location is an important prediction of numerical simulations of the magnetosphere, yet the models can err, either under-predicting or over-predicting the motion of the boundary. This study compares results from two of the most widely used magnetohydrodynamic (MHD) models, the Lyon–Fedder–Mobarry (LFM) model and the Space Weather Modeling Framework (SWMF), to data from the GOES 13 and 15 satellites during the geomagnetic storm on 22 June 2015, and to THEMIS A, D, and E during a quiet period on 31 January 2013. The models not only reproduce the magnetopause crossings of the spacecraft during the storm, but they also predict spurious magnetopause motion after the crossings seen in the GOES data. We investigate the possible causes of the over-predictions during the storm and find the following. First, using different ionospheric conductance models does not significantly alter predictions of the magnetopause location. Second, coupling the Rice Convection Model (RCM) to the MHD codes improves the SWMF magnetopause predictions more than it does for the LFM predictions. Third, the SWMF produces a stronger ring current than LFM, both with and without the RCM and regardless of the LFM spatial resolution. During the non-storm event, LFM predicts the THEMIS magnetopause crossings due to the southward interplanetary magnetic field better than the SWMF. Additionally, increasing the LFM spatial grid resolution improves the THEMIS predictions, while increasing the SWMF grid resolutions does not.

magnetohydrodynamics↗
NASA NTRSDate not supplied

Modeling and Visualization of Geomagnetic Storms at the CCMC

The Community Coordinated Modeling Center is greatly expanding activities in geospace in recent years, including the addition of new models or outputs (including WACCM-X, SAMI3-TIEGCM, HYPERS, GAMERA test runs and WAM-IPE real time outputs) that expand the range of available views or analysis activities in geospace during the upcoming Solar Maximum and Heliophysics Big Year. We are now routinely adding to a library of geomagnetic storms using anew request interface for the Space Weather Modeling Framework(SWMF). We are placing continuous run model simulation outputs as run series onto the CCMC web site where look at quick-look graphics, perform online visualization and request outputs for any day covered by the results.We demonstrate examples and results of online visualization and analysis tools that are also placed onto the cloud to support Open Science and collaborative research.

Lutz Rastaetter↗
NASA NTRS2009

Halo Coronal Mass Ejections and Geomagnetic Storms

In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

Gopalswamy, Nat↗
NASA NTRS1987

Solar activity, magnetic clouds, and geomagnetic storms

Associational aspects of magnetic clouds and solar activity, and of magnetic clouds and geomagentic storms are described. For example, recent research has shown associations to exist between the launch of magnetic clouds directed Earthward from the Sun and, in particular, two forms of solar activity: flare-related, type II metric radio bursts and disappearing filaments (prominences). Furthermore, recent research has shown an association to exist between the onset of magnetic clouds on Earth and the initiation of geomagnetic storms. Based on these findings, STIP Intervals XV-XIX are examined for possible occurrences of Earthward-directed magnetic clouds.

Wilson, Robert M.↗
NASA NTRS2020

Conditions of Loss Cone Filling by Scattering on the Curved Field Lines for 30 keV Protons During Geomagnetic Storm as Inferred From Numerical Trajectory Tracing

The rate of pitch angle scattering on the curved magnetic field lines is well parameterized by the ratio of the minimum field line curvature radius to the maximum effective particle gyroradius (K = RC/rg). The critical value of this ratio (Kcr) corresponding to the loss cone filling is of special interest since it corresponds to the low altitude isotropic boundaries (IBs). The early theoretical estimates gave Kcr = 8, whereas recent estimations of the K parameter on the field lines corresponding to the observed IBs during the geomagnetic storms revealed KIB values in the range of 3–30. We numerically trace the trajectories of the 30 keV protons in the magnetic field of the global magnetohydrodynamic simulation of the intense storm in order to infer statistical distribution of Kcr. The electric field and effects of nonstationarity are neglected in this study. It is found that although the Kcr values do show some variations during the course of the storm, its range is rather narrow 4 < Kcr < 8. The result suggests that higher KIB values found in the observational studies, if not caused by the magnetosphere-ionosphere mapping error, should be attributed to some other mechanism of pitch angle scattering. The Kcr values tend to be lower (4–6) during the main phase because the region of low K values approaches the Earth and the equatorial loss cone size becomes larger due to a larger equatorial magnetic field in the near earth region. The remaining variation of Kcr is explained by the presence of the guide component of the magnetic field.

S Dubyagin↗
NASA NTRS1989

Multi-spacecraft testing of time-dependent interplanetary MHD models for operational forecasting of geomagnetic storms

An MHD 2-1/2D, time-dependent model is used, together with observations of six solar flares during February 3-7, 1986, to demonstrate global, large-scale, compound disturbances in the solar wind over a wide range of heliolongitudes. This scenario is one that is likely to occur many times during the cruise, possibly even encounter, phases of the Multi-Comet Mission. It is suggested that a model such as this one should be tested with multi-spacecraft data (such as the MCM and earth-based probes) with several goals in view: (1) utility of the model for operational real-time forecasting of geomagnetic storms, and (2) scientific interpretation of certain forms of cometary activities and their possible association with solar-generated activity.

Dryer, M.↗
NASA NTRS2017

Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm

The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated interplanetary shock waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge shock wave and a sheath carrying a large and highly variable interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasmasheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasmasheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe.

Coffey, Victoria↗
NASA NTRS2017

Observations of Deep Ionospheric F-Region Density Depletions with FPMU Instrumentation and Their Relationship with the Global Dynamics of the June 22-23, 2015 Geomagnetic Storm

The magnetic storm that commenced on June 22, 2015 was one of the largest storms in the current solar cycle, resulting from an active region on the Sun that produced numerous coronal mass ejections (CMEs) and associated interplanetary shock waves. On June 22 at 18:36 UT the magnetosphere was impacted by the leading-edge shock wave and a sheath carrying a large and highly variable interplanetary magnetic field (IMF) Bz with values ranging from +25 to -40 nT. During the subsequent interval from 0000 to 0800 UT, there was a second intensification of the geomagnetic storm resulting from the impact of the CME. We present dramatic responses of simultaneous particle measurements from the high-altitude Magnetospheric Multiscale Mission (MMS) at high altitudes in the magnetosphere (approx. 9-12 Re) and from the low-altitude (F-region) Floating Potential Measurement Unit (FPMU) on board the International Space Station (ISS). We analyze potential causes of these dramatic particle flux dropouts by putting them in the context of storm-time electrodynamics, and support our results with numerical simulations of the global magnetosphere and ionosphere. During the sheath phase of the storm, the MMS spacecraft in the near-earth equatorial plane observed a rapid reconfiguration of the magnetic field near 1923 UT. Initially in the warm plasma sheet, particle flux dropouts were observed as they tracked the plasma-sheet to lobe transitions with the stretching and thinning of the plasma sheet. Anti-sunward flowing O+ ions of ionospheric origin were also measured during this period, confirming that the MMS spacecraft temporarily was in a lobe.

Coffey, Victoria↗
NASA NTRS1992

Terrestrial Response to Eruptive Solar Flares: Geomagnetic Storms

This paper describes the interplanetary structures that are associated with the large-amplitude and long-duration negative B subscript z fields that are found in the sheath field and/or driver gas regions of the shock and are thought to be the main cause of the intense storms.

solar flares geomagnetic storms magnetic field dat↗
NASA NTRS1992

The semiannual variation of great geomagnetic storms and the postshock Russell-Mcpherron effect preceding coronal mass ejecta

Recent results indicate that the intense southward interplanetary magnetic fields (IMFs) responsible for great storms can reside in the postshock plasma preceding the driver gas of coronal mass ejections (CMEs) as well as in the driver gas itself. It is proposed here that strong southward fields in the postshock flow result from a major increase in the Russell-McPherron polarity effect through a systematic pattern of compression and draping within the ecliptic plane. Differential compression at the shock increases the Parker spiral angle and, consequently, the azimuthal field component that projects as a southward component onto earth's dipole axis. The resulting prediction is that southward fields in the postshock plasma maximize at the spring (fall) equinox in CMEs emerging from toward (away) sectors. This pattern produces a strong semiannual variation in postshock IMF orientation and may account at least in part for the observed semiannual variation of the occurrence of great geomagnetic storms.

Crooker, N. U.↗
NASA NTRS1995

Large Enhancements in the O/N2 Ratio in the Evening Sector of the Winter Hemisphere During Geomagnetic Storms

In this paper, we have looked for enhancements of the O/N2 ratio in data measured by the Dynamics Explorer 2 (DE 2) satellite in the middle latitudes of the winter hemisphere, based on a prediction that was made by the National Center for Atmospheric Research thermosphere/tonosphere general circulation model (NCAR-TIGCM) that such increases occur. The NCAR-TIGCM predicts that these enhancements should be seen throughout the low latitude region and in many middle latitude locations, but that the enhancements in O/N2 are particularly strong in the middle-latitude, evening-to-midnight sector of the winter hemisphere. When this prediction was used to look for these effects in DE 2 NACS (neutral atmosphere composition spectrometer) data, large enhancements in the O/N2 ratio (approx. 50 to 90%) were seen. These enhancements were observed during the main phase of a storm that occurred on November 24, 1982, and were seen in the same region of the winter hemisphere predicted by the NCAR-TIGCM. They are partially the result of the depletion of N2 and, as electron loss is dependent on dissociative recombination at F(sub 2) altitudes, they have implications for electron densities in this area. Parcel trajectories, which have been followed through the NCAR-TIGCM history file for this event, show that large O/N2 enhancements occur in this limited region in the winter hemisphere for two reasons. First, these parcels of air are decelerated by the antisunward edge of the ion convection pattern; individual parcels converge and subsidence occurs. Thus molecular-nitrogen-poor air is brought from higher to lower heights. Because neutral parcels that are found a little poleward of the equatorial edge of the eveningside convection pattern are swept inward toward the center of the auroral oval, the enhancements occur only in a very limited range of latitudes. Second, nitrogen-poor air is transported from regions close to the magnetic pole in the winter hemisphere. During geomagnetic storms, enhanced meridional winds are driven by the increased pressure-gradient force that is associated with intensified Joule heating in the auroral oval. These pressure-driven winds decrease rapidly on the dayside beyond the auroral oval where the parcels originate, limiting the region into which the parcels can be transported. Thus these two processes drive values of O/N2 in a limited region of the winter hemisphere, and reinforce only in the evening sector, causing large changes in this region.

Burns, A. G.↗
NASA NTRS2014

Mid-Latitude Ionospheric Disturbances Due to Geomagnetic Storms at ISS Altitudes

Spacecraft charging of the International Space Station (ISS) is dominated by interaction of the US high voltage solar arrays with the F2-region ionosphere plasma environment. ISS solar array charging is enhanced in a high electron density environment due to the increased thermal electron currents to the edges of the solar cells. High electron temperature environments suppress charging due to formation of barrier potentials on the charged solar cell cover glass that restrict the charging currents to the cell edge [Mandell et al., 2003]. Environments responsible for strong solar array charging are therefore characterized by high electron densities and low electron temperatures. In support of the ISS space environmental effects engineering community, we are working to understand a number of features of solar array charging and to determine how well future charging behavior can be predicted from in-situ plasma density and temperature measurements. One aspect of this work is a need to characterize the magnitude of electron density and temperature variations that occur at ISS orbital altitudes (approximately 400 km) over time scales of days, the latitudes over which significant variations occur, and the time periods over which the disturbances persist once they start. This presentation provides examples of mid-latitude electron density and temperature disturbances at altitudes relevant to ISS using data sets and tools developed for our ISS plasma environment study. "Mid-latitude" is defined as the extra-tropical region between approx. 30 degrees to approx. 60 degrees magnetic latitude sampled by ISS over its 51.6 degree inclination orbit. We focus on geomagnetic storm periods because storms are well known drivers for disturbances in the ionospheric plasma environment.

Minow, Joseph I.↗