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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 415 records · Page 23
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NASA NTRS2012

Solar Sources of Severe Space Weather

Severe space weather is characterized by intense particle radiation from the Sun and severe geomagnetic storm caused by magnetized solar plasma arriving at Earth. Intense particle radiation is almost always caused by coronal mass ejections (CMEs) traveling from the Sun at super-Alfvenic speeds leading to fast-mode MHD shocks and particle acceleration by the shocks. When a CME arrives at Earth, it can interact with Earth's magnetopause resulting in solar plasma entry into the magnetosphere and a geomagnetic storm depending on the magnetic structure of the CME. Particle radiation starts affecting geospace as soon as the CMEs leave the Sun and the geospace may be immersed in the radiation for several days. On the other hand, the geomagnetic storm happens only upon arrival of the CME at Earth. The requirements for the production of particles and magnetic storms by CMEs are different in a number of respects: solar source location, CME magnetic structure, conditions in the ambient solar wind, and shock-driving ability of CMEs. Occasionally, intense geomagnetic storms are caused by corotating interaction regions (CIRs) that form in the interplanetary space when the fast solar wind from coronal holes overtakes the slow wind from the quiet regions. CIRs also accelerate particles, but when they reach several AU from the Sun, so their impact on Earth's space environment is not significant. In addition to these plasma effects, solar flares that accompany CMEs also produce excess ionization in the ionosphere causing sudden ionospheric disturbances. This paper highlights these space weather effects using space weather events observed by space and ground based instruments during of solar cycles 23 and 24.

Gopalswamy, N.↗
NASA NTRS2004

Ring Current Electrodynamic Coupling

In this talk we will address the two primary issues of ring current (RC) electrodynamic coupling: 1. RC self-consistent coupling with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic coupling); and 2. RC self-consistent magnetosphere-ionosphere coupling that includes calculation of the magnetospheric electric field (large scale electrodynamic coupling). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002, 20031 couples the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic coupling processes and provides a self-consistent simulation of RC ions, electrons and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale coupling changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale coupling altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned currents and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic coupling processes and to examine their interactions with each other on a global scale. We also discuss the nonlinear coupling of EMIC and lower hybrid waves in the RC region during the May 2-7, 1998 storm period.

Khazanov, G. V.↗
NASA NTRS1984

Dependence of the High Latitude Middle Atmosphere Ionization on Structures in Interplanetary Space

The precipitation of high energetic electrons during and after strong geomagnetic storms into heights below 100 km in middle and subauroral latitudes is markedly modulated by the structure of the interplanetary magnetic field (IMF). Under relative quiet conditions the D-region ionization caused by high energetic particle precipitation (energies greater than 20 to 50 keV) depends on changes of the interplanetary magnetic field and also on the velocity of the solar wind. To test this assumption, the influence of the IMF-sector boundary crossings on ionospheric absorption data of high and middle latitudes by the superposed-epoch method was investigated.

Bremer, J.↗
NASA NTRS2011

Rapid Rebuilding of the Outer Radiation Belt

Recent observations by the radiation monitor (RDM) on the spacecraft Akebono have shown several cases of greater than 2.5 MeV radiation belt electron enhancements occurring on timescales of less than a few hours. Similar enhancements are also seen in detectors on board the NOAA/POES and TWINS 1 satellites. These intervals are shorter than typical radial diffusion or wave-particle interactions can account for. We choose two so-called "rapid rebuilding" events that occur during high speed streams (4 September 2008 and 22 July 2009) and simulated them with the Space Weather Modeling Framework configured with global magnetosphere, radiation belt, ring current, and ionosphere electrodynamics model. Our simulations produce a weaker and delayed dipolarization as compared to observations, but the associated inductive electric field in the simulations is still strong enough to rapidly transport and accelerate MeV electrons resulting in an energetic electron flux enhancement that is somewhat weaker than is observed. Nevertheless, the calculated flux enhancement and dipolarization is found to be qualitatively consistent with the observations. Taken together, the modeling results and observations support the conclusion that storm-time dipolarization events in the magnetospheric magnetic field result in strong radial transport and energization of radiation belt electrons.

Glocer, A.↗
NASA NTRS1970

A unified theory of stable auroral red arc formation at the plasmapause

A theory is proposed that SAR-arcs are generated at the plasmapause as a consequence of the turbulent dissipation of ring current energy. During the recovery phase of a geomagnetic storm, the plasmapause expands outward into the symmetric ring current. When the cold plasma densities reach about 100/cu cm, ring current protons become unstable and generate intense ion cyclotron wave turbulence in a narrow region 1/2 earth radius wide (just inside the plasmapause). Approximately one-half of the ring current energy is dissipated into wave turbulence which in turn is absorbed through a Landau resonant interaction with plasma spheric electrons. The combined thermal heat flux to the ionosphere due to Landau absorption of the wave energy and proton-electron Coulomb dissipation is sufficient to drive SAR-arcs at the observed intensities. It is predicted that the arcs should be localized to a narrow latitudinal range just within the stormtime plasmapause. They should occur at all local times and persist for the 10 to 20 hour duration of the plasma-pause expansion.

Cornwall, J. M.↗
NASA NTRS1998

Modeling of the Magnetosphere-Ionosphere-Atmosphere System

This grant covered the transition period between the ISTP/GGS main mission MAMI work (NAGW5-1097) to the extended mission of GGS/SolaxMax. During this period we concentrated on the following subjects: (1) Ionospheric modeling and in particular the coupling of the ionosphere and the magnetosphere require knowledge of the ionospheric conductances. We have an algorithm to derive these conductances from POLAR UVI or POLAR VIS images. The image analysis requires carefully calibrated measurements, separation of auroral brightness from scattered solar EUV and emissions caused by photoelectrons, and modeling of the auroral conditions, Under this grant we evaluated the various sources of uncertainty that contribute to the conductance calculation by comparing different model approaches and we conducted sensitivity studies. A joint modeling effort between our ionospheric models and a global MHD magnetospheric model with S. Slinker and J. Fedder lead to improved parameterizations for the MHD model. The predictions of that new model were validated using data from ground based instruments, POLAR UVI images, and DMSP satellites. These findings were presented at the GEM meeting in Snowmass, and at the Huntsville modeling workshop in Guntersville. A manuscript for publication is in preparation. A study to evaluate the thermospheric effects of large substorms and storms was con- ducted with the TIE-GCM model. Of particular interest are compositional changes of the thermosphere in the southern hemisphere. Southern hemisphere effects are stronger than those on the northern hemisphere because of the larger offset of the magnetic dipole from the rotational axis. These results were presented at the Huntsville modeling workshop in Guntersville.

Source record↗
NASA NTRS1993

Plasmasphere dynamics in the duskside bulge region: A new look at old topic

Data acquired during several multiday periods in 1982 at ground stations Siple, Halley, and Kerguelen and on satellites Dynamics Explorer 1, International Sun Earth Explorer 1, and GEOS 2 have been used to investigate thermal plasma structure and dynamics in the duskside plasmasphere bulge region of the Earth. The distribution of thermal plasma in the dusk bulge sector is difficult to describe realistically, in part because of the time integral manner in which the thermal plasma distribution depends upon on the effects of bulk cross-B flow and interchange plasma flows along B. While relatively simple MHD models can be useful for qualitatively predicting certain effects of enhanced convection on a quiet plasmasphere, such as an initial sunward entrainment of the outer regions, they are of limited value in predicting the duskside thermal plasma structures that are observed. Furthermore, use of such models can be misleading if one fails to realize that they do not address the question of the formation of the steep plasmapause profile or provide for a possible role of instabilities or other irreversible processes in plasmapause formation. Our specific findings, which are based both upon the present case studies and upon earlier work, include the following: (1) during active periods the plasmasphere appears to become divided into two entities, a main plasmasphere and a duskside bulge region. (2) in the aftermath of an increase in convection activity, the main plasmasphere tends (from a statistical point of view) to become roughly circular in equatorial cross section, with only a slight bulge at dusk; (3) the abrupt westward edge of the duskside bulge observed from whistlers represents a state in the evolution of sunward extending streamers; (4) in the aftermath of a weak magnetic storm, 10 to 30% of the plasma 'removed' from the outer plasmasphere appears to remain in the afternoon-dusk sector beyond the main plasmasphere. (5) outlying dense plasma structures may circulate in the outer duskside magetosphere for many days following an increase in convection, unless there is extremely deep quieting; (6) a day-night plasmatrough boundary may be identified in equatorial satellite data; (7) factor-of-2-to-10 density irregularities appear near the plasmatrough from the ionosphere at L = 4.6, predominantly bidirectional field aligned and equatorially trapped light ion pitch angle distributions give away to a predominantly isotropic distribution (as seen by DE 1) when the plasma density reaches a level a factor of about 3 below the satured plasmasphere level; (9) some outlying dense plasma structures are effectively detached from the main plasmasphere, while others appear to be connected to that body.

Carpenter, D. L.↗
NASA NTRS1972

Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm.

On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high-altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. We also show that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation.

Scarf, F. L.↗
NASA NTRS1980

Coincident particle observations from AE-C and ATS 6 during the October 28, 1977, geomagnetic storm

Simultaneous measurements of ion and electron energy spectra recorded during the October 28, 1977 geomagnetic storm by the AE-C and ATS 6 spacecraft when both were nearly on the same L shell are evaluated and compared. The orbit of the AE-C generates wide longitudinal coverage of the auroral oval, whereas the ATS 6, which is located at geosynchronous orbit, samples the equatorial particle population. It is shown that the coincident electron energy spectra obtained by the two satellites agree well above 5 keV and the spectra of electrons peak near 1 keV at ionospheric altitudes, while no peaks in energy appear at synchronous altitude.

Zanetti, L. J.↗
NASA NTRS1972

Twilight and nighttime ionospheric temperatures from oxygen 6300- and 5577-A spectral-line profiles.

Use of Fabry-Perot interferometer measurements of atomic-oxygen 6300- and 5577-A line profiles from twilight and nightglow to determine the neutral temperatures in the F2 and E regions of the earth's ionosphere. The exospheric temperatures determined from the 6300-A profiles are usually somewhat higher than the temperatures calculated from Jacchia's model, and differences as large as about 300 K are noted when the exospheric temperature equals 1500 to 1600 K. The postsunset and predawn rate of change of the exospheric temperature is often substantially larger than the Jacchia prediction. The 5577-A (E region) measured temperatures range from 200 to 220 K on quiet nights to 500 to 600 K during geomagnetic storms.

Feibelman, W. A.↗
NASA NTRS2021

A Comparison of the CIR- and CME-Induced Geomagnetic Activity Effects on Mesosphere and Lower Thermospheric Temperature

Neutral temperature responses in the mesosphere and lower thermosphere (MLT) to severe geomagnetic storms induced by coronal mass ejections (CMEs) are of growing interest to the space science research community. Recently, it was found that geomagnetic activities produced by the corotating interaction regions (CIRs) caused comparable effects on the Earth's upper atmosphere. In this work, we carried out a comparative study of the temperature responses in the MLT region to these two types of geomagnetic activities, using the temperature measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. Our results demonstrate that CIR-induced geomagnetic activity produced temperature variations in the MLT region and that this effect can penetrate downward to ∼100 km at high latitudes in both hemispheres. Temperature enhancements penetrated deeper during CME-induced geomagnetic activities, but the heating effects lasted longer during CIR-induced geomagnetic activities. There is a hemispherical asymmetry in the geomagnetical activity induced temperature changes in the MLT region. The temperature enhancements are stronger in the southern hemisphere than in the northern hemisphere during CME events.

geomagnetic activity↗
NASA NTRS1989

Remote sensing of the ring current using energetic neutral atoms

Energetic neutral atom images of the storm-time ring current obtained from the ISEE-1 spacecraft provide information for a 'zero-order' global model of the energetic ion distribution. With the assumption of isotropic pressure and magnetostatic, nonconvective pressure balance, the global system of electrical currents driven by the ion pressure can be calculated using Euler potentials for the divergenceless current density. Radial pressure gradients drive azimuthal currents, and azimuthal pressure gradients drive radial currents. The radial currents cause current lines in the inner magnetosphere to close in the ionosphere, forming a partial ring current. The intensities and locations of these field-aligned currents driven into and out of the ionosphere resemble those of the observed Region 2 current system, but not all observed properties of the Region 2 system are reproduced by the zero-order model.

Roelof, Edmond C.↗
NASA NTRS1973

Field-aligned currents, plasma waves, and anomalous resistivity in the disturbed polar cusp.

During the magnetic storm of November 1, 1968, the Ogo 5 spacecraft encountered the polar cusp region at low magnetic latitudes. We show that the region just outside the last closed field lines contained a warm magnetosheath plasma, magnetic field perturbations interpretable as field-aligned current layers, and electrostatic waves possibly due to plasma instabilities driven by these currents. Estimates of anomalous resistivity extrapolated along the field lines due to these electrostatic waves lead to estimates of field-aligned potential drops between Ogo 5 and the ionosphere on the order of 2 kV.

Fredricks, R. W.↗
NASA NTRS1984

The magnetospheric currents - An introduction

It is pointed out that the scientific discipline concerned with magnetospheric currents has grown out from geomagnetism and, in particular, from geomagnetic storm studies. The International Geophysical Year (IGY) introduced a new area for this discipline by making 'man-made satellites' available for the exploration of space around the earth. In this investigation, a brief description is provided of the magnetospheric currents in terms of eight component current systems. Attention is given to the Sq current, the Chapman-Ferraro current, the ring current (the symmetric component), the current systems driven by the solar wind-magnetosphere dynamo (SMD), the cross-tail current system, the average ionospheric current pattern, an example of an instantaneous current pattern, field-aligned currents, and driving mechanisms and models.

Akasofu, S.-I.↗
NASA NTRS1985

Local time distribution of the SSC-associated HF-Doppler frequency shifts

The HF-Doppler frequency shift observed at the storm's sudden commencement is composed of a frequency increase (+) and decrease (-), and classified into four types, SCF(+ -), SCF(- +), SCF(+) and SCF(-). Since the latter two types are special cases of the former two types, two different kinds of electrical field exist in the F region and cause the ExB drift motion of plasma. HUANG (1976) interpreted the frequency increase of SCF(+ -) as due to the westward induction electric field proportional to delta H/ delta t and the succeeding frequency decrease due to the eastward conduction electric field which produces ionospheric currents responsible for the magnetic increase on the ground. In spite of his success in interpreting the SCF(+ -), some other interpretations are needed for the explanation of the whole set of SCF's, particularly SCF(- +). Local time distributions of the SCF's are derived from 41 SCF's which are observed on the HF standard signal (JJY) as received in Okinawa (path length =1600 km) and Kokubunji (60 km). It is shown that the SCF(+ -) appears mainly during the day, whereas the SCF(- +) is observed during the night. The results indicate that the preliminary frequency shift (+) of SCF(+ -) and (-) of SCF(- +) is caused by a westward electric field in the dayside hemisphere, while by an eastward electric field in the nightside hemisphere. The main frequency shift (-) of SCF(+ -) and (+) of SCF(- +) is caused by the reversed electric field. Consequently, the preliminary frequency shift is caused by the dusk-to-dawn electric field, while the main frequency shift by the dawn-to-dusk electric field.

Kikuchi, T.↗
NASA NTRS2007

Image RPI Reawakens Plasmaspheric Refilling Research

The plasmasphere is a toroidal region of cold plasma surrounding the Earth that results from ionospheric outflow and accumulation. The physics of refilling and the dynamics of this region have been studied for nearly 50-years. During that time many models have been proposed, but little has been done to test these models due to a lack of observational information. With the launch of the IMAGE Mission in March 2000 the Radio Plasma Imager has provided true field aligned density measurements that uniquely enable the testing of these models and a final determination of the physical processes important for the plasmasphere's recovery from storm-time conditions.

Gallagher, D. L.↗
NASA NTRS2018

Predicting Global Ground Geoelectric Field With Coupled Geospace and Three-Dimensional Geomagnetic Induction Models

We forecast the global effects of space weather on the geoelectric and geomagnetic fields using a novel combination of methods. We use a realistic three-dimensional (3-D) model of Earth's electrical conductivity and a realistic representation of magnetospheric and ionospheric current systems. Our scheme involves the following steps: (1) We run a global magnetohydrodynamic model of the magnetosphere coupled to an electrostatic model of the ionosphere. (2) We calculate a global time series of the ground magnetic field resulting from the ionospheric, field-aligned, and magnetospheric currents of the global magnetohydrodynamic model. (3) We approximate this external field by an equivalent source current flowing in a thin shell above Earth. (4) We calculate a global time series of geoelectric and geomagnetic fields from the equivalent current and a 3-D conductivity model of Earth that also takes into account the coast effect due to large horizontal conductivity gradient. We verify our implementation by comparing the results against known analytic and numeric solutions, and then apply our scheme to the geomagnetic storm of 14 and 15 December 2006. In particular, we show that accounting for 3-D structure of Earth's conductivity results in significantly enhanced geoelectric field at large lateral gradients of conductivity, especially in coastal regions, both at middle and high latitudes. In the studied geomagnetic storm the largest values of 3-D geoelectric field are detected at high latitudes reaching 2.5 volts per kilometer and the 3-D effect extends inland by a few hundred kilometers.

Honkonen, I.↗
NASA NTRS1971

Twilight and nighttime ionospheric temperatures from oxygen wavelengths 6300 and 5577 spectral line profiles

Fabry-Perot interferometer measurements of atomic oxygen 6300 A and 5577 A line profiles from twilight and nightglow are used to determine the neutral temperatures in F2 and E regions of the earth's ionosphere. The exospheric temperatures T sub n (infinity) determined from the 6300 A profiles are usually somewhat higher than those calculated from Jacchia's model, with differences as large as approximately 300 K noted when T sub n (infinity) = 1500 to 1600 K. The post-sunset and pre-dawn rate of change of T sub n (infinity) is often substantially larger than the Jacchia prediction. The 5577 A (E-region) measured temperatures range from 200 to 220 K on quiet nights to 500 to 600 K during geomagnetic storms.

Feibelman, W. A.↗