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NASA NTRS2015

The Earth's Plasmasphere

The Earth's plasmasphere is an inner part of the magneteosphere. It is located just outside the upper ionosphere located in Earth's atmosphere. It is a region of dense, cold plasma that surrounds the Earth. Although plasma is found throughout the magnetosphere, the plasmasphere usually contains the coldest plasma. Here's how it works: The upper reaches of our planet's atmosphere are exposed to ultraviolet light from the Sun, and they are ionized with electrons that are freed from neutral atmospheric particles. The results are electrically charged negative and positive particles. The negative particles are electrons, and the positive particles are now called ions (formerly atoms and molecules). If the density of these particles is low enough, this electrically charged gas behaves differently than it would if it were neutral. Now this gas is called plasma. The atmospheric gas density becomes low enough to support the conditions for a plasma around earth at about 90 kilometers above Earth's surface. The electrons in plasma gain more energy, and they are very low in mass. They move along Earth's magnetic field lines and their increased energy is enough to escape Earth's gravity. Because electrons are very light, they don't have to gain too much kinetic energy from the Sun's ultraviolet light before gravity loses its grip on them. Gravity is not all that holds them back, however. As more and more electrons begin to escape outward, they leave behind a growing net positive electric charge in the ionosphere and create a growing net negative electric charge above the ionosphere; an electric field begins to develop (the Pannekoek-Rosseland E-field). Thus, these different interacting charges result in a positively charged ionosphere and negatively charged region of space above it. Very quickly this resulting electric field opposed upward movement of the electrons out of the ionosphere. The electrons still have this increased energy, however, so the electric field doesn't just go away. Instead the ions react to the electric field and are attracted to it. They begin to move upward out of the ionosphere too. Since all this happens on a small scale, it simply looks like the electrons and ions move out of the ionosphere together. Ultimately the effect is that the lighter ions of hydrogen, helium and oxygen are able to escape from the ionosphere. For a planet like Earth with a strong planetary magnetic field, these outward moving particles remain trapped near the planet unless other processes further draw them away and into interplanetary space. As is always the case with nature, there is much more story to tell about this "upwardly mobile" plasma and these other processes. Over only a short time period of hours and days this escaping plasma can, in some places, build up in concentration until an equilibrium is reached where as much plasma flows inward into the ionosphere as flows outward. This "donut shaped" region of cold (about 1 electron volt in energy) plasma encircling the planet is called the plasmasphere. Because of space weather storms (kind of a generic phrase for those other processes) this cold and dense plasmaspheric plasma can actually end up all over the place. Generally, that region of space where plasma from the ionosphere has the time to build up to become identified as the plasmasphere rotates or nearly rotates with the Earth. That region shrinks in size with increased space weather activity and expands or refills during times of inactivity. As it shrinks with increasing activity, some of the plasmasphere is drawn away from its main body (plasmaspheric erosion) in the sunward direction toward the boundary in space between that region dominated by Earth's magnetic field and the much larger region dominated by the Sun's magnetic field. The region dominated by Earth's magnetic field is called the magnetosphere. The larger Sun dominated region is called the heliosphere.

plasmasphere↗

NASA NTRS1990

A review of extraterrestrial magnetosphere research, 1987-1989

A review of research carried out during the biennium 1987-1989 on the magnetospheres of planets other than the earth is presented. The first part of the review consists of an overview and comparison of the work done in the area of radio astronomy of the two planets, Jupiter and Uranus. The second half of the review is composed of brief summaries of papers published in the literature dealing with the magnetospheres of Mercury, Venus, Jupiter, Saturn and Neptune.

Eviatar, A.↗

DOE OSTI2020

When the Moon had a magnetosphere

Apollo lunar samples reveal that the Moon generated its own global magnetosphere, lasting from ~4.25 to ~2.5 billion years (Ga) ago. At peak lunar magnetic intensity (4 Ga ago), the Moon was volcanically active, likely generating a very tenuous atmosphere, and, it is believed, was at a geocentric distance of ~18 Earth radii (R E ). Solar storms strip a planet’s atmosphere over time, and only a strong magnetosphere would be able to provide maximum protection. We present simplified magnetic dipole field modeling confined within a paraboloidal-shaped magnetopause to show how the expected Earth-Moon coupled magnetospheres provide a substantial buffer from the expected intense solar wind, reducing Earth’s atmospheric loss to space.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2016

Modeling the Ionosphere-Thermosphere Response to a Geomagnetic Storm Using Physics-based Magnetospheric Energy Input: OpenGGCM-CTIM Results

The magnetosphere is a major source of energy for the Earth's ionosphere and thermosphere (IT) system. Current IT models drive the upper atmosphere using empirically calculated magnetospheric energy input. Thus, they do not sufficiently capture the storm-time dynamics, particularly at high latitudes. To improve the prediction capability of IT models, a physics-based magnetospheric input is necessary. Here, we use the Open Global General Circulation Model (OpenGGCM) coupled with the Coupled Thermosphere Ionosphere Model (CTIM). OpenGGCM calculates a three-dimensional global magnetosphere and a two-dimensional high-latitude ionosphere by solving resistive magnetohydrodynamic (MHD) equations with solar wind input. CTIM calculates a global thermosphere and a high-latitude ionosphere in three dimensions using realistic magnetospheric inputs from the OpenGGCM. We investigate whether the coupled model improves the storm-time IT responses by simulating a geomagnetic storm that is preceded by a strong solar wind pressure front on August 24, 2005. We compare the OpenGGCM-CTIM results with low-earth-orbit satellite observations and with the model results of Coupled Thermosphere-Ionosphere-Plasmasphere electrodynamics (CTIPe). CTIPe is an up-to-date version of CTIM that incorporates more IT dynamics such as a low-latitude ionosphere and a plasmasphere, but uses empirical magnetospheric input. OpenGGCMCTIM reproduces localized neutral density peaks at approx. 400 km altitude in the high-latitude dayside regions in agreement with in situ observations during the pressure shock and the early phase of the storm. Although CTIPe is in some sense a much superior model than CTIM, it misses these localized enhancements. Unlike the CTIPe empirical input models, OpenGGCM-CTIM more faithfully produces localized increases of both auroral precipitation and ionospheric electric fields near the high-latitude dayside region after the pressure shock and after the storm onset, which in turn effectively heats the thermosphere and causes the neutral density increase at 400 km altitude.

Connor, Hyunju K.↗

NASA NTRS1999

Origins and Transport of Ions during Magnetospheric Substorms

We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had alread@, entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft.

Ashour-Abdalla, Maha↗

NASA NTRS1998

Sources and Transport of Plasma Sheet Ions During Magnetospheric Substorms

This study investigates the sources and transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that took place on November 24, 1996. The sources and acceleration mechanisms of ions observed at Geotail were determined by calculating the trajectories of thousands of ions backward in time. We found that during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and were already in the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase more plasma mantle ions reached the Geotail location. Indeed, during the expansion phase more than 90% of the ions were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the energy gained was achieved by non-adiabatic acceleration during the ions' crossing of the equatorial current sheet just prior to the detection of the ions.

Ashour-Abdalla, M.↗

NASA NTRS1993

Magnetospheric convection pattern and its implications

When we use 14 months of the Fast Plasma Experiment ion velocity measurements, the mean magnetospheric circulation pattern is constructed. It is shown that the magnetospheric convection velocity is of the order tens of kilometers per second. The convection is largely restricted to the outer magnetosphere. During magnetically active periods the convection velocity increases and the convection boundary extends to the region closer to the Earth, indicating more magnetic field flux is being transported to the dayside magnetosphere. It is also shown that the convective flows tend to follow contours of constant unit flux volume as they move around the Earth, especially on the duskside of the magnetosphere. This helps to avoid the pressure balance inconsistency often found in two-dimensional magnetotail models.

Zhu, Xiaoming↗

NASA NTRS2000

Under the Weather: Space Weather. The Magnetic Field of the Heliosphere

Normally, only people in the far north can enjoy the dancing beauty of the aurora borealis; however, an intense collision of charged solar particles with the Earth's magnetic field can magnify the Northern Lights so much that they are visible in the southern United States. Behind the light show lies enough flux of energetic particles carried by solar wind to render our planet uninhabitable. The Earth's magnetic field, also known as the magnetosphere, is the only thing that shields us from the Sun. Even the magnetosphere cannot fully guard us from the wrath of the Sun. In March 1989, a powerful solar flare hit Earth with such energy that it burned out transformers in Quebec's electrical grid, plunging Quebec and the eastern United States into darkness for more than 9 hours. Northern lights and energy grid overloads are not the only ways that a solar wind can affect us. A solar storm in July 1999 interrupted radio broadcasts. Solar activity can disorient radars and satellite sensors, break up cell phone connections, and threaten the safety of astronauts. A large bombardment of solar particles can even reduce the amount of ozone in the upper atmosphere. Magnetohydrodynamics (MHD), the study of magnetic fields in magnetized plasmas, can help scientists predict, and therefore prepare for, the harmful side effects of solar weather in the magnetosphere.

Roberts, Aaron↗

NASA NTRS1972

The magnetospheric plasma tail

The structural nature of the earth's plasmasphere at onset and immediately following an intense magnetic storm is examined. Thermal proton density measurements by the RF ion mass spectrometer on the low altitude polar orbiting satellite OGO-4 were compared on five consecutive nightside passes during the early recovery stage of an intense storm occuring in September 1967. Observational results revealed (1) characteristic termination of the dense plasmapause, (2) secondary enhancement of the ion density poleward of the first abrupt plasmapause, and (3) an elongated plasma tail during the recovery phase of the storm.

Grebowsky, J. M.↗

NASA NTRS1973

On limits to Jupiter's magnetospheric diffusion rates.

X-ray fluxes at earth estimated from hypothetical fluxes and spectra of energetic particles trapped in Jupiter's magnetic field are found to be 1/170000 times the upper limit X-ray flux from Jupiter based on published results from a rocket experiment. Detection of the calculated X-ray flux from Jupiter does not necessarily provide information on an energetic trapped proton component because the X-ray flux due to the hypothetical trapped energetic proton fluxes alone is comparable in magnitude to that due alone to trapped energetic electron fluxes as Jupiter.

Mihalov, J. D.↗

NASA NTRS1976

The position and shape of the neutral sheet at 30-earth radii distance

An examination of Explorer 34 encounters with the neutral sheet reveals a much broader arching of the neutral sheet at 30 earth radii than closer to the earth at 20 earth radii. The location of the neutral sheet hinging point in the geomagnetic equatorial plane is found to be a strong function of geomagnetic activity. For Kp less than 2 the apparent hinging distance is close to 11 earth radii. For Kp greater than 4 the apparent hinging distance is close to zero. This dependency reflects a negligible return of the neutral sheet to the solar magnetospheric equatorial plane with distance behind the earth at quiet times but reflects a rapid return at disturbed times, in addition to possible variations in the location of the hinging point in the geomagnetic equatorial plane.

Bowling, S. B.↗

NASA NTRS2021

Generation of High-frequency Whistler Waves in the Earth's Quasi-Perpendicular Bow Shock

We use observations from the Magnetospheric Multiscale spacecraft to identify a free energy source for high-frequency whistler waves in the Earth's quasi-perpendicular bow shock. In the considered measurements, whistlers propagate both parallel and antiparallel to the background magnetic field B0 with frequencies around 100 Hz (0.15 fce, where fce is the electron cyclotron frequency) and amplitudes between 0.1 and 1 nT. Their growth can be attributed to localized pitch angle anisotropy in the electron velocity distribution function that cannot be precisely described by macroscopic parameters like heat flux or temperature anisotropy. However, the presence of heat flux along −B0 does create preferential conditions for the high-frequency whistler waves that propagate in this direction. These waves are directed partially toward the shock, meaning they can scatter electrons that are streaming from the shock. This prolongs the time the electrons spend in the shock transition region and thereby promotes electron energization.

Brent Page↗

NASA NTRSDate not supplied

The Electron Heat Fluxes Associated with Electron Precipitation in the Region of Diffuse Aurora

Electron heat flux that comes from the magnetosphere to the upper ionospheric altitudes controls the value of electron temperature in the core plasma, and, as a result, the total electron density content that is required for different kinds of space weather applications. Knowing the thermal electron heat flux at the upper ionospheric boundaries is the Achilles' heel of all ionospheric models. Such a thermal heat flux setting is especially difficult to justify in the region of the diffuse aurora that is connected to a large energy reservoir of electrons with energies of a few kiloelectron volts, the Earth's plasma sheet, where magnetosphere-ionosphere coupling processes are strongly interconnected. We use the simulated heat flux provided by SuperThermal Electron Transport (STET) code to estimate electron temperatures at the upper ionospheric altitudes and compare these results with corresponding observations from the Defense Meteorological Satellite Program satellite during Saint Patrick's Days 2013 and 2015 Geomagnetic Storms.

George V. Khazanov↗

NASA NTRS2022

Kelvin-Helmholtz Vortices as an Interplay of Magnetosphere-Ionosphere Coupling

The solar wind-magnetosphere interaction drives diverse physical processes on the flanks of Earth’s magnetopause, and in turn these processes couple to the ionosphere. We investigate simultaneous multipoint in-situ spacecraft and ground-based measurements to determine the role of Kelvin-Helmholtz waves at the Earth’s magnetopause and the low-latitude boundary layer in the magnetosphere-ionosphere coupling process. Nonlinear Kelvin-Helmholtz waves develop into flow vortices that twist and/or shear flux tube magnetic fields, thereby generating localized field-aligned currents. Kelvin-Helmholtz vortices on the dusk (dawn) flanks of the magnetosphere generate clockwise (counter-clockwise) rotations and upward (downward) field-aligned currents inside the flux tubes, consistent with the region-1 field-aligned current. We present in-situ MMS and Cluster spacecraft observations of Kelvin-Helmholtz vortices at the magnetopause that map to the poleward edge of the auroral regions. The FAST spacecraft and the ground-based magnetometers from which spherical elementary currents (acting as a proxy for vertical currents) can be calculated observe corresponding field-aligned current signatures. This study demonstrates the role played by the Kelvin-Helmholtz waves in linking magnetopause boundary fluctuations to ionospheric phenomena.

K-J Hwang↗

DOE OSTI2015

Future beam experiments in the magnetosphere with plasma contactors: The electron collection and ion emission routes

Experiments where a high-voltage electron beam emitted by a spacecraft in the low-density magnetosphere is used to probe the magnetospheric configuration could greatly enhance our understanding of the near-Earth environment. Their challenge, however, resides in the fact that the background magnetospheric plasma cannot provide a return current that balances the electron beam current without charging the spacecraft to such high potential that in practice prevents beam emission. In order to overcome this problem, a possible solution is based on the emission of a high-density contactor plasma by the spacecraft prior to and after the beam. In this paper, we perform particle-in-cell simulations to investigate the conditions under which a high-voltage electron beam can be emitted from a magnetospheric spacecraft, comparing two possible routes that rely on the high-density contactor plasma. The first is an “electron collection” route, where the contactor has lower current than the electron beam and is used with the goal of connecting to the background plasma and collecting magnetospheric electrons over a much larger area than that allowed by the spacecraft alone. The second is an “ion emission” route, where the contactor has higher current than the electron beam. Ion emission is then enabled over the large quasi-spherical area of the contactor cloud, thus overcoming the space charge limits typical of ion beam emission. Finally, our results indicate that the ion emission route offers a pathway for performing beam experiments in the low-density magnetosphere, while the electron collection route is not viable because the contactor fails to draw a large neutralizing current from the background.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1981

Further determination of the characteristics of magnetospheric plasma vortices with Isee 1 and 2

Further studies of the vortices in magnetospheric plasma flow with the Los Alamos Scientific Laboratory/Max-Planck-Institut (LASL/MPI) fast plasma experiment on Isee 1 and 2 have revealed that the pattern of vortical flow has a wavelength of approximately 20-40 earth radii and moves tailward through the magnetosphere at speeds of several hundred kilometers per second. The tendency toward vorticity pervades the total breadth of the plasma sheet tailward of the dawn-dusk meridian. The sense of rotation of the plasma flow (as viewed from above the ecliptic plane) is clockwise in the morning side of the plasma sheet and counterclockwise in the evening side. The sense of rotation in the morning and evening boundary layers is reversed from that in the contiguous regions of the plasma sheet. The occurrence of vortical flow is independent of the level of geomagnetic activity but is associated with long-period geomagnetic pulsations.

Hones, E. W., Jr.↗

NASA NTRS1976

Low-energy electron intensities at large distances over the earth's polar cap

The eccentric-orbiting satellite Imp 5 penetrated the distant polar magnetosphere at positions corresponding to those for magnetic field lines which intersect the earth's northern polar cap. Measurements of electron intensities with E not less than 250 eV in these regions of extremely low plasma densities were gained with an electrostatic analyzer. The observational period was January-October 1970. Electron intensities within the energy range 250 eV-50 keV were less by orders of magnitude than those typically encountered within the plasma sheet and over the auroral oval. However, dramatic temporal variations of average electron intensities in the polar cap region were found for orbit-to-orbit comparisons. The observed intensity variations showed a remarkable correlation with the polarity of the magnetic sector structure in the interplanetary medium: high intensities for 'away from the sun' sectors and low intensities for 'toward' sectors.

Yeager, D. Y.↗

NASA NTRS2024

Preface to the Special Issue on Modeling and Data Analysis Methods for the SMILE mission

The SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) project (http://www.nssc.cas.cn/smile/, https://www.cosmos.esa.int/web/smile/mission) is a joint spacecraft mission of the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) with an expected launch in 2025. SMILE aims to study the global interactions of solar wind–magnetosphere–ionosphere innovatively by imaging the Earth’s magnetosheath and cusps in soft X-rays and the northern auroral region in ultraviolet (UV) while simultaneously measuring plasma and magnetic field parameters in the solar wind and magnetosheath along a highly-elliptical and highly-inclined orbit. This special issue is composed of 22 articles, presenting recent progress in modeling and data analysis techniques developed for the SMILE mission. In this preface, we categorize the articles into the following seven topics and provide brief summaries: (1) instrument descriptions of the Soft X-ray Imager (SXI), (2) numerical modeling of the X-ray signals, (3) data processing of the X-ray images, (4) boundary tracing methods from the simulated images, (5) physical phenomena and a mission concept related to the scientific goals of SMILE-SXI, (6) studies of the aurora, and (7) ground-based support for SMILE.

SMILE↗