Hot Plasma Environment Research Articles

Surface unequal charging effect of GEO satellite

When a satellite is in orbit, the plasma environment interacts with the surface material, and the surface charge accumulation of different structures is inconsistent,resulting in an unequal charging effect. In serious cases, this leads to electrostatic discharge and affects the normal operation of the satellite. In this study, a three-dimensional model of a geosynchronous orbit (GEO) satellite is constructed, and the particle cloud grid algorithm (Particle-In-Cell,PIC) was used to simulate the charging process and the unequal charged state between the satellite panels in the solar wind plasma environment and the hot plasma environment. The simulation results show that in the solar wind plasma environment, the charging balance potential of solar panels is low and the charging difference between panels is small, which does not affect the normal operation of the satellite. However, when the satellite is in an hot plasma environment, if some parts of the satellite suddenly encounter extremely strong interference, the charging balance of the satellite in the solar wind plasma will be destroyed, and there will be a large potential difference between the irradiated part and the adjacent structure, which can easily cause electrostatic discharge to harm the normal operation of the satellite.

Extreme brightness laser-based neutron pulses as a pathway for investigating nucleosynthesis in the laboratory

With the much-anticipated multi-petawatt (PW) laser facilities that are coming online, neutron sources with extreme fluxes could soon be in reach. Such sources would rely on spallation by protons accelerated by the high-intensity lasers. These high neutron fluxes would make possible not only direct measurements of neutron capture and β-decay rates related to the r-process of nucleosynthesis of heavy elements, but also such nuclear measurements in a hot plasma environment, which would be beneficial for s-process investigations in astrophysically relevant conditions. This could, in turn, finally allow possible reconciliation of the observed element abundances in stars and those derived from simulations, which at present show large discrepancies. Here, we review a possible pathway to reach unprecedented neutron fluxes using multi-PW lasers, as well as strategies to perform measurements to investigate the r- and s-processes of nucleosynthesis of heavy elements in cold matter, as well as in a hot plasma environment.

Energetic particle pressure in Saturn's magnetosphere measured with the Magnetospheric Imaging Instrument on Cassini

The Magnetospheric Imaging Instrument on board Cassini has been providing measurements of energetic ion intensities, energy spectra, and ion composition, combining the Charge Energy Mass Spectrometer over the range 3 to 236 keV/e, the Low Energy Magnetospheric Measurements System for ions in the range 0.024 to 18 MeV, and the Ion and Neutral Camera for ions and energetic neutral atoms in the range 3 to > 200 keV. Results of the energetic (E > 3 keV) particle pressure distribution throughout the Saturnian magnetosphere and comparison with in situ measurements of the magnetic pressure are presented. The study offers a comprehensive depiction of the average, steady state hot plasma environment of Saturn over the 3 years since orbit insertion on 1 July 2004, with emphasis on ring current characteristics. The results may be summarized as follows: (1) The Saturnian magnetosphere possesses a dynamic, high‐beta ring current located approximately between 8 and ∼15 RS, primarily composed of O+ ions, and characterized by suprathermal (E > 3 keV) particle pressure, with typical values of 10−9 dyne/cm2. (2) The planetary plasma sheet shows significant asymmetries, with the dayside region being broadened in latitude (±50°) and extending to the magnetopause, and the nightside appearing well confined, with a thickness of ∼10 RS and a northward tilt of some 10° with respect to the equatorial plane beyond ∼20 RS. (3) The average radial suprathermal pressure gradient appears sufficient to modify the radial force balance and subsequently the azimuthal currents. (4) The magnetic perturbation due to the trapped energetic particle population is ∼7 nT, similar to values from magnetic field–based studies (9 to 13 nT).

Oscillator strengths and polarizabilities of the hot-dense plasma-embedded helium atom

The effect of weakly coupled hot plasma environment on the oscillator strengths of the ultraviolet and visible series and the polarizabilities of helium has been investigated using variational highly correlated wave functions within the non-relativistic framework. The Debye shielding approach that admits a variety of plasma conditions is used to simulate the plasma effects. For each shielding parameter, dipole oscillator strengths are calculated for the 1 1S– n 1P ( n=2, 3), 2 1S–2 1P, 2 3S– n 3P ( n=2, 3) and 2 1,3P– n 1,3D ( n=3, 4) transitions. The dipole and quadrupole polarizabilities for the ground He (1s 2 1S) state are also reported for each screening parameter. Results obtained are useful in plasma diagnostic purposes besides several other applications.

<i>Introduction</i>: The Equator-S mission

Abstract. In spite of its short operational life of only five months, the major goals of the Equator-S mission were fulfilled, except that its contribution to the ISTP science is restricted to the morning sector of the outer magnetosphere. A set of twelve papers following this introduction is a first documentation of the achievements. They span from the successful testing and operation of the most advanced and complex way of measuring electric fields in a hot plasma environment by means of electron beams, to various investigations at or near the equatorial magnetopause and in the plasma sheet.

Filtering of the interstellar dust flow near the heliopause: the importance of secondary electron emission for the grain charging

The deflection of interstellar dust grains in the magnetic field near the heliopause depends on their surface electric charge. We study the electric charging of the grains with emphasis on the secondary electron emission because of its importance in the hot plasma environment near the heliopause. We correct previous models of the secondary electron emission that overestimate the electric charge of dust near the heliopause. Our model calculations of the grain charge, when combined with results from in situ measurements of interstellar dust in the heliosphere, place an upper limit on the magnetic field strength. We find that the detection of interstellar dust with mass of 10−18 kg indicates the component of the magnetic field perpendicular to the interstellar dust flow to be less than 0.4 nT.

The Equator-S mission

In spite of its short operational life of only five months, the major goals of the Equator-S mission were fulfilled, except that its contribution to the ISTP science is restricted to the morning sector of the outer magnetosphere. A set of twelve papers following this introduction is a first documentation of the achievements. They span from the successful testing and operation of the most advanced and complex way of measuring electric fields in a hot plasma environment by means of electron beams, to various investigations at or near the equatorial magnetopause and in the plasma sheet.

The Hot Plasma Environment at Jupiter: Ulysses Results

Measurements of the hot plasma environment during the Ulysses flyby of Jupiter have revealed several new discoveries related to this large rotating astrophysical system. The Jovian magnetosphere was found by Ulysses to be very extended, with the day-side magnetopause located at approximately 105 Jupiter radii. The heavy ion (sulfur, oxygen, and sodium) population in the day-side magnetosphere increased sharply at approximately 86 Jupiter radii. This is somewhat more extended than the "inner" magnetosphere boundary region identified by the Voyager hot plasma measurements. In the day-side magnetosphere, the ion fluxes have the anisotropy direction expected for corotation with the planet, with the magnitude of the anisotropy increasing when the spacecraft becomes more immersed in the hot plasma sheet. The relative abundances of sulfur, oxygen, and sodium to helium decreased somewhat with decreasing radial distance from the planet on the day-side, which suggests that the abundances of the Jupiter-derived species are dependent on latitude. In the dusk-side, high-latitude region, intense fluxes of counter-streaming ions and electrons were discovered from the edge of the plasma sheet to the dusk-side magnetopause. These beams of electrons and ions were found to be very tightly aligned with the magnetic field and to be superimposed on a time- and space-variable isotropic hot plasma background. The currents carried by the measured hot plasma particles are typically approximately 1.6 x 10(-4) microamperes per square meter or approximately 8 x 10(5) amperes per squared Jupiter radius throughout the high-latitude magnetosphere volume. It is likely that the intense particle beams discovered at high Jovian latitudes produce auroras in the polar caps of the planet.

Coagulation of dust particles in a plasma

The electrostatic charge of small dust grains in a plasma in which the temperature varies in time is discussed, pointing out that secondary electron emission might introduce charge separation. If the sign of the charge on small grains is opposite to that on big ones, enhanced coagulation can occur which will affect the size distribution of grains in a plasma. Two scenarios where this process might be relevant are considered: a hot plasma environment with temperature fluctuations and a cold plasma environment with transient heating events. The importance of the enhanced coagulation is uncertain, because the plasma parameters in grain-producing environments such as a molecular cloud or a protoplanetary disk are not known. It is possible, however, that this process is the most efficient mechanism for the growth of grains in the size range of 0.1-500 microns.

The ionospheric contribution to the plasma environment in near‐earth space

Many C3I systems rely on satellites in geostationary and other near‐earth orbits that are largely within the earth's magnetosphere. It has only recently been observed that the ionosphere plays a major role in determining the hot plasma environment in which these satellites must operate. Spacecraft charging, radiation effects, and degradation of sensitive surfaces used in optical and thermal control systems are attributal to the interaction of spacecraft with this ambient hot plasma, and these effects are especially serious for the newer satellite systems designed to function in orbit for a decade or longer. Recent energetic ion mass spectrometer observations have shown that the hot magnetospheric plasma in the energy range from about 100 eV to about 30 keV contains a large and variable O+ fraction which is essentially all of ionospheric origin. The other principal constituent is H+ which can be either of ionospheric or solar wind origin. The O+/H+ ratio of the plasma is an important parameter in modelling the spacecraft‐plasma interactions to attempt to predict the magnitude of the above described effects. This report reviews the mass spectrometer observations by the International Sun Earth Explorer (ISEE 1) and the Spacecraft Charging at High Altitudes (SCATHA) satellites and examines the data for various signatures of the plasma sources. The relative contributions of the ionosphere and the solar wind to the plasma density are estimated in the altitude range from about 25,000 to 70,000 km on the basis of the ion composition. It is found that the ionosphere is an important or dominant source during both quiet and storm time conditions.

A hydromagnetic vortex seen by ISEE-1 and 2

Magnetometer and plasma data from the dual ISEE spacecraft are combined in a study of the initial plasma vortex event reported by Hones et al. (1978) in the dawn plasma sheet. The event is a transient hydromagnetic wave of two cycles duration with a six minute period. Large amplitude compressional and transverse magnetic components were present. Particle and magnetic pressure oscillations were in strict antiphase, but did not balance. When combined with the plasma velocity data these properties show that substantial Earthward field-aligned flows of electromagnetic energy and heat flux occurred during the vortex. The nett energy flow perpendicular to B was in the antisolar direction. This event possesses hydromagnetic features unique to a hot plasma environment.

The hot plasma environment and floating potentials of an electron‐beam‐emitting rocket in the ionosphere

With an extensive array of particle sensors the plasma environment surrounding the Echo III accelerator payload is studied. From measurements of the thermal ion spectrum, negative payload potentials referenced to the unperturbed ionospheric plasma are obtained. Multiple detectors determined the electron population from a fraction of an eV up to 40‐keV energy. An intense electron population extending up to the energy of injected electrons by the accelerator is produced when the acceleration is turned on. The energetic tail of this population is returned to the payload principally from directions in which the beam was fired, with the most intense fluxes coming from the atmosphere for downward injections of the beam. The atmospheric‐scattered beam and secondary electrons are called ‘quick echoes.’ Electrons of energy less than several keV down to the detector threshold (0.1 eV) are called the suprathermal component. These electrons are produced isotropically around the payload during gun firings and decay away in approximately 32 ms. The largest directional intensities of this component are observed at the higher altitudes. Quick echo electrons are also observed to produce suprathermal electrons when they encounter the payload. The mechanism by which the suprathermal electrons are produced is discussed but remains unknown at the present time. The hot electrons surrounding the accelerator payload during gun injections bring sufficient charge to the payload to neutralize it provided the loss of charge by secondary production on the payload skin is small, presumably owing to a positive payload floating potential during injection. Since the hot population exists for tens of milliseconds after the gun turn off, it results in driving the payload up to 4 volts negative during this time. Secondary production on the payload skin apparently prevents much larger negative potentials after gun turnoff when the payload is immersed in the hot population. Quick echo electrons creating suprathermal electrons around the payload also drive the payload to a few volts negative. This is an important consideration when discussing the origin of the suprathermal electrons, since electrical discharge and beam plasma discharge mechanisms do not apply to the quick echo beams.