A Case for Electron-Astrophysics (original) (raw)

Perspectives on Space and Astrophysical Plasma Physics

Symposium - International Astronomical Union

We summarize the discussion of the current status and future prospects of space and astrophysical plasma research prepared by the Panel on Space and Astrophysical plasmas, a part of the study on Physics administered by the National Research Council of the National Academy of Sciences. The Study on Physics is chaired by W. Brinkman of Bell Laboratories and will be completed in 1984.

Microphysics of Cosmic Plasmas: Background, Motivation and Objectives

With the maturing of space plasma research in the solar system, a more general approach to plasma physics in general, applied to cosmic plasmas, has become appropriate. There are both similarities and important differences in describing the phenomenology of space plasmas on scales from the Earth's magnetosphere to galactic and inter-galactic scales. However, there are important aspects in common, related to the microphysics of plasma processes. This introduction to a coordinated collection of papers that address the several aspects of the microphysics of cosmic plasmas that have unifying themes sets out the scope and ambition of the broad sweep of topics covered in the volume, together with an enumeration of the detailed objectives of the coverage.

Energy in Astrophysical Plasmas

The impact of this finding in astrophysical systems across a range of scales can be explored with current and future spacecraft and telescopes. Unpacking the energy transfer process across scales will be crucial to solving key cosmic mysteries, the paper said.

Toward a Theory of Astrophysical Plasma Turbulence at Subproton Scales

The Astrophysical Journal, 2013

We present an analytical study of subproton electromagnetic fluctuations in a collisionless plasma with a plasma beta of the order of unity. In the linear limit, a rigorous derivation from the kinetic equation is conducted focusing on the role and physical properties of kinetic-Alfvén and whistler waves. Then, nonlinear fluid-like equations for kinetic-Alfvén waves and whistler modes are derived, with special emphasis on the similarities and differences in the corresponding plasma dynamics. The kinetic-Alfvén modes exist in the lower-frequency region of phase space, ω k ⊥ v T i , where they are described by the kinetic-Alfvén system. These modes exist both below and above the ion-cyclotron frequency. The whistler modes, which are qualitatively different from the kinetic-Alfvén modes, occupy a different region of phase space, k ⊥ v T i ω k z v T e , and they are described by the electron magnetohydrodynamics (MHD) system or the reduced electron MHD system if the propagation is oblique. Here, k z and k ⊥ are the wavenumbers along and transverse to the background magnetic field, respectively, and v T i and v T e are the ion and electron thermal velocities, respectively. The models of subproton plasma turbulence are discussed and the results of numerical simulations are presented. We also point out possible implications for solar-wind observations.

Space Plasma Physics: A Review

arXiv (Cornell University), 2022

Owing to the ever-present solar wind, our vast solar system is full of plasmas. The turbulent solar wind, together with sporadic solar eruptions, introduces various space plasma processes and phenomena in the solar atmosphere all the way to the Earth's ionosphere and atmosphere and outward to interact with the interstellar media to form the heliopause and termination shock. Remarkable progress has been made in space plasma physics in the last 65 years, mainly due to sophisticated in-situ measurements of plasmas, plasma waves, neutral particles, energetic particles, and dust via space-borne satellite instrumentation. Additionally high technology ground-2 To appear in IEEE Transactions on Plasma Science

Universality of Solar-Wind Turbulent Spectrum from MHD to Electron Scales

Physical Review Letters, 2009

To investigate the universality of magnetic turbulence in space plasmas we analyze seven time periods in the free solar wind under different plasma conditions. Three instruments on Cluster spacecraft operating in different frequency ranges give us the possibility to resolve spectra up to 300 Hz. We show that the spectra form a quasiuniversal spectrum following the Kolmogorov's law ∼ k −5/3 at MHD scales, a ∼ k −2.8 power-law at ion scales and an exponential ∼ e −(kρe) 1/2 at scales kρe ∼ [0.1, 1], where ρe is the electron gyroradius. This is the first observation of an exponential magnetic spectrum in space plasmas, that may indicate the onset of dissipation. We distinguish for the first time between the role of different spatial kinetic plasma scales and show that the electron Larmor radius plays the role of a dissipation scale in space plasma turbulence. PACS numbers: 52.35.Ra,94.05.-a,96.60.Vg,95.30.Qd

Electron temperature anisotropy constraints in the solar wind

Journal of Geophysical Research, 2008

1] We have performed a statistical study of a substantial amount of electron data acquired in the solar wind to understand the constraints on electron temperature anisotropy by plasma instabilities and Coulomb collisions. We use a large data set of electron measurements from three different spacecraft (Helios I, Cluster II, and Ulysses) collected in the low ecliptic latitudes covering the radial distance from the Sun from 0.3 up to 4 AU. We estimate the electron temperature anisotropy using fits of the measured electron velocity distribution functions acquired in situ. We use a two population (core and halo) analytical model and properties of both populations are studied separately. We examine all the acquired data in terms of temperature anisotropy versus parallel electron plasma beta, and we relate the measurements to the growth rates of unstable modes. The effect of Coulomb collisions is expressed by the electron collisional age A e defined as the number of collisions suffered by an electron during the expansion of the solar wind. We show that both instabilities and collisions are strongly related to the isotropisation process of the electron core population. In addition we examine the radial evolution of these effects during the expansion of the solar wind. We show that the bulk of the solar wind electrons are constrained by Coulomb collisions, while the large departures from isotropy are constrained by instabilities.

New Experimental Constraints on the Electron Screening Effect in Astrophysical Plasma

Proceedings of XIII Nuclei in the Cosmos — PoS(NIC XIII), 2015

Study of the d+d reactions at very low energies in metallic environments in the terrestrial laboratories, enables us to determine the strength of the screening effect in the strongly coupled astrophysical plasma in stars. So far, experimentally determined screening energies were extremely high in comparison to the theoretical predictions, and the reason for the observed discrepancies remained unrecognized. New measurements of the electron screening effect in 2 H(d, p) 3 H and 2 H(d, n) 3 H reactions at energies from 6 to 25 keV were performed in zirconium under ultra-high * Speaker.

On energetic electrons (>38 keV) in the central plasma sheet: Data analysis and modeling

Journal of Geophysical Research: Space Physics, 2011

The spatial distribution of >38 keV electron fluxes in the central plasma sheet (CPS) and the statistical relationship between the CPS electron fluxes and the upstream solar wind and interplanetary magnetic field (IMF) parameters are investigated quantitatively using measurements from the Geotail satellite (1998-2004) at geocentric radial distances of 9-30 R E in the night side. The measured electron fluxes increase with closer distance to the center of the neutral sheet, and exhibit clear dawn-dusk asymmetry, with the lowest fluxes at the dusk side and increasing toward the dawn side. The asymmetry persists along the Earth's magnetotail region (at least to Geotail's apogee of 30 R E during the period of interest). Both the individual case and the statistical analysis on the relationship between >38 keV CPS electron fluxes and solar wind and IMF properties show that larger (smaller) solar wind speed and southward (northward) IMF B z imposed on the magnetopause result in higher (lower) energetic electron fluxes in the CPS with a time delay of about 1 hour, while the influence of solar wind ion density on the energetic electrons fluxes is insignificant. Interestingly, the energetic electron fluxes at a given radial distance correlate better with IMF B z than with the solar wind speed. Based on these statistical analyses, an empirical model is developed for the first time to describe the 2-D distribution (along and across the Earth's magnetotail) of the energetic electron fluxes (>38 keV) in the CPS, as a function of the upstream solar wind and IMF parameters. The model reproduces the observed energetic electron fluxes well, with a correlation coefficient R equal to 0.86. Taking advantage of the time delay, full spatial distribution of energetic electron fluxes in the CPS can be predicted about 2 hours in advance using the real-time solar wind and IMF measurements at the L1 point: 1 hour for the solar wind to propagate to the magnetopause and a 1 hour delay for the best correlation. Such a prediction helps us to determine whether there are enough electrons in the CPS available to be transported inward to enhance the outer electron radiation belt.