Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1402.0735

Dependence of geosynchronous relativistic electron enhancements on geomagnetic parameters

A. V. Dmitriev·J. -K. Chao
View original source ↗Read source document ↗Export metadata ↓

Abstract

Relativistic electron fluxes observed in geosynchronous orbit by GOES-8 in 1997 to 2000 were considered as a complex function of geomagnetic indices PC, Kp, and Dst as well as parameters of the magnetosphere size, subsolar Rs and terminator Rf magnetopause distances. A geosynchronous relativistic electron enhancement (GREE) is determined as daily maximal electron flux exceeding the upper root mean square deviation (RMSD) threshold of about 1500 (cm2s sr)-1. Comparison analysis of the GREE dynamics and geomagnetic conditions on the rising phase of current solar cycle revealed suppression of the relativistic electron enhancements by substantially increased strong geomagnetic activity in the solar maximum. Statistical consideration of a relationship between the GREEs and the geomagnetic parameters showed that the most important parameters controlling the geosynchronous relativistic electron enhancements were 4-day averaged Kp index, PC index and magnetopause termination distance Rf delayed respectively on 3 and 14 hours. Relatively high averaging time for Kp was explained by cumulative effect of substorm energy release in a gradual mechanism accelerating the relativistic electrons in the magnetosphere. Very short time delay for PC index was interpreted as intensification of a fast acceleration mechanism producing the GREEs during severe geomagnetic storms. Substantial increase of the PC index (PC>5) was founded as a sufficient condition for GREE occurrence. The fast response of the geosynchronous relativistic electron fluxes on the magnetosphere compression was explained by drift losses of the energetic electrons at the magnetopause which approaches the Earth during geomagnetic storms.

Explore related subjects

physics.space-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A. V. Dmitriev, J. -K. Chao. 2014-02-04. Dependence of geosynchronous relativistic electron enhancements on geomagnetic parameters. https://doi.org/10.1029/2002ja009664

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Microphysical Diversity in Two Very Closely Spaced Magnetic Switchbacks Observed by Parker Solar Probe

Parker Solar Probe observations near the Sun reveal frequent, sudden reversals of the magnetic field known as switchbacks (SBs). Despite their ubiquity, the internal plasma structure and associated heating within SBs remain poorly understood. We present a case study of two closely spaced SBs (referred in text as SB_1 and SB_2) observed on 24 January 2020 using high-cadence magnetic and plasma measurements. Magnetic fluctuations are decomposed into components parallel and perpendicular to the mean field, and their power spectra are analyzed to characterize the turbulent cascade. The Partial Variance of Increments (PVI) method is applied to identify intermittent current-sheet-like features. Both SB intervals exhibit clear Alfvenic behavior and enhanced radial flow; however, their microphysics differ: SB_1 shows a higher proton temperature, larger fluctuation amplitudes, and a denser population of current sheets compared to SB_2. The two events also differ in spectral index, with SB_1 exhibiting a steeper perpendicular slope than SB_2. The elevated intermittency, proton temperature, and transient $β> 1$ excursion in SB_1 suggest that localized dissipation at small-scale structures is a plausible driver of the observed heating. These findings demonstrate that SBs are not uniform kinematic deflections but dynamically evolving plasma structures whose internal turbulence may regulate local energy conversion and contribute to the spatially intermittent heating of the near-Sun solar wind.

physics.space-ph↗
arXiv2026

In-situ measurements of space plasma: recent progress and future challenges

Space plasmas like the solar wind or the Earth's space environment offer unique opportunities to observe fundamental plasma processes and their impact in situ. With modern space instrumentation, we measure the velocity distribution function of the plasma particles as well as the electromagnetic fields at high resolution and with minimal perturbation of the observed plasma systems. Plasma measurements like this are often not possible in laboratory settings on Earth. This review article focuses on modern diagnostic methods for the in-situ detection of plasma particles in space. It presents the detection principle of top-hat electrostatic analysers and highlights recent examples of scientific discoveries based on data from the heliospheric space missions Parker Solar Probe and Solar Orbiter. These examples demonstrate the capabilities of modern space plasma instrumentation. The article then discusses future directions in space plasma physics as well as the involved challenges in terms of the required plasma diagnostics. These new developments include, for example, upcoming and proposed space missions such as the operational space-weather mission Vigil, the multi-spacecraft mission HelioSwarm, the Mars mission M-MATISSE, and the electron-astrophysics mission Debye.

physics.space-ph↗
arXiv2026

Alfvénicity and Proximity to Parallel-Mode Marginal Stability in the Slow Solar Wind

The proton temperature anisotropy in the solar wind is bounded by the thresholds of pressure-anisotropy-driven kinetic instabilities, and the distance at which the plasma settles from these thresholds is thought to be regulated by compressive fluctuations through the fluctuating anisotropy effect. We test whether the level of Alfvénicity is associated with this distance in the slow solar wind. Using five years of Wind/SWE bi-Maxwellian proton measurements (2004--2008), we separate slow-wind intervals into Alfvénic and non-Alfvénic populations on the basis of normalized cross helicity and residual energy. We compare their magnetic compressive fraction and normalized compressive amplitude, and measure their proximity to marginal stability in the plane of parallel proton beta and temperature anisotropy using the maximum growth rate over the scanned parallel wavenumbers, $γ_{\parallel,\max}$, from a Vlasov dispersion solver. At low matched parallel beta, the Alfvénic slow wind has lower normalized field-strength fluctuation amplitude and reaches the parallel-mode marginal-stability criterion more often than the non-Alfvénic slow wind. This association is consistent with a weaker fluctuating-anisotropy effect in the Alfvénic slow wind, but does not establish a causal relation.

physics.space-ph↗