Observations of Time-Domain Structures in the Plasmaspheric Plume by Van Allen Probes

Time-domain structures (TDS), manifested as ≥ 1 ms pulses with significant parallel electric fields, play an important role in accelerating electrons in the field-aligned direction. These precipitated electrons contribute to the formation of aurora. In this study, we present observations of time-domain structures that occurred in the plasmaspheric plumes at the post-midnight to dawn sector. The close correlation between TDS and plasmaspheric plumes implies that the generation of TDS might be modulated by plasma density. During the wave occurrence, protons with an energy level below 1 keV show the enhanced field-aligned pitch-angle distributions, and the electron fluxes with the energies ranging from tens to hundreds of eV are also significantly enhanced. The correlation between TDS and scattered particles indicates the importance of including time-domain structures in future studies of radiation belt dynamics

Whistler-mode chorus waves at Mars

Abstract Chorus waves are naturally occurring electromagnetic emissions in space and are known to produce highly energetic electrons in the hazardous radiation belt. The characteristic feature of chorus is its fast frequency chirping, whose mechanism remains a long-standing problem. While many theories agree on its nonlinear nature, they differ on whether or how the background magnetic field inhomogeneity plays a key role. Here, using observations of chorus at Mars and Earth, we report direct evidence showing that the chorus chirping rate is consistently related to the background magnetic field inhomogeneity, despite orders of magnitude difference in a key parameter quantifying the inhomogeneity at the two planets. Our results show an extreme test of a recently proposed chorus generation model and confirm the connection between the chirping rate and magnetic field inhomogeneity, opening the door to controlled plasma wave excitation in the laboratory and space

Whistler-mode chorus waves at Mars.

Chorus waves are naturally occurring electromagnetic emissions in space and are known to produce highly energetic electrons in the hazardous radiation belt. The characteristic feature of chorus is its fast frequency chirping, whose mechanism remains a long-standing problem. While many theories agree on its nonlinear nature, they differ on whether or how the background magnetic field inhomogeneity plays a key role. Here, using observations of chorus at Mars and Earth, we report direct evidence showing that the chorus chirping rate is consistently related to the background magnetic field inhomogeneity, despite orders of magnitude difference in a key parameter quantifying the inhomogeneity at the two planets. Our results show an extreme test of a recently proposed chorus generation model and confirm the connection between the chirping rate and magnetic field inhomogeneity, opening the door to controlled plasma wave excitation in the laboratory and space

Observations of the Beam‐Driven Whistler Mode Waves in the Magnetic Reconnection Region at the Dayside Magnetopause

We report observations of the whistler mode waves in the magnetic reconnection region at the dayside magnetopause using the magnetospheric multiscale (MMS) mission on January 11, 2016. In this event, whistlers mostly occur on the magnetospheric side of the reconnection central plane and are closely related to counter-streaming electron beams in the medium energy range (200–300 eV). These counter-streaming electron beams can be attributed to the accelerated magnetosheath electrons by the reconnection. Through quantitatively testing the Landau resonance condition and solving the kinetic dispersion relations, we present the evidence for whistler excitation by electron beams in the medium energy range. Additionally, the whistlers are observed simultaneously with the pitch-angle scattering of electrons in the high-energy range (300–3,000 eV). The calculation results show that this scattering is likely to occur through electron cyclotron wave-particle interactions, which can isotropize electrons and exchange energy between plasmas and waves

Observations of the Beam‐Driven Whistler Mode Waves in the Magnetic Reconnection Region at the Dayside Magnetopause

We report observations of the whistler mode waves in the magnetic reconnection region at the dayside magnetopause using the magnetospheric multiscale (MMS) mission on January 11, 2016. In this event, whistlers mostly occur on the magnetospheric side of the reconnection central plane and are closely related to counter-streaming electron beams in the medium energy range (200–300 eV). These counter-streaming electron beams can be attributed to the accelerated magnetosheath electrons by the reconnection. Through quantitatively testing the Landau resonance condition and solving the kinetic dispersion relations, we present the evidence for whistler excitation by electron beams in the medium energy range. Additionally, the whistlers are observed simultaneously with the pitch-angle scattering of electrons in the high-energy range (300–3,000 eV). The calculation results show that this scattering is likely to occur through electron cyclotron wave-particle interactions, which can isotropize electrons and exchange energy between plasmas and waves

Observations of an Electron‐Cold Ion Component Reconnection at the Edge of an Ion‐Scale Antiparallel Reconnection at the Dayside Magnetopause

Solar wind parameters play a dominant role in reconnection rate, which controls the solar wind-magnetosphere coupling efficiency at Earth's magnetopause. Besides, low-energy ions from the ionosphere, frequently detected on the magnetospheric side of the magnetopause, also affect magnetic reconnection. However, the specific role of low-energy ions in reconnection is still an open question under active discussion. In the present work, we report in situ observations of a multiscale, multi-type magnetopause reconnection in the presence of low-energy ions using NASA's Magnetospheric Multiscale data on September 11, 2015. This study divides ions into cold (10–500 eV) and hot (500–30,000 eV) populations. The observations can be interpreted as a secondary reconnection dominated by electrons and cold ions (mainly in $XY_{GSE}$ plane) located at the edge of an ion-scale reconnection (mainly in $XY_{GSE}$ plane). This analysis demonstrates a dominant role of cold ions in the secondary reconnection without hot ions' response. Cold ions and electrons are accelerated and heated by the secondary process. The case study provides observational evidence for the simultaneous operation of antiparallel and component reconnection. Our results imply that the pre-accelerated and heated cold ions and electrons in the secondary reconnection may participate in the primary ion-scale reconnection affecting the solar wind-magnetopause coupling and the complicated magnetic field topology could affect the reconnection rate

Observations of an Electron-Cold Ion Component Reconnection at the Edge of an Ion-Scale Antiparallel Reconnection at the Dayside Magnetopause

International audienceSolar wind parameters play a dominant role in reconnection rate, which controls the solar wind-magnetosphere coupling efficiency at Earth's magnetopause. Besides, low-energy ions from the ionosphere, frequently detected on the magnetospheric side of the magnetopause, also affect magnetic reconnection. However, the specific role of low-energy ions in reconnection is still an open question under active discussion. In the present work, we report in situ observations of a multiscale, multi-type magnetopause reconnection in the presence of low-energy ions using NASA's Magnetospheric Multiscale data on September 11, 2015. This study divides ions into cold (10-500 eV) and hot (500-30,000 eV) populations. The observations can be interpreted as a secondary reconnection dominated by electrons and cold ions (mainly in XYGSE plane) located at the edge of an ion-scale reconnection (mainly in XZGSE plane). This analysis demonstrates a dominant role of cold ions in the secondary reconnection without hot ions' response. Cold ions and electrons are accelerated and heated by the secondary process. The case study provides observational evidence for the simultaneous operation of antiparallel and component reconnection. Our results imply that the pre-accelerated and heated cold ions and electrons in the secondary reconnection may participate in the primary ion-scale reconnection affecting the solar wind-magnetopause coupling and the complicated magnetic field topology could affect the reconnection rate