Ultra-relativistic electron’s pitch angle distribution narrowing associated with the solar wind density enhancement

2020 ◽  
Author(s):  
Lun Xie ◽  
Ying Xiong ◽  
Suiyan Fu ◽  
Zuyin Pu
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Pitch Angle ◽  
Dense Plasma ◽  
Particle Interaction ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Solar Wind Density ◽  
Wave Particle Interaction ◽  
Emic Waves

<p>Electron pitch angle distribution (PAD) is a critical parameter in the study of the dynamics of the radiation belt electrons. It is well known that solar wind pressure has an impact on the PAD of the geomagnetically trapped electrons. Using the Van Allen Probes' data, we find that the MeV electron PAD at 4.5<L*<5.5 became narrowing (PAD is mainly concentrated at 90 degree) for over three days during a prolonged enhancement of the solar wind number density on November 27-30, 2015. During that period, the EMIC waves are observed by Van Allen Probe-A and ground stations on the afternoon and dusk MLTs at L>4. Meanwile, the precipitations of tens of keV protons and MeV electrons are observed by POES satellites. Additionally, there is a growing dip in electron phase space density at L*~5, indicating a local loss caused by the wave-particle interaction. The narrowing of the electron PAD is energy-dependent and the PAD is more anisotropic for electrons with higher energy, which is consistent with the wave-particle interaction with the EMIC waves. Furthermore, previous studies have shown that high solar wind density can lead to a hot and dense plasma sheet. The inward penetration of a dense plasma-sheet down to 4 Re has been confirmed by THEMIS spacecraft. We suggest that the overlap of the plasma sheet and the plasmasphere provide a favorable condition for exciting EMIC waves and the loss of small pitch angle electrons by EMIC waves can lead to the electron PAD narrowing. </p><div> </div>

scholarly journals Ring Current Proton Dynamics Driven by Wave-Particle Interactions During a Nonstorm Period

2021 ◽  
pp. 98-104
Author(s):  
Sergei V. Smolin
Keyword(s):  
Pitch Angle ◽  
Ring Current ◽  
Activity Index ◽  
Proton Flux ◽  
Angle Distribution ◽  
Particle Interactions ◽  
Pitch Angle Distribution ◽  
Ion Cyclotron ◽  
Wave Particle Interactions ◽  
Emic Waves

Modeling of pitch angle scattering of ring current protons at interaction with electromagnetic ion cyclotron waves during a nonstorm period was considered very seldom. Therefore it is used correlated observation of enhanced electromagnetic ion cyclotron (EMIC) waves and dynamic evolution of ring current proton flux collected by Cluster satellite near the location L = 4.5 during March 26–27, 2003, a nonstorm period (Dst > –10 nT). Energetic (5–30 keV) proton fluxes are found to drop rapidly (e.g., a half hour) at lower pitch angles, corresponding to intensified EMIC wave activities. As mathematical model is used the non-stationary one-dimensional pitch angle diffusion equation which allows to compute numerically density of phase space or pitch angle distribution of the charged particles in the Earth’s magnetosphere. The model depends on time t, a local pitch angle and several parameters (the mass of a particle, the energy, the McIlwain parameter, the magnetic local time or geomagnetic eastern longitude, the geomagnetic activity index, parameter of the charged particle pitch angle distribution taken for the 90 degrees pitch angle at t = 0, the lifetime due to wave–particle interactions). This model allows numerically to estimate also for different geophysical conditions a lifetime due to wave–particle interactions. It is shown, that EMIC waves can yield decrements in proton flux within 30 minutes, consistent with the observational data. The good consent is received. Comparison of results on full model for the pitch angle range from 0 up to 180 degrees and on the model for the 90 degrees pitch angle is lead. For a perpendicular differential flux of the Earth’s ring current protons very good consent with the maximal relative error approximately 3.23 % is received

Early Observations from the Solar Orbiter SWA/Electron Analyser System

2021 ◽  
Author(s):  
Christopher Owen ◽  
Keyword(s):  
Solar Wind ◽  
Field Vector ◽  
Field Of View ◽  
High Time Resolution ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Burst Mode ◽  
Steering Mechanism ◽  
Operational Issues ◽  
Electrostatic Analyser

<p>Solar Orbiter carries a total of 10 instrument suites making up the payload for the mission.  One of these, the Solar Wind Analyser (SWA) instrument, is comprised of 3 sensor units which are together served by a central DPU unit.  Of particular focus in this presentation are the early measurements from one of these sensors, the Electron Analyser System (EAS).  EAS is a dual-head, top-hat electrostatic analyser system that is capable of making 3D measurements of solar wind electrons at energies below ~5 keV from a vantage point at the end of a 4-metre boom extending into the shadow of the spacecraft.  The sensor was accommodated in this location to both maximise the unobstructed field of view and to minimise the effect of spacecraft related disturbances on the low-energy (less than a few tens of eV) electrons expected the core population of the solar wind.</p><p>To date the SWA instrument sensors have operated sporadically during the mission cruise phase, which began in June 2020.  This is due to a number of operational issues faced by the SWA team, which mean we have not been able to take data in a continuous manner.  However, the data that has been taken shows the clear promise of the SWA measurements, in general, once these issues can be overcome.  For example, EAS is using a novel sample steering mechanism in burst mode which, with reference to a magnetic field vector shared onboard by the MAG instrument, allows the capture of the electron pitch angle distribution at unusually high time resolution.  We discuss these observations here, and illustrate the potential science returns from the burst mode.  We also present results from the new EAS observations in the vicinity of reconnecting current sheets in the solar wind, to more generally illustrate the capability of the sensor. </p>

scholarly journals Cold and Dense Plasma Sheet Caused by Solar Wind Entry: Direct Evidence

Atmosphere ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 831
Author(s):  
Yue Yu ◽  
Zuzheng Chen ◽  
Fang Chen
Keyword(s):  
Solar Wind ◽  
Plasma Sheet ◽  
Cross Correlation ◽  
Direct Evidence ◽  
Dense Plasma ◽  
Ion Density ◽  
Average Value ◽  
Magnetospheric Multiscale ◽  
Cross Correlation Analysis ◽  
Solar Wind Entry

We present a coordinated observation with the Magnetospheric Multiscale (MMS) mission, located in the Earth’s magnetotail plasma sheet, and the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission, located in the solar wind, in order to understand the formation mechanism of the cold and dense plasma sheet (CDPS). MMS detected two CDPSs composed of two ion populations with different energies, where the energy of the cold ion population is the same as that of the solar wind measured by ARTEMIS. This feature directly indicates that the CDPSs are caused by the solar wind entry. In addition, He+ was observed in the CDPSs. The plasma density in these two CDPSs are ~1.8 cm−3 and ~10 cm−3, respectively, roughly 4–30 times the average value of a plasma sheet. We performed a cross-correlation analysis on the ion density of the CDPS and the solar wind, and we found that it takes 3.7–5.9 h for the solar wind to enter the plasma sheet. Such a coordinated observation confirms the previous speculation based on single-spacecraft measurements.

scholarly journals Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat Imaging Riometer and NOAA satellite

2005 ◽  
Vol 23 (5) ◽  
pp. 1555-1563 ◽  
Author(s):  
Y.-M. Tanaka ◽  
M. Ishii ◽  
Y. Murayama ◽  
M. Kubota ◽  
H. Mori ◽  
...  
Keyword(s):  
Pitch Angle ◽  
Electron Flux ◽  
Energetic Electron ◽  
Energetic Particles ◽  
Electron Precipitation ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Loss Cone ◽  
Isotropic Pitch ◽  
Trapped Electron

Abstract. The cosmic noise absorption (CNA) is compared with the precipitating electron flux for 19 events observed in the morning sector, using the high-resolution data obtained during the conjugate observations with the imaging riometer at Poker Flat Research Range (PFRR; 65.11° N, 147.42° W), Alaska, and the low-altitude satellite, NOAA 12. We estimate the CNA, using the precipitating electron flux measured by NOAA 12, based on a theoretical model assuming an isotropic pitch angle distribution, and quantitatively compare them with the observed CNA. Focusing on the eight events with a range of variation larger than 0.4dB, three events show high correlation between the observed and estimated CNA (correlation coefficient (r0)>0.7) and five events show low correlation (r0<0.5). The estimated CNA is often smaller than the observed CNA (72% of all data for 19 events), which appears to be the main reason for the low-correlation events. We examine the assumption of isotropic pitch angle distribution by using the trapped electron flux measured at 80° zenith angle. It is shown that the CNA estimated from the trapped electron flux, assuming an isotropic pitch angle distribution, is highly correlated with the observed CNA and is often overestimated (87% of all data). The underestimate (overestimate) of CNA derived from the precipitating (trapped) electron flux can be interpreted in terms of the anisotropic pitch angle distribution similar to the loss cone distribution. These results indicate that the CNA observed with the riometer may be quantitatively explained with a model based on energetic electron precipitation, provided that the pitch angle distribution and the loss cone angle of the electrons are taken into account. Keywords. Energetic particles, precipitating – Energetic particles, trapped – Ionosphere-magnetosphere interactions

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