Relativistic Electron Losses in the Outer Radiation Belts

Relativistic electrons in the magnetosphere are both energized and lost via their interaction with plasma waves such as whister chorus, plasmaspheric hiss and EMIC waves. These waves are usually localized in different regions of the magnetosphere as well as being located either inside or outside the plasmapause. We study relativistic electron losses in the outer radiation belts by characterizing decay times scales at low and high altitudes and their relationship to microbursts. We use data collected by SAMPEX, a low Earth orbiting spacecraft in a highly inclined polar orbit and the HEO spacecraft in a high altitude Molniya orbit. The sensors onboard these spacecraft measure electrons of energies > 0.6 MeV, > 1 MeV, > 3 MeV, 2-6 MeV, 3-16 MeV. High time resolution data enable identifying and characterizing electron microbursts observed at low altitudes

Electron Micro Bursts as a Mechanism of Electron Loss Via Wave-Particle Interactions

Electron microbursts are rapid fluctuations of electron fluxes occurring on time scales of milliseconds. They are thought be due to scattering into the loss cone by plasma waves of various types from chorus to the recently observed large amplitude whistlers. They may be a major process of loss of realtivistic electrons from the Earth's outer radiation belts. One of the key issues that new mission s such as RBSP will address is to understand the loss of relativistic electrons. The SAMPEX mission launched in 1992 and still collecting data has the HILT sensor onboard with the capability of measuring> 1 MeV electrons with a high time resolution of 20 milliseconds suited admirably for the study of microbursts. We will use the data collected by the HILT for over a decade to characterize the relationship between electron microbursts and macroscopic electron decay lifetimes. With the launch of RBSP it is expected that SAMPEX will continue to collect data and overlap with RBSP. The latter will provide valuable information regarding plasma waves which coupled with low altitude measurements of microbursts may help elucidate details of the physics of electron loss from the radiation belt

A multispacecraft study of a small flux rope entrained by rolling back magnetic field lines

We present a small flux rope (SFR) with smooth magnetic field rotations entrained by rolling back magnetic field lines around 1 AU. Such SFRs have only been seldom reported in the literature. This SFR was adjacent to a heliospheric plasma sheet (HPS), which is defined as a high plasma beta region in the vicinity of a heliospheric current sheet. Even though the SFR and HPS have different plasma beta, they possess similar plasma signatures (such as temperature, density, and bulk speed), density ratio of alpha particleâ toâ proton (Nα/Np), and heavy ion ionization states, which imply that they may have a similar origin in the corona. The composition and the configuration of the rolling back magnetic field lines suggested that the SFR originated from the streamer belt through interchange reconnection. The origin processes of the SFR are presented here. Combining the observations of STEREO and ACE, the SFR was shown to have an axis tilted to the ecliptic plane and the radius may vary with different spatial positions. In this study, we suggest that interchange reconnection can play an important role for the origin of, at least, some SFRs and slow solar wind.Key PointsCompositional data are used to diagnose the origin of the SFR in this studyInterchange reconnection can play an important role for the origin of some SFRs and slow solar windSpacecraft may miss the in situ SFRs due to their morphologiesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138376/1/jgra53590_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138376/2/jgra53590.pd

Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet

Here, and in a companion paper by Hamrin et al. (2009) [Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs) in the Earth's plasma sheet. In total we have studied 151 ECRs within 660 h of plasma sheet data from the summer and fall of 2001 when Cluster was close to apogee at an altitude of about 15–20 RE. Cluster offers appropriate conditions for the investigation of energy conversion by the evaluation of the power density, E·J, where E is the electric field and J the current density. From the sign of the power density, we have identified more than three times as many Concentrated Load Regions (CLRs) as Concentrated Generator Regions (CGRs). We also note that the CLRs appear to be stronger. To our knowledge, these are the first in situ observations confirming the general notion of the plasma sheet, on the average, behaving as a load. At the same time the plasma sheet appears to be highly structured, with energy conversion occurring in both directions between the fields and the particles. From our data we also find that the CLRs appear to be located closer to the neutral sheet, while CGRs prefer locations towards the plasma sheet boundary layer (PSBL). For both CLRs and CGRs, E and J in the GSM y (cross-tail) direction dominate the total power density, even though the z contribution occasionally can be significant. The prevalence of the y-direction seems to be weaker for the CGRs, possibly related to a higher fluctuation level near the PSBL.This work is distributed under the Creative Commons Attribution 3.0 License</p