Electron dynamics near diamagnetic regions of comet 67P/Churyumov- Gerasimenko

Madanian, H.Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA. (författare)

The Rosetta spacecraft detected transient and sporadic diamagnetic regions around comet 67P/Churyumov-Gerasimenko. In this paper we present a statistical analysis of bulk and suprathermal electron dynamics, as well as a case study of suprathermal electron pitch angle distributions (PADs) near a diamagnetic region. Bulk electron densities are correlated with the local neutral density and we find a distinct enhancement in electron densities measured over the southern latitudes of the comet. Flux of suprathermal electrons with energies between tens of eV to a couple of hundred eV decreases each time the spacecraft enters a diamagnetic region. We propose a mechanism in which this reduction can be explained by solar wind electrons that are tied to the magnetic field and after having been transported adiabatically in a decaying magnetic field environment, have limited access to the diamagnetic regions. Our analysis shows that suprathermal electron PADs evolve from an almost isotropic outside the diamagnetic cavity to a field-aligned distribution near the boundary. Electron transport becomes chaotic and non-adiabatic when electron gyroradius becomes comparable to the size of the magnetic field line curvature, which determines the upper energy limit of the flux variation. This study is based on Rosetta observations at around 200 km cometocentric distance when the comet was at 1.24 AU from the Sun and during the southern summer cometary season.

Burch, J. L.Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA. (författare)
Eriksson, A. , I (författare)
Cravens, T. E.Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. (författare)
Galand, M.Imperial Coll London, Dept Phys, Prince Consort Rd, London, England. (författare)
Vigren, ErikUppsala universitet,Institutet för rymdfysik, Uppsalaavdelningen(Swepub:uu)erivi300 (författare)
Goldstein, R.Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA. (författare)
Nemeth, Z.Wigner Res Ctr Phys, Budapest, Hungary. (författare)
Mokashi, P.Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA. (författare)
Richter, ITU Braunschweig, Inst Geophys & Extraterr Phys, Braunschweig, Germany. (författare)
Rubin, M.Univ Bern, Phys Inst, Bern, Switzerland. (författare)
Southwest Res Inst, 6220 Culebra Rd, San Antonio, TX 78238 USA.Univ Kansas, Dept Phys & Astron, Lawrence, KS 66045 USA. (creator_code:org_t)

Ingår i:Planetary and Space Science: PERGAMON-ELSEVIER SCIENCE LTD1870032-06331873-5088

Av författaren/redakt...: Madanian, H.; Burch, J. L.; Eriksson, A. , I; Cravens, T. E.; Galand, M.; Vigren, Erik; visa fler...; Goldstein, R.; Nemeth, Z.; Mokashi, P.; Richter, I; Rubin, M.; visa färre...

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