Signatures of electric fields from high and low altitude farticles distributions

Abstract

Measurements of high altitude ((1.3 R•o) ions and electrons at auroral energies are used provide evidence of parallel electric field acceleration over the dusk to midnight auroral regions for both the north and south hemispheres. The data, taken on August 1Z, 1976 by charged particle spectrometers on tl•-e' S3-3 satellite, show evidence of potential differences of ~Z kV below and ~1 kV above a satellite altitude of 7300 km. Introduction The study of the coupling between the magnetosphere and the ionosphere remains one of the most actively pursued subjects in space sciences. In the auroral regions, electric fields play a dominant role in the deSCription of the dynamics of charged particles (Banks, 1975). One such result of the predicted parallel electric fields are the inverted 'V' structures widely discussed by Frank (1975), (Frank and Ackerson 1971, 197Z), Gurnett (197Z) and others (Reasoner and Chappell, 1973). Another signature of parallel electric fields that extend down to the ionosphere are ion beams accelerated to high altitudes (Shelley et al. 1976). The S3-3 satellite has provided evidence of strong electric fields which are ascribed as electrostatic shocks by Mozer et al., (1976). The data presented in this letter, taken by the S3-3 satellite on August 1Z, 1976, Provides convincing evidence of the acceleration of particles by electric fields parallel to B above and below a satellite altitude of 7300 kin. For this particula r event, a total potential difference of ~ 3 kV is inferred,. Z/3 of which is located below the satellite. Instrumentation The data were obtained bytwo cylindrical electrostatic analyzers (ESAs) built byThe Aerospace Corporation and flown on the polar ørbiting satellite, S3-3. The nominal orbital parameters were: apogee of •8040 kin, perigee of -• 240 kin' inclinatio n of 97.5 ø. The ESA's measured ions with energy to charge ratios in the range of 0.09 to 3.9 keV/q and electrons with energies of 0.17 to 8.4 keV in eight logarithmic steps. A COmplete ion and electron Spectrum was taken every seCOnd and a complete angular distribution was me_• sUred every .•0 se$-' The •metric factors of 1.8 x 10and 1.7 x 10 -• cm--ster--•--•. -for the ions and electrons r•ectively give the ins•'rument high sensitivity with low background signals. The angular fields of view were ~7 ø x 10 'ø FWHM and ~14 ø x 10 ø FwHM for the electron and ion ESA respectively. Channeltrons were used as detectors with a post acceleration to 1.6 kV in the ion ESA. A companion instrument provides measurements of electrons and protons with energies from 0.01Z to 1.6 MeV and 0.080 to 1.5 MeV respectively.

Mirror instability and the origin of morningside auroral structure

“…The cross-magnetospheric "convection" electric field necessarily undergoes a sharp reversal (a near-discontinuity) in its meridional Pedersen conductivity, and ohmic resistivity in the ionosphere [Chiu, 19741. Moreover, the hot collisionless magnetospheric plasma in the same flux tube supports such a parallel + (to B) electric field and thus causes the ED to remain substantial, even at altitudes up to about 10 4 km. The signature of this ED (upward in the PM sector) is plainly evident in ion and electron distributions observed from the 53-3 satellite [Mizera and Fennell, 1977].…”

Signature of a Parallel Electric Field in Ion and Electron Distributions in Velocity Space.

“…When vIewed in terms of precipitating flux , this ridge is seen as a peak in the energy flux spectrum at the acceleration potential, as predicted by Evans (1974) and shown in Figure 3 of Mizera and Fennell (1977). Inside the 1 keV circle on the upper half of Figure electron populations are very well delineated by appli cation of t he theory of adiabat ic…”

“…In the following discussion the data reported by Mizera and Fennell (1977), shown in Figure 1, will be examined in relation to boundaries determined by equations (2) and (3). It will be ascertained that particle populations manifested as contours of velocit y d~tribution function are distinctly different across these boundaries.…”

A comparison between ion characteristics observed by the POLAR and DMSP spacecraft in the high-latitude magnetosphere

“…Ionospheric outflow has been observed in the auroral regions in the form of ion beams and conics with energies of 0.1 to 10 keV (e.g. Mizera and Fennell, 1977;Ghielmetti et al, 1978). This could possibly lead to significant discrepancies between our survey and that of Newell and Meng.…”