Energetic particle population in the high-latitude geomagnetosphere

Antonova, A.E.; Gubar, Yu. I.; Kropotkin, A. P.

doi:10.1016/s1464-1917(99)00034-3

Cited by 11 publications

(12 citation statements)

References 5 publications

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“…The occurrence of a substorm is consistent with the proposed idea that CEPs result from substorm processes in the magnetotail (Delcourt et al, 1999;Blake et al, 1999;Antonova et al, 2000). The CEPs observed by ISEE-1 and ISEE-2 in this event, however, show no time-energy dispersion, as would be expected from energetic particles injected into the nightside magnetosphere and subsequently drifting to the dayside.…”

Section: Discussionsupporting

confidence: 87%

Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

et al. 2007

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Abstract.Observations by the ISEE-1 and ISEE-2 spacecraft on 29 September 1978 show large CEP (Cusp Energetic Particle) fluxes while passing through the dayside magnetospheric cusp in near coincident orbits. The event was observed around 11:00 MLT between roughly 12:30 and 13:00 UT by ISEE-1 and 12:00 and 13:00 UT by ISEE-2. During these periods, both electron and ion fluxes increased by more than two orders of magnitude, with the electron flux showing a strong peak at a pitch angle of 90 • . The solar wind was ∼710 km s −1 and the Dst was ∼-200 nT, suggesting the occurrence of a strong geomagnetic storm. The ISEE-1 and ISEE-2 observations, however, show no time-energy dispersion of the CEPs, leading us to believe that these particles could not be the result of substorm processes in the magnetotail. The local magnetic field was depressed and extremely turbulent. Changes in the magnitude of the magnetic field anticorrelate closely to variations of the electron flux. The observations in electron flux peaking at 90 • and the close anticorrelation between the local magnetic field strength and electron flux are unique and provide evidence of a potential local source for these energetic particles.

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Section: Discussionsupporting

confidence: 87%

Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

et al. 2007

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“…However, the origin of the Cusp Energetic Particles (CEP) remains controversial. The CEPs have been suggested to have three possible sources, (1) the ions are accelerated to tens of keV at the bow shock and arrive in the cusp along a magnetically guided trajectory (Chang et al, 1998), (2) the CEPs are produced by substorms in the geomagnetic tail (Delcourt and Sauvaud, 1999;Blake, 1999;Antonova et al, 2000) and arrive in the cusp through a "Shabansky" orbit (Shabansky, 1971;Antonova and Shabansky, 1975), and (3) the electrons and ions are both accelerated locally up to energies of hundreds of keV to several MeV .…”

Section: Introductionmentioning

confidence: 99%

Energetic particle sounding of the magnetospheric cusp with ISEE-1

et al. 2007

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Abstract. Observations on 30October 1978 show the ISEE-1 spacecraft passing though the high-altitude dayside northern magnetospheric cusp region from roughly 16:00 to 18:30 UT, during a slow solar wind period (∼380 km/s). More than two orders of magnitude enhancements of the cusp energetic particle (CEP) fluxes were observed along with a depressed and turbulent local magnetic field. The observed variations of the pitch angle distributions (PAD) provide a unique opportunity to determine the structure of the cusp and the origin of the CEP. Through a boundary sounding technique, the location and orientation of the cusp poleward (or backside) boundary was observed for almost 10 min during which time it appeared initially to be stationary in the GSM/GSE X-direction and then moved sunward about 0.12 Earth radii (R E ). The orientation remained approximately perpendicular to the GSM/GSE X-axis until it was observed to rotate by 60 degrees in ∼3 min before ISEE-1 was fully inside the cusp cavity. The cavity itself was filled with CEP fluxes displaying large anisotropies, indicative of their source being located below (Earthward) of the satellite location. The spacecraft entered from the backside of the cusp, then traveled ∼4 R E through the cavity, and exited through the "top" of the cavity leaving a region of energetic ions below. The PADs demonstrate that the bow shock cannot be the main source of the observed CEPs. The CEP fluxes were measured at about 8.5 h MLT when the IMF had both an 8-10 nT duskward and southward component.

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“…The connection between cusp particles and nightside particles through their drift paths has been showed by numerical simulations using different tracing codes (Delcourt and Sauvaud, 1999;Blake, 1999;Fritz et al, 2000;Antonova et al, 2000). Table 1 indicates that from 07:00 UT to 12:00 UT on 3 March 1979, the IMF had a negative B y (dawnward) component.…”

Section: Cusp Sourcementioning

confidence: 97%

Implications of unusual pitch-angle distributions observed by ISEE-1 and 2

et al. 2006

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Abstract. Unusual energetic particle pitch angle distributions (PADs) were observed by the ISEE-1 and 2 satellites at 3 h MLT and a radial distance of about 10-15 R E during the time period of 07:00-14:00 UT on 3 March 1979. The ISEE-1 satellite obtained complete 3-D distributions of energetic proton and electron fluxes as a function of energy, while ISEE-2 was configured to provide higher time resolution but less angular resolution than ISEE-1. The ISEE-1 observed a butterfly PAD (a minimum in the 90 • PA particle flux) for a period of about 2 h (10:00-12:00 UT) for the electrons, and 3 h (09:00-12:00 UT) for the protons over an energy range of 22.5-189 keV (E1-E4) for the electrons and 24-142 keV (P1-P4) for the protons. The small pitch angle (15 • , 30 • ) charged particles (electrons and protons) are seen to behave collectively in all four energy ranges. The relative differences in electron fluxes between 15 • PA and 90 • PA are more significant for higher energy channels during the butterfly PAD period. Three different types of electron PADs (butterfly, isotropic, and peaked-at-90 • ) were observed at the same location and time as a function of energy for a short period of time before 10:00 UT. Electron butterfly distributions were also observed by the ISEE-2 for about 1.5 h over 28-62 keV (E2-E4), although less well resolved than ISEE-1. Unlike the ISEE-1, no butterfly distributions were resolved in the ISEE-2 proton PADs due to less angular resolution. The measured drift effects by ISEE-1 suggest that the detected protons were much closer to the particle source than the electrons along their trajectories, and thus ruled out a nightside source within 18:00 MLT to 03:00 MLT. Compared to 07:30 UT, the charged particle fluxes measured by ISEE-1 were enhanced by up to three orders of magnitude during the period 08:30-12:00 UT. From 09:10:00 UT to 11:50 UT, the geomagnetic conditions were quiet (AE<100 nT), the LANL geosynchronous satellites observed no substorms, and the loCorrespondence to: T. A. Fritz (fritz@bu.edu) cal magnetic field measured by ISEE-1 was almost constant, while the small PA charged particle (both electron and proton) fluxes measured by ISEE-1 increased gradually, which implies a particle source other than the substorm source. Based on detailed particle trajectory tracings in a realistic geomagnetic field model, the 50-200 keV protons with small PA at 10:00 UT ISEE-1 location on 3 March 1979 were passing through the northern high-altitude and high-latitude morningside region where the cusp should be located under a dawnward IMF component condition, while those protons with large PA may connect to the high-latitude morningside magnetopause. It is possible that the cusp source is responsible for the all particles observed during the event.

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Energetic particle population in the high-latitude geomagnetosphere

Cited by 11 publications

References 5 publications

Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

Energetic particle sounding of the magnetospheric cusp with ISEE-1

Implications of unusual pitch-angle distributions observed by ISEE-1 and 2

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