References

ANGEO

Annales Geophysicae

ANGEO

Ann. Geophys.

1432-0576

Copernicus Publications

Göttingen, Germany

10.5194/angeo-24-3099-2006

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

Zuluaga

C. A.

¹ Beiser

E. S.

¹ Chen

¹ Fritz

T. A.

Center for Space Physics, Boston University, Boston MA, USA

22 11 2006

24 11 3099 3113

2006

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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 <i>R<sub>E</sub></i> 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 local 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.

References 1

Chen, J. and Fritz, T. A.: High-altitude cusp: The extremely dynamic region in geospace, in The Magnetospheric Cusps: Structure and Dynamics, edited by: Fritz, T. A. and Fung, S. F., Surveys in Geophysics, 26:1-3, 71–93, 2005. \bibitem[] Chen, J., Fritz, T. A., and Sheldon, R. B.: Comparison of energetic ions in cusp and outer radiation belt, J. Geophys. Res., 110, A12219, https://doi.org/10.1029/2004JA010718, 2005.

Chen, J., Fritz, T. A., Sheldon, R. B., et al.: A new, temporarily confined population in the polar cap during the August 27, 1996 geomagnetic field distortion period. Geophys. Res. Lett., 24, 1447–1450, 1997.

Chen, J., Fritz, T. A., Sheldon, R. B., et al.: Cusp energetic particle events: Implications for a major acceleration region of the magnetosphere, J. Geophys. Res., 103, 69–78, 1998. \bibitem Cowley, S. W. H., Morelli, J. P., and Lockwood, M.: Dependence of convective flows and particle precipitation in the high-latitude dayside ionosphere and the X and Y components of the interplanetary magnetic field, J. Geophys. Res., 96, 5557–5564, 1991. \bibitem Crooker, N. U., Lyon, J. G., and Fedder, J. A.: MHD model merging with IMF By: Lobe cells, sunward polar cap convection, and overdraped lobes, J. Geophys. Res., 103, 9143–9152, 1998.

Delcourt, D. C. and Sauvaud, J.-A.: Populating of the cusp and boundary layers by energetic (hundreds of keV) equatorial particles, J. Geophys. Res., 104, 22 635–22 648, 1999.

Eccles, A. A. and Fritz, T. A.: Energetic particle observations at the subsolar magnetopause, Ann. Geophys., 20, 445–460, 2002.

Fritz, T. A. and Chen, J.: The cusp as a source of magnetospheric particles, Radiation Measurements, 30(5), 599–608, 1999.

Fritz, T. A., Chen, J., Sullivan, J. D., and Karra, M.: Is the cusp a source or a sink for magnetospheric energetic particles?, Proc. Int. Symposium: From solar corona through interplanetary space, into Earth's magnetosphere and ionosphere: Interball, ISTP satellites, and ground-based observations, (Kyiv, Ukraine), 205–209, 2000.

Fritz, T. A., Alothman, M., Bhattacharjya, J., Matthews, D L., and Chen, J.: Butterfly Pitch-angle Distributions Observed by \mboxISEE-1, Planetary and Space Sciences, 51, 205–219, 2003a. \bibitem Fritz, T. A., Chen, J., and Siscoe, G. L.: Energetic ions, large diamagnetic cavities, and Chapman-Ferraro cusp, J. Geophys. Res., 108(A1), 1028–1036, 2003b.

Konradi, A., Williams, D J., and Fritz, T. A.: Energy spectra and pitch angle distributions of storm-time and substorm injected protons, J. Geophys. Res., 80, 543–552, 1975.

Kosik, J. C.: Influence of electric field on charged particle motion and electron fluxes at synchronous altitudes, in Quantitative Modeling of Magnetospheric Processes, edited by: Olson, W. P., Geophys. Monogr. Series, 21, 569–581, 1979.

Mead, G. D.: Deformation of geomagnetic field by the solar wind, J. Geophys. Res., 69, 1181–1195, 1964.

McIlwain, C. E.: Coordinates for mapping the distribution of magnetically trapped particles, J. Geophys. Res., 66, 3681–3691, 1961.

McIlwain, C. E.: Substorm injection boundaries in Magnetospheric Physics, edited by: McCormac, B. M., D. Reidel, Dordrecht, Holland, 1974.

Pfitzer, K., Lezniak, T. W., and Winckler, J. R.: Experimental verification of drift shell splitting in the distorted magnetosphere, J. Geophys. Res., 74, 4687–4693, 1969.

Reeves, G. D., R. D. Belian, R. D., and Fritz, T. A.: Numerical tracing of energetic particle drifts in a model magnetosphere, J. Geophys. Res., 96, 13 997–14 008, 1991.

Roederer, J. G.: On the adiabatic motion of energetic particles in a model magnetosphere, J. Geophys. Res., 72, 981–992, 1967.

Roederer, J. G.: Dynamics of Geomagnetically Trapped Radiation, Springer-Verlag, New York, 23–28, 1970.

Russell, C. T.: The ISEE1 and 2 fluxgate magnetometers, IEEE Trans. Geosci. Electr., GE-16, 239–242, 1978.

Shabansky, V. P.: Some processes in the magnetosphere, Space Sci. Rev., 12, 299–418, 1971.

Shabansky, V. P. and Antonova, A. E.: Topology of particle drift shells in the Earth's magnetosphere, Geomangn. Aeron., 8, 993–997, 1968.

Sheldon, R. B., Spence, H. E., Sullivan, J. D., Fritz, T. A.,and Chen, J.: The discovery of trapped energetic electrons in the outer cusp, Geophys. Res. Lett., 25, 1825–1828, 1998.

Sibeck, D. G., McEntire, R. W., Lui, A. T. Y., Lopez, R. E., and Krimigis, S. M.: Magnetic field drift shell splitting: Cause of unusual dayside particle pitch angle distributions during storms and substorms, J. Geophys. Res., 92, 13 485–13 497, 1987.

Smets, R., Delcourt, D., Sauvard, J. A., and Koperski, P.: Electron pitch angle distributions following the dipolarization phase of a substorm: Interball-Tail observations and modeling. J. Geophys. Res. 104, 14 571–14 581, 1999.

Sullivan, J. D.: Hunstsville 2000 conference proceedings CDROM Software Section Models: TRAJGEN at http://science.msfc.nasa.gov/ssl/pad/sppb/workshop7/html/cd.htm, 2002.

Tsyganenko, N. A. and Usmanov, A V.: Determination of the magnetospheric current system parameters and development of experimental geomagnetic field models based on data from IMP and HEOS satellites, Planet. Space Sci., 30, 985–998, 1982.

Tsyganenko, N. A.: Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause. J. Geophys. Res., 100, 5599–5612, 1996.

Tsyganenko, N. A. and Fairfield, D. H.: Global shape of the magnetotail current sheet as derived from Geotail and Polar data, J. Geophys. Res., 109, A03218, https://doi.org/10.1029/2003JA010062, 2004.

West Jr., H. I.: Some Observations of the trapped electrons produced by the Russian high altitude nuclear detonation of October 28, 1962, Radiation Trapped in the Earth's Magnetic Field, edited by: McCormac, B. M., D. Reidel Publishing Company, Dordrecht, Holland, 634, 1965.

West Jr., H. I., Buck, R. M., and Walton, J. R.: Shadowing of electron azimuthal drift motions near the noon magnetopause, Nature Phys. Sci., 240, 6–7, 1972.

West Jr., H. I., Buck, R. M., and Walton, J. R.: Electron pitch angle distributions of energetic electrons throughout the magnetosphere as observed by OGO-5. J. Geophys. Res. 78, 1064–1081, 1973.

Williams, D. J., Keppler, E., Fritz, T. A., Wilken, B., and Wibberenz, G. W.: The \mboxISEE-1 and 2 medium energy particles experiment, IEEE Trans. Geosci. Electr., GE-16, 270–278, 1978.