Kilometric Continuum and its Relation with Geomagnetic Activities

Kozo Hashimoto (1), Hiroshi Matsumoto (1), Roger R. Anderson (2), and
James L. Green (3)

(1) Radio Science Center for Space and Atmosphere, Kyoto University,
Uji, Kyoto 611-0011, JAPAN, E-mail: kozo@kurasc.kyoto-u.ac.jp, FAX:
0774-31-8463 (2) The University of Iowa, Department of Physics and
Astronomy, Iowa City, IA 52242, USA (3) NASA Goddard Space Flight
Center, Greenbelt, MD 20771, USA

Kilometric continuum found by Geotail has a frequency range from 100
to 800 kHz and is the high frequency extension of the escaping
continuum [1]. It is observed only near the magnetic equator and
appears to be unrelated with magnetic activity. Its source is expected
to be inside of the plasmapause and the topside equatorial
region. Recently IMAGE Radio Plasma Imager (RPI) and Extreme
ultraviolet (EUV) have found that kilometric continuum is generated at
the plasmapause, in or near the magnetic equator, within a bite-out
region [2] and have confirmed the expectation. Within the bite-out
structure the flux tubes have much less density than their adjacent
flux tubes. According to recent data observed around 2000 and 2001,
the occurrence probability of kilometric continuum becomes higher when
Kp is higher than 6. It should be noted that is observed even if Kp
is zero. Its relation with geomagnetic activities when Kp is very high
or low will be examined.

References: [1] K. Hashimoto, W. Calvert, and H. Matsumoto, Kilometric
continuum detected by Geotail, JGR, 104, 28,645, 1999. [2] J. L. Green
et al., On the origin of kilometric continuum, JGR, in press, 2002.

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To be presented at the COSPAR Frontiers of Magnetospheric Plasma 
Physics Workshop, Sagamihara, Japan, July 24-26, 2002