Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities

Details Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities

Mar 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999angeo..17..338g&link_type=abstract

Annales Geophysicae, vol. 17, Issue 3, pp.338-350

Physics

18

Scientific paper

Giant pulsations are nearly monochromatic ULF-pulsations of the Earth's magnetic field with periods of about 100 s and amplitudes of up to 40 nT. For one such event ground-magnetic observations as well as simultaneous GEOS-2 magnetic and electric field data and proton flux measurements made in the geostationary orbit have been analysed. The observations of the electromagnetic field indicate the excitation of an odd-mode type fundamental field line oscillation. A clear correlation between variations of the proton flux in the energy range 30-90 keV with the giant pulsation event observed at the ground is found. Furthermore, the proton phase space density exhibits a bump-on-the-tail signature at about 60 keV. Assuming a drift-bounce resonance instability as a possible generation mechanism, the azimuthal wave number of the pulsation wave field may be determined using a generalized resonance condition. The value determined in this way, m = - 21 +/- 4, is in accord with the value m = - 27 +/- 6 determined from ground-magnetic measurements. A more detailed examination of the observed ring current plasma distribution function f shows that odd-mode type eigenoscillations are expected for the case partialf/partialW>0, much as observed. This result is different from previous theoretical studies as we not only consider local gradients of the distribution function in real space, but also in velocity space. It is therefore concluded that the observed giant pulsation is the result of a drift-bounce resonance instability of the ring current plasma coupling to an odd-mode fundamental standing wave. The generation of the bump-on-the-tail distribution causing partialf/partialW>0 can be explained due to velocity dispersion of protons injected into the ring current. Both this velocity dispersion and the necessary substorm activity causing the injection of protons into the nightside magnetosphere are observed.

Affiliated with

Also associated with

No associations

Rating

Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Concerning the generation of geomagnetic giant pulsations by drift-bounce resonance ring current instabilities will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1443411