Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail

Details Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail

Dec 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufmsm13c1460s&link_type=abstract

American Geophysical Union, Fall Meeting 2007, abstract #SM13C-1460

Physics

2752 Mhd Waves And Instabilities (2149, 6050, 7836), 2764 Plasma Sheet, 2790 Substorms

Scientific paper

Spacecraft observations indicate that low-frequency (0.006-0.025 Hz) fluctuations of the magnetic field appear a few minutes prior to substorm-associated dipolarization onsets. On the basis of Geotail observations, we investigate such fluctuations in the vicinity of the magnetic equator in particular in the near-Earth magnetotail at X= -8 to -12 RE. In order to characterize the observed fluctuations both physically and quantitatively, we propose a new method for estimating characteristics of wave parameters, such as the mode, the phase velocity in the plasma frame, the wave number, and the Doppler shift. In this method, the inhomogeneity of the ambient magnetic field is taken into account. Band-passed data of magnetic field and ion velocity fluctuations are analyzed on the basis of the linear MHD equations. It is found that the fluctuations in the low-frequency range consist of various modes of MHD waves. Particularly, the fast magnetosonic wave was identified and was propagating tailward a few minutes prior to a dipolarization onset, though there are also dipolarization events in which no fast wave was identified. A more prominent finding in the present study is the presence of a mode that has almost zero frequency in the plasma frame. Such a zero-frequency mode can convect with the ambient plasma flow and hence can be measured with a finite frequency by a spacecraft. This mode may correspond to a linear stage of the ballooning instability. These characteristics of the MHD waves may provide crucial constraints on the conventional substorm initiation models.

Affiliated with

Also associated with

No associations

Rating

Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail 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 Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Geotail observations of low-frequency MHD waves prior to dipolarization onsets in the near- Earth magnetotail will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1421119