Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufmsm71a0574m&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #SM71A-0574
Physics
2740 Magnetospheric Configuration And Dynamics, 2744 Magnetotail
Scientific paper
On August 15, 2001 the Cluster spacecraft passed through the plasma sheet at 0100 LT at a distance of 18 Re. During the passage, three substorms were observed. Each substorm was characterized by an increase in Bz or dipolarization. The first and last substorms were also accompanied by strong earthward flows. We utilize observations from the four fluxgate magnetometers to calculate the gradient of each component of the magnetic field. From the gradient matrix we determine the divergence and curl of the magnetic field, and convert the curl to current density. We find that the integral of the observed current density is too small by at least a factor of two to account for the measured lobe field. We then use a static Harris model of the magnetic field and again show that the measured current density is less than expected. Finally we use a nonlinear fitting procedure to calculate the thickness (h), and location (z0) of a Harris sheet. The time series for these parameters show systematic variations with the phase of a substorm. The location of the neutral sheet moves away from its statistical location during the growth phase and recovers in the expansion/recovery phase. The thickness of the current sheet systematically decreases prior to the onset of major expansions and increases afterwards. These temporal changes in the current sheet can be taken into account by plotting the current density scaled by the current sheet thickness ( 0hJy) against the normalized spacecraft location ((z-z0)/h). The resulting plot shows that Ampere's law is correct, and there is sufficient current to account for the observed lobe field. We have also carried out the same analysis for a quiet crossing on September 22, 2001. The current sheet was quite thin (h~0.5 Re) during this rapid crossing and only the growth phase of one substorm occurred during the passage. Again the measured current apparently does not account for the lobe field. However, a time varying fit of a Harris sheet again demonstrates that Ampere's law is satisfied.
Amm Olaf
Baker Joseph B.
Balogh André
Connors Martin
Cretuzberg F.
No associations
LandOfFree
A Comparison of Cluster Observations of the Tail Current during Substorms and Quiet Times 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 A Comparison of Cluster Observations of the Tail Current during Substorms and Quiet Times, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Comparison of Cluster Observations of the Tail Current during Substorms and Quiet Times will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1439421