Spacecraft Observations of Intense Electric and Magnetic Field Fluctuations and Associated Earthward Magnetic Field -aligned Poynting Flux Throughout the Plasma Sheet at 4-6 Re Altitudes during Major Geomagnetic Storms

Details Spacecraft Observations of Intense Electric and Magnetic Field Fluctuations and Associated Earthward Magnetic Field -aligned Poynting Flux Throughout the Plasma Sheet at 4-6 Re Altitudes during Major Geomagnetic Storms Spacecraft Observations of Intense Electric and Magnetic Field Fluctuations and Associated Earthward Magnetic Field -aligned Poynting Flux Throughout the Plasma Sheet at 4-6 Re Altitudes during Major Geomagnetic Storms

May 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sm61b01w&link_type=abstract

American Geophysical Union, Spring Meeting 2001, abstract #SM61B-01

Physics

2704 Auroral Phenomena (2407), 2736 Magnetosphere/Ionosphere Interactions, 2764 Plasma Sheet

Scientific paper

We present observations from the EFI and MFE instruments on the Polar spacecraft obtained during several major geomagnetic storms (Dst<-100 nT)of intense electric field (> 40 mV/m, ptp) and magnetic field fluctuations (40-80 nT, ptp). The fluctuations have periods ranging from 0.25 to 600 seconds. These spatially extensive field fluctuations are observed at altitudes of 4-6 Re and last for 10-30 minutes in the spacecraft frame and can exist over the entire spatial extent of the plasma sheet. The fields map to a latitudinal extent on the ground of 4-6 degrees. This is a much larger spatial extent than the previously reported (Wygant et al., 2000;Keiling et al., 2000) observations of intense Poynting flux due to Alfven wave at the outer boundary of the plasma sheet. The Poynting flux associated with the fields presented herein is directed along the magnetic field direction towards the Earth and exceeds .25 erg/cm2 . If mapped to 100 km altitude along converging magnetic field lines, the Poynting flux peak values can exceed 30 ergs/cm2s. This is sufficient to power some of the most intense aurora in the Polar UVI data set. Preliminary analysis indicates that the ratio of E/B for these waves is consistent with a mixture of Alfvenic fluctuations interspersed with steady state electric fields closing in the ionosphere through field aligned currents. Spacecraft potential measurements indicate the presence of a strong density depletion (<0.1 cm**-3)during these electric field fluctuations. We will compare these observations of intense Poynting flux to simultaneously obtained images of the aurora obtained from Polar and IMAGE spacecraft UVI images . We will also use data from the four CLUSTER spacecraft obtained during similar plasmsheet crossings to analyze the spatial-temporal structure of these electric field fluctuations.

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