National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Storm-time sub-auroral electric fields: Ionospheric and magnetospheric control

ROSES ID: NNH05ZDA001N      Selection Year: 2006      

Program Element: Focused Science Topic

Principal Investigator: Pontus Brandt

Affiliation(s): The Johns Hopkins University Applied Physics Laboratory

Project Member(s):
Zheng, Yihua Co-I NASA Goddard Space Flight Center
Sotirelis, Thomas Co-I JHU/APL
DeMajistre, Robert Co-I The Johns Hopkins University Applied Physics Laboratory


The role of electric fields in the sub-auroral ionosphere have been

underestimated for a long time largely due to the lack of

understanding of their origin and global behavior. Solar irradiation,

Joule heating and the ring current cause ionospheric electric

fields. Separation of their different origins is inherently difficult

due to limited spatial coverage of measurements (radars, low-latitude


We propose to provide a realistic model of the sub-auroral electric

field, produced by the ionospheric closure of the ring current, using

observations and modeling, and investigate how it is controlled by

magnetospheric activity and ionospheric conductance. The output

electric fields is intended to be used as input by other thermospheric

models investigating the transport and density of the

ionosphere/thermosphere. Our work can be divided into the following


TASK I - Perform a correlative statistical study of ionospheric

electric fields. Three types of electric fields will be investigated:

(1) Penetration (or undershielding) electric fields; (2) Sub-auroral

Polarization Streams (SAPS); (3) Midnight-dawnside, sub-auroral flow

reversals. Observational parameters will include solar wind

conditions, ionospheric conductance, Region-2 current intensity.

TAKS II - The sub-auroral, ionospheric electric field of selected

storm events will be modeled using the Comprehensive Ring Current

Model (CRCM), which computes the electric field, self-consistently

arising from the closure of the ring current through the ionosphere.

TAKS III - The results from the observational and model study will be

combined into a climatological model of the behavior of the

sub-auroral, ionospheric electric fields.

The most outstanding ionospheric effect is the uplift of plasma

through penetration electric fields on the low-latitude dayside,

causing storm enhanced densities (SED) in the F-layer. The SEDs

corotate into the duskside ionosphere where ring-current driven

electric fields transport plasma to mid-latitudes and sunward. The

SEDs have far reaching consequenses for a number of technological

systems over our heavily populated continent. For example, the Wide

Area Augmentation System (WAAS) assists positioning of civil aircraft

by providing time delay of Global Positioning System (GPS) signals

from geosynchronous satellites. However, WAAS can only provide time

delays from about a two dozen of stations over the North American

continent, forcing aircraft to interpolate the time delay value

between stations. At disturbed times, the ionosphere display very high

densities in very confined regions which makes the position

determination by interpolation invalid.

The proposed work fulfills the NASA National Objective: ``Study the

Earth system from space and develop new space-based and related

capabilities for this purpose.'' and all of its sub-objectives. As

recommended by the LWS TR\&T Science Definition Team, the proposed

work relies on large-scale modeling work that addresses the coupling

between the two traditional domains of the storm-time magnetosphere

and ionosphere and offers to provide its output (large-scale,

sub-auroral electric fields driven by the magnetosphere) to be used

further by thermospheric models. We therefore believe that the

proposed work will be a useful strategic capability in understanding

the storm-effects on the global electrodynamics and the mid- and low

latitude ionosphere/thermosphere system.


Performance YearReferenceActions
1Zheng, Y.; Brandt, P. C.; Sotirelis, T. S.; Talaat,...
1Brandt, P. C.; Zheng, Y.; Talaat, E.; Sotirelis, T.;...
1Talaat, E. R.; Sotirelis, T. S.; Hairston, M. R.; B...

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