Coupling of Magnetosphere and Ionosphere by Alfvén Waves at High and Mid-Latitudes
Location
Yosemite National Park
Start Date
2-11-2014 6:10 PM
End Date
2-11-2014 6:40 PM
Description
Electrodynamic coupling of the magnetosphere and ionosphere is accomplished by the passage of MHD waves that propagate between these regions. Field-aligned currents can be generated by flow shears in the outer magnetosphere, and these currents are carried to lower latitudes by shear mode Alfvén waves. Pressure changes in the outer magnetosphere drive magnetosonic waves that can propagate throughout the magnetosphere. These waves modes are coupled by gradients in the Alfvén speed across magnetic field lines as well as by the Hall conductivity in the ionosphere, complicating the signals generated by magnetospheric dynamics. A new threedimensional model of ULF waves in a dipole geometry has been developed that simulates the propagation and coupling of these waves. This model includes distributed conductivities in a height-resolved ionosphere and directly calculates the ground magnetic fields produced by these currents. This model will be applied to the propagation of Pi1/Pc1 waves that interact in the ionospheric Alfvén resonator as well as to lower frequency Pi2 pulsations that propagate globally. Emphasis will be placed on the comparison of magnetic and electric fields observed on the ground, in the ionosphere, and by spacecraft in the magnetosphere.
Coupling of Magnetosphere and Ionosphere by Alfvén Waves at High and Mid-Latitudes
Yosemite National Park
Electrodynamic coupling of the magnetosphere and ionosphere is accomplished by the passage of MHD waves that propagate between these regions. Field-aligned currents can be generated by flow shears in the outer magnetosphere, and these currents are carried to lower latitudes by shear mode Alfvén waves. Pressure changes in the outer magnetosphere drive magnetosonic waves that can propagate throughout the magnetosphere. These waves modes are coupled by gradients in the Alfvén speed across magnetic field lines as well as by the Hall conductivity in the ionosphere, complicating the signals generated by magnetospheric dynamics. A new threedimensional model of ULF waves in a dipole geometry has been developed that simulates the propagation and coupling of these waves. This model includes distributed conductivities in a height-resolved ionosphere and directly calculates the ground magnetic fields produced by these currents. This model will be applied to the propagation of Pi1/Pc1 waves that interact in the ionospheric Alfvén resonator as well as to lower frequency Pi2 pulsations that propagate globally. Emphasis will be placed on the comparison of magnetic and electric fields observed on the ground, in the ionosphere, and by spacecraft in the magnetosphere.