North-south asymmetry of the amplitude of high-latitude Pc 3-5 pulsations: Observations at conjugate stations

The north-south asymmetry of the amplitude of ULF pulsations in the Pc 3-5 band is studied using magnetic field data from the magnetically conjugate stations at L similar to 5.4: Kotzebue (KOT) in the northern hemisphere and Macquarie Island (MCQ) in the southern hemisphere. We obtained the followin...

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Bibliographic Details
Main Authors: Obana, Y., Yoshikawa, A., Olson, J. V., Morris, R. J., Fraser, Brian J., Yumoto, K.
Format: Article in Journal/Newspaper
Language:English
Published: American Geophysical Union 2005
Subjects:
finite ionosphere conductivities
period magnetic pulsations
field
line oscillations
divergent hall-current
standing alfven waves
pc
3,4 pulsations
geomagnetic-pulsations
ulf waves
hydromagnetic-waves
magnetometer-array
Macquarie Island
Online Access:http://hdl.handle.net/1959.13/25237
Description
Summary:The north-south asymmetry of the amplitude of ULF pulsations in the Pc 3-5 band is studied using magnetic field data from the magnetically conjugate stations at L similar to 5.4: Kotzebue (KOT) in the northern hemisphere and Macquarie Island (MCQ) in the southern hemisphere. We obtained the following results for the northward (H) component of magnetic pulsations: (1) The north to south power ratio shows a maximum in the northern winter and a minimum in the northern summer. This "seasonal variation'' is stronger at higher frequencies (Pc 3 and Pc 4 frequencies). (2) The north to south power ratio for the Pc 4 and Pc 5 frequency band is basically greater than 1.0 for all seasons. This "positive offset'' is stronger at lower frequencies. The "seasonal variation'' implies that the magnetohydrodynamic (MHD) waves incident from the magnetosphere are more strongly shielded when the ionospheric conductivity is higher. The "positive offset'' may result from the difference of the background magnetic field intensity between KOT and MCQ.

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