Physics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm..sm52a01c&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #SM52A-01
Physics
2784 Solar Wind/Magnetosphere Interactions, 2788 Storms And Substorms
Scientific paper
We determined the phases of the maxima (spring, fall) and minima (summer, winter) in the curve of smoothed daily averages of the aa geomagnetic index, available from 1868-1998. The dates we obtained are consistent with the equinoctial hypothesis which has aberration-adjusted theoretical maxima on 25 March (experimentally determined to be 27 March) and 27 September (27 September) and minima on 26 June (26 June) and 26 December (27 December). We also show that the overall shape of the modulation curve throughout the year (broad minima, narrow peaks) bears greater fidelity (r = -0.96) to the solar declination D (the controlling angle for the seasonal variation under the equinoctial hypothesis) than to the solar B angle (r = 0.83; axial hypothesis) or the solar P angle (r = 0.80; Russell-McPherron effect). Lastly, a three-parameter fit of the smoothed annual variation of the aa data with a function consisting of the sum of the smoothed yearly curves for the D, B, and P angles yielded an amplitude of 0.58 for the D component vs. 0.20 for B and 0.16 for P. Generally similar results for each of these analyses (timing, shape, relative contributions) were obtained for shorter intervals of data for the ap and am indices. We conclude that the semiannual modulation of average values of mid-latitude range indices such as aa and ap is primarily controlled by the equinoctial hypothesis.
Cliver Edward W.
Kamide Yohsuke
Ling A. G.
No associations
LandOfFree
The semiannual variation of geomagnetic activity: Phases and profiles for 130 years of aa data 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 The semiannual variation of geomagnetic activity: Phases and profiles for 130 years of aa data, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The semiannual variation of geomagnetic activity: Phases and profiles for 130 years of aa data will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1278310