On the Relationship Between Solar Wind Speed, Geomagnetic ...

[Pages:24]NASA/TP--2008?215249

On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

Robert M. Wilson and David H. Hathaway Marshall Space Flight Center, Marshall Space Flight Center, Alabama

February 2008

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NASA/TP--2008?215249

On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

Robert M. Wilson and David H. Hathaway Marshall Space Flight Center, Marshall Space Flight Center, Alabama

National Aeronautics and Space Administration Marshall Space Flight Center ? MSFC, Alabama 35812

February 2008

Available from: NASA Center for AeroSpace Information

7115 Standard Drive Hanover, MD 21076?1320

301?621?0390

This report is also available in electronic form at

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TABLE OF CONTENTS 1. INTRODUCTION............................................................................................................................ 1 2. RESULTS AND DISCUSSION....................................................................................................... 2 3. SUMMARY...................................................................................................................................... 9 REFERENCES...................................................................................................................................... 10

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LIST OF FIGURES

1.

Annual variation of (a) sunspot number R and (b) the corrected aa geomagnetic

index for the years 1860?2006. The thin, vertical lines mark the sunspot minimum

years and the numbers refer to the sunspot cycles 10?23. Notice that most cycles

have their largest aa index after sunspot maximum (except cycles 12 and 13)

and their minimum aa index value either in the sunspot minimum year or the year

following the sunspot minimum year (except cycle 21) ......................................................... 3

2.

Scatterplot of the annual aa index values against R for the years 1868?2006.

Notice that all aa index values lie on or above the line denoted aaR, which is used to compute the leading sporadic component of the aa index (i.e., the solar cycle

component) .............................................................................................................................. 4

3.

Annual variation of the residual or following recurrent interplanetary component

of the aa index, computed as aaI = aa ? aaR for the years 1868?2006. The thin, vertical lines mark the sunspot minimum years; the thick, vertical lines mark

the sunspot maximum years; and the numbers refer to the sunspot cycles 11?23.

Plainly, the maximum recurrent component of the aa index usually occurs after

sunspot maximum (except cycles 12 and 13). Notice that the largest observed value

of the recurrent component (24.3) occurred in 2003 during the decline of cycle 23 .............. 4

4.

Annual variation of (a) R, (b) aa, (c) aaI, (d) solar wind speed v, and (e) number

of hours of solar wind observations for the years 1950?2006. The thin and thick

vertical lines and the numbers 19?23 have the same meanings as before. See

text for details .......................................................................................................................... 6

5.

Scatterplots of (a) aa and (b) aaI versus v for the years 1964?2006. See text

for details ................................................................................................................................. 7

6.

Cyclic variation of (a) , (b) , (c) , and (d) and for cycles 11?23.

See text for details ................................................................................................................... 8

IPinterplanetary

PI

prediction interval

TP

Technical Publication

LIST OF ACRONYMS

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