Is geomagnetic activity increasing?

Details Is geomagnetic activity increasing? Is geomagnetic activity increasing?

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmsm51a1736l&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #SM51A-1736

Astronomy and Astrophysics

Astrophysics

[1530] Geomagnetism And Paleomagnetism / Rapid Time Variations, [7537] Solar Physics, Astrophysics, And Astronomy / Solar And Stellar Variability, [7900] Space Weather, [7954] Space Weather / Magnetic Storms

Scientific paper

Geomagnetic-activity indices are simple summary metrics of magnetic-field activity derived from data acquired at ground-based observatories. The K index records the maximum variational range of magnetic-field disturbance over 3-hr durations of time at each individual observatory. The global-activity aa index is derived from K values from a pair of observatories, one in the northern hemisphere (Britain) and one in the southern hemisphere (Australia). Since the aa time series extends from 1868 to the present, it is often used for studies of long-term trends. In this study we examine the source K values used for constructing aa, and we compare them with K values from Germany (1890-present). While we identify numerous problems and biases in aa, we also find that it does provide a qualitative measure of long-term change in global-scale geomagnetic activity, which, in addition to showing an 11-year solar-cycle modulation, has generally been increasing over the past 140 years. More definitive conclusions can be drawn from consistent patterns in the (independently measured) K indices from different observatories: (1) The well-known tendency for magnetic storms to occur during the declining phase of a solar cycle was not clearly seen until about 1902, with the commencement of solar cycle 14; or, at least, it was not obviously present in solar cycles 11-13. (2) Since about 1954, with the commencement of solar cycle 19, magnetic quiescence has diminished disproportionately when compared to trends in sunspot number. (3) Extrapolations of past trends in solar and geomagnetic activity levels are unlikely to be useful for making quantitative predictions. (4) No significant correlation exists from 1868-present between geomagnetic activity and Earth’s global surface temperature, nor, indeed, between sunspot number and global surface temperature. These observations have implications for solar physics, geophysics, and for space-weather prediction and hazard mitigation. They also highlight the value of both continuous long-term monitoring and preserving historical data in their original and unaltered numerical form.

Affiliated with

Also associated with

No associations

Rating

Is geomagnetic activity increasing? 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 Is geomagnetic activity increasing?, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Is geomagnetic activity increasing? will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1473264