Long-term trends of the magnetospheric ring current

PATRICIA FERNANDEZ DE CAMPRA; MARTA ZOSSI DE ARTIGAS; ANA G. ELIAS

Atibaia, San Pablo

Congreso; 7ma COLAGE, Conferencia LatinoAmericana de Geofísica Espacial; 2004

ALAGE, Asociacion LatinoAmericana de Geofisica Espacial

As a consequence of the increasing interest in global changes and sun-climate relations, long-term variation of geomagnetic activity has become an important subject. There are many studies concerning geomagnetic indices variability pointing out its periodicities and links to solar activity cycle. In this work we are concerned with Dst long-term variations of time-scales longer than the 11-year solar cycle during the period 1957-2000. Linear trends are estimated for the periods 1957-2000 and 1965-2000. If we look at the low-pass filtered Dst series the year 1965 appears as an inflection point. The linear trend for the period 1957-2000 was estimated with ordinary least squares for a given hour and a given month of the year (that is 12x24 series). This trend is negative in almost all the cases, which would mean an increasing geomagnetic activity during this period. When the trend is estimated for the period 1965-2000 only, the negative trend is enhanced. This is due to a pronounced increasing trend during 1957-1965, which tends to mask the downward trend following 1965. This long-term Dst variability may be part of a long-term periodic variation.