The Relations Between Solar Wind Variations and the North Atlantic Oscillation Rasheed Al-Nuaimi and Kais Al-Jumily Department of Atmospheric Sciences College of Science, Al-Mustansiriyah University Baghdad, Iraq,

 Heat radiation from the Sun is believed to be the primary factor for the Earth’s climate condition.  This phenomenon is not sufficient to explain the observed global climate fluctuations on Earth during the last century.  Several attempts have been made over the last decade to clarify if variations in the solar activity could, to some extent, be responsible for these climate fluctuations.

 Investigate the possible relation between solar wind variations and the North Atlantic Oscillation (NAO).

 The NAO is the dominant mode of winter climate variability in the North Atlantic region ranging from central North America to Europe and much into Northern Asia.  The NAO is a large scale seesaw in atmospheric mass between the subtropical high (the Azores High) and the polar low (the Icelandic Low) in the North Atlantic region.  The corresponding index varies from year to year, but also exhibits a tendency to remain in one phase for intervals lasting several years.

 An Index can be constructed that represents the phase of NAO  Most commonly the NAO index is based on the surface pressure (SLP) between the Subtropical (Azores) high and the Subpolar (Island) low  Very often the pressure readings from two stations one on Iceland and the other either Azores, Lisbon or Gibraltar are used to construct the NAO index

 The NAO index shows large variations from year to year. This interannual signal was especially strong during the end of 19 th century  Sometimes the NAO index stays in one phase for several years in a row. This decadal variability was quit strong at the beginning and the end of the 20 th century

 The positive NAO index phase shows a stronger than usual subtropical high pressure center and a deep than normal Icelandic low.  The increased pressure results in more and stronger winter storms crossing the Atlantic Ocean and more northerly track.  This results in warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland.  The eastern US experiences mild and wet winter conditions.

 The negative NAO index phase shows a weak subtropical high pressure a weak Icelandic low.  The reduced pressure gradients results in a fewer and weaker winter storms crossing on a more west-east pathway.  They bring moist air into the Mediterranean and cold weather in northern Europe.  The US east coast experiences more cold air outbreaks and hence snowy winter conditions.  Greenland, however, will have milder winter temperature s.

Charge particles (mostly protons and electrons) streaming outward from the sun at 450 km/s

 Some of the most geoeffective solar wind parameters are: Flow speed (V) Proton density (n) Southward component (B s )of the interplanetary magnetic field  B s is equal to -B z when B z < 0 and equal to 0 when B z ≥0, where B z is the interplanetary magnetic field component parallel to the Earth’s magnetic dipole.

 By using these three parameters one can construct proxies for: The dynamical pressure (P) The electric field strength (E) of the solar wind. The pressure (P) exerted on the Earth’s magnetosphere is best represented by (nV 2 ) whereas the electric field (E) can be described by (B s V).

 A widely used measure of the overall geomagnetic activity is the planetary magnetospheric (K p ) index.  The K p index is evaluated using the amplitude of the variation of the horizontal magnetic components X and Y at the Earth’s surface at geomagnetic latitudes between 48 o and 63 o.

 The NAO indices were obtain from 02/cook2002.html 02/cook2002.html  The solar wind data and the planetary magnetospheric Kp index were obtained from  The group sunspot numbers were obtained from:

 Annual averages of E, P, and K p for the period of were used to investigate the possibility of solar wind relation with the NAO.

Cor=0.56

Cor=0.36

Cor=0.52

Cor=0.56 Maunder Minima (cycles -10 to -4) and Dalton Minima (cycles 6 and 7) are evident in the NAO data

 Results indicated that there is a low correlation between (P) and NAO (~ 0.36)  Relatively high correlation exists between (K p ) and NAO (~ 0.56) and between (E) and NAO (~0.52)  This suggests that solar wind is in some way affecting the large-scale pressure systems in Earth.

 A more in depth study is needed through analysis of monthly means of data.

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