Is coverage a factor in non-Gaussianity of IMF parameters?

Conference · Thu Jun 01 04:00:00 EDT 1995

OSTI ID:266945

Ahluwalia, H S; Fikani, M M

Recently, Feynman and Ruzmaikin showed that IMF parameters for the 1973 to 1990 period are not log-normally distributed as previously suggested by Burlaga and King for the data obtained over a shorter time period (1963-75). They studied the first four moments, namely: mean, variance, skewness, and kurtosis. For a Gaussian distribution, moments higher than the variance should vanish. In particular, Feynman and Ruzmaikin obtained very high values of kurtosis during some periods of their analysis. The authors note that the coverage for IMF parameters is very uneven for the period analyzed by them, ranging from less than 40% to greater than 80%. So a question arises as to whether the amount of coverage is a factor in their analysis. The authors decided to test this for the B{sub z} component of IMF, since it is an effective geoactive parameter for short term disturbances. Like them, the authors used 1-hour averaged data available on the Omnitape. They studied the scatter plots of the annual mean values of B{sub z}(nT) and its kurtosis versus the percent coverage for the year. They obtain a correlation coefficient of 0.48 and 0.42 respectively for the 1973-90 period. The probability for a chance occurrence of these correlation coefficients for 18 pair of points is less than 8%. As a rough measure of skewness, the authors determined the percent asymmetry between the areas of the histograms representing the distributions of the positive and the negative values of B{sub z} and studied its correlation with the coverage for the year. This analysis yields a correlation coefficient of 0.41. When they extended the analysis for the whole period for which IMF data are available (1963-93) the corresponding correlation coefficients are 0.59, 0.14, and 0.42. These findings will be presented and discussed.

• Research Organization: Jet Propulsion Lab., Pasadena, CA (United States)
• OSTI ID: 266945
• Report Number(s): N--96-24651; NASA-CR--199940; JPL-PUBL--95-13; NAS--1.26:199940; NIPS--95-06571; CONF-9506256--
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ASYMMETRY
DISTRIBUTION FUNCTIONS
INTERPLANETARY MAGNETIC FIELDS
MOMENTS METHOD
STATISTICS