IRREGULAR MAGNETIC ACTIVITY IN NORTHERN CANADA WITH SPECIAL REFERENCE TO AEROMAGNETIC SURVEY PROBLEMS

Geophysics ◽  
1957 ◽  
Vol 22 (3) ◽  
pp. 646-659 ◽  
Author(s):  
K. Whitham ◽  
E. I. Loomer
Keyword(s):  
Magnetic Activity ◽  
Auroral Zone ◽  
Maximum Activity ◽  
High Latitudes ◽  
Aeromagnetic Survey ◽  
Northern Canada ◽  
K Index ◽  
Seasonal Characteristics ◽  
Short Period ◽  
Two Peaks

An investigation of the diurnal and seasonal characteristics of irregular magnetic activity in northern Canada, using two indices of disturbance, shows that in general the K index provides a reliable but smoothed measure of short period activity. Two peaks of activity are evident, a day‐time peak, dominant inside the polar cap, and a night peak, dominant south of the auroral zone. The latter occurs within one hour of local geomagnetic midnight at four Canadian observatories, whereas the day‐time peak occurs progressively later at higher latitudes. The maximum activity occurs in the equinoxes at latitudes near the auroral zone, and during the summer solstice at very high latitudes. Measurements of range at the most disturbed observatory suggest that aeromagnetic surveying in high latitudes is in general feasible, but that for accurate reconnaissance work it is very advantageous to plan operations, so far as conditions permit, taking account of the systematic diurnal variation of disturbance. It is shown that errors of about one half the assumed diurnal change between base lines will occur and sufficient data is given to allow approximate predictions of the optimum length of flight lines.

THE DIURNAL PROBLEM IN AEROMAGNETIC SURVEYING IN CANADA

Geophysics ◽  
1961 ◽  
Vol 26 (2) ◽  
pp. 211-228 ◽  
Author(s):  
K. Whitham ◽  
E. R. Niblett
Keyword(s):  
Direct Methods ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Aeromagnetic Survey ◽  
Autocorrelation Functions ◽  
Frequency Distributions ◽  
Practical Applications ◽  
Field Fluctuations ◽  
Survey Results ◽  
Time Variations

Errors introduced into aeromagnetic survey results because of geomagnetic time variations have been analyzed in two ways. In the first, statistical properties of average magnetic disturbance have been calculated for five locations well distributed in latitude in Canada. The autocorrelation functions of vertical magnetic field fluctuations have been used to estimate errors in aeromagnetic surveying as a function of the length of the base loop and the length of the traverse lines or profiles, for five latitudes. In practical applications, the r.m.s. errors are proportional to the square root of elapsed time. These results can be explained in terms of the shape of the autocorrelation functions, and models of disturbance which might produce them are discussed. In the second part experimental results are presented of a comparison of total field intensity fluctuations measured with recording proton precession magnetometers at two pairs of stations, one pair 26 miles apart and the other 94 miles apart. The measurements were taken in Western Canada south of the auroral zone. The r.m.s. differences in the time variations have been determined quantitatively for each hour for both pairs of stations; statistically, it was found that these differences were proportional to the r.m.s. level of magnetic activity and, in this region, to the separation of the stations. The frequency distributions of the r.m.s. differences between the two pairs of stations for the month of September 1959 have been determined. A comparison of the indirect and direct methods of correction indicates that scientifically, in this region, there is little to choose between them in terms of accuracy. Operational considerations are mentioned.

scholarly journals The diurnal variation of magnetic disturbance in high latitudes

1935 ◽  
Vol 149 (867) ◽  
pp. 298-311 ◽  
Keyword(s):  
Diurnal Variation ◽  
Natural Disturbance ◽  
Universal Time ◽  
Sudden Commencement ◽  
General View ◽  
High Latitudes ◽  
Limited Region ◽  
Short Period ◽  
Distinctive Type ◽  
Unlimited Variety

1―The effect of natural disturbance on the earth’s magnetic field at any one place is at least twofold: (i) to introduce a regular variation (S d ) periodic within the day and additional to, as well as different in type from (except in a limited region round the magnetic axis pole), the variation associated with quiet days (S q ); and (ii) to suppose on S d irregular changes which may either be of the distinctive type peculiar to large storms especially in low latitudes and generally preceded by the particular type of perturbation known as a sudden commencement, or the changes in the field may be of the apparently nondescript class which comprises an unlimited variety of short-period irregular oscillations. Of these effects of disturbances S d is definitely a local time phenomenon: the sudden commencement with subsequent depression in the horizontal component of the field as definitely follows universal time. For the irregular and unclassified oscillations in moderate and high latitudes a diurnal variation in their incidence has been shown to exist for a few isolated localities. But in the general view it is not known whether this aspect of disturbance is controlled by local or universal time. Nor is it known whether the form of the diurnal variation in disturbance (which variation we shall denote by D) varies in any systematic way with latitude.

scholarly journals V802 Aquilae: A Short-Period Eclipsing Binary with Magnetic Activity

2008 ◽  
Vol 60 (4) ◽  
pp. 803-808 ◽  
Author(s):  
Yuan-Gui Yang ◽  
Sheng-Bang Qian ◽  
Li-Ying Zhu ◽  
Liang Liu ◽  
Kazuhiro Nakajima
Keyword(s):  
Magnetic Activity ◽  
Eclipsing Binary ◽  
Short Period

Glycogenolytic Enzymes of Cod (Gadus callarias) Muscle

1966 ◽  
Vol 23 (4) ◽  
pp. 527-538 ◽  
Author(s):  
J. R. Burt
Keyword(s):  
Muscle Glycogen ◽  
Maximum Activity ◽  
Chloride Ions ◽  
Relative Importance ◽  
Optimum Temperature ◽  
Short Period ◽  
Wide Range

Some properties of the enzymes amylase, phosphorylase, and phosphoglucomutase in homogenates of cod muscle have been investigated. Amylase is activated by a short period of autolysis and by chloride ions; hydrolyses cod muscle glycogen at about half the rate it hydrolyses mussel glycogen; has an optimum temperature of 52 C for up to 5 hr incubation; and has a wide range of activity with maxima around pH 5.1 and between pH. 7.0 and 7.5. Using phloridzin, an estimate of the relative importance of hydrolytic and phosphorolytic cleavage of polysaccharide in cod muscle homogenates has been made. Phosphorylase shows two activity maxima at pH 5.5 and 6.7. The properties of phosphoglucomutase, with the exception of its pH activity, in cod muscle are similar to those reported for this enzyme in other tissues. Cod muscle phosphoglucomutase has maximum activity between pH 8 and 9.

scholarly journals SABRE observations of Pi2 pulsations: case studies

1997 ◽  
Vol 15 (1) ◽  
pp. 40-53 ◽  
Author(s):  
E. G. Bradshaw ◽  
M. Lester
Keyword(s):  
Case Studies ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Field Of View ◽  
Ionospheric Currents ◽  
Pi2 Pulsation ◽  
First Case ◽  
Pi2 Pulsations ◽  
Generation Region

Abstract. The characteristics of substorm-associated Pi2 pulsations observed by the SABRE coherent radar system during three separate case studies are presented. The SABRE field of view is well positioned to observe the differences between the auroral zone pulsation signature and that observed at mid-latitudes. During the first case study the SABRE field of view is initially in the eastward electrojet, equatorward and to the west of the substorm-enhanced electrojet current. As the interval progresses, the western, upward field-aligned current of the substorm current wedge moves westward across the longitudes of the radar field of view. The westward motion of the wedge is apparent in the spatial and temporal signatures of the associated Pi2 pulsation spectra and polarisation sense. During the second case study, the complex field-aligned and ionospheric currents associated with the pulsation generation region move equatorward into the SABRE field of view and then poleward out of it again after the third pulsation in the series. The spectral content of the four pulsations during the interval indicate different auroral zone and mid-latitude signatures. The final case study is from a period of low magnetic activity when SABRE observes a Pi2 pulsation signature from regions equatorward of the enhanced substorm currents. There is an apparent mode change between the signature observed by SABRE in the ionosphere and that on the ground by magnetometers at latitudes slightly equatorward of the radar field of view. The observations are discussed in terms of published theories of the generation mechanisms for this type of pulsation. Different signatures are observed by SABRE depending on the level of magnetic activity and the position of the SABRE field of view relative to the pulsation generation region. A twin source model for Pi2 pulsation generation provides the clearest explanation of the signatures observed.

scholarly journals Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices

2011 ◽  
Vol 29 (4) ◽  
pp. 673-678 ◽  
Author(s):  
S. Tomita ◽  
M. Nosé ◽  
T. Iyemori ◽  
H. Toh ◽  
M. Takeda ◽  
...  
Keyword(s):  
Local Time ◽  
Geomagnetic Field ◽  
Field Data ◽  
Geomagnetic Latitude ◽  
Magnetic Activity ◽  
Auroral Zone ◽  
Magnetic Local Time ◽  
Geomagnetic Disturbances ◽  
Current Systems ◽  
Local Time Dependence

Abstract. The Auroral Electrojet (AE) indices, which are composed of four indices (AU, AL, AE, and AO), are calculated from the geomagnetic field data obtained at 12 geomagnetic observatories that are located in geomagnetic latitude (GMLAT) of 61.7°–70°. The indices have been widely used to study magnetic activity in the auroral zone. In the present study, we examine magnetic local time (MLT) dependence of geomagnetic field variations contributing to the AU and AL indices. We use 1-min geomagnetic field data obtained in 2003. It is found that both AU and AL indices have two ranges of MLT (AU: 15:00–22:00 MLT, ~06:00 MLT; and AL: ~02:00 MLT, 09:00–12:00 MLT) contributing to the index during quiet periods and one MLT range (AU: 15:00–20:00 MLT, and AL: 00:00–06:00 MLT) during disturbed periods. These results are interpreted in terms of various ionospheric current systems, such as, Sqp, Sq, and DP2.

THE EFFECT OF GEL WATER ON CATALYTIC ACTIVITY: III. THE DECOMPOSITION OF FORMIC ACID OVER ALUMINA

1943 ◽  
Vol 21b (2) ◽  
pp. 21-33
Author(s):  
L. A. Munro ◽  
D. J. Dewar ◽  
S. Gertsman ◽  
G. Monteith
Keyword(s):  
Surface Modification ◽  
Catalytic Activity ◽  
Formic Acid ◽  
Water Content ◽  
Maximum Activity ◽  
Hydrous Oxide ◽  
X Ray ◽  
Fibril Structure ◽  
Two Peaks ◽  
Catalytic Power

The effect of gel water content on the catalytic activity of alumina in the decomposition of formic acid at 215 and 250 °C. has been investigated. The previous observations on the dehydration of ethyl alcohol to ether and ethylene are paralleled by the results with formic acid. There are two peaks in the curves showing the relation between activity and gel water content. The ratio CO/CO2 changes with gel water content, i.e., the course of the reaction can be altered by surface modification of the catalyst. The gel showing maximum catalytic activity exhibits greatest sorption. The temperature of activation of a hydrous oxide is not as accurate a measure of the catalytic power as the gel water content. X-ray studies of the catalysts show a threefold change in the structure in the 36 to 0% range of water content, but the fibril structure of the gel of maximum activity (5.3% water) is the same as that for minimum activity. An explanation is suggested.

scholarly journals The Rotational Modulation of Ca II K in the Sun

1991 ◽  
Vol 130 ◽  
pp. 266-267
Author(s):  
I. Sattarov ◽  
A. Hojaev
Keyword(s):  
Solar Cycle ◽  
Active Regions ◽  
Magnetic Activity ◽  
Astronomical Observatory ◽  
Rigid Rotation ◽  
Longitudinal Distribution ◽  
The Sun ◽  
K Index ◽  
Rotational Modulation ◽  
Line Core

The most widely used indicator of the stellar magnetic activity is the flux in the CaII K-line core (K-index) (Baliunas and Vaughan, 1985). The K-index data have also been used for measuring the rotation of stars. But using the method for the Sun gives different results (Keil and Worden, 1984; Singh and Livingston, 1987). The reason for the observed differences, besides those indicated by Singh and Livingston, may be the character of the distribution of active regions. This study is based on observations made at Tashkent Astronomical Observatory and the data published in SGD for solar cycle 21. We study the longitudional distribution of sunspots and plages. Some intervals of active longitudes (IAL) were selected and the evolution of them was studied. Active regions were found to concentrate in certain longitude intervals which are in nearly rigid rotation. Fig. 1 shows the longitudinal distribution of sunspots areas for 1983-84, as an example.

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