HORIZONTAL MOTIONS IN RADAR ECHOES FROM AURORA

A systematic motion of 48.2 Mc/sec echoes associated with aurora is found at Saskatoon. The motion is towards the west before midnight and towards the east after midnight, the mean velocity in either direction showing a statistical relation to variations in the earth's magnetic field. No correlation is found between individual echo velocity and magnetic disturbance, and no period of zero velocity is observed. There is also evidence of an ordered relation between motion in the north–south direction and disturbances in the earth's magnetic field.

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Night-time Sferic Propagation at Frequencies Below 10 KHz

Australian Journal of Physics ◽

10.1071/ph670101 ◽

1967 ◽

Vol 20 (1) ◽

pp. 101 ◽

Cited By ~ 11

Author(s):

KJW Lynn ◽

J Crouchley

Keyword(s):

Magnetic Field ◽

Geographic Distribution ◽

Angle Of Incidence ◽

European Studies ◽

Earth’S Magnetic Field ◽

Night Time ◽

The West ◽

Earth's Magnetic Field ◽

Effective Angle

Results of a study at Brisbane of individual night-time sferics of known origin are described. A propagation attenuation minimum was observed in the 3-6 kHz range. The geographic distribution of sferic types was also examined. Apparent propagation asynunetries were observed, since sferics were detected at greater ranges to the west than to the east at 10 kHz, whilst the number of tweek-sferics arising from the east was about four times that arising from the west. Comparison with European studies suggest that these asymmetries are general. These results are then " interpreted in terms of an ionospheric reflection cgefficient which is a function of the effective angle of incidence of the wave on the ionosphere and of orientation with respect to the Earth's magnetic field within the ionosphere.

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The archaeomagnetic field recorded in ancient kiln walls in Si Satchanalai, Sukhothai

Journal of Physics Conference Series ◽

10.1088/1742-6596/2145/1/012049 ◽

2021 ◽

Vol 2145 (1) ◽

pp. 012049

Author(s):

R Supakulopas

Keyword(s):

Magnetic Field ◽

Confidence Limit ◽

Field Model ◽

Luminescence Dating ◽

Human History ◽

Earth’S Magnetic Field ◽

Argon Dating ◽

Dating Methods ◽

Earth's Magnetic Field ◽

The Mean

Abstract Archaeological dating is crucial in archaeology as it is a key to understand human history. However, traditional dating methods used by archaeologists such as potassium-argon dating and luminescence dating can provide ambiguous age results, e.g., argon loss during the dating returns young apparent ages. Therefore, I plan to establish an archaeomagnetic secular variation (ASV) curve to resolve this problem and use the ASV curve as an alternative tool to date archaeological artefacts. However, archaeomagnetic data in Thailand are absent from literature. Therefore, the ASV curve cannot be constructed from the archaeomagnetic data for this locality. To provide archaeomagnetic data to construct the ASV curve, the directions of the Earth’s magnetic field recorded in kiln walls from Ban Ko Noi (KN123, age 1,370 ± 100 A.D.), Si Satchanalai were measured. The mean declination and inclination of 49.6° and 32.6° with 95% confidence limit of 5.4° were determined from 10 samples from kiln KN123. Mean directions from this study were also compared with the directions of the Earth’s magnetic field in Thailand during 1,370 A.D. from the global archaeomagnetic field model ARCH3k.1. Declination and inclination from this study show significant departure from the field predicted by the ARCH3k.1 model.

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Paleomagnetism of the Abitibi dyke swarm, southern Superior Province, and implications for the Logan Loop

Canadian Journal of Earth Sciences ◽

10.1139/e93-167 ◽

1993 ◽

Vol 30 (9) ◽

pp. 1886-1897 ◽

Cited By ~ 52

Author(s):

Richard E. Ernst ◽

Kenneth L. Buchan

Keyword(s):

Magnetic Field ◽

Secular Variation ◽

Dyke Swarm ◽

Earth’S Magnetic Field ◽

The North ◽

Apparent Polar Wander Path ◽

Earth's Magnetic Field ◽

Reversed Polarity ◽

Magma Pulses ◽

Middle Proterozoic

The trace of the Middle Proterozoic Logan Loop of the North American apparent polar wander path is controversial. The older 1270–1110 Ma limb of the loop is poorly constrained, while the depth of the loop, based on the 1110–1080 Ma Keweenawan data of the younger limb, is thought by some to be largely an artifact of reversal asymmetry in the Earth's magnetic field. Paleomagnetism of the 1141 Ma Abitibi mafic dyke swarm is one of the keys to constraining the geometry of the Logan Loop.Unfortunately, previous paleomagnetic studies failed to distinguish dykes of the northeast-trending Middle Proterozoic olivine-bearing Abitibi swarm from subparallel Early Proterozoic olivine-free Biscotasing (formerly Preissac) dykes, and hence paleomagnetic poles determined in these studies should no longer be used. In the present study, sampling of eight Abitibi dykes has identified 23 normally magnetized sites in four dykes and, for the first time, five reversely magnetized sites in three dykes. One of the normally magnetized sites corresponds to the locality for which a high-precision U–Pb age was previously reported. A baked contact test establishes that the characteristic remanence of one normally magnetized dyke is primary. In addition, sites along individual dykes exhibit much smaller secular variation than is observed between dykes, indicating that the remanences of the other dykes are also primary. One of the normally magnetized dykes, the 700 km long Great Abitibi dyke, exhibits two primary directions that correspond to two geochemically distinct magma pulses. The five normally magnetized units, which consist of four separate dykes plus the second pulse of the Great Abitibi dyke, yield a well-defined mean paleomagnetic pole at 42.8°N, 151.5°W, dm = 16.3°, dp = 12.5°. It falls close to the reversely magnetized poles from the Keweenawan Track and establishes a minimum depth for the Logan Loop of about 40°. The reversed-polarity data from three other dykes are more scattered and may not average out secular variation. Hence, the present study is inconclusive regarding asymmetry of the Earth's magnetic field at 1141 Ma, even though a mean pole based on combined normal-and reversed-polarity dykes is indistinguishable from that based on normal-polarity dykes alone.

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Space weather effects on drilling accuracy in the North Sea

Annales Geophysicae ◽

10.5194/angeo-23-3081-2005 ◽

2005 ◽

Vol 23 (9) ◽

pp. 3081-3088 ◽

Cited By ~ 14

Author(s):

S. J. Reay ◽

W. Allen ◽

O. Baillie ◽

J. Bowe ◽

E. Clarke ◽

...

Keyword(s):

Magnetic Field ◽

External Field ◽

North Sea ◽

Survey Method ◽

Magnetic Observatory ◽

Magnetic Survey ◽

Earth’S Magnetic Field ◽

The North ◽

Earth's Magnetic Field ◽

The North Sea

Abstract. The oil industry uses geomagnetic field information to aid directional drilling operations when drilling for oil and gas offshore. These operations involve continuous monitoring of the azimuth and inclination of the well path to ensure the target is reached and, for safety reasons, to avoid collisions with existing wells. Although the most accurate method of achieving this is through a gyroscopic survey, this can be time consuming and expensive. An alternative method is a magnetic survey, where measurements while drilling (MWD) are made along the well by magnetometers housed in a tool within the drill string. These MWD magnetic surveys require estimates of the Earth's magnetic field at the drilling location to correct the downhole magnetometer readings. The most accurate corrections are obtained if all sources of the Earth's magnetic field are considered. Estimates of the main field generated in the core and the local crustal field can be obtained using mathematical models derived from suitable data sets. In order to quantify the external field, an analysis of UK observatory data from 1983 to 2004 has been carried out. By accounting for the external field, the directional error associated with estimated field values at a mid-latitude oil well (55° N) in the North Sea is shown to be reduced by the order of 20%. This improvement varies with latitude, local time, season and phase of the geomagnetic activity cycle. By accounting for all sources of the field, using a technique called Interpolation In-Field Referencing (IIFR), directional drillers have access to data from a "virtual" magnetic observatory at the drill site. This leads to an error reduction in positional accuracy that is close to matching that of the gyroscopic survey method and provides a valuable independent technique for quality control purposes.

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Roald Amundsen's contributions to our knowledge of the magnetic fields of the Earth and the Sun

History of Geo- and Space Sciences ◽

10.5194/hgss-2-99-2011 ◽

2011 ◽

Vol 2 (2) ◽

pp. 99-112

Author(s):

A. Egeland ◽

C. S. Deehr

Keyword(s):

Magnetic Field ◽

Analytical Techniques ◽

Short Review ◽

Polar Regions ◽

Earth’S Magnetic Field ◽

Late 20Th Century ◽

The North ◽

Earth's Magnetic Field ◽

Regular Manner

Abstract. Roald Amundsen (1872–1928) was known as one of the premier polar explorers in the golden age of polar exploration. His accomplishments clearly document that he has contributed to knowledge in fields as diverse as ethnography, meteorology and geophysics. In this paper we will concentrate on his studies of the Earth's magnetic field. With his unique observations at the polar station Gjøahavn (geographic coordinates 68°37'10'' N; 95°53'25'' W), Amundsen was first to demonstrate, without doubt, that the north magnetic dip-pole does not have a permanent location, but steadily moves its position in a regular manner. In addition, his carefully calibrated measurements at high latitudes were the first and only observations of the Earth's magnetic field in the polar regions for decades until modern polar observatories were established. After a short review of earlier measurements of the geomagnetic field, we tabulate the facts regarding his measurements at the observatories and the eight field stations associated with the Gjøa expedition. The quality of his magnetic observations may be seen to be equal to that of the late 20th century observations by subjecting them to analytical techniques showing the newly discovered relationship between the diurnal variation of high latitude magnetic observations and the direction of the horizontal component of the interplanetary magnetic field (IMF By). Indeed, the observations at Gjøahavn offer a glimpse of the character of the solar wind 50 yr before it was known to exist. Our motivation for this paper is to illuminate the contributions of Amundsen as a scientist and to celebrate his attainment of the South Pole as an explorer 100 yr ago.

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On certain average characteristics of world wide magnetic disturbance

Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character ◽

10.1098/rspa.1927.0090 ◽

1927 ◽

Vol 115 (771) ◽

pp. 242-267 ◽

Cited By ~ 30

Keyword(s):

Magnetic Field ◽

Diurnal Variation ◽

Local Time ◽

World Wide ◽

Magnetic Storms ◽

The Other ◽

Magnetic Disturbance ◽

Earth’S Magnetic Field ◽

Earth's Magnetic Field ◽

Three Components

1. This paper forms a sequel to one entitled “An Outline of a Theory of Magnetic Storms,” published several years ago. In that paper I determined the average additional variations in the three components of the earth's magnetic field (for observatories in magnetic latitudes up to about 60°N.) which during times of considerable magnetic disturbance—commonly called magnetic storms —are superposed on the normal variations. The storms dealt with were such as had a commencement sufficiently definite for its epoch to be estimated to within an hour. The average additional variations of the field were shown to be separable into two parts, one depending on “storm-time” (that is, time reckoned from the commencement of the storm), and the other being a “diurnal” variation depending on local time. Besides these average variations there are, of course, less regular features peculiar to each individual storm.

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Observing Earth’s magnetic environment with the GRACE-FO mission

Earth Planets and Space ◽

10.1186/s40623-021-01364-w ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

C. Stolle ◽

I. Michaelis ◽

C. Xiong ◽

M. Rother ◽

Th. Usbeck ◽

...

Keyword(s):

Magnetic Field ◽

Local Time ◽

Noise Level ◽

High Amplitude ◽

Magnetic Data ◽

Storm Event ◽

Earth’S Magnetic Field ◽

Magnetic Field Model ◽

Earth's Magnetic Field ◽

The Mean

AbstractThe Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission carries magnetometers that are dedicated to enhance the satellite’s navigation. After appropriate calibration and characterisation of artificial magnetic disturbances, these observations are valuable assets to characterise the natural variability of Earth’s magnetic field. We describe the data pre-processing, the calibration, and characterisation strategy against a high-precision magnetic field model applied to the GRACE-FO magnetic data. During times of geomagnetic quiet conditions, the mean residual to the magnetic model is around 1 nT with standard deviations below 10 nT. The mean difference to data of ESA’s Swarm mission, which is dedicated to monitor the Earth’s magnetic field, is mainly within ± 10 nT during conjunctions. The performance of GRACE-FO magnetic data is further discussed on selected scientific examples. During a magnetic storm event in August 2018, GRACE-FO reveals the local time dependence of the magnetospheric ring current signature, which is in good agreement with results from a network of ground magnetic observations. Also, derived field-aligned currents (FACs) are applied to monitor auroral FACs that compare well in amplitude and statistical behaviour for local time, hemisphere, and solar wind conditions to approved earlier findings from other missions including Swarm. On a case event, it is demonstrated that the dual-satellite constellation of GRACE-FO is most suitable to derive the persistence of auroral FACs with scale lengths of 180 km or longer. Due to a relatively larger noise level compared to dedicated magnetic missions, GRACE-FO is especially suitable for high-amplitude event studies. However, GRACE-FO is also sensitive to ionospheric signatures even below the noise level within statistical approaches. The combination with data of dedicated magnetic field missions and other missions carrying non-dedicated magnetometers greatly enhances related scientific perspectives.

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