Equatorial auroral records reveal dynamics of the paleo-West Pacific geomagnetic anomaly

Localized regions of low geomagnetic intensity such as the South Atlantic Anomaly allow energetic particles from the Van Allen radiation belt to precipitate into the atmosphere and have been linked to a signature in the form of red aurora–like airglow visible to the naked eye. Smoothed global geomagnetic models predict a low-intensity West Pacific Anomaly (WPA) during the sixteenth to nineteenth centuries characterized by a simple time dependence. Here, we link the WPA to an independent database of equatorial aurorae recorded in Seoul, South Korea. These records show a complex fluctuating behavior in auroral frequency, whose overall trend from 1500 to 1800 AD is consistent with the locally weak geomagnetic field of the WPA, with a minimum at 1650 AD. We propose that the fluctuations in auroral frequency are caused by corresponding and hitherto unknown fluctuations in the regional magnetic intensity with peaks at 1590 and 1720 AD, a time dependence that has been masked by the smoothing inherent in regularized global geomagnetic models. A physical core flow model demonstrates that such behavior requires localized time-dependent upwelling flows in the Earth’s core, possibly driven by regional lower-mantle anomalies.

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Time-dependence of the spatial pattern of accumulation rate in East Antarctica deduced from isochronic radar layers using a 3-D numerical ice flow model

Journal of Geophysical Research Atmospheres ◽

10.1029/2010jf001785 ◽

2011 ◽

Vol 116 (F2) ◽

Cited By ~ 22

Author(s):

Gwendolyn J.-M. C. Leysinger Vieli ◽

Richard C. A. Hindmarsh ◽

Martin J. Siegert ◽

Sun Bo

Keyword(s):

Spatial Pattern ◽

Time Dependence ◽

Flow Model ◽

Accumulation Rate ◽

East Antarctica ◽

Ice Flow

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Effect of quantum fluctuations on soliton regimes in microlasers

Journal of Physics Conference Series ◽

10.1088/1742-6596/2103/1/012150 ◽

2021 ◽

Vol 2103 (1) ◽

pp. 012150

Author(s):

S V Fedorov ◽

N N Rosanov ◽

N A Veretenov

Keyword(s):

Hopf Bifurcation ◽

Time Dependence ◽

Theoretical Investigation ◽

Stochastic Equation ◽

Quantum Fluctuations ◽

Low Intensity ◽

Explicit Expressions

Abstract We present a theoretical investigation of effect of quantum fluctuations on laser solitons. Derivation of the stochastic equation, linearized with respect to quantum perturbations is carried out and the solutions are found. Explicit expressions are obtained for the time dependence of the soliton coordinates and momentum dispersion (variance) for perturbations averaged over the reservoir. It is shown that the dispersion of the soliton momentum becomes constant. It is shown that the dispersion of quantum perturbations tends to infinity near the Andronov-Hopf bifurcation threshold. The magnitude of quantum perturbations near the threshold of the appearance of hysteresis is estimated. It is shown that quantum perturbations do not significantly noise the soliton profile even with a very low intensity tending to zero. The number of photons in such solitons without supporting radiation, can reach unity.

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PENELITIAN GAYABERAT DAN GEOMAGNIT KEPULAUAN ARU, CEKUNGAN WOKAM

JURNAL GEOLOGI KELAUTAN ◽

10.32693/jgk.12.1.2014.241 ◽

2016 ◽

Vol 12 (1) ◽

pp. 1

Author(s):

Tatang Patmawidjaya ◽

Subagio Subagio

Keyword(s):

Gravity Anomaly ◽

Normal Fault ◽

High Gravity ◽

The South ◽

Shallow Subsurface ◽

The North ◽

Residual Gravity Anomaly ◽

Geomagnetic Anomaly ◽

Geomagnetic Models ◽

Geomagnetic Anomalies

Paparan Arafura di bagian selatan Kepulauan Aru merupakan depresi Lempeng Indo-Australia yang ditunjukkan oleh anomali gayaberat dan geomagnet tinggi. Sedangkan depresi di bagian utara yang tertahan Palung Aru diperlihatkan oleh anomali gayaberat tinggi dan anomali geomagnet rendah. Anomali ini diduga sebagai penebalan batuan metamorf yang mengalami pangangkatan sebagai alas cekungan Wokam. Analisis data gayaberat dan geomagnet mengindikasikan penurunan cekungan ini ke arah utara. Penurunan anomali gayaberat ke arah Pulau Wokam yang berarah baratdaya-timurlaut di selatan dan baratlaut-tenggara di daerah utara ditafsirkan sebagai struktur sesar. Hal ini dicirikan oleh arah sungai atau selat sebagai pemisah pulau-pulau di Kepulauan Aru. Anomali gayaberat residual mengindikasikan cekungan dan punggungan berarah baratdaya-timurlaut yang membentuk antiklin dan sinklin. Sesar dan lipatan ini menerus sebagai struktur geologi dangkal bawah permukaan. Berdasarkan pemodelan gayaberat dan geomagnet dapat dikatakan bahwa Cekungan Wokam cenderung menurun ke arah utara akibat sesar normal. Kata Kunci : gayaberat, geomagnet, pemodelan geologi, Cekungan Wokam Arafura Shelf in the southern part of the Aru Islands is a depression of the Indo-Australian crust at the south that indicated by high gravity and geomagnetic anomalies. While the northern depression blocked by the Aru Trough indicated by high gravity anomaly and low geomagnetic anomaly. These anomalies presumed as a thickening of the metamorphic rocks due to uplifting and acting as the basement of Wokam Basin. Gravity and geomagnetic analyses indicate a northward subsidence of the basin. The decreasing of the southwestâ€“northeast gravity anomaly in the south and the northwest-southeast in the north, interpreted as a fault. It this characterized by the river direction or strait as islands separation in Aru Archipilagoes. Residual gravity anomaly indicates a southwest-northeast basin and ridge form anticline and syncline. These faults and folds are continuous as the shallow subsurface geological structures. On the base gravity and geomagnetic models, it can be concluded that Wokam Basin tends to subside northward as the result of a normal fault. Keywords: gravity, geomagnetic, geological models, Wokam Basin

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Improvement of the Stability of X-Ray Emission by Thermal Excitation of a Pyroelectric Single Crystal

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.582.174 ◽

2013 ◽

Vol 582 ◽

pp. 174-177 ◽

Cited By ~ 1

Author(s):

Fumihiko Naruse ◽

Hiroyuki Honda ◽

Yoshikazu Nakanishi ◽

Shinji Fukao ◽

Yuuki Sato ◽

...

Keyword(s):

Time Dependence ◽

Temperature Cycle ◽

Cycle Period ◽

Thermal Excitation ◽

Crystal Temperature ◽

X Ray ◽

Low Intensity ◽

Creeping Discharge ◽

The Stability ◽

Pyroelectric Crystals

X-ray emission using pyroelectric crystals is intermittent, and has low intensity and stability. One of the factors for low stability is related to creeping discharge, due to the accumulation of surface electric charges that change in response to the temperature. The time dependence of the net amount of electric charge was investigated by changing the cycle period of the crystal temperature. The stability of the X-ray emission is demonstrated to be strongly dependent on the temperature cycle period.

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Siphon Flows in Stratified Coronal Loops

International Astronomical Union Colloquium ◽

10.1017/s0252921100025288 ◽

1994 ◽

Vol 144 ◽

pp. 185-187

Author(s):

S. Orlando ◽

G. Peres ◽

S. Serio

Keyword(s):

Heat Flux ◽

Scaling Laws ◽

Flow Model ◽

Supersonic Flows ◽

Coronal Loops ◽

Characteristic Parameters

AbstractWe have developed a detailed siphon flow model for coronal loops. We find scaling laws relating the characteristic parameters of the loop, explore systematically the space of solutions and show that supersonic flows are impossible for realistic values of heat flux at the base of the upflowing leg.

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The O–C diagrams of minor planets − a new approach to modelling the rotation

International Astronomical Union Colloquium ◽

10.1017/s0252921100031407 ◽

1999 ◽

Vol 173 ◽

pp. 185-188

Author(s):

Gy. Szabó ◽

K. Sárneczky ◽

L.L. Kiss

Keyword(s):

Error Analysis ◽

Time Dependence ◽

Theoretical Work ◽

Minor Planet ◽

Minor Planets ◽

New Approach ◽

Preliminary Results ◽

Ccd Observations

AbstractA widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.

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