Annual variations of the amplitude characteristic of the noise magnetic field in the ELF frequency range based on the results of high-latitude observations

2014 ◽  
Vol 54 (5) ◽  
pp. 640-644
Author(s):  
V. V. Pchelkin
Keyword(s):  
Magnetic Field ◽  
High Latitude ◽  
Amplitude Characteristic ◽  
Frequency Range ◽  
Annual Variations

scholarly journals Interplanetary magnetic field control of Saturn's polar cusp aurora

2005 ◽  
Vol 23 (4) ◽  
pp. 1405-1431 ◽  
Author(s):  
E. J. Bunce ◽  
S. W. H. Cowley ◽  
S. E. Milan
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Field Line ◽  
High Latitude ◽  
Closed Field ◽  
Vortical Flows ◽  
Dayside Magnetopause ◽  
Closed Field Line ◽  
Lobe Reconnection

Abstract. Dayside UV emissions in Saturn's polar ionosphere have been suggested to be the first observational evidence of the kronian "cusp" (Gérard et al., 2004). The emission has two distinct states. The first is a bright arc-like feature located in the pre-noon sector, and the second is a more diffuse "spot" of aurora which lies poleward of the general location of the main auroral oval, which may be related to different upstream interplanetary magnetic field (IMF) orientations. Here we take up the suggestion that these emissions correspond to the cusp. However, direct precipitation of electrons in the cusp regions is not capable of producing significant UV aurora. We have therefore investigated the possibility that the observed UV emissions are associated with reconnection occurring at the dayside magnetopause, possibly pulsed, akin to flux transfer events seen at the Earth. We devise a conceptual model of pulsed reconnection at the low-latitude dayside magnetopause for the case of northwards IMF which will give rise to pulsed twin-vortical flows in the magnetosphere and ionosphere in the vicinity of the open-closed field-line boundary, and hence to bi-polar field-aligned currents centred in the vortical flows. During intervals of high-latitude lobe reconnection for southward IMF, we also expect to have pulsed twin-vortical flows and corresponding bi-polar field-aligned currents. The vortical flows in this case, however, are displaced poleward of the open-closed field line boundary, and are reversed in sense, such that the field-aligned currents are also reversed. For both cases of northward and southward IMF we have also for the first time included the effects associated with the IMF By effect. We also include the modulation introduced by the structured nature of the solar wind and IMF at Saturn's orbit by developing "slow" and "fast" flow models corresponding to intermediate and high strength IMF respectively. We then consider the conditions under which the plasma populations appropriate to either sub-solar reconnection or high-latitude lobe reconnection can carry the currents indicated. We have estimated the field-aligned voltages required, the resulting precipitating particle energy fluxes, and the consequent auroral output. Overall our model of pulsed reconnection under conditions of northwards and southwards IMF, and for varying orientations of IMF By, is found to produce a range of UV emission intensities and geometries which is in good agreement with the data presented by Gérard et al. (2004). The recent HST-Cassini solar wind campaign provides a unique opportunity to test the theoretical ideas presented here.

scholarly journals Birkeland current effects on high‐latitude ground magnetic field perturbations

2015 ◽  
Vol 42 (18) ◽  
pp. 7248-7254 ◽  
Author(s):  
K. M. Laundal ◽  
S. E. Haaland ◽  
N. Lehtinen ◽  
J. W. Gjerloev ◽  
N. Østgaard ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Latitude ◽  
Ground Magnetic

NATIONAL SECURITY AND SOLAR-TERRESTRIAL COUPLING

2021 ◽  
Vol 4 (1) ◽  
pp. 24-34
Author(s):  
A.V. Volkov ◽  
◽  
A.A. Khadartsev ◽  
L.V. Kashintseva ◽  
O.A. Sedova ◽  
...  
Keyword(s):  
Public Health ◽  
Magnetic Field ◽  
National Security ◽  
Economic Security ◽  
The State ◽  
Complex Dynamic ◽  
Scientific Publications ◽  
Annual Variations ◽  
Biological Environment ◽  
Small Disturbances

The paper presents the results of the analysis of scientific publications in order to identify heliogeophysical interactions and their impact on the state of biospheric processes. It is demonstrated that small disturbances in the biological environment lead to global process-es with little predictable consequences that radically change politics, economics and public health. These processes pose a serious threat to national and economic security. The studies have shown that the Earth's ionosphere is a complex dynamic system, the state of which is de-termined not only by the parameters of the atmosphere itself, but also by variations in helium and geomagnetic factors. Investigation of interrelated processes in the lower and upper lay-ers of the atmosphere is one of the priority geophysical and meteorological tasks. Key words: solar activity, heliogeophysical interactions; the Earth's magnetic field; interplanetary field; annual variations; cosmic rays.

The variability of naturally occurring magnetic field levels: 10 Hz to 8 kHz

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. F187-F197 ◽  
Author(s):  
Ben K. Sternberg
Keyword(s):  
Magnetic Field ◽  
Noise Level ◽  
Monsoon Season ◽  
Signal Frequency ◽  
Time Interval ◽  
Frequency Range ◽  
Noise Levels ◽  
Controlled Source ◽  
Naturally Occurring ◽  
Minimum Noise

The variability of naturally occurring magnetic fields in the frequency range from [Formula: see text] over a period of one year was studied. Contour plots for the [Formula: see text], [Formula: see text], and [Formula: see text] components and for frequencies of 10, 100, 1000, 2000, and 8000 Hz were produced. Average, minimum, maximum, and the standard deviations of these fields were also calculated for 12 distinctive time intervals. In the 1– to 8–kHz frequency range, the noise levels are typically higher at night. In the 10- to 100-Hz frequency range, the noise levels are typically higher during the day. During mid- to late-summer, there is frequent thunderstorm activity, known in the southwest United States as the monsoon season. The magnetic field levels are often very high during this time period. These variability ranges can be used to estimate the lowest levels of noise that may be encountered during field surveys, which iswhat the authors are looking for when running controlled-source electrical method surveys. These variability ranges can also be used to estimate the highest levels that may be encountered, which is what the authors are looking for when running natural-source electrical methods surveys, such as audio frequency magnetotelluric (AMT) surveys. These measurements of magnetic field strength variability show that better data for controlled-source electrical measurements can be obtained using the minimum noise level measurements, as opposed to using signal integration or signal averaging with all of the data. The minimum noise level is found by using frequency bins adjacent to the signal-frequency bin. Likewise, if one is interested in measuring the naturally occurring magnetic field data, using the maximum values during each time interval makes AMT measurements possible when the natural signal level is very low, particularly in the AMT dead zone around [Formula: see text].

Absorption of hydromagnetic waves in the ionosphere

1970 ◽  
Vol 48 (3) ◽  
pp. 362-366
Author(s):  
M. Abbas
Keyword(s):  
Magnetic Field ◽  
Frequency Range ◽  
Parallel Propagation ◽  
Hydromagnetic Waves ◽  
The Magnetic Field

Absorption of hydromagnetic waves in the ionosphere propagated normal to the magnetic field is calculated at various frequencies and compared with the absorption for parallel propagation. Data corresponding to both daytime and nighttime ionospheres are used. Waves propagated normal to the magnetic field are highly absorbed through the daytime ionosphere at frequencies above a few Hz; the nighttime ionosphere, however, is virtually transparent to waves in the frequency range of 10−3 to 20 Hz. A comparison of the absorption processes for waves propagated parallel and normal to the magnetic field is made.

scholarly journals High Frequency Magnetoimpedance of FeNi/Cu/FeNi Sensitive Elements with Different Geometries

2009 ◽  
Vol 152-153 ◽  
pp. 373-376 ◽  
Author(s):  
Stanislav O. Volchkov ◽  
Andrey V. Svalov ◽  
G.V. Kurlyandskaya
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
External Magnetic Field ◽  
Finite Elements ◽  
Magnetic Anisotropy ◽  
Constant Magnetic Field ◽  
High Frequency ◽  
Complex Impedance ◽  
Rf Sputtering ◽  
Frequency Range

In this work magnetoimpedance (MI) behaviour was studied experimentally for Fe19Ni81(175 nm)/Cu(350 nm)/Fe19Ni81(175 nm) sensitive elements deposited by rf-sputtering. A constant magnetic field was applied in plane of the sandwiches during deposition perpendicular to the Cu-lead in order to induce a magnetic anisotropy. Sandwiches with different width (w) of FeNi parts were obtained. The complex impedance was measured as a function of the external magnetic field for a frequency range of 1 MHz to 700 MHz for MI elements with different geometries. Some of MI experimental data are comparatively analysed with finite elements numerical calculations data. The obtained results can be useful for optimization of the design of miniaturized MI detectors.

scholarly journals A broadband two axis flux-gate magnetometer

1998 ◽  
Vol 41 (3) ◽  
Author(s):  
P. Palangio
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
High Sensitivity ◽  
Magnetic Sensors ◽  
Frequency Range ◽  
Field Station ◽  
Low Weight ◽  
Highly Sensitive ◽  
Flux Gate ◽  
Magnetic Field Variations

A broadband two axis flux-gate magnetometer was developed to obtain high sensitivity in magnetotelluric measurements. In magnetotelluric sounding, natural low frequency electromagnetic fields are used to estimate the conductivity of the Earth's interior. Because variations in the natural magnetic field have small amplitude(10-100 pT) in the frequency range 1 Hz to 100 Hz, highly sensitive magnetic sensors are required. In magnetotelluric measurements two long and heavy solenoids, which must be installed, in the field station, perpendicular to each other (north-south and east-west) and levelled in the horizontal plane are used. The coil is a critical component in magnetotelluric measurements because very slight motions create noise voltages, particularly troublesome in wooded areas; generally the installation takes place in a shallow trench. Moreover the coil records the derivative of the variations rather than the magnetic field variations, consequently the transfer function (amplitude and phase) of this sensor is not constant throughout the frequency range 0.001-100 Hz. The instrument, developed at L'Aquila Geomagnetic Observatory, has a flat response in both amplitude and phase in the frequency band DC-100 Hz, in addition it has low weight, low power, small volume and it is easier to install in the field than induction magnetometers. The sensivity of this magnetometer is 10 pT rms.

scholarly journals Смена знака магнитоемкости в парамагнитной области в катион-замещенном селениде марганца

2018 ◽  
Vol 60 (4) ◽  
pp. 670
Author(s):  
С.С. Аплеснин ◽  
М.Н. Ситников ◽  
А.М. Живулько
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Magnetic Susceptibility ◽  
Dielectric Loss ◽  
Dielectric Permittivity ◽  
Room Temperature ◽  
Frequency Range ◽  
Wagner Model ◽  
Paramagnetic Region ◽  
Orbital Electron

AbstractThe capacity and the dielectric loss tangent of a Gd_ x Mn_1– x Se ( x ≤ 0.2) solid solution have been measured in the frequency range 1–300 kHz without a magnetic field and in a magnetic field of 8 kOe in the temperature range 100–450 K, and the magnetic moment of the solid solution has been measured in a field of 8.6 kOe. The magnetocapacity effect and the change in the magnetocapacity sign have been observed in room temperature in the paramagnetic region. A correlation of the changes in the dielectric permittivity and the magnetic susceptibility with temperature has been revealed. The magnetocapacity is described using the model with orbital electron ordering and the Maxwell–Wagner model.

scholarly journals Обнаружение высокочастотных альфвеновских колебаний в омических разрядах сферического токамака Глобус-М2

2021 ◽  
Vol 47 (12) ◽  
pp. 17
Author(s):  
И.М. Балаченков ◽  
Ю.В. Петров ◽  
В.К. Гусев ◽  
Н.Н. Бахарев ◽  
В.И. Варфоломеев ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Standing Wave ◽  
High Frequency ◽  
Low Density ◽  
Frequency Range ◽  
High Frequency Oscillations ◽  
Model Predictions ◽  
Mode Excitation ◽  
Order Of Magnitude ◽  
Frequency Chirping

In Globus-M2 ohmic discharges with low density, by means of Mirnov coils array, magnetic field oscillations with frequencies in 1 MHz range were detected. Frequency range of these oscillations significantly exceed the range of TAE and RSAE frequencies, which were previously observed on Globus-M and Globus-M2 tokamaks, and their amplitude, contrary, turned out to be up to an order of magnitude lower. It was found that high frequency oscillations are interrelated with suprathermal electron fraction. At the same time the observed instability seems to have Alfvenic nature, since its frequency correlates well with Alfven frequency scaling. It was also found that magnetic perturbation always forms standing wave with predominantly low toroidal wavenumbers, including n = 0 structure, which makes gap (e.g. TAE) mode excitation impossible. Frequency chirping during single bursts with δω ~ √t is consistent with hole-clump model predictions.

scholarly journals Practice and perspectives of using ultrasensitive magnetometers in biomedical research.

2021 ◽  
Author(s):  
Yu.V. Maslennikov ◽  
◽  
◽  
Keyword(s):  
Magnetic Field ◽  
Biomedical Research ◽  
Magnetic Measurements ◽  
Signal To Noise Ratio ◽  
Frequency Range ◽  
Optically Pumped ◽  
Technical Solutions ◽  
Further Development ◽  
The Magnetic Field

There are a large number of sensors for measuring the magnetic field of biological objects. They are characterized by the type of the measured physical parameter (magnetic field strength, magnetic flux, etc.), the level of intrinsic sensitivity, and the frequency range of the recorded signals. The long-term practice of studying biomagnetic signals shows that only SQUID-based magnetometers and optically pumped magnetometers have sensitivity levels sufficient for recording biomagnetic signals with the required signal-to-noise ratio. This chapter reflects the main directions of using such magnetometers and methods of magnetic measurements in biomedical research, gives examples of existing technical solutions, and shows possible ways of their further development.

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