27-Day Recurrence Phenomena in the Geomagnetic Field at Alert

1971 ◽  
Vol 8 (11) ◽  
pp. 1382-1387 ◽  
Author(s):  
R. N. Edwards ◽  
R. D. Kurtz
Keyword(s):  
Power Spectrum ◽  
Geomagnetic Storm ◽  
Amplitude Modulation ◽  
Geomagnetic Field ◽  
Current System ◽  
Temporal Variations

The temporal variations of the geomagnetic field at Alert are studied for a two-year period during a minimum of the 11-year sun-spot cycle. During this period (27 August 1962 to 21 September 1964), a recurrent geomagnetic storm is observed, persisting for 29 solar rotations. It produces lines in the geomagnetic power spectrum at frequencies corresponding to the harmonics of 27 days. A further 13 lines, equispaced in frequency by (1/27) cycles/day, are associated with sidebands of the daily line and are believed to result from amplitude modulation of the SqP/DS current system.

scholarly journals An intense SFE and SSC event in geomagnetic <i>H</i>, <i>Y</i> and <i>Z</i> fields at the Indian chain of observatories

1997 ◽  
Vol 15 (10) ◽  
pp. 1301-1308 ◽  
Author(s):  
R. G. Rastogi ◽  
D. R. K. Rao ◽  
S. Alex ◽  
B. M. Pathan ◽  
T. S. Sastry
Keyword(s):  
Solar Flare ◽  
Geomagnetic Storm ◽  
Geomagnetic Field ◽  
Current System ◽  
Equatorial Electrojet ◽  
Start Time ◽  
Low Latitude ◽  
Ionospheric Current ◽  
Ionospheric Current System ◽  
Solar Flare Effects

Abstract. Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518 h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in ΔH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. ΔY registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. ΔZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.

scholarly journals Variability of Geomagnetic Field with Interplanetary Magnetic Field at Low, Mid and High Latitudes

2018 ◽  
Vol 10 (2) ◽  
pp. 133-144
Author(s):  
S. Bhardwaj ◽  
P. A. Khan ◽  
R. Atulkar ◽  
P. K. Purohit
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejection ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Storm ◽  
High Latitude ◽  
Geomagnetic Field ◽  
The State ◽  
High Latitudes ◽  
Storm Events ◽  
Mass Ejection

 The fluctuations in the Interplanetary Magnetic Field significantly affect the state of geomagnetic field particularly during the Coronal Mass Ejection (CME) events. In the present investigation we have studied the influence of Interplanetary Magnetic Field changes on the geomagnetic field components at high, low and mid latitudes. To carry out this investigation we have selected three stations viz. Alibag (18.6°N, 72.7°E), Beijing MT (40.3°N, 116.2°E) and Casey (66.2°S, 110.5°E) one each in the low, mid and high latitude regions. Then we selected geomagnetic storm events of three types namely weak (-50≤Dst≤-20), moderate (100≤Dst≤-50) and intense (Dst≤-100nT). In each storm category 10 events were considered. From our study we conclude that geomagnetic field components are significantly affected by the changes in the IMF at all the three latitudinal regions during all the storm events. At the same time we also found that the magnitude of change in geomagnetic field components is highest at the high latitudes during all types of storm events while at low and mid latitude stations the magnitude of effect is approximately the same.

scholarly journals Two-dimensional current-carrying plasma sheet in the near-Earth geomagnetic tail region:a quasi-stationary evolution

2003 ◽  
Vol 21 (12) ◽  
pp. 2259-2269 ◽  
Author(s):  
A. V. Manankova
Keyword(s):  
Current Sheet ◽  
Plasma Sheet ◽  
Geomagnetic Field ◽  
Exact Analytical Solution ◽  
Current System ◽  
Field Configuration ◽  
Transitional Region ◽  
Two Dimensional ◽  
Geomagnetic Tail ◽  
Magnetospheric Configuration And Dynamics

Abstract. A problem concerning stationary configurations of an inhomogeneous, current-carrying, two-dimensional plasma sheet as the solution of the Grad–Shafranov equation with boundary conditions given on cross-sheet profiles at the  foot of the sheet and at infinity is considered, with the aim of using its solution for the description of the interaction of two current systems: the current system of the geomagnetic field, and the tail currents. The obtained solution is an exact analytical solution which contains 5 independent parameters characterizing the intensity of the current sheet. As the solution is exact, it may be applied to describe the most interesting transitional magnetospheric region: that of a strong interaction between the magnetic fields of the geodipole and of the current sheet, i.e. the region where characteristic scales of the change of all variables along and across the sheet are of the same order. This makes it possible to model the structure of the transitional region and its dynamics under quasi-stationary variation of the input parameters. The obtained solution describes the principal processes developing at various phases of magnetospheric disturbances, such as (1) formation of a very intense thin current sheet localized within the transition region, (2) changing from the quasi-dipolar magnetic field to the configuration when a "neck" is formed in this region. An important feature of the obtained solution is the existence of a critical value of one of the parameters of the problem, which leads to the change in the geomagnetic field configuration described above. The solution can be used as an initial condition in simulating dynamical processes in the magnetotail current sheet, as well as in testing the current sheet stability. In the summary a series of limitations in the model problem under consideration is discussed. Key words. Magnetospheric physics (magnetotail; plasma sheet; magnetospheric configuration and dynamics)

scholarly journals FEATURES OF EXCITATION AND AZIMUTHAL AND MERIDIONAL PROPAGATION OF LONG-PERIOD Pi3 OSCILLATIONS OF THE GEOMAGNETIC FIELD ON DECEMBER 8, 2017

2020 ◽  
Vol 6 (3) ◽  
pp. 56-72
Author(s):  
Aleksey Moiseev ◽  
Sergei Starodubtsev ◽  
Vladimir Mishin
Keyword(s):  
Geomagnetic Field ◽  
Large Scale ◽  
Current System ◽  
Dynamic Pressure ◽  
Small Scale ◽  
Frequency Range ◽  
Latitude Range ◽  
Magnetospheric Convection ◽  
Long Period ◽  
Geomagnetic Observations

We study the Pi3 pulsations (with a period T=15–30 min) that were recorded on December 8, 2017 at ground stations in the midnight sector of the magnetosphere at the latitude range of DP2 current system convective electrojets. We have found that Pi3 are especially pronounced in the pre-midnight sector with amplitude of up to 300 nT and duration of up to 2.5 hrs. The pulsation amplitude rapidly decreased with decreasing latitude from F′=72° to F′=63°. The event was recorded during the steady magnetospheric convection. In the southward Bz component of the interplanetary magnetic field, irregular oscillations were detected in the Pi3 frequency range. They correspond to slow magnetosonic waves occurring without noticeable variations in the dynamic pressure Pd. Ground-based geomagnetic observations have shown azimuthal propagation of pulsations with a 0.6–10.6 km/s velocity east and west of the midnight meridian. An analysis of the dynamics of pulsations along the meridian has revealed their propagation to the equator at a velocity 0.75–7.87 km/s. In the projection onto the magnetosphere, the velocities are close in magnitude to the observed propagation velocities of substorm injected electrons. In the dawn-side magnetosphere during ground-observed Pi3 pulsations, compression mode oscillations were recorded. We conclude that propagation of geomagnetic field oscillations in this event depends on the dynamics of particle injections under the action of a large-scale electric field of magnetospheric convection, which causes the plasma to move to Earth due to reconnection in the magnetotail. Small-scale oscillations in the magnetosphere were secondary, excited by the solar wind oscillations penetrating into the magnetosphere.

scholarly journals GEOMAGNETIC EFFECT OF TURKISH EARTHQUAKE OF JANUARY 24, 2020

2020 ◽  
Vol 25 (4) ◽  
pp. 276-289
Author(s):  
Y. Luo ◽  
◽  
L. F. Chernogor ◽  
K. P. Garmash ◽  
◽  
...  
Keyword(s):  
Fourier Transform ◽  
Flash Memory ◽  
Geomagnetic Field ◽  
Temporal Variations ◽  
Fixed Number ◽  
Mhd Waves ◽  
Geomagnetic Disturbances ◽  
Period Range ◽  
Geomagnetic Effect ◽  
S Period

Purpose:The main cause of geomagnetic disturbances are cosmic sources, processes acting in the solar wind and in the interplanetary medium, as well as large celestial bodies entering the terrestrial atmosphere. Earthquakes (EQs) also act to produce geomagnetic effects. In accordance with the systems paradigm, the Earth–atmosphere–ionosphere–magnetosphere system (EAIMS) constitute a unified system, where positive and negative couplings among the subsystems, as well as feedbacks and precondition among the system components take place. The mechanisms for the action of EQs and processes acting in the lithosphere on the geomagnetic field are poorly understood. It is considered that the EQ action is caused by cracking of rocks, fluctuating motion in the pore fluid, static electricity discharges, etc. In the course of EQs, the seismic, acoustic, atmospheric gravity waves (AGWs), and magnetohydrodynamic (MHD) waves are generated. The purpose of this paper is to describe the magnetic effects of the EQ, which took place in Turkey on 24 January 2020. Design/methodology/approach: The measurements are taken with the fluxmeter magnetometer delivering 0.5-500 pT sensitivity in the 1-1000 s period range, respectively, and in a wide enough studied frequency band within 0.001 to 1 Hz. The EM-II magnetometer with the embedded microcontroller digitizes the magnetometer signals and performs preliminary filtering over 0.5 s time intervals, while the external flash memory is used to store the filtered out magnetometer signals and the times of their acquisition. To investigate quasi-periodic processes in detail, the temporal variations in the level of the H and D components of the geomagnetic field were applied to the systems spectral analysis, which makes use of the short-time Fourier transform, the wavelet transform using the Morlet wavelet as a basis function, and the Fourier transform in a sliding window with a width adjusted to be equal to a fixed number of harmonic periods. Findings: The train of oscillations in the level of the D component observed 25.5 h before the EQ on 23 January 2020 is supposed to be associated with the magnetic precursor. The bidirectional pulse in the H component observed on 24 January 2020 could be due to the piston action of the EQ, which had generated an MHD pulse. The quasi-periodic variations in the level of the H and D components of the geomagnetic field, which followed 75 min after the EQ, were caused by a magnetic disturbance produced by the traveling ionospheric disturbances due to the AGWs launched by the EQ. The magnetic effect amplitude was estimated to be close to 0.3 nT, and the quasi-period to be 700-900 s. The amplitude of the disturbances in the electron density in the AGW field was estimated to be about 8 % and the period of 700-900 s. Damping oscillations in both components of the magnetic field were detected to occur with a period of approximately 120 s. This effect is supposed to be due to the shock wave generated in the atmosphere in the course of the EQ. Conclusions: The magnetic variations associated with the EQ and occurring before and during the EQ have been studied in the 1-1000 s period range. Key words: earthquake, fluxmeter magnetometer, quasi-periodic disturbance, seismic wave, acoustic-gravity wave, MHD pulse

Temporal variations in the bioenergetic reserves of Concholepas concholepas (Gastropoda: Muricidae) in contrasting coastal environments from the Humboldt current system

2021 ◽  
Vol 167 ◽  
pp. 101970 ◽  
Author(s):  
Jorge Lazo-Andrade ◽  
Fabián A. Guzmán-Rivas ◽  
Pepe Espinoza ◽  
M. Roberto García-Huidobro ◽  
Marcela Aldana ◽  
...  
Keyword(s):  
Current System ◽  
Temporal Variations ◽  
Coastal Environments ◽  
Humboldt Current ◽  
Concholepas Concholepas ◽  
Humboldt Current System

Investigation of the ionospheric plasma parameters variations in the range of planetary waves periods using Warsaw ionosonde and Belsk observatory data

2021 ◽  
Author(s):  
Svetlana Riabova ◽  
Sergei Shalimov
Keyword(s):  
Geomagnetic Field ◽  
Planetary Wave ◽  
Critical Frequency ◽  
Winter Season ◽  
Temporal Variations ◽  
Planetary Waves ◽  
Polish Academy ◽  
Neutral Atmosphere ◽  
Plasma Parameters ◽  
Academy Of Sciences

&lt;p&gt;There has long been interest in the sources of ionospheric variability, especially in how this variability can be caused by the dynamics of the neutral atmosphere. Many studies have found planetary wave fluctuations in ionospheric parameters, especially f0F2, with periods ranging from 2 to 20 days. We investigate variations of the geomagnetic field and critical frequency of the F2-layer in the range of planetary waves in winter. We used the data of geomagnetic monitoring at the Central Geophysical Observatory at Belsk of Institute of Geophysics of the Polish Academy of Sciences (Poland, Belsk) and the results of high-frequency sounding of the ionosphere in the form of ionograms obtained by the Space Research Center of the Polish Academy of Sciences (Poland, Warsaw).&amp;#160; In the spectra of temporal variations of the geomagnetic field and the critical frequency of the ionospheric F2 layer in the range of planetary waves periods in winter season, we found both harmonics associated with the modulation effect of longer-period (annual and 11-year) variations and tidal effects, and a harmonic corresponding to a quasi 16-day planetary wave. Possible mechanisms of their manifestations in the upper atmosphere are discussed.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document