Earth's magnetic field

About: Earth's magnetic field is a research topic. Over the lifetime, 20360 publications have been published within this topic receiving 446747 citations. The topic is also known as: magnetic field of Earth & geomagnetic field.

The morphology of the electron distribution in the outer radiation zone and near the magnetospheric boundary as observed by Explorer 12

Abstract: The elliptic orbit satellite Explorer 12 made possible the routine survey of the heart of the outer radiation zone as well as the region of transition between the magnetosphere and interplanetary space on the sunward side of the earth by means of a variety of particle and magnetic field detectors. The data received from the SUI detectors during the entire 112-day lifetime have been comprehensively analyzed. Salient features observed include: confirmation of the enhancement of soft electron fluxes and diminution of hard electron fluxes in the outer zone during magnetically disturbed times; the outward motion of the outer zone hard electron maximum during periods of enhancement; confirmation of the general Chapman and Ferraro picture of a well-defined magnetosphere with compression of the geomagnetic field during the initial phases of magnetic storms; the existence of a layer of quasi-thermalized plasma immediately outside the magnetosphere; confirmation of the result of Frank and Van Allen that the contours of constant counting rate for electrons with E ≥ 40 kev tend to protrude outward near 90° from the subsolar point and draw closer to the earth on the night side; and general support for the result of Gringauz, Kurt, Moroz, and Shklovskii that there exists a region beyond some 8Re on the night side of the earth dominated by very-low-energy electrons.

Plasma Wave Observations with GEOTAIL Spacecraft

Abstract: The main scientific objectives of GEOTAIL Plasma Wave Instrument (PWI) are to investigate the characteristic features of wave phenomena which are generated by a variety of plasma processes occurring within the Earth's magnetosphere. The PWI measures plasma waves in the frequency range from 5.62 Hz to 800 kHz for the electric components and from 5.62 Hz to 12.5 kHz for the magnetic components. The instrument is composed of three distinct sets of receivers: (1) the Sweep Frequency Analyzer (SFA), (2) the Multi-Channel Analyzer (MCA) and (3) the Wave-Form Capture (WFC). The first two receivers are dedicated to wave spectra measurement, while the last one is used to capture actual wave forms of two electric and three magnetic field components for the measured plasma wave emissions. The present paper describes the PWI subsystems and their functions. We also report some results from initial observations made during the traversal of the geomagnetic tail and a skimming pass of the dayside magnetopause. These observational results are useful in providing a good overview of the PWI capabilities as well as elucidating the characteristic features of the wave spectra in these regions.

Middle latitude LF (40 kHz) phase variations associated with earthquakes for quiet and disturbed geomagnetic conditions

Abstract: The phase (P) and amplitude (A) anomalies in subionospheric LF signal (40 kHz) along the path Japan–Kamchatka of 2300 km have been studied for the data observed by means of a digital OminiPAL receiver for 2 years. The empirical model of background P and A daily variations for quiet and disturbed geomagnetic conditions in the absence of seismic activity is developed. We pay special attention to the P and A features during large magnetic storms. A sensitivity threshold of LF signal to deforming influence of the geomagnetic and seismic factors is defined. Two cases of bay-like behavior of LF phase and amplitude in nighttime are described as a clear earthquake precursor of LF signal. We have found from the statistical study that LF signal effect is observed only for earthquakes with M⩾5.5 and we discuss the possible mechanisms of the effect.

Dipolar reversal states of the geomagnetic field and core–mantle dynamics

Abstract: Palaeomagnetic records from lavas suggest that at least two specific inclined dipolar field configurations have dominated the reversal process for the past ten million years. These long-lived states provide a way to explain directional rebounds, aborted reversals and the recording in sediments of what appear to be preferred longitudinal paths of the virtual geomagnetic pole. The polar orientations correlate with near-radial flux concentrations recognizable when today's field is stripped of its axial dipole, and with lower-mantle seismic anomalies, suggesting a tie to deep-Earth dynamics.

Possible evidence of flux transfer events in the polar ionosphere

Abstract: We present magnetic field data from the cusp-latitude South Pole station that exhibit, under appropriate local time and interplanetary magnetic field conditions, the signature expected in the ionosphere from a flux transfer event (FTE) at the magnetopause. In particular, the model of multiple X-line reconnection at the magnetopause predicts field-aligned currents in helical flux tubes, with transverse magnetic fields propagating as Alfven waves toward the ionosphere. The distinctive magnetic signature at a polar cap magnetic station, particularly in the vertical component, can be used to infer the signs of the By and Bz components of the interplanetary magnetic field.