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The results of comparative analysis of the behavior of paleointensity and polarity (intervals between reversals) of the geomagnetic field for the last 167 Ma are presented. Similarities and differences in the behavior of these characteristics of the geomagnetic field are discussed. It is shown that bursts of paleointensity and long intervals between reversals occurred at high mean values of paleointensity in the Cretaceous and Paleogene. However, there are differences between the paleointensity behavior and the reversal regime: (1) the characteristic times of paleointensity variations are less than the characteristic times of the frequency of geomagnetic reversals, (2) the achievement of maximum values of paleointensity at the Cretaceous-Paleogene boundary and the termination of paleointensity bursts after the boundary of 45-40 Ma are not marked by explicit features in the geomagnetic polarity behavior. [ABSTRACT FROM AUTHOR]

The M flare that arises after magnetic field emersion in a small spot is analyzed. The disturbance, which propagated downwards and generated a source of acoustic waves (sunquake), was simultaneous with an outburst of hard X-radiation. The reasons of such sunquakes are discussed. Rearrangement of the magnetic configuration in the analyzed event is confirmed: field lines and strong currents at low altitudes above the polarity boundary line are transformed into the currents along the system of loops oriented at wide angles to the neutral line. This rearrangement occurred in the proximity of a small region (sigmoid) presumably identified by the location of the primary pulse energy release. In this case, there was no development of a high-energy sigmoid flare with the formation and ejection of large-scale magnetized ropes. Apparently, this was hindered by the nonstationarity of the phenomena at this activity center with a magnetic field of composite topology and multiple flare-generating centers. [ABSTRACT FROM AUTHOR]

As an observational case study, we consider the origin of a prominent poleward surge of leading polarity, visible in the magnetic butterfly diagram during Solar Cycle 24. A new technique is developed for assimilating individual regions of strong magnetic flux into a surface-flux transport model. By isolating the contribution of each of these regions, the model shows the surge to originate primarily in a single high-latitude activity group consisting of a bipolar active region present in Carrington Rotations 2104 - 05 (November 2010 - January 2011) and a multipolar active region in Rotations 2107 - 08 (February - April 2011). This group had a strong axial dipole moment opposed to Joy's law. On the other hand, the modelling suggests that the transient influence of this group on the butterfly diagram will not be matched by a large long-term contribution to the polar field because it is located at high latitude. This is in accordance with previous flux-transport models. [ABSTRACT FROM AUTHOR]

The article discusses geomagnetic reversal and the consequences that may occur due to this problem. Topics discussed include relationship of magnetic field and geomagnetic reversal, geomagnetic field polarity, and magnetic field excursions. Also discussed is the analysis of Late Cretaceous–Cenozoic (C-sequence).

We consider the motion of high-energy charged particles (cosmic rays) in Parker's spiral magnetic field. We show that under radial particle ejection from a sphere outside which there is Parker's magnetic field, all of the particles escaping from the sphere are focused either along the field symmetry axis or in the equatorial plane, depending on the field polarity. Based on the results obtained, we propose a possible model that explains the origin of relativistic jets. [ABSTRACT FROM AUTHOR]

Our investigation has been carried using the instruments onboard the Solar Dynamics Observatory (SDO) providing a high resolution of images (AIA photographs and HMI magnetograms). We have investigated the structure and magnetic evolution of several coronal bright points and small scale N-S polarity magnetic fluxes closely associated with them. We also compare the evolution of the magnetic polarities of elementary isolated sources of positive and negative fluxes (magnetic bipoles) and coronal bright points. Tiny ('elementary') coronal bright points have been detected. A standard coronal bright point is shown to be a group of 'elementary' coronal bright points that flare up sequentially. Our investigation shows that a change in the magnetic fluxes of opposite polarities is observed before the flare of a coronal bright point. We show that not all cases of the formation of coronal bright points are described by the magnetic reconnection model. This result has not been considered previously and has not been pointed out by other authors. [ABSTRACT FROM AUTHOR]

We present the results of our new spectropolarimetric observations of FKCom aimed to measure the longitudinal component B of its magnetic field. The most interesting interpretation of our results suggests that the B value has significantly decreased compared to the 2008 observations of this star. Such a decrease of the longitudinal component of the magnetic field can be similar to the secular variations of B registered earlier for another chromospherically active star II Peg. On the other hand, assuming the existence of B variations with the rotation phase, we suggest that the variations of the phase curve B from 2008 to 2012 originated because of the strengthening of the negative polarity spot, its domination, and as a result-a generally more symmetric distribution of magnetic regions. [ABSTRACT FROM AUTHOR]

We present a method for generating isolated monopolar vortices in rotating tank experiments. The technique is based on the electromagnetic forcing commonly used in nonrotating systems, which consists of setting a vertical magnetic field-parallel to the rotation axis-and a horizontal density current in an electrolytic fluid layer. The magnetic field is provided by a permanent magnet placed underneath the central point of the fluid container, while a radial density current is established between a central electrode and a number of opposite-sign electrodes at the periphery. The resulting azimuthal Lorentz force creates a monopolar vortex. It is shown that the generated vortices are axisymmetric and isolated, that is, their total circulation is zero. Cyclonic or anticyclonic vortices can be generated by choosing the appropriate polarity of the electrodes or the orientation of the magnet. The strength of the vortices is regulated by the magnitude of the density current and by the forcing time. This method allows the systematic study of the unstable evolution of isolated vortices, which is characterized by the formation of multipolar vortices. [ABSTRACT FROM AUTHOR]

We analyzed transient Ca ii H brightening associated with small-scale canceling magnetic features (CMFs) in the quiet Sun near disk center using Ca ii H filter images and Na D magnetograms of Hinode/SOT. We found that in most Ca ii brightening events related to CMFs the Ca ii H intensity peaks after the magnetic flux cancellation. Moreover, the brightening tends to appear as a pair of bright points of similar size and brightness overlying a magnetic bipole. Then a new opposite polarity fragment moves to them and cancels out. These results imply that magnetic reconnection takes place there and is responsible for CMFs. [ABSTRACT FROM AUTHOR]

This work aims at investigating unstable modes of oscillation of quasi-vertical two-dimensional current sheets with sheared magnetic fields under physical conditions typical for the solar corona. We use linear magnetohydrodynamic equations to obtain sets of unstable modes related to the longitudinal inhomogeneity of the current sheet. It is shown that these modes of current sheet oscillations can modulate the current sheet thickness along the polarity inversion line. Based on the obtained results, we propose a scenario which can naturally explain both the quasi-periodic pulsations of hard X-ray emission and the parallel movement of their double footpoint-like sources along the polarity inversion line observed in some eruptive two-ribbon solar flares. [ABSTRACT FROM AUTHOR]

In this paper, we examine the nature of the main source of the sporadic solar wind on the Sun: coronal mass ejections (CMEs). Analysis of data from Mark 3 and Mark 4, the Digital Prominence Monitor (MLSO), and STEREO (EUVI) spacecraft has revealed the existence of two types of CMEs: gradual and impulse. They differ in the place, velocity, and angular size at the instant of their emergence. The source of gradual CMEs is located in the corona, at a distance of 1.1 R < R ≤ 1.7 R from the center of the Sun. They start moving from a state of rest, having an angular size ≈15-65° (in the heliographic coordinate system). Impulse CMEs are probably formed under the Sun's photosphere. This may be due to the supersonic emergence of magnetic tubes (ropes) from the convective zone. The possibility of this phenomenon has been demonstrated earlier in theory. The radial velocity of such tubes at the photospheric level may be 100 km/s or higher; the minimum angular size is ∼1°. [ABSTRACT FROM AUTHOR]

We present detailed observations of the formations of four distinct coronal dimmings during a flare of 17 September 2002, which was followed by an eruption of a huge coronal loop system, and then an over-and-out partial halo coronal mass ejection (CME), with the same direction as the loop system eruption but laterally far offset from the flare site. Among the four dimmings, two compact ones were symmetrically located in the opposite polarity regions immediately adjacent to the highly sheared magnetic polarity inversion line in the flare region, and hence were probably composed of bipolar double dimmings due to a flux-rope eruption and represented its evacuated footpoints. However, another nearby compact dimming and a remote diffuse one were formed in the opposite polarity footpoint regions of the eruptive loop system, and thus probably consisted of a pair of dimmings magnetically linked by the erupting loop system and also indicated its evacuated footpoints. The loop system might have played a role in guiding the erupting flare field and producing the over-and-out CME, but its eruption might simply have been pushed out by the erupting flare field, because there was no reconnection signature between them. From comparison with a derived potential-field source-surface (PFSS) magnetic configuration, our observations consistently suggest that the dimmings were formed in pairs and originated from the eruptions of the two different magnetic systems. We thus define them as 'quadrupolar dimmings.' [ABSTRACT FROM AUTHOR]

Solar filaments show the position of large-scale polarity-inversion lines and are used for the reconstruction of large-scale solar magnetic field structure on the basis of Hα synoptic charts for the periods that magnetographic measurements are not available. Sometimes crossing filaments are seen in Hα filtergrams. We analyze daily Hα filtergrams from the archive of Big Bear Solar Observatory for the period of 1999 - 2003 to find crossing and interacting filaments. A number of examples are presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in the corona. [ABSTRACT FROM AUTHOR]

In a vortex-state magnetic nanodisc, the static magnetization curls in the plane, except in the core region, where it points out of plane, either up or down, leading to two possible stable states of opposite core polarity p. Dynamical reversal of p by large-amplitude motion of the vortex core has recently been demonstrated experimentally, raising the prospect of practical applications, in particular in magnetic-storage devices. Here we demonstrate coherent control of p by single- and double-microwave-pulse sequences, taking advantage of the resonant vortex dynamics in a perpendicular-bias magnetic field. Experimental optimization of the microwave-pulse duration required for switching p also yields information about the characteristic decay time of the vortex core in the large-oscillation regime. This time is found to be less than half the length seen in the small-oscillation regime, suggesting a nonlinear behaviour of magnetic dissipation. [ABSTRACT FROM AUTHOR]

Theoretical and experimental results are considered that explain the type of the signal from a flaw in a ferromagnetic object that is tangentially magnetized by successively applied oppositely oriented fields in the course of its magnetographic inspection. [ABSTRACT FROM AUTHOR]

This paper considers the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields and polar activity. Such indices include: dipole–octopole index, area and average latitude of the field with dominant polarity in each hemisphere, polar activity seen in polar faculae and Ca ii K line bright points, coronal emission line intensity (5303 Å) and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle. The obtained relationships allow us to presume that the polar field is formed from the sources of both preceding and the current activity cycles during the decay phase and at the activity minimum. The balance in these sources would therefore determine the features of the following sunspot cycle. The prediction for the 24th activity cycle using these results leads to W=102±13. [ABSTRACT FROM AUTHOR]

The cells of photospheric background magnetic fields during Carrington rotation 2009 in October–November 2003 are considered. The small number of large sunspots and the high activity on the Sun in this period allow the correspondence between the activity of background field cells (flares) and the appearance of coronal mass ejections (CMEs) observed with the LASCO coronagraphs to be established without statistical analyses. The sunspots of opposite polarities in one background field cell are shown to serve as the legs of the same CME. The separation between them is close to 30°. [ABSTRACT FROM AUTHOR]

Electron motion in magnetic field of dipole imitating straight magnet (undulator consists of such magnets with reversing polarity along 0y placed periodically) is studied. We consider it on the basis of quantum description. [ABSTRACT FROM AUTHOR]

The article presents questions and answers related to earth science including magnetic field on earth, the polarity on earth, and connection between magnetic field reverse behavior and plate tectonics.

The polarity sign imbalance of the photospheric magnetic field is examined using synoptic maps produced by the Kitt Peak National Solar Observatory (NSO) (1976 - 2016). An imbalance of fluxes with opposite sign polarities is analyzed for a field strength B>50 G in the sunspot zone at latitudes 5∘-40∘ and for a field strength B<50 G at higher latitudes 40∘-90∘. A 22-year periodicity in the imbalance of positive and negative fluxes is found; this periodicity is maintained during four solar cycles. While for the sunspot zone the sign of the imbalance always agrees with the polarity sign of the northern hemisphere polar field, for the high latitudes the sign of the imbalance always agrees with the polarity sign of the southern hemisphere polar field. A good agreement of the imbalance of high-latitude fields with the quadrupole moment of the photospheric magnetic field g20 is observed and also holds for the low-latitude fields, but with a reversed sign, i.e.−g20. The polarity sign imbalance of the sunspot zone correlates with the Sun's mean magnetic field on the one hand, and with the sector structure of the heliospheric magnetic field on the other. The obtained results clearly show the interconnection of the magnetic fields in the activity zone with the Sun's polar magnetic field. The weakest fields B<5 G represent quite a special group, with the magnetic flux developing in antiphase to the fluxes of the stronger fields. [ABSTRACT FROM AUTHOR]