scholarly journals A Magnetospheric Dichotomy for Pulsars with Extreme Inclinations

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 455
Author(s):  
Fan Zhang
Keyword(s):  
Magnetic Field ◽  
Pair Production ◽  
Small Range ◽  
Polar Cap ◽  
Stable Regime ◽  
Regime Changes ◽  
Period Derivative ◽  
High Fraction ◽  
Pulsar Wind ◽  
The Magnetic Field

In this work, we expand on a comment by Lyne et al. (2017), that intermittent pulsars tend to congregate near a stripe in the logarithmic period versus period-derivative diagram. Such a stripe represents a small range of polar cap electric potential. Taking into account also the fact (already apparent in their Figure 7, but not explicitly stated there) that high-fraction nulling pulsars also tend to reside within this and an additional stripe, we make the observation that the two stripes further match the “death lines” for double- and single-pole interpulses, associated with nearly orthogonal and aligned rotators, respectively. These extreme inclinations are known to suffer from pair production deficiencies, so we propose to explain intermittency and high-fraction nulling by reinvigorating some older quiescent (no pulsar wind or radio emission) “electrosphere” solutions. Specifically, as the polar potential drops below the two threshold bands (i.e., the two stripes), corresponding to the aligned and orthogonal rotators, their respective magnetospheres transition from being of the active pair-production-sustained-type into becoming the electrospheres, in which charges are only lifted from the star. The borderline cases sitting in the gap outside of the stable regime of either case manifest as high-fraction nullers. Hall evolution of the magnetic field inside orthogonally rotating neutron stars can furthermore drive secular regime changes, resulting in intermittent pulsars.

scholarly journals Lepton-driven Nonresonant Streaming Instability

2021 ◽  
Vol 923 (2) ◽  
pp. 208
Author(s):  
Siddhartha Gupta ◽  
Damiano Caprioli ◽  
Colby C. Haggerty
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetized Plasma ◽  
Ion Current ◽  
Pulsar Wind Nebulae ◽  
Particle In Cell ◽  
Streaming Instability ◽  
Electrons And Positrons ◽  
Pulsar Wind ◽  
The Magnetic Field

Abstract A strong super-Alfvénic drift of energetic particles (or cosmic rays) in a magnetized plasma can amplify the magnetic field significantly through nonresonant streaming instability (NRSI). While the traditional analysis is done for an ion current, here we use kinetic particle-in-cell simulations to study how the NRSI behaves when it is driven by electrons or by a mixture of electrons and positrons. In particular, we characterize the growth rate, spectrum, and helicity of the unstable modes, as well the level of the magnetic field at saturation. Our results are potentially relevant for several space/astrophysical environments (e.g., electron strahl in the solar wind, at oblique nonrelativistic shocks, around pulsar wind nebulae), and also in laboratory experiments.

scholarly journals Fallback Disks, Magnetars and Other Neutron Stars

2012 ◽  
Vol 8 (S290) ◽  
pp. 93-100 ◽  
Author(s):  
M. Ali Alpar ◽  
Ş. Çalışkan ◽  
Ü. Ertan
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Neutron Stars ◽  
Initial Conditions ◽  
Disk Model ◽  
Dipole Component ◽  
Salient Points ◽  
Period Derivative ◽  
The Magnetic Field ◽  
Broad Overview

AbstractThe presence of matter with angular momentum, in the form of a fallback disk around a young isolated neutron star will determine its evolution. This leads to an understanding of many properties of different classes of young neutron stars, in particular a natural explanation for the period clustering of AXPs, SGRs and XDINs. The spindown or spinup properties of a neutron star are determined by the dipole component of the magnetic field. The natural possibility that magnetars and other neutron stars may have different strengths of the dipole and higher multipole components of the magnetic field is now actually required by observations on the spindown rates of some magnetars. This talk gives a broad overview and some applications of the fallback disk model to particular neutron stars. Salient points are: (i) A fallback disk has already been observed around the AXP 4U 0142+61 some years ago. (ii) The low observed spindown rate of the SGR 0418+5729 provides direct evidence that the dipole component of the field is in the 1012G range. All properties of the SGR 0418+5729 at its present age can be explained by spindown under torques from a fallback disk. (iii) The anomalous braking index of PSR J1734-3333 can also be explained by the fallback disk model which gives the luminosity, period, period derivative and the period second derivative at the present age. (iv) These and all applications to a variety of other sources employ the same disk physics and evolution, differing only in the initial conditions of the disk.

CHARACTERISTIC AGE AND TRUE AGE OF PULSARS

2013 ◽  
Vol 23 ◽  
pp. 95-98
Author(s):  
LONG JIANG ◽  
CHENG-MIN ZHANG ◽  
ALI TANNI ◽  
HAI-HUI ZHAO
Keyword(s):  
Magnetic Field ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Millisecond Pulsar ◽  
Spin Period ◽  
Field Evolution ◽  
Period Derivative ◽  
The Difference ◽  
The Relationship ◽  
The Magnetic Field

Age of a pulsar is a useful parameter, but it is difficult to get the age from observation. We can only derive the characteristic age from the observed parameters: spin period (P) and period derivative (Ṗ). In this paper, we discussed the relationship between characteristic age and magnetic field of a pulsar. Monte Carlo simulation is also used to support the idea: it is useless to study the magnetic field evolution using characteristic age. From some observation evidences we get that: the characteristic age cannot be used as true age, especially for millisecond pulsar (MSP). The difference between them is also discussed. From the studying of breaking index and MSP's initial spin period (P0), we get the conclusion that: the problem cannot be resolved using different radiation models.

scholarly journals Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF: relation to reconnection pulses and FTE signatures

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1613-1640 ◽  
Author(s):  
M. Lockwood ◽  
A. Fazakerley ◽  
H. Opgenoorth ◽  
J. Moen ◽  
A. P. van Eyken ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Boundary Layer ◽  
Normal Component ◽  
Phase Speed ◽  
Propagation Delay ◽  
Polar Cap ◽  
Transfer Event ◽  
Field Lines ◽  
Pass Through ◽  
The Magnetic Field

Abstract. We study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ( [ XGSM, YGSM, ZGSM ] ≈ [ 2, 7, 9 ] RE). The events take place during an interval of northward IMF, as seen in the data from the ACE satellite and lagged by a propagation delay of 75 min that is welldefined by two separate studies: (1) the magnetospheric variations prior to the northward turning (Lockwood et al., 2001, this issue) and (2) the field clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth et al., 2001, this issue). With an additional lag of 16.5 min, the transient LLBL events correlate well with swings of the IMF clock angle (in GSM) to near 90°. Most of this additional lag is explained by ground-based observations, which reveal signatures of transient reconnection in the pre-noon sector that then take 10–15 min to propagate eastward to 15 MLT, where they are observed by Cluster. The eastward phase speed of these signatures agrees very well with the motion deduced by the cross-correlation of the signatures seen on the four Cluster spacecraft. The evidence that these events are reconnection pulses includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower latitudes; transient and travelling enhancements of the flow into the polar cap, imaged by the AMIE technique; and poleward-moving events moving into the polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15 satellite reveals that the open field lines near noon have been opened for some time: the more recently opened field lines were found closer to dusk where the flow transient and the poleward-moving event intersected the satellite pass. The events at Cluster have ion and electron characteristics predicted and observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with allowance for magnetospheric ion reflection at Alfvénic disturbances in the magnetopause reconnection layer. Like FTEs, the events are about 1 RE in their direction of motion and show a rise in the magnetic field strength, but unlike FTEs, in general, they show no pressure excess in their core and hence, no characteristic bipolar signature in the boundary-normal component. However, most of the events were observed when the magnetic field was southward, i.e. on the edge of the interior magnetic cusp, or when the field was parallel to the magnetic equatorial plane. Only when the satellite begins to emerge from the exterior boundary (when the field was northward), do the events start to show a pressure excess in their core and the consequent bipolar signature. We identify the events as the first observations of FTEs at middle altitudes.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions; solar wind-magnetosphere interactions)

scholarly journals On the Nature of Radio Eclipsing

2000 ◽  
Vol 177 ◽  
pp. 533-534
Author(s):  
Ya. N. Istomin
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Electric Current ◽  
Plasma Waves ◽  
Bow Shock ◽  
Companion Star ◽  
Atmosphere Density ◽  
Pulsar Wind ◽  
Transverse Electromagnetic ◽  
The Magnetic Field

AbstractIt is shown that the phenomena of radio eclipsing can be explained by the linear mechanism of transformation of the transverse electromagnetic wave, propagating in the pulsar wind, into the plasma waves in the region of interaction of wind with a companion star atmosphere. The coefficient of the passingηdepends on the wave frequencyωby the exponential mannerη= exp{–const ·ω−1}. The estimated scale for the pulsar wind and star’s atmosphere density gradients are of the order of 100 meters. Such gradient can be obtained in the bow shock forming when the pulsar wind enters into the companion star atmosphere. Annihilation of the part of the wind’s positrons with the star’s electrons produces the electric current. This current generates the magnetic field from which the pulsar wind’s particles are reflected. The magnitude of the magnetic field in this shock of about several Gauss.

scholarly journals Storm-time related mass density anomalies in the polar cap as observed by CHAMP

2010 ◽  
Vol 28 (1) ◽  
pp. 165-180 ◽  
Author(s):  
R. Liu ◽  
H. Lühr ◽  
S.-Y. Ma
Keyword(s):  
Magnetic Field ◽  
Geomagnetic Storms ◽  
Mass Density ◽  
Small Scale ◽  
Polar Cap ◽  
Ion Outflow ◽  
The North ◽  
Scale Field ◽  
Density Enhancement ◽  
The Magnetic Field

Abstract. Strong and localized thermospheric mass density events are observed in the polar cap region by the CHAMP satellites at about 400 km altitude during geomagnetic storms. During the 4 years considered (2002–2005) 29 storms with Dst<−100 nT occurred, in 90% of them polar cap density anomalies were detected. Based on the altogether 56 anomaly events a statistical analysis was performed. The anomalies are of medium scale (500–1500 km) and seem to have a short dwell-time (<1.5 h) in the polar cap. The relative density enhancement is found to range around 2 in both hemispheres. The peak density is in the Northern Hemisphere by a factor of 1.4 larger than in the southern. Also the number of detected events in the north is twice as large as that in the south (37 vs. 19). Mass density anomalies in the polar cap occur under all interplanetary magnetic field (IMF) directions. Numerous strong anomalies have been detected in positive and negative IMF Bz conditions when the magnetic field strength is above 5 nT. Rather few events occurred for small |Bz| (<5 nT) or for positive Bz combined with vanishing By. Some of the density anomalies are accompanied by intensive small-scale field-aligned currents (FACs). But about as many show no relation to FACs. If FACs are present there, the current density is believed to be correlated with the strength of the IMF Bz. Although this paper concentrates on the presentation of the observations, we show for one event that the ion outflow mechanism could be responsible for the mass density anomalies in the polar cap.

scholarly journals Pulsars with Strong Magnetic Fields: Polar Gaps, Bound Pair Creation and Nonthermal Luminosities

1995 ◽  
Vol 48 (4) ◽  
pp. 571 ◽  
Author(s):  
VV Usov ◽  
DB Melrose
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Thermionic Emission ◽  
Pair Creation ◽  
Radio Pulsars ◽  
Polar Cap ◽  
Polar Gap ◽  
Gap Models ◽  
The Magnetic Field ◽  
Frequency Radiation

Modifications to polar-gap models for pulsars are discussed for the case where the surface magnetic field, Bs, of the neutron star is strong. For B ~ 4 X 108 T, the curvature ,-quanta emitted tangentially to the curved force lines of the magnetic field are captured near the threshold of bound pair creation and are channelled along the magnetic field as bound electron-positron pairs (positronium). The stability of such bound pairs against ionization by the parallel electric field,. Ell' in the polar cap, and against photoionization is discussed. Unlike free pairs, bound pairs do not screen Ell near the neutron star. As a consequence, the energy flux in highly relativistic particles and high-frequency (X-ray and/or ,-ray) radiation from the polar gaps can be much greater than in the absence of positronium formation. We discuss this enhancement for (a) Arons-type models, in which particles flow freely from the surface, and find any enhancement to be modest, and (b) Ruderman-Sutherland-type models, in which particles are tightly bound to the surface, and find that the enhancement can be substantial. In the latter case we argue for a self-consistent model in which partial screening of Ell maintains it close to the threshold value for field ionization of the bound pairs, and in which a reverse flux of accelerated particles maintains the polar cap at a temperature such that thermionic emission supplies the particles needed for this screening. This model applies only in a restricted range of periods, P2 < P < PI, and it implies an energy flux in high-energy particles that can correspond to a substantial fraction of the spin-down power of the pulsar. Nonthermal, high-frequency radiation has been observed from six radio pulsars and Geming is usually included as a seventh case. The nonthermal luminosity can be higher than can be explained in terms of conventional polar-gap and outer-gap models. The self-consistent polar-gap model proposed here alleviates this difficulty, provided the magnetic field satisfies B ;G 4 X 108 T (which is so for five of these pulsars, and plausibly for the other two if a modest nondipolar component is assumed), and the surface temperature (in the absence of heating by the reverse flux) satisfies T; ;S 0 .5 X 106 K, so that thermionic emission from the surface is unimportant. It is argued that sufficient power is available to explain the observed high-frequency radiation of most of these pulsars. However, the Crab and PSR 0540-69 have periods P < P2, and we suggest that an outer-gap model is more appropriate for these. Our model implies a death line at P = PI "-J 0�5 s for B ;G 4 X 108 T, and we speculate on why, nevertheless, radio pulsars with strong fields are found at P > Pl.

The Boomerang PWN G106.6+2.9 and the Magnetic Field Structure in Pulsar Wind Nebulae

2006 ◽  
Vol 638 (1) ◽  
pp. 225-233 ◽  
Author(s):  
Roland Kothes ◽  
Wolfgang Reich ◽  
Bulent Uyanıker
Keyword(s):  
Magnetic Field ◽  
Field Structure ◽  
Pulsar Wind Nebulae ◽  
Magnetic Field Structure ◽  
Pulsar Wind ◽  
The Magnetic Field

scholarly journals The braking index of PSR B0540−69 and the associated pulsar wind nebula emission after spin-down rate transition

2020 ◽  
Vol 494 (2) ◽  
pp. 1865-1870 ◽  
Author(s):  
L J Wang ◽  
M Y Ge ◽  
J S Wang ◽  
S S Weng ◽  
H Tong ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Observational Evidence ◽  
The Other ◽  
High Quality ◽  
X Ray ◽  
Dipole Magnetic Field ◽  
Pulsar Wind ◽  
The Magnetic Field ◽  
High Cadence

ABSTRACT In 2011 December, PSR B054−69 experienced a spin-down rate transition (SRT), after which the spin-down power of the pulsar increased by $\sim 36{{\ \rm per\ cent}}$. About 1000 d after the SRT, the X-ray luminosity of the associated pulsar wind nebula (PWN) was found to brighten by $32\pm 8{{\ \rm per\ cent}}$. After the SRT, the braking index n of PSR B0540−69 changes from n = 2.12 to 0.03 and then keeps this value for about five years before rising to n = 0.9 in the following years. We find that most of the current models have difficulties in explaining the measured braking index. One exceptive model of the braking index evolution is the increasing dipole magnetic field of PSR B0540−69. We suggest that the field increase may result from some instabilities within the pulsar core that enhance the poloidal component at the price of toroidal component of the magnetic field. The increasing dipole magnetic field will result in the X-ray brightening of the PWN. We fit the PWN X-ray light curve by two models: one assumes a constant magnetic field within the PWN during the brightening and the other assumes an enhanced magnetic field proportional to the energy density of the PWN. It appears that the two models fit the data well, though the later model seems to fit the data a bit better. This provides marginal observational evidence that magnetic field in the PWN is generated by the termination shock. Future high-quality and high-cadence data are required to draw a solid conclusion.

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