Ion acoustic instability of HPT particles,FAC density,anomalous resistivity and parallel electric field in the auroral region

During the magnetic storm of 21st March 1990, the DE-1 spacecraft encountered the auroral region at high invariant latitude at altitudes ranging from a few thousand kilometers in the ionosphere to many earth radii in the magnetosphere. The magnetic field perturbations interpretable as field aligned current (FAC) layers and the electrostatic turbulence possibly due to electrostatic ion acoustic instability driven by these currents are shown. The critical drift velocity of Hot Plasma Torus (HPT) electrons and the growth rate of ion acoustic wave as a function of electron to ion temperature ratio (T _e/T_i) for low and high current densities and energy of HPT electrons are found out. The intense FAC destabilizes the ion acoustic wave and the resultant electrostatic turbulence creates an anomalous resistivity. The current driven resistivity produces parallel electric field and high power dissipation. The anomalous resistivityη, potential difference along the auroral field lines V_t|, intensity of electric field turbulenceE _t| and power produced per unit volumeP are computed. It is found that the change in westward magnetic perturbation increasesJ _t|, η, V_t|, E_t| andP. Hence HPT electrons are heated and accelerated due to power dissipation during magnetically active periods in the auroral region. Concerning, applications, such HPT electrons can be used in particle accelerators like electron ring accelerator, smokatron etc.     

The pulsar PSR B1931+24 as an orthogonal rotator

The angles of the magnetic moment μ and the line of sight L to the rotation axis Ω are estimated for the pulsar PSR B1921+24, which displays “on” and “off” periods in its radio emission. It is shown that this object is an orthogonal rotator, i.e., the angle β between μ and Ω is equal to 88°.2 and the angle between L and Ω is ζ = 98.7°, and that its rotation period should be twice the usually adopted value (P = 1.626 s). One possible reason for the peculiarities of this pulsar could be the precession of a relic disk in the equatorial region of the object. Further observations (in particular, in the infrared) are required to confirm the existence of such a disk. Polarization data for other pulsars whose radiation switches on and off (transients) are also required, to determine if they are likewise orthogonal rotators. Calculations for PSR B0656+14 show that β ∼ 20°, and the sharp increase of its pulse intensities is due to intrinsic reasons, and is not associated with a relic disk. Original Russian Text ? I.F. Malov, 2007, published in Astronomicheskiĭ Zhurnal, 2007, Vol. 84, No. 6, pp. 531–535.     

Polarization of radiation in turbulent magnetized atmospheres

Multiple scattering of radiation in a semi-infinite electron atmosphere in the absence of true absorption (the Milne problem) is considered. The electron plasma is assumed to be turbulent, i.e., the magnetic field B has a regular B ₀ and a stochastic B′ component (B = B ₀ + B′). Faraday rotation of the plane of polarization (s8 λ² B ₀ cos gJ) due to the field B ₀ depolarizes the outcoming radiation due to the superposition of rays with different polarization-angle rotations, corresponding to different paths traveled before they left the atmosphere. Stochastic Faraday rotation due to isotropic fluctuations, B′, efficiently decreases the amplitude of the polarization of each individual beam as it travels through the turbulent atmosphere. This effect is proportional to λ⁴ 〈(B′)²〉, and becomes the dominant factor at large λ. We use the Ambartsumian-Chandrasekhar invariance principle, which results in six nonlinear equations (for the field B ₀ perpendicular to the surface of the medium). We also compute the degree of polarization for the cases B ₀ = 0, B′ ≠ 0, and B′ = 0, B ₀ ≠ 0, and for a number of versions of the general case, B ₀ ≠ 0, B′ ≠ 0. The spectra of the degree of polarization (for the case B ₀ = 0) are presented for optical (λ = 0 ? 1 μm), infrared (λ = 1?5 μm), and X-ray (1–50 keV) wavelengths.     

Method for Estimating the Doppler Factors of Relativistic Radio Jets

An expression for the intensity of synchrotron emission from a radio source (in the optically thin regime) in terms of the energy densities in the magnetic field and particles is obtained, based on a definition of a relativistic electron related to its rest energy. A relationship is obtained between the energy densities in particles E_e and the magnetic field E_H for a physical system containing a magnetic field and relativistic electrons in a minimum-energy state. A method for estimating the Doppler factors of the relativistic electrons has been developed. This method does not requires that all radio sources have the same radiation energies (brightness temperatures): it is sufficient that the energies of the magnetic fields and relativistic particles in the source be approximately equal. The method yields Doppler-factor estimates with reasonably good accuracy, even when there are modest deviations from energy equipartition in the radio source,making it applicable to many radio sources. The method is used to estimate the Doppler factor of the radio jet in CTA 21.

     

The generation of hard X-rays and relativistic protons observed during solar flares

The flare source of thermal X-rays above a magnetic arch in the corona arises from the dissipation of the magnetic energy of the current sheet formed at the reconnection of magnetic-field lines. The sources of hard X-rays emitted from the footpoints of the magnetic arch are beams of electrons accelerated in field-aligned currents induced by the Hall electric field generated in the current sheet. Both the hard X-rays detected above the active region and the type III radio emission are radiated by electrons accelerated in the field-aligned currents induced by Alfven waves. The solar cosmic rays are emitted promptly at the instant of the flare. It is important that the Lorentz electric field accelerates protons along the singular magnetic X line. The relativistic protons propagate along the interplanetary magnetic field. These protons have exponential spectra, typical for acceleration occurring in current sheets. A mechanism that is relevant for the generation of delayed cosmic rays, which demonstrate significant anisotropy and a power-law spectrum with γ ∼5, is also discussed.     

早期地球的热管构造:来自木卫一的启示

构造体制极大地制约着地球和其他太阳系类地天体（类地行星、岩石质卫星和小行星等）的地表散热、内部温度和物质演化。现有的少量地质记录表明，地球在板块构造启动之前就存在非常活跃的"前板块构造"运动并可能对其早期壳幔分异产生了重要的影响，在这些构造体制下，物质和能量循环的规模和速率可能是后续的板块运动无法比拟的。但受限于早期地质记录的稀缺以及研究手段不成熟等因素，对前板块构造运动的研究一直被学界所忽视，人们对其的认识主要局限于停滞盖层（stagnant-lid tectonics）等。长期以来的空间探测和地基观测表明，木星系统的木卫一存在大规模的火山活动，随之形成了极高的地表热流和地表更新速率以及活跃的造山作用。这些观测事实不同寻常，颠覆了人们对类地天体构造演化模式的一些固有认识，需要新的构造模式——"热管构造"（heat-pipe tectonics）予以解释，其涵义为：类似木卫一上的大规模火山作用可使类地天体的软流圈-岩石圈-地表之间发生快速的物质和能量循环，该循环以岩浆的形成-上升-喷发-冷却和沉降-折返为主要形式，可将天体内部的热散快速散发到外太空。上述过程涉及类地天体内、外部之间物质的大规模、快速迁移和相变，其导热原理与热管相同，因而被称为"热管构造"，其散热效率远高于现今大多数类地天体单纯依赖岩石圈进行内外热传导的停滞盖层构造，以及地球上以板块的形成和俯冲过程主导内部散热的板块构造体制。尽管早期地球与木卫一在内生热机制等方面存在显著差异，但二者的内部温度和内生热率较高，导致其岩浆作用总体均较为活跃，这些关键动力学特征的相似性暗示其构造体制可能类似。因此，研究木卫一的热管构造体制对揭示地球的前板块构造的性质和演化有重要的启示意义。本文综述了近40年来人类对木卫一的主要探测成果，论述了热管构造提出的必要性和依据，总结了该构造体制的特征和发生条件，讨论了早期地球发生热管构造的可能性。早期地球可能经历了热管构造阶段，期间地球通过大规模火山作用散发了内部热量、促进了壳幔分异，并在地球内生热作用减弱、热管构造不能继续维持时被板块构造等取代。由于热管构造的垂向物质循环较为强烈，不利于保留TTG等低密度的壳幔分异产物，我们依据TTG大规模形成的时间上限推测：地球发生热管构造时间可能限于冥古宙-始太古代时期（约38亿年以前）。由于前板块构造时期地球自身的地质记录十分有限，对其热管构造体制的性质和确切的形成条件等很大程度上需要从木卫一获得答案。     

The electric fields of radio pulsars with asymmetric nondipolar magnetic fields

The effect of the curvature of open magnetic field lines on the generation of electric fields in radio pulsars is considered in the framework of a Goldreich-Julian model, for both a regime with a free outflow of electrons from the neutron-star surface and the case of a small thermoemission current. An expression for the electron thermoemission current in a strong magnetic field is derived. The electric field associated with the curvature of the magnetic flux tubes is comparable to the field generated by the relativistic dragging of the inertial frames.     

Returning positron flux in the polar-cap regions of a radio pulsar

An approximate method for calculating the returning positron flux in the polar-cap regions of a radio pulsar is proposed. The pulsar is considered in the Goldreich-Julian model for a regime of free-electron emission from the neutron-star surface in the region of open lines of the dipolar magnetic field. Calculations have been done for the case when the dipolar magnetic moment is aligned with the star's rotational axis. The acceleration of primary electrons is assumed to occur near the neutron-star surface on scales comparable to the transverse radius of the tube of open field lines. The generation of electron-positron pairs by curvature radiation of the primary electrons is taken into account. A considerable contribution to the returning flux is made by the region where the electric field is screened by the electron-positron plasma.     

Large-scale stratification of the ionosphere during earthquake preparation

Modulation of ionospheric plasma density by acoustic waves (AW) is investigated. A rigorous electrodynamic model of the interaction of acoustic waves, generated by the lithospheric displacements during the seismic event preparation, with the cold dense ionospheric plasma in the presence of a magnetic field is constructed in conjunction with the actual height variations of the plasma particles' mobility and conductivity tensors in the ionosphere. A mechanism of creation of ionospheric inhomogeneities with different scales and with various degree of disturbance ΔN/N₀=10⁻⁴–10⁻⁵ (N₀ is the concentration of plasma electrons (ions) in background ionospheric plasma) is presented.     

高应力条件下的岩芯电磁性能变化

根据标准晶格模型理论,在高应力作用下,岩石的Si-O键最外层电子将被挤入晶格间隙里,松散外逸的电子云在电场中将产生直流电流（DC）,进而吸收电磁波,转换成交流电流（AC）。直流电流来源于量子力学穿隧效应电子和断键电子。穿隧效应电子的形成过程和原理:氧原子的最外电子被束缚在浅位能井（shallow potential well）（0.38 V）,当高应力作用时,电子吸收部分能量,增加其动能,虽然这种轻微的动能增加不足以使电子克服并跳出它的位能井（potential well）,但它足以增加穿过井壁（well wall）进入晶格空隙间的概率,这个概率乘以可用氧原子的数目即为由于隧穿效应形成电子云的电子数量,其量级通常为微微库伦（picocoulombs）到纳米库伦（nanocoulombs）。断键电子的形成过程和原理:从微裂纹开始断裂键释放电子,并且裂纹成核点极可能开始是平行排列的,每当Si-O键断裂时,就会产生一个+Si悬键,伴随着一个自由电子附着在-O原子上,这个电子将从原子跃迁到原子,这种电子电流与裂纹的表面积和电池电极的收集效率成正比。断键形成的电子云比穿隧效应多很多。两种电子均被试验所证实。在高应力条件下岩石破裂之前,由电子穿隧效应,DC缓慢增加,随着岩石破裂的发生而导致断键电子增多,DC急剧增加;AC的电压振幅（V）随电流（I）增大而减小,当电流减小到正常时,在岩石破裂后电压振幅回归正常;遵守能量守恒原理,吸收的电磁波能量（E）与交流电流功率（V×I）相等,即E=V×I。研究结果表明电磁波监测可用于探测地壳高应力变化和岩石破裂特征,当应力达到岩体断裂的临界强度时,其应变晶体结构开始释放越来越多的外逸电子,最终岩体晶体结构断裂产生一个地震或滑动事件。岩石破裂的电磁性能变化研究可用于研发电磁波地学监测仪器,电磁波监测可以作为地应力监测的一种补充和对比分析方法,两种方法相结合比地应力监测一种方法更可靠。此外,在高应力条件下岩石还有其它现象:应变蠕变辐射、光发射、声发射、静电等,这些现象的观测也是预测地质事件需要考虑的条件。      

Mean absolute strength of the solar magnetic field in 1968–2006

Measurements of the mean magnetic field of the Sun as a star (the line-of-sight component of the magnetic field of the visible hemisphere for a given day) carried out at six observatories are used to compile a catalog of the mean magnetic field for 1968–2006 (containing about 18 000 daily values). The cataloged data are compared with direct daily measurements of the absolute line-of-sight field made at the Kitt Peak Observatory in 2003–2006 (original data with a resolution of 1″ averaged over the solar disk). The true absolute mean field strength averaged over the visible solar hemisphere is determined for 1968–2006 to be B ₀ = 7.7 ± 0.2 G. This figure exceeds previous estimates by almost a factor of four. B ₀ exhibits no appreciable slow trend over the entire 39-year interval, but varies substantially with the cycle. The period of this variation is 10.5 ± 0.7 yr, and its harmonic amplitude is 1.7 G. The magnetic flux of spots and active regions makes B ₀ almost twice the field strength in the “normal” photosphere at the solar minimum, i.e., for the “quiet” Sun.     

Drift loss cone instability in the ring current and plasma sheet

The drift loss cone instability, propagating nearly transverse to the ambient magnetic field, is studied in the ring current plasma taking into account the relative driftU between electrons and protons due to density gradients. The growth rates attain maxima and then decrease as the wave number parallel to the magnetic fieldk _II increases. The peak values of the growth rates, maximised with respect tok _II, are enhanced by the increase in number density, electron temperature and loss cone index, and by the decrease in β_t, the ratio of the proton thermal pressure to magnetic field pressure. The unstable frequencies fall in the range of 5 to 30Ω_p with the growth rate γ ≥Ω_p. In the ring current region betweenL=4 and 5, the instability will generate a strong turbulence in the frequency range between 5–500 Hz which can produce fluctuating electric fields 0. 5–5 mV/m and magnetic field 0.8–80mγ. This instability can also occur on the auroral field lines, which connect to the region of intense earthward plasma flow in the distant magnetotail and produce a broad band electrostatic noise.     

Predictive crystal-chemical relations in Ti-silicates based on the TS block

In a group of minerals of reasonable complexity in which the structure topology is related but not identical, the general relation between structure topology and chemical composition is not known. This problem is of major significance. The structural hierarchy and stereochemistry are described for 27 titanium disilicate minerals that contain the TS (titanium-silicate) block, a central trioctahedral (O) sheet and two adjacent (H) sheets of [5]- and [6]-coordinated polyhedra and (Si₂O₇) groups and related delindeite. The TS block is characterized by a planar cell based on translation vectors, t ₁ and t ₂ , with t ₁ ～ 5.5 and t ₂ ～ 7 Å and t ₁ ∧ t ₂ close to 90°. The general formula of the TS block is A ₂ ^P B ₂ ^P M ₂ ^H M ₄ ^O (Si ₂ O ₇ ) ₂ X _{4 + n}, where M ₂ ^H and M ₄ ^O = cations of the H and O sheets; M^H = Ti (= Ti + Nb), Zr, Mn²⁺, Ca; M^O = Ti, Zr, Mn²⁺, Ca, Na; A ^P and B ^P are cations at the peripheral (P) sites = Na, Ca, Ba; X = anions = O, OH, F; n = 0, 2, 4; the core part of the TS block is shown in bold and is invariant. Cations in each sheet of the TS block form a close-packed layer and the three layers are cubic close packed.There are three topologically distinct TS blocks, depending on the type of linkage of two H sheets and the central O sheet. The H sheets of one TS block attach to the O sheet in the same manner. All structures consist of a TS block and an I (intermediate) block that comprises atoms between two TS blocks. Usually, the I block consists of alkali and alkaline-earth cations, (H₂O) groups and oxyanions (PO₄)^3?, (SO₄)^2? and (CO₃)^2?. These structures naturally fall into four groups, based on differences in topology and stereochemistry of the TS block. In Group I, Ti = 1 apfu Ti occurs in the O sheet, and (Si₂O₇) groups link to a Na polyhedron of the O sheet (linkage 1). In Group II, Ti = 2 apfu, Ti occurs in the H sheet, and (Si₂O₇) groups link to two M ²⁺ octahedra of the O sheet adjacent along t ₂ (linkage 2). In Group III, Ti = 3 apfu, Ti occurs in the O and H sheets, and (Si₂O₇) groups link to the Ti octahedron of the O sheet (linkage 1). In Group IV, Ti = 4 apfu (the maximum possible content of Ti in the TS block), Ti occurs in the O and H sheets, and (Si₂O₇) groups link to two Ti octahedra of the O sheet adjacent along t ₁ (linkage 3). The stability of the TS block is due to the ability of Ti (Nb) to have an extremely wide range in Ti (Nb)-anion bond lengths, 1.68–2.30 Å, which allows the chemical composition of the TS block to vary widely. In crystal structures so far known, only one type of TS block occurs in a structure. The TS block propagates close-packing of cations onto the I block. The general structural principles and the relation between structure topology and chemical composition are described for the TS-block minerals. These principles allow prediction of structural arrangements and possible chemical compositions, and testing whether or not all aspects of the structure and chemical formula of a mineral are correct. Here, I show how these principles work, and review recent results that show the effectiveness of these principles as a predictive technique.     

Single-crystal polarized FTIR spectroscopy and neutron diffraction refinement of cancrinite

We relate a single-crystal FTIR (Fourier transform infrared) and neutron diffraction study of two natural cancrinites. The structural refinements show that the oxygen site of the H₂O molecule lies off the triad axis. The water molecule is almost symmetric and slightly tilted from the (0001) plane. It is involved in bifurcated hydrogen bridges, with Ow···O donor–acceptor distances >2.7 Å. The FTIR spectra show two main absorptions. The first at 3,602 cm^?1 is polarized for E ⊥ c and is assigned to the ν₃ mode. The second, at 3,531 cm^?1, is also polarized for E ⊥ c and is assigned to ν₁ mode. A weak component at 4,108 cm^?1 could possibly indicate the presence of additional OH groups in the structure of cancrinite. Several overlapping bands in the 1,300–1,500 cm^?1 range are strongly polarized for E ⊥ c, and are assigned to the vibrations of the CO₃ group.     

Global solar magnetology and reference points of the solar cycle

The solar cycle can be described as a complex interaction of large-scale/global and local magnetic fields. In general, this approach agrees with the traditional dynamo scheme, although there are numerous discrepancies in the details. Integrated magnetic indices introduced earlier are studied over long time intervals, and the epochs of the main reference points of the solar cycles are refined. A hypothesis proposed earlier concerning global magnetometry and the natural scale of the cycles is verified. Variations of the heliospheric magnetic field are determined by both the integrated photospheric i(B _r )_ph and source surface i(B _r )_ss indices, however, their roles are different. Local fields contribute significantly to the photospheric index determining the total increase in the heliospheric magnetic field. The i(B _r )_ss index (especially the partial index ZO, which is related to the quasi-dipolar field) determines narrow extrema. These integrated indices supply us with a “passport” for reference points, making it possible to identify them precisely. A prominent dip in the integrated indices is clearly visible at the cycle maximum, resulting in the typical double-peak form (the Gnevyshev dip), with the succeeding maximum always being higher than the preceding maximum. At the source surface, this secondary maximum significantly exceeds the primary maximum. Using these index data, we can estimate the progression expected for the 23rd cycle and predict the dates of the ends of the 23rd and 24th cycles (the middle of 2007 and December 2018, respectively).     

Comment: A study of “probabilistic” and “deterministic” geostatistics

Stochastic process theory involves integrals of measurable functions over probability measure spaces. One of these is the ensemble space, Ω, whose members are sample functions on Euclidean spaceR ^k and the other isR ^k itself. What geostatisticians call the “theory of regionalized variables” is said to based on stochastic theory. A recent paper inMathematical Geology proclaims a distinction between “probabilistic” and “deterministic” geostatistics. The former is said to rely on “ensemble integrals” over Ω and the latter on “spatial integrals” overR ^k. This study shows that the proposed distinction rests on an arbitrary choice between two estimators for the covariance of a stochastic process; neither is an ensemble integral, both are spatial integrals, and both are Kolmogorov inconsistent. The “deterministic” estimator is identical with that of classical bivariate least-squares regression in which “spatial structure” is of no consequence. This study shows that both stochastic models are suboptimal approximations to the unique nonstationary classical statistical multivariate regression model generated by each sample pattern. The stochastic process model and its “spatial continuity measures,” thus, appear as questionable mathematical embellishments on suboptimal estimates, correspondence with geomorphic reality is tenuous, and estimates are biased and distorted. Various related misconceptions in the paper are also discussed.     

The generation of magnetic field via convective motions in the photosphere,Alvén waves,and the origin of chromospheric spicules

The basis is laid out for a theory relating various phenomena in the solar atmosphere, including localized concentrations of magnetic field at the bases of coronal magnetic arches, chromospheric spicules, twisted coronal magnetic flux tubes, and flows of energy carried by Alfvén waves propagating upward into the corona. The structure of photospheric currents localized in the vicinity of supergranule boundaries and excited by convective motions is studied. These currents exist primarily in a “dynamo layer” of sharply enhanced transverse conductivity, which forms in the weakly ionized thermal photospheric plasma located in the solar gravitational field. The motions of the electrons and ions in this layer have appreciably different characters: the ions are collisionly driven by the flows of neutral atoms, while the electrons drift in the crossed electric and magnetic fields. The electric field supporting the current arises due to the polarization of the electrons and ions. This field also gives rise to Alfvén perturbations that propagate upward into the corona, together with their associated longitudinal currents. The character of this “loading” makes the system of fields and currents uniquely defined. Moreover, the momentum flux carried by these Alfvén waves should be transferred to the cool chromospheric gas, facilitating the vertical ejection of this gas in the form of spicules, as was first proposed in 1992 by Haerendel.     

Magnetic measurements in electrical prospecting by resistivity methods

The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio.     

On Possible Types of Magnetospheres of Hot Jupiters

As a rule, the orbits of “hot Jupiter” exoplanets are located close to the Alfven point of the stellar wind of the host star. Many hot Jupiters could be in the sub-Alfven zone, where the magnetic pressure of the stellar wind exceeds the dynamical pressure. Therefore, the magnetic field in the wind should play an extremely important role in the process of stellar wind flowing around the atmosphere of a hot Jupiter. This must be taken into account when constructing theoretical models and interpreting observational data. Analyses show that many typical hot Jupiters should have shockless induced magnetospheres, which have no analogs in the solar system. Such magnetospheres are characterized first and foremost by the fact that there is no bow shock, and the magnetic barrier (ionopause) is formed by induced currents in upper layers of the ionosphere. This conclusion is confirmed here using three-dimensional numerical simulations of the flow of the stellar wind from the host star around the hot Jupiter HD 209458b, taking into account both the intrinsic magnetic field of the planet and the magnetic field in the wind.

     

Sources of the global magnetic field of the Sun

Data on the global magnetic field (GMF) of the Sun as a star for 1968–1999 are used to determine the correlation of the GMF with the radial component of the interplanetary magnetic field (IMF) |B _r|; all data were averaged over a half year. The time variations in the GMF |H| are better correlated with variations in |B _r|; than the results of extrapolating the field from the “source surface” to the Earth’s orbit in a potential model based on magnetic synoptic maps of the photosphere. Possible origins for the higher correlation between the GMF and IMF are discussed. For both the GMF and IMF, the source surface actually corresponds to the quiet photosphere—i.e., background fields and coronal holes—rather than to a spherical surface artificially placed ≈2.5 R _⊙ from the center of the Sun, as assumed in potential models (R _⊙ is the solar radius). The mean effective strength of the photospheric field is about 1.9 G. There is a nearly linear dependence between |H| and |B _r|. The strong correlation between variations in |H| and |B _r| casts doubt on the validity of correcting solar magnetic fields using the so-called “saturation” factor δ^?1 (for magnetograph measurements in the λ 525.0 nm FeI line).