Examination of artifact in vector magnetic field SDO/HMI measurements

In this paper, we came to conclusion that there is a significant systematic error in the SDO/HMI vector magnetic data, which reveals itself in a significant deviation of the lines of the knot magnetic fields from the radial direction. The value of this deviation demonstrates a clear dependence on the distance to the disk center. This paper suggests a method for correction of the vector magnetograms that eliminates the detected systematic error.Comment: 12 pages, 8 figure

Waves in vertically inhomogeneous dissipative atmosphere

A method of construction of solution for acoustic-gravity waves (AGW) above a wave source, taking dissipation throughout the atmosphere into account (Dissipative Solution above Source, DSAS), is proposed. The method is to combine three solutions for three parts of the atmosphere: an analytical solution for the upper isothermal part and numerical solutions for the real non-isothermal dissipative atmosphere in the middle part and for the real non-isothermal small dissipation atmosphere in the lower one. In this paper the method has been carried out for the atmosphere with thermal conductivity but without viscosity. The heights of strong dissipation and the total absorption index in the regions of weak and average dissipation are found. For internal gravity waves the results of test calculations for an isothermal atmosphere and calculations for a real non-isothermal atmosphere are shown in graphical form. An algorithm and appropriate code to calculate DSAS, taking dissipation due to finite thermal conductivity into account throughout the atmosphere, are developed. The results of test DSAS calculations for an everywhere isothermal atmosphere are given. The calculation results for DSAS for the real non-isothermal atmosphere are also presented. A method for constructing of the 2x2 Green's matrix fully taking dissipation into account and allowing to find disturbance from some source of AGW in the atmosphere is proposed.Comment: 48 pages, 8 figure

Waveguide gravity disturbances in vertically inhomogeneous dissipative atmosphere

Trapped atmosphere waves, such as IGW waveguide modes and Lamb modes, are described using dissipative solution above source (DSAS) (Dmitrienko and Rudenko, 2016). Accordingly this description, the modes are disturbances penetrating without limit in the upper atmosphere and dissipating their energy throughout the atmosphere; leakage from a trapping region to the upper atmosphere is taken in consideration. The DSAS results are compared to those based on both accurate and WKB approximated dissipationless equations. It is shown that the spatial and frequency characteristics of modes in the upper atmosphere calculated by any of the methods are close to each other and are in good agreement with the observed characteristics of traveling ionospheric disturbances.Comment: 32 pages, 17 figure

Gravitational Hertz experiment with electromagnetic radiation in a strong magnetic field

Brief review of principal ideas in respect of the high frequency gravitational radiation generated and detected in the laboratory condition is presented. Interaction of electro-magnetic and gravitational waves into a strong magnetic field is considered as a more promising variant of the laboratory GW-Hertz experiment. The formulae of the direct and inverse Gertsenshtein-Zeldovich effect are derived. Numerical estimates are given and a discussion of a possibility of observation of these effects in a lab is carried out.Comment: 10 pages , to be published in Physica Script

Photospheric magnetic field variations accompanying the 2011 June 7 eruptive event

From vector measurements of the photospheric magnetic field with the SDO/HMI instrument, we studied the field variations within the 2011 June 7 eruptive event related to the filament eruption (FE), flare, and coronal mass ejection (CME). We analyzed the variations in modulus (B), in radial (Br) and transversal (Bt) magnetic induction components, as well as in the field line inclination angle ({\alpha}) to the radial direction from the Sun center were. The conclusion is that the most probable cause for the FE onset being the trigger related to the flares and CME, as well as for Stage 1 of the filament dramatic acceleration, is {\guillemotleft}magnetic flux cancellation{\guillemotright} in several sites inside and around the filament channel. We assumed that the flare and the stage of the filament fastest acceleration are related to a spot emergence near the south-eastern filament footpoint, in which the field polarity and value satisfy a possibility of this field magnetic reconnection with the field surrounding the filament. We studied in detail the time variations in the field line inclination angles within different sites of the eruptive event. During the filament slow emergence, a decrease in the field line inclination angles was revealed to occur in its channel neighboring, whereas the field line inclination angles dramatically grew in the neutral line neighboring within the flare region after the flare onset. The flare ribbons at all the stages of their existence are shown to be located under the photosphere sites with the field modulus local maxima and with minima of the field line inclination angles. We show that, near the photospheric magnetic field polarity inversion line (PIL), the azimuth decreases after the flare onset, which means a decrease in the angle \b{eta} between PIL and the magnetic induction vector projection onto the sky plane

Azimuth ambiguity removal and non-linear force-free extrapolation of near-limb magnetic regions

Possibilities in principle for satisfactory removal of the 180-azimuthal ambiguity in the transverse field of vector magnetograms and the extrapolation of magnetic fields independently of their position on the solar disk are shown. Revealed here is an exact correspondence between the estimated field and the nonpotential loop structure on the limb. The Metropolis's algorithm modified to work in spherical geometry is used to resolve the azimuthal ambiguity. Based on a version of the optimization method from Rudenko and Myshyakov (2009), we use corrected magnetograms as boundary conditions for magnetic field extrapolation in the nonlinear force-free approximation

Low frequency signals of large scale GW-interferometers

Application of the large scale gravitational wave interferometers for measurement of geophysical signals at very low frequencies is considered. Analysis is concentrated on the mechanism of penetration of quasistatic geophysical perturbation through the main interferometer output. It is shown that it has a parametrical nature resulted in slow variations of the optical transfer function of the interferometer. Geophysical modulation index is calculated for any harmonical component of the output spectrum, but mainly for a photon circulation frequency appeared in the case of stochastic illumination of modes neighbour to the central resonance. Value of the effect is estimated for different operational regimes of the device. For improvement of geophysical signal readout a modernization of the instrument with using of two component resonance optical pump is proposed and a correspondent calculation is carried out. Numerical estimations for different regimes of the setup are given together with discussion of possible application for measuring some weak gravitational effects.Comment: 29 pages, 1 figure, submitted to Classical and Quantum Gravit

Evidence of the Relationship between the Emerging Magnetic Fields, Electric Currents, and Solar Flares Observed on May 10, 2012

We have analyzed multi-wavelength observations and magnetic-field data for the solar flare of May 10, 2012 (04:18 UT) and have detected a sign inversion of the signal in the line-of-sight magnetic measurements in the umbra of a small spot. This effect is associated, at least partly, with the emergence of a new magnetic field. Almost at the same time, a burst of hard X-rays was recorded, and a wave in the vacuum ultraviolet (EUV) range (a "sunquake") was generated due to the impact of the disturbance in the energy release range on the photosphere. At the beginning of the event, a sigmoid flare was recorded, but it did not spread, as it usually does, along the polarity inversion (neutral) line. SDO/HMI full-vector measurements were used to extrapolate the AR 11476 magnetic field to the corona, and the distribution of vertical currents $j_z$ in the photosphere was obtained. The distribution of currents in the active region shows that the relationship between them and the occurrence of flares is very intricate. We have corroborated that the expected "ideal" behavior of the current system before and after the flare (e.g., see (Sharykin and Kosovichev, 2015)) is observed only in the sigmoid region. The results obtained were compared with the observations of two other flares recorded in this AR on the same day, one of which was similar to the flare under discussion and the other was of different type. Our results confirm that the formation and eruption of large-scale magnetic flux ropes in sigmoid flares are associated with the shear motions in the photosphere and the emergence of twisted magnetic tubes, as well as with the subsequent development of the torus instability.Comment: 16 pages, 6 figures; corrected versio

The antenna phase center motion effect in space-based experiments for fundamental physics and astronomy

We consider the effect of phase center motion of mechanically steerable high-gain parabolic antennas for ground-based and spacecraft-mounted antennas. For spacecrafts on highly elliptic Earth orbits the magnitude of the effect is as large as several mm/s in terms of the required velocity correction, both for ground-based and spacecraft-mounted antennas. We illustrate this with real data from the RadioAstron spacecraft and also provide results of our simulations for the concept of a possible follow-up space very long baseline radio astronomy mission. We also consider a specific configuration of satellite communication links, with simultaneously operating one-way down link and two-way loop link, pioneered by the Gravity Probe A experiment. We find that this configuration provides for complete compensation of the phase center motion effect due to the onboard antenna and significant compensation of that due to the ground antenna. This result is important for future space-based fundamental physics experiments, primarily those concerned with studies of gravity

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. III. Catastrophe of the Eruptive Filament at a Magnetic Null Point and Formation of an Opposite-Handedness CME

Our analysis in Papers I and II (Grechnev et al., 2014, Solar Phys. 289, 289 and 1279) of the 18 November 2003 solar event responsible for the 20 November geomagnetic superstorm has revealed a complex chain of eruptions. In particular, the eruptive filament encountered a topological discontinuity located near the solar disk center at a height of about 100 Mm, bifurcated, and transformed into a large cloud, which did not leave the Sun. Concurrently, an additional CME presumably erupted close to the bifurcation region. The conjectures about the responsibility of this compact CME for the superstorm and its disconnection from the Sun are confirmed in Paper IV (Grechnev et al., Solar Phys., submitted), which concludes about its probable spheromak-like structure. The present paper confirms the presence of a magnetic null point near the bifurcation region and addresses the origin of the magnetic helicity of the interplanetary magnetic clouds and their connection to the Sun. We find that the orientation of a magnetic dipole constituted by dimmed regions with the opposite magnetic polarities away from the parent active region corresponded to the direction of the axial field in the magnetic cloud, while the pre-eruptive filament mismatched it. To combine all of the listed findings, we come to an intrinsically three-dimensional scheme, in which a spheromak-like eruption originates via the interaction of the initially unconnected magnetic fluxes of the eruptive filament and pre-existing ones in the corona. Through a chain of magnetic reconnections their positive mutual helicity was transformed into the self-helicity of the spheromak-like magnetic cloud.Comment: 30 pages, 14 figures. Accepted for publication in Solar Physics. The final publication is available at Springer via http://dx.doi.org/10.1007/s11207-014-0536-