Author name code: zharkova ADS astronomy entries on 2022-09-14 author:"Zharkova, Valentina A." ------------------------------------------------------------------------ Title: Kinetic turbulence generated in a 3D current sheet with two magnetic islands Authors: Zharkova, Valentina; Xia, Qian Bibcode: 2022cosp...44.1487Z Altcode: his paper investigates kinetic turbulence generated by accelerated particles in a reconnecting current sheet (RCS) with X- and O-nullpoints with simulations of magnetic reconnection using particle-in-cell (PIC) approach in a thin current sheet with 3D magnetic field topology with two large magnetic islands. The model utilises a strong guiding field that leads to separation of the particles of opposite charges, generation of a strong polarisation electric field across the RCS and suppression of kink instability in the 'out-of-plane' direction. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the `bump-in-tail' velocity distributions that, in turn, can generates plasma turbulence in different locations. The turbulence produced by either electron or proton beams is identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis the kinetic turbulence is found to be generated by accelerated particle beams, whose distribution later evolves into a phase-space hole happening at about 7$d_i$ (ion inertial depth) for the electron beam and 12$d_i$ for the proton beam. The spectral index of the power spectrum In a wavenumber space of the turbulent magnetic field near the ion inertial length approaches -2.7. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high and low-frequency waves are explored in the kinetic turbulence in parallel and perpendicular directions to the local magnetic field showing noticeable lower hybrid turbulence occurring between the electron's gyro- and plasma frequencies seen also in the wavelet spectra. Title: Grand minimum of solar magnetic field and its links with the solar and terrestrial activity features Authors: Zharkova, Valentina; Vasilieva, Irina; Popova, Elena; Shepherd, Simon Bibcode: 2022cosp...44.1558Z Altcode: Principal Component Analysis (PCA) was performed on the full disk synoptic maps of solar background magnetic field (SBMF) captured from the Wilcox Solar Observatory for 30 latitudinal bands for cycles 21-24 allowing to obtain principal components (PCs), or eigen vectors of solar magnetic field. The addition of extra-cycle 24 fully verifies the previous results obtained for cycles 21-23 and confirms the modern grand solar minimum (2020-2053). The PCs are shown to come in pairs with he first pair being linked to dipole magnetic waves. Their summary curve reveal a reasonable fit to the averaged sunspot numbers in cycles 21-24 suggesting to use the summary curve as a new proxy of solar activity complementary to the sunspots indices. Some connections of the summary curve to terrestrial activity features (earthquakes, volcanos) are also presented. The second pair of PCs generated by quadruple magnetic sources is shown to have twice smaller amplitudes than the first pair with their summary curve correlating closely with SXR fluxes in solar flares in cycles 21-24. Flare occurrences are found linked to the variations of quadruple and sextuple components revealing in every cycle additional periodicity of about 2.75-3.1 years. Strong latitudinal asymmetries in quadruple and sextuple components also correlate with flare occurrences skewed to southern hemisphere in even cycles and to northern hemisphere in odd ones. Connections of magnetic field with the other solar activity proxies (radio flux, Lyman emission etc.) are also investigated. Eigen vectors of solar magnetic field are found to provide very important insight into solar activity, in addition to the existing proxies. Title: Comparison of solar activity proxies: eigen vectors versus averaged sunspot numbers Authors: Zharkova, V.; Vasilieva, I.; Shepherd, S. J.; Popova, E. Bibcode: 2022arXiv220714708Z Altcode: We attempt to establish links between a summary curve, or modulus summary curve, MSC, of the solar background magnetic field (SBMF) derived from Principal Component Analysis, with the averaged sunspot numbers (SSN). The comparison of MSC with the whole set of SSN reveals rather close correspondence of cycle timings, duration and maxima times for the cycles 12- 24, 6,7 and -4,-3. Although, in 1720-1760 and 1830-1860 there are discrepancies in maximum amplitudes of the cycles, durations and shifts of the maximum times between MSC and SSN curves. The MSC curve reveals pretty regular cycles with double maxima (cycles 1-4), triple maximum amplitude distributions for cycles 0 and 1 and for cycles -1 and -2 just before Maunder minimum. The MSC cycles in 1700-1750 reveal smaller maximal magnitudes in cycles -3 to 0 and in cycle 1-4 than the amplitudes of SSN, while cycles -2 to 0 have reversed maxima with minima with SSN. Close fitting of MSC or Bayesian models to the sunspot curve distorts the occurrences of either Maunder Minimum or/and modern grand solar minimum (2020-2053). These discrepancies can be caused by poor observations and by difference in solar magnetic fields responsible for these proxies. The dynamo simulations of toroidal and poloidal magnetic field in the grand solar cycle (GSC) from 1650 until 2050 demonstrate the clear differences between their amplitude variations during the GSC. The use of eigen vectors of SBMF can provide additional information to that derived from SSN that can be useful for understanding solar activity. Title: Terrestrial volcanic eruptions and their association with solar activity Authors: Vasilieva, I.; Zharkova, V. Bibcode: 2022arXiv220303637V Altcode: Frequencies of volcanic eruptions in the past 270 years are compared with variations of solar activity and summary curve of principal components of the solar background magnetic field (SBMF).Frequency analysis with Morlet wavelet reveals the most pronounced period of volcanic eruptions of 22 years. There is a strong correlation (0.84) between volcanic frequencies and the summary curve of SBMF for 11 cycles after 1868. The maxima of volcanic eruptions are shown to occur during solar activity cycles with the southern magnetic polarity. The next anticipated maximum of volcanic eruptions is expected to occur during cycle 26, when SBMF have a southern magnetic polarity. Title: Comparison of magnetic dynamo waves of the Sun and Grand Solar Minimum details derived from full disk magnetic field using WSO and MWO observations Authors: Zharkova, Valentina; Shepherd, Simon Bibcode: 2021AGUFMSH55D1884Z Altcode: In this paper we will compare the Eigen vectors of solar magnetic field dynamo derived from the WSO and MWO observations in cycles 21-24 using Principle Component Analysis. The waves produced by dipole and quadruple magnetic sources will be evaluated and described by analytical expressions and compared with the averaged sunspot numbers. We evaluate possible effects of different observing instruments of WSO and MWO on the derived parameters of the pairs of dynamo waves induced by dipole and quadruple sourcesand the their effecton the duration and power of the Grand Solar minimum, into which the Sun entered in 2020. Title: Particle Pitch Angle Distributions after Passing Through 3d Current Sheets in the Heliosphere Authors: Zharkova, Valentina; Malandraki, Olga; Khabarova, Olga; Xia, Qian Bibcode: 2021AGUFMSH11A..02Z Altcode: We present diagnostic tools for particle energy and pitch angle distributions at acceleration in 3D Harris-type reconnecting current sheets with a single or multiple X-nullpoints taking into account the ambient plasma feedback to the presence of accelerated particles. We explore accel- eration of particles during their passage through 3D reconnecting current sheets occurring in the interplanetary space using particle-in-cell (PIC) approach with single and multiple X-nullpoints (magnetic islands). We consider coalescent and squashed magnetic islands formed in the cur- rent sheets with different thicknesses, ambient density and mass ratios, and simulate energy, density and pitch-angle distributions of accelerated particles. We report distinct populations of two groups of particles: transit and bounced ones, which have very different energy and asymmetric pitch-angle distributions associated with the magnetic field parameters. The sim- ulated pitch angle distributions of accelerated particles are presented for different angles of the spacecraft paths through reconnecting current sheets. The outcomes are compared with some in-situ observations of solar wind particles from Ace, Wind and Parker Probe. This comparison indicates that locally generated superthermal electrons can account for the counter-streaming strahls often observed in the pitch-angle distribution spectrograms of the satellites crossing local current sheets. Title: Plasma turbulence generated in 3D current sheets with single and multiple X-nullpoints Authors: Zharkova, Valentina; Xia, Qian Bibcode: 2021FrASS...8..178Z Altcode: In this paper we aim to investigate the kinetic turbulence in a reconnecting current sheet (RCS) with X- and O-nullpoints and to explore its link to the features of accelerated particles. We carry out simulations of magnetic reconnection in a thin current sheet with 3D magnetic field topology affected by tearing instability until the formation of two large magnetic islands using particle-in-cell (PIC) approach. The accelerated particles of the same charge entering an RCS from the opposite edges are shown accelerated to different energies forming the `bump-in-tail' velocity distributions that, in turn, can generates plasma turbulence in different locations. The turbulence-generated waves produced by either electron or proton beams can be identified from the energy spectra of electromagnetic field fluctuations in the phase and frequency domains. From the phase space analysis we gather that the kinetic turbulence is mainly generated by accelerated particle beams, which are later found to evolve into a phase-space hole indicating the beam breakage. In a wavenumber space the spectral index of the power spectrum of the turbulent magnetic field near the ion inertial length is found to be -2.7 that is consistent with other estimations. The collective turbulence power spectra are consistent with the high-frequency fluctuations of perpendicular electric field, or upper hybrid waves, to occur in a vicinity of X-nullpoints, where the Langmuir (LW) can be generated by accelerated electrons with high growth rates, while further from X-nullponts or on the edges of magnetic islands, where electrons become ejected and start moving across the magnetic field lines, Bernstein waves can be generated. The frequency spectra of high and low-frequency waves are explored in the kinetic turbulence in parallel and perpendicular directions to the local magnetic field showing noticeable lower hybrid turbulence occurring between the electron's gyro- and plasma frequencies seen also in the wavelet spectra. Fluctuation of the perpendicular electric field component of turbulence can be consistent with the oblique whistler waves generated on the ambient density fluctuations by intense electron beams. This study brings attention to a key role of particle acceleration in generation kinetic turbulence inside current sheets. Title: Pitch-angle distribution of accelerated electrons in 3D current sheets with magnetic islands Authors: Zharkova, V.; Xia, Q. Bibcode: 2021A&A...648A..51Z Altcode:
Aims: This research aims to explore variations of electron pitch-angle distributions (PADs) during spacecraft crossing of reconnecting current sheets (RCSs) with magnetic islands. Our results can benchmark the sampled characteristic features with realistic PADs derived from in situ observations.
Methods: Particle motion is simulated in 2.5D Harris-type RCSs using the particle-in-cell method and considering the plasma feedback to electromagnetic fields induced by accelerated particles. We evaluate particle energy gains and PADs in different locations with virtual spacecraft passing the current sheet while moving in the different directions. The RCS parameters are comparable to heliosphere and solar wind conditions.
Results: The energy gains and the PADs of particles would change depending on the specific topology of the magnetic fields. In addition, the observed PADs also depend on the crossing paths of the spacecraft. When the guiding field is weak, the bi-directional electron beams (strahls) are mainly present inside the islands and are located just above or below the X-nullpoints in the inflow regions. The magnetic field relaxation near the X-nullpoint alters the PADs towards 90°. As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of RCSs. Mono-directional strahls are quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature-drift acceleration. Meanwhile, the high-energy electrons confined inside magnetic islands create PADs of around 90°.
Conclusions: Our results link the electron PADs to local magnetic structures and the directions of spacecraft crossings. This can help to explain a variety of the PAD features reported in recent observations in the solar wind and the Earth's magnetosphere. Title: Particle acceleration in erupting 3D coronal mass ejections in the breakout model Authors: Xia, Qian; Zharkova, Valentina; Dahlin, Joel; Antiochos, Spiro Bibcode: 2021cosp...43E1005X Altcode: We examine particle energisation in CMEs generated via the breakout mechanism and explore both 2D and 3D MHD configurations. In the breakout scenario, reconnection at a breakout current sheet (CS) initiates the flux rope eruption by destabilizing the quasi-static force balance. Reconnection at the flare CS triggers the fast acceleration of the CME, which forms flare loops below and triggers particle acceleration in flares. We present test-particle studies that focus on two selected times during the impulsive and decay phases of the eruption and obtain particle energy gains and spatial distributions. We find that particles are accelerated more efficiently in the flare CS than in the breakout CS even in the presence of large magnetic islands. The maximum particle energy gain is estimated from the energization terms based on the guiding-centre approximation. Particles are first accelerated in the CSs (with or without magnetic islands) where Fermi-type acceleration dominates. Accelerated particles escape to the interplanetary space along open field lines rather than trapped in flux ropes, precipitate into the chromosphere along the flare loops, or become trapped in the flare loop top due to the magnetic mirror structure. Some trapped particles are re-accelerated, either via re-injection to the flare CS or through a local Betatron-type acceleration associated with compression of the magnetic field. The energy gains of particles result in relatively hard energy spectra during the impulsive phase. During the gradual phase, the relaxation of the shear in the magnetic field reduces the guiding magnetic field in the flare CS, which leads to a decrease in particle energization efficiency. Title: Sunquake with a second-bounce, other sunquakes and emission associated with X9.3 flare of 6 September 2017 Authors: Zharkov, Sergei; Matthews, Sarah A.; Inoue, Satoshi; Zharkova, Valentina; Dammasch, Ingolf; Druett, Malcolm Bibcode: 2021cosp...43E.856Z Altcode: We present observations of gamma-ray (GR), hard (HXR) and soft X-rays (SXR), extra ultra-violate (EUV), H$\alpha$ and white light emission recorded during the two flaring events 1 and 2 of the flare of 6 September 2017 occurring at 11:55:37 UT (FE1) and 12:06:40 UT (FE2). For the first time we report the detection of seismic waves with two bounces in the largest sunquake and the other four sunquakes observed with GR, HXR, Ly$\alpha$ line, extra ultra-violate (EUV) emission and H$\alpha$ with white light radiation in the locations of sunquakes. We propose some likely scenarios of heating of flaring atmospheres in the footpoints with sunquakes, which can account for the blue shifts derived with EIS from the EUV emission and the red shifts observed by CRISP/SST in H$\alpha$ line emission. The parameters of hydrodynamic shocks produced in flaring atmospheres are used as the initial conditions for the hydrodynamic models of acoustic wave propagation in the solar interior to simulate the sets of acoustic waves produced in the solar interior and compare the depths for acoustic waves production by weaker and stronger particle beams. We evaluate the directivity of detected sunquakes and compare simulated and observed acoustic signatures of three sunquakes with ripples including the largest sunquake with a second bounce. Title: Diagnostics of particle energy and pitch angle distributions at their acceleration in 3D current sheets in the heliosphere Authors: Zharkova, Valentina; Khabarova, Olga; Malandraki, Olga; Xia, Qian Bibcode: 2021cosp...43E.908Z Altcode: We present diagnostic tools for particle energy and pitch angle distributions at acceleration in 3D Harris-type reconnecting current sheets with a single or multiple X-nullpoints taking into account the ambient plasma feedback to the presence of accelerated particles. We explore acceleration of particles during their passage through 3D reconnecting current sheets occurring in the interplanetary space using particle-in-cell (PIC) approach with single and multiple X-nullpoints (magnetic islands). We consider coalescent and squashed magnetic islands formed in the current sheets with different thicknesses, ambient density and mass ratios, and simulate energy, density and pitch-angle distributions of accelerated particles. We report distinct populations of two groups of particles: transit and bounced ones, which have very different energy and asymmetric pitch-angle distributions associated with the magnetic field parameters. The simulated pitch angle distributions of accelerated particles are presented for different angles of the spacecraft paths through reconnecting current sheets. The outcomes are compared with some in-situ observations of solar wind particles from Ace, Wind and Parker Probe. This comparison indicates that locally generated superthermal electrons can account for the counter-streaming 'strahls' often observed in the pitch-angle distribution spectrograms of the satellites crossing local current sheets. Title: Double dynamo effect on solar activity and the modern grand solar minimum Authors: Popova, Helen; Zharkova, Valentina; Zharkov, Sergei; Shepherd, Simon Bibcode: 2021cosp...43E1729P Altcode: In this paper we present prediction of solar activity for the next three solar cycles and millennium using as a proxy the solar background magnetic field based on principal component analysis. Using symbolic regression analysis we present mathematical formulae for the dipole magnetic waves and calculate their summary curve, which is shown linked to solar activity index. Extrapolation of the PCs backward for 3000 years reveals the 350-400 year grand cycles superimposed on 22 year-cycles whose the occurrence has a remarkable resemblance to sunspot activity reported in the past including Maunder, Wolf, Oort, Homeric and other grand solar minima and warming periods. The summary curve calculated for the next millennium predicts further three grand cycles with the closest grand minimum, which started in 2020 and expected to last to 2053. These grand cycle variations are probed by α − Ω dynamo model with meridional circulation. Dynamo waves are found generated with close frequencies whose interaction leads to beating effects responsible for the grand cycles (350-400 years) superimposed on a standard 22 year cycle. We present also butterfly diagrams for the modern grand solar minimum and compare with that occurred during Maunder Minimum. The dynamo approach is also extended by considering magnetic waves produced by quadruple magnetic sources and their interference with the dipole waves. The revised summary curve for the last 400 years is shown to account for the additional minima of solar activity occurred at the beginning of 19th (Dalton minimum) and 20th centuries. Title: Solar magnetic field and irradiance variations on millennial timescale and their effects on the terrestrial temperature Authors: Zharkova, Valentina; Popova, Helen Bibcode: 2021cosp...43E.677Z Altcode: Daily variations of the Sun-Earth distances derived from VSOP87 and JPL ephemeris are explored in the two millennia of 600-2600 showing essential deviation of the Sun-Earth distances from the third Kepler's law. The Sun-Earth (S-E) distances are found decreasing in January-June and increasing in July-December by up to 0.005 au in the millennium M1 (600-1600) and by more than 0.01 au in millennium M2 (1600-2600). These S-E distance variations are imposed by the shift of the Sun's position from the ellipse focus towards the spring equinox imposed by the gravitation of large planets of the solar system, or solar inertial motion (SIM). The longest distances of the Earth orbit (aphelion) are steadily shifted during the millennia M1 and M2 from the summer solstice on 21 June in 1100 towards 28 June in 1600, 5 July in 2020 and 15 July in 2600, while the shortest distances (perihelion) are moved from the winter solstice on 21 December forwards 28 December, 5 January and 15 January in the same years, respectively. These S-E distance variations are reflected in the millennial oscillations of the baseline magnetic field of the Sun measured from Earth reported by Zharkova et al., 2019. Daily solar irradiance calculated with these S-E distances is found to increase in February-June by up to 11-13 $W/m^2$ ($\simeq$1.0$%$) in M1 and 14-18 $W/m^2$ ($\simeq$1.3$%$) in M2, or by up to 2.3$%$, in total. Despite the solar irradiance is expected to decrease in the next 6 months (July-December) of each year because of the elliptic orbit of the Earth, the balance of the annual solar irradiance is not equal to zero as expected from Kepler's third law. In fact, the annual sums of average monthly irradiance magnitudes in years of millennium M2 are higher by up to 1.3 $W/m^2$ than for the years in millennium M1 that closely fit the solar irradiance observations with modern instruments Although, the annual sums of the daily solar irradiance magnitudes in the years of millennium M2 are found to be higher by up to 20-25 $W/m^2$ than in years of millennium M1. This annual excess of solar irradiance is expected to be unevenly distributed over Northern and Southern hemispheres depending on the areas exposed towards the Sun. This would lead to complex scenarios of additional solar forcing in the terrestrial atmosphere and ocean heating. The shifts of the aphelion and perihelion from their classic location of the summer and winter solstices can naturally explain the millennial variations of the baseline solar magnetic field and solar irradiance, known as Hallstatt's cycle. Possible implications of this extra solar forcing on the terrestrial atmosphere heating in conjunction with the modern grand solar minima: GSM1 (2020-2053) and GSM2 (2375-2415) are also discussed. Title: Solar activity, solar irradiance and terrestrial temperature Authors: Zharkova, Valentina Bibcode: 2020arXiv200800439Z Altcode: In this study we overview recent advances with prediction of solar activity using as a proxy solar background magnetic field and detection of grand solar cycles of about 400 years separated by grand solar minima (GSMs).The previous GSM known as the Maunder minimum was recorded from 1645 to 1715. The terrestrial temperature during Maunder Minimum was reduced by up to 1.0C that led to freezing rivers, cold winters and summers. The modern GSM started in 2020 and will last for three solar cycles until 2053. During this GSM two processes will affect the input of solar radiation: a decrease of solar activity and an increase in total solar irradiance because of solar inertial motion (SIM). For evaluation of the latter this study uses daily ephemeris of the Sun-Earth (SE) distances in two millennia from 600 to 2600 showing significant decreases of SE distances in the first 6 months of a year by 0.005 au in 600 to 1600 and by more than 0.01 au in 1600 to 2600 with consequent increases of SE distances in the second halves of a year. Although, these increases are not fully symmetric in the second millennium (1600 to 2600), during which the longest SE distances are gradually shifted from 21 June to 15 July in 2600 while the shortest ones from 21 December to 15 January. These distance variations impose significant increases of solar irradiance in the first six months of each year in the two millennia, which are not fully offset by the solar radiation decreases in the last six months in millennium 1600 to 2600. This misbalance creates an annual surplus of solar radiation to be processed by the terrestrial atmosphere and ocean environments that can lead to an increase of terrestrial temperature. We estimate that decrease of solar activity during GSM combined with its increase imposed by SIM will lead to a reduction of terrestrial temperature during the modern GSM to the levels of 1700. Title: Sunquake with a second bounce, other sunquakes, and emission associated with the X9.3 flare of 6 September 2017. I. Observations Authors: Zharkov, Sergei; Matthews, Sarah; Zharkova, Valentina; Druett, Malcolm; Inoue, Satoshi; Dammasch, Ingolf E.; Macrae, Connor Bibcode: 2020A&A...639A..78Z Altcode:
Aims: The 6 September 2017 X9.3 solar flare produced very unique observations of magnetic field transients and a few seismic responses, or sunquakes, detected by the Helioseismic and Magnetic Imager (HMI) instrument aboard Solar Dynamic Observatory (SDO) spacecraft, including the strongest sunquake ever reported. This flare was one of a few flares occurring within a few days or hours in the same active region. Despite numerous reports of the fast variations of magnetic field, and seismic and white light emission, no attempts were made to interpret the flare features using multi-wavelength observations. In this study, we attempt to produce the summary of available observations of the most powerful flare of the 6 September 2017 obtained using instruments with different spatial resolutions (this paper) and to provide possible interpretation of the flaring events, which occurred in the locations of some seismic sources (a companion Paper II).
Methods: We employed non-linear force-free field extrapolations followed by magnetohydrodynamic simulations in order to identify the presence of several magnetic flux ropes prior to the initiation of this X9.3 flare. Sunquakes were observed using the directional holography and time-distance diagram detection techniques. The high-resolution method to detect the Hα line kernels in the CRISP instrument at the diffraction level limit was also applied.
Results: We explore the available γ-ray (GR), hard X-ray (HXR), Lyman-α, and extreme ultra-violet (EUV) emission for this flare comprising two flaring events observed by space- and ground-based instruments with different spatial resolutions. For each flaring event we detect a few seismic sources, or sunquakes, using Dopplergrams from the HMI/SDO instrument coinciding with the kernels of Hα line emission with strong redshifts and white light sources. The properties of sunquakes were explored simultaneously with the observations of HXR (with KONUS/WIND and the Reuven Ramaty High Energy Solar Spectroscopic Imager payload), EUV (with the Atmospheric Imaging Assembly (AIA/SDO and the EUV Imaging Spectrometer aboard Hinode payload), Hα line emission (with the CRisp Imaging Spectro-Polarimeter (CRISP) in the Swedish Solar Telescope), and white light emission (with HMI/SDO). The locations of sunquake and Hα kernels are associated with the footpoints of magnetic flux ropes formed immediately before the X9.3 flare onset.
Conclusions: For the first time we present the detection of the largest sunquake ever recorded with the first and second bounces of acoustic waves generated in the solar interior, the ripples of which appear at a short distance of 5-8 Mm from the initial flare location. Four other sunquakes were also detected, one of which is likely to have occurred 10 min later in the same location as the largest sunquake. Possible parameters of flaring atmospheres in the locations with sunquakes are discussed using available temporal and spatial coverage of hard X-ray, GR, EUV, hydrogen Hα-line, and white light emission in preparation for their use in an interpretation to be given in Paper II. Title: Sunquake with a second bounce, other sunquakes, and emission associated with the X9.3 flare of 6 September 2017. II. Proposed interpretation Authors: Zharkova, Valentina; Zharkov, Sergei; Druett, Malcolm; Matthews, Sarah; Inoue, Satoshi Bibcode: 2020A&A...639A..79Z Altcode: In this paper we present the interpretation of the observations of the flare from 6 September 2017 reported in Paper I. These include gamma-ray (GR), hard X-ray (HXR), soft X-rays, Lyα line, extreme ultraviolet (EUV), Hα, and white light (WL) emission, which were recorded during the two flaring events 1 (FE1) and 2 (FE2) that occurred at 11:55:37 UT (FE1) and 12:06:40 UT (FE2). Paper I also reported the first detection of the sunquake with first and second bounces of seismic waves combined with four other sunquakes in different locations supported with the observations of HXR, GR, EUV, Hα, and WL emission with strongly varying spatial resolution and temporal coverage. In the current paper, we propose some likely scenarios for heating of flaring atmospheres in the footpoints with sunquakes which were supported with EUV and Hα emission. We used a range of parameters derived from the HXR, EUV, and Hα line observations to generate hydrodynamic models, which can account for the blueshifts derived from the EUV emission and the redshifts observed with the EUV Imaging Spectrometer in the He II line and by the CRisp Imaging Spectro-Polarimeter in the Swedish Solar Telescope in Hα line emission. The parameters of hydrodynamic shocks produced by different beams in flaring atmospheres were used as the initial conditions for another type of hydrodynamic models that were developed for acoustic wave propagation in the solar interior. These models simulate the sets of acoustic waves produced in the interior by the hydrodynamic shocks from atmospheres above deposited in different footpoints of magnetic loops. The Hα line profiles with large redshifts in three kernels (two in FE1 and one in FE2) were interpreted with the full non-local thermodynamic equilibrium radiative simulations in all optically thick transitions (Lyman lines and continuum Hα, Hβ, and Pα) applied for flaring atmospheres with fast downward motions while considering thermal and non-thermal excitation and ionisation of hydrogen atoms by energetic power-law electron beams. The observed Hα line profiles in three kernels were fit with the simulate blue wing emission of the Hα line profiles shifted significantly (by 4-6 Å) towards the line red wings, because of strong downward motions with velocities about 300 km s-1 by the shocks generated in flaring atmospheres by powerful beams. The flaring atmosphere associated with the largest sunquake (seismic source 2 in FE1) is found consistent with being induced by a strong hydrodynamic shock produced by a mixed beam deposited at an angle of -30° from the local vertical. We explain the occurrence of a second bounce in the largest sunquake by a stronger momentum delivered by the shock generated in the flaring atmosphere by a mixed beam and deeper depths of the interior where this shock was deposited. Indeed, the shock with mixed beam parameters is found deposited deeply into the interior beneath the flaring atmosphere under the angle to the local vertical that would allow the acoustic waves generated in the direction closer to the surface to conserve enough energy for the second bounces from the interior layers and from the photosphere. The wave characteristics of seismic sources 1 and 3 (in FE1) were consistent with those produced by the shocks generated by similar mixed beams deposited at the angles -(0 - 10)° (seismic source 1) and +30° (seismic source 3) to the local vertical. The differences of seismic signatures produced in the flares of 6 September 2011 and 2017 are also discussed. Title: Millennial solar irradiance forcing (Hallstatt's cycle) in the terrestrial temperature variations Authors: Zharkova, Valentina; Shepherd, Simon; Popova, Elena Bibcode: 2020EGUGA..2211107Z Altcode: In this paper we explore the millennial oscillations (or Hallstatt cycle) of the baseline solar magnetic field, total solar irradiance and baseline terrestrial temperature detected from Principal Component Analysis of the observed solar background magnetic field. We confirm the existence of these oscillations with a period of 2100-2200 years with the similar oscillations detected in carbon 14C isotope abundances and with wavelet analysis of solar irradiance in the past 12 millennia indicating the presence of this millennial period among a few others. We also test again the idea expressed in our paper Zharkova et al, 2019 that solar inertial motion (SIM) can cause these millennial variations because of a change of the distance between the Sun and Earth. In this paper we use the S-E distance derived from the current JPL ephemeris, finding that currently starting from the Maunder minimum the Sun-Earth distance is reducing by 0.00025 au per 100 years, or by 0.0025 au per 1000 years.. We present the estimation of variations of solar irradiance caused by this variation of the S-E distance caused by solar inertial motion (SIM) demonstrating these variations to be closely comparable with the observed variations of the solar irradiance measured by the SATIRE payload. We also estimate the baseline temperature variations since Maunder Minimum caused by the increase of solar irradiance caused by the recovery from grand solar minimum and by reduction of the S-E distance caused by SIM. These estimations show that the Sun will still continue moving towards the Earth in the next 700 years that will result in the increase of the baseline terrestrial temperature by up to 2.5°C in 2700. These variations of solar irradiance will be over-imposed by the variations of solar activity of 11 cycles and the two grand solar minima occurring in 2020-2053 and 2370-2415 caused by the double dynamo actions inside the Sun. Title: Solar wind re-acceleration in local current sheets and their diagnostics from observations Authors: Xia, Qian; Zharkova, Valentina Bibcode: 2020EGUGA..22.9446X Altcode: We explore solar wind re-acceleration during their passage through reconnecting current sheets in the interplanetary space using the particle-in-cell approach. We investigate particle acceleration in 3D Harris-type reconnecting current sheets with a single or multiple X-nullpoints taking into account the ambient plasma feedback to the presence of accelerated particles. We also consider coalescent and squashed magnetic islands formed in the current sheets with different magnetic field topologies, thickness, ambient density, and mass ratios. With the PIC approach, we detected distinct populations of two groups of particles, transit and bounced ones, which have very different energy and asymmetric pitch-angle distributions associated with the magnetic field parameters. We present a few cross-sections of the simulated pitch-angle distributions of accelerated particles and compare them with the in-situ observations of solar wind particles. This comparison indicates that locally generated superthermal electrons can account for the counter-streaming 'strahls' often observed in pitch-angle distribution spectrograms of the satellites crossing heliospheric current sheets. Title: Counterstreaming strahls and dropouts observed in pitch angle distributions of suprathermal electrons as possible signatures of local particle acceleration in the solar wind Authors: Khabarova, Olga; Zharkova, Valentina; Xia, Qian; Malandraki, Olga Bibcode: 2020EGUGA..2210819K Altcode: We present multi-spacecraft observations of pitch-angle distributions (PADs) of suprathermal electrons at ~1 AU which cannot be easily interpreted within the classical paradigm that all suprathermal electrons originate in the solar corona. We suggest that suprathermal electrons accelerated locally in the solar wind are mixed up with the well-known population of electrons of solar origin. Using PIC simulations, we show that key PAD features such as (i) heat flux dropouts and vertical PAD stripes encompassing reconnecting current sheets (RCSs), (ii) bi-directionality of strahls, and (iii) dramatically different PAD patterns observed in different energy channels can be explained by the behavior of electrons accelerated up to hundreds eV directly in the solar wind while thermal particles pass through local RCSs and/or dynamical 3D plasmoids (or 2D magnetic islands). Title: Effects of local particle acceleration in the solar wind Authors: Khabarova, Olga; Zharkova, Valentina; Xia, Qian; Malandraki, Olga Bibcode: 2020EGUGA..22.3711K Altcode: Recent observational and theoretical studies have shown that there is an unaccounted population of electrons and protons accelerated locally to suprathermal energies at reconnecting current sheets (RCSs) and 3-D dynamical plasmoids or 2-D magnetic islands (MIs) in the solar wind. The findings can be summarized as following: (i) RCSs are often subject to instabilities breaking those into 3D small-scale plasmoids/blobs or 2D magnetic islands (MIs) with multiple X- and O-nullpoints; (ii) RCSs and dynamical MIs can accelerate particles up to the MeV/nuc energies; (iii) accelerated particles may form clouds expanding far from a reconnecting region; and (iv) bi-directional(or counterstreaming) strahls observed in pitch-angle distributions (PADs) of suprathermal electrons may simply represent a signature of magnetic reconnection occurring at closed IMF structures (e.g., MIs), not necessarily connected to the Sun (Zharkova & Khabarova, 2012, 2015; Zank et al. 2014, 2015; Khabarova et al. 2015, 2016, 2017; 2018; le Roux 2016, 2017, 2018, 2019; Khabarova & Zank, 2017; Adhikari et al. 2019; Xia & Zharkova, 2018, 2020; Malandraki et al. 2019; Mingalev et al. 2019). We will briefly present an overview of the effects of local ion acceleration as observed at different heliocentric distances and focus on the impact of the locally-borne population of suprathermal electrons on typical patterns of PADs. Suprathermal electrons with energies of ~70eV and above are observed at 1 AU as dispersionless halo and magnetic field-aligned beams of strahls. For a long time, it has been thought that both populations originate only from the solar corona. This view has consequently impacted interpretation of typical patterns of suprathermal electron PADs observed in the solar wind. We present multi-spacecraft observations of counterstreaming strahls and dropouts in PADs within a previously reported region filled with plasmoids and RCSs, comparing observed PAD features with those predicted by PIC simulations extended to heliospheric conditions. We show typical features of PADs determined by acceleration of the ambient thermal electrons up to suprathermal energies in single RCSs and dynamical plasmoids. Our study suggests that locally-accelerated suprathermal electrons co-exist with those of solar origin. Therefore, some heat flux dropout and bi-directional strahl events observed in the heliosphere can be explained by local dynamical processes involving magnetic reconnection. Possible implications of the results for the interpretation of the strahl/halo relative density change with heliocentric distance and puzzling features of suprathermal electrons observed at crossings of the heliospheric current sheet and cometary comas are also discussed. Title: Acceleration of particles in different parts of erupting coronal mass ejections Authors: Zharkova, Valentina; Xia, Qian; Dahlin, Joel; Antiochos, Spiro Bibcode: 2020EGUGA..2220181Z Altcode: We examine particle energisation in CMEs generated via the breakout mechanism and explore both 2D and 3D MHD configurations. In the breakout scenario, reconnection at a breakout current sheet (CS) initiates the flux rope eruption by destabilizing the quasi-static force balance. Reconnection at the flare CS triggers the fast acceleration of the CME, which forms flare loops below and triggers particle acceleration in flares. We present test-particle studies that focus on two selected times during the impulsive and decay phases of the eruption and obtain particle energy gains and spatial distributions. We find that particles accelerated more efficiently in the flare CS than in the breakout CS even in the presence of large magnetic islands. The maximum particle energy gain is estimated from the energization terms based on the guiding-center approximation. Particles are first accelerated in the CSs (with or without magnetic islands) where Fermi-type acceleration dominates. Accelerated particles escape to the interplanetary space along open field lines rather than trapped in flux ropes, precipitate into the chromosphere along the flare loops, or become trapped in the flare loop top due to the magnetic mirror structure. Some trapped particles are re-accelerated, either via re-injection to the flare CS or through a local betatron-type acceleration associated with compression of the magnetic field. The energy gains of particles result in relatively hard energy spectra during the impulsive phase. During the gradual phase, the relaxation of the shear in magnetic field reduces the guiding magnetic field in the flare CS, which leads to a decrease in particle energization efficiency. Title: Particle Acceleration and Transport during 3D CME Eruptions Authors: Xia, Qian; Dahlin, Joel T.; Zharkova, Valentina; Antiochos, Spiro K. Bibcode: 2020ApJ...894...89X Altcode: We calculate particle acceleration during coronal mass ejection (CME) eruptions using combined magnetohydrodynamic and test-particle models. The 2.5D/3D CMEs are generated via the breakout mechanism. In this scenario a reconnection at the "breakout" current sheet (CS) above the flux rope initiates the CME eruption by destabilizing a quasi-static force balance. Reconnection at the flare CS below the erupting flux rope drives the fast acceleration of the CME, which forms flare loops below and produces the energetic particles observed in flares. For test-particle simulations, two times are selected during the impulsive and decay phases of the eruption. Particles are revealed to be accelerated more efficiently in the flare CS rather than in the breakout CS even in the presence of large magnetic islands. Particles are first accelerated in the CSs (with or without magnetic islands) by the reconnection electric field mainly through particle curvature drift. We find, as expected, that accelerated particles precipitate into the chromosphere, become trapped in the loop top by magnetic mirrors, or escape to interplanetary space along open field lines. Some trapped particles are reaccelerated, either via reinjection to the flare CS or through a local Betatron-type acceleration associated with compression of the magnetic field. The energetic particles produce relatively hard energy spectra during the impulsive phase. During the gradual phase, the relaxation of magnetic field shear reduces the guiding field in the flare CS, which leads to a decrease in particle energization efficiency. Important implications of our results for observations of particle acceleration in the solar coronal jets are also discussed. Title: Counterstreaming Strahls and Heat Flux Dropouts as Possible Signatures of Local Particle Acceleration in the Solar Wind Authors: Khabarova, O.; Zharkova, V.; Xia, Q.; Malandraki, O. E. Bibcode: 2020ApJ...894L..12K Altcode: Suprathermal electrons with energies of ∼70 eV and above are observed at 1 au as dispersionless halo electrons and magnetic field-aligned beams of strahls. For a long time, it has been thought that both populations originate only from the solar corona, and that the only active process impacting their properties in the solar wind is scattering. This view has consequently impacted the interpretation of typical patterns of pitch-angle distributions (PADs) of suprathermal electrons. Meanwhile, recent observational studies supported by numerical simulations have shown that there is an unaccounted population of electrons accelerated to suprathermal energies at reconnecting current sheets (RCSs) and 3D dynamical plasmoids (or 2D magnetic islands (MIs)) directly in the heliosphere. We present multispacecraft observations of counterstreaming strahls and heat flux dropouts in PADs within a region filled with plasmoids and RCSs unaffected by interplanetary shocks, comparing observed PAD features with those predicted by particle-in-cell simulations. We show typical PAD patterns determined by local acceleration of thermal-core electrons up to hundreds of electron volts. Resulting PAD views depend on properties and topology of particular RCSs, MIs, and plasma/magnetic field parameters. Our study suggests that solar wind-borne suprathermal electrons coexist with those of solar origin. Therefore, some of heat flux dropout and bidirectional strahl events can be explained by local dynamical processes involving magnetic reconnection. Possible implications of the results for the interpretation of the actively debated decrease in the strahl/halo relative density with heliocentric distance and puzzling features of suprathermal electrons observed at crossings of the heliospheric current sheet and cometary comas are also discussed. Title: Particle acceleration in coalescent and squashed magnetic islands. II. Particle-in-cell approach Authors: Xia, Q.; Zharkova, V. Bibcode: 2020A&A...635A.116X Altcode:
Aims: Particles are known to have efficient acceleration in reconnecting current sheets with multiple magnetic islands that are formed during a reconnection process. Using the test-particle approach, the recent investigation of particle dynamics in 3D magnetic islands, or current sheets with multiple X- and O-null points revealed that the particle energy gains are higher in squashed magnetic islands than in coalescent ones. However, this approach did not factor in the ambient plasma feedback to the presence of accelerated particles, which affects their distributions within the acceleration region.
Methods: In the current paper, we use the particle-in-cell (PIC) approach to investigate further particle acceleration in 3D Harris-type reconnecting current sheets with coalescent (merging) and squashed (contracting) magnetic islands with different magnetic field topologies, ambient densities ranging between 108 - 1012 m-3, proton-to-electron mass ratios, and island aspect ratios.
Results: In current sheets with single or multiple X-nullpoints, accelerated particles of opposite charges are separated and ejected into the opposite semiplanes from the current sheet midplane, generating a strong polarisation electric field across a current sheet. Particles of the same charge form two populations: transit and bounced particles, each with very different energy and asymmetric pitch-angle distributions, which can be distinguished from observations. In some cases, the difference in energy gains by transit and bounced particles leads to turbulence generated by Buneman instability. In magnetic island topology, the different reconnection electric fields in squashed and coalescent islands impose different particle drift motions. This makes particle acceleration more efficient in squashed magnetic islands than in coalescent ones. The spectral indices of electron energy spectra are ∼ - 4.2 for coalescent and ∼ - 4.0 for squashed islands, which are lower than reported from the test-particle approach. The particles accelerated in magnetic islands are found trapped in the midplane of squashed islands, and shifted as clouds towards the X-nullpoints in coalescent ones.
Conclusions: In reconnecting current sheets with multiple X- and O-nullpoints, particles are found accelerated on a much shorter spatial scale and gaining higher energies than near a single X-nullpoint. The distinct density and pitch-angle distributions of particles with high and low energy detected with the PIC approach can help to distinguish the observational features of accelerated particles. Title: Overview of appearance of energetic particles in the solar corona and heliosphere Authors: Zharkova, Valentina Bibcode: 2019EGUGA..21.6854Z Altcode: This is an overview of appearance of energetic particles in the solar corona and heliosphere and additional acceleration mechanisms of solar and solar wind particles in the heliosphere. We will explore possible acceleration associated with reconnecting current sheets, termination shocks , current sheets with magnetic islands and associated turbulent structures. We will evaluate timing, energy and pitch angle distributions of energetic particles produced during the evolution of reconnecting current sheets with and without magnetic islands, formation of turbulent structures and their effect on accelerated particles. These distributions will be probed by observational characteristics of energetic particles in solar flares and solar wind particles at different distances from the Sun. Title: Particle acceleration in coalescent and squashed magnetic islands. I. Test particle approach Authors: Xia, Q.; Zharkova, V. Bibcode: 2018A&A...620A.121X Altcode:
Aims: Magnetic reconnection in large Harris-type reconnecting current sheets (RCSs) with a single X-nullpoint often leads to the occurrence of magnetic islands with multiple O- and X-nullpoints. Over time these magnetic islands become squashed, or coalescent with two islands merging, as has been observed indirectly during coronal mass ejection and by in-situ observations in the heliosphere and magnetotail. These points emphasise the importance of understanding the basic energising processes of ambient particles dragged into current sheets with magnetic islands of different configuration.
Methods: Trajectories of protons and electrons accelerated by a reconnection electric field are investigated using a test particle approach in RCSs with different 3D magnetic field topologies defined analytically for multiple X- and O-nullpoints. Trajectories, densities, and energy distributions are explored for 106 thermal particles dragged into the current sheets from different sides and distances.
Results: This study confirms that protons and electrons accelerated in magnetic islands in the presence of a strong guiding field are ejected from a current sheet into the opposite semiplanes with respect to the midplane. Particles are found to escape O-nullpoints only through the neighbouring X-nullpoints along (not across) the midplane following the separation law for electrons and protons in a given magnetic topology. Particles gain energy either inside O-nullpoints or in the vicinity of X-nullpoints that often leads to electron clouds formed about the X-nullpoint between the O-nullpoints. Electrons are shown to be able to gain sub-relativistic energies in a single magnetic island. Energy spectra of accelerated particles are close to power laws with spectral indices varying from 1.1 to 2.4. The more squashed the islands the larger the difference between the energy gains by transit and bounced particles, which leads to their energy spectra having double maxima that gives rise to fast-growing turbulence.
Conclusions: Particles are shown to gain the most energy in multiple X-nullpoints between O-nullpoints (or magnetic islands). This leads to the formation of electron clouds between magnetic islands. Particle energy gains are much larger in squashed islands than in coalescent ones. In summary, particle acceleration by a reconnection electric field in magnetic islands is much more effective than in an RCS with a single X-nullpoint. Title: Lost and found sunquake in the 6 September 2011 flare caused by beam electrons Authors: Macrae, Connor; Zharkov, Sergei; Zharkova, Valentina; Druett, Malcolm; Matthews, Sarah; Kawate, Tomoko Bibcode: 2018A&A...619A..65M Altcode: The active region NOAA 11283 produced two X-class flares on 6 and 7 September 2011 that have been well studied by many authors. The X2.1 class flare occurred on September 6, 2011 and was associated with the first of two homologous white light flares produced by this region, but no sunquake was found with it despite the one being detected in the second flare of 7 September 2011. In this paper we present the first observation of a sunquake for the 6 September 2011 flare detected via statistical significance analysis of egression power and verified via directional holography and time-distance diagram. The surface wavefront exhibits directional preference in the north-west direction We interpret this sunquake and the associated flare emission with a combination of a radiative hydrodynamic model of a flaring atmosphere heated by electron beam and a hydrodynamic model of acoustic wave generation in the solar interior generated by a supersonic shock. The hydrodynamic model of the flaring atmosphere produces a hydrodynamic shock travelling with supersonic velocities toward the photosphere and beneath. For the first time we derive velocities (up to 140 km s-1) and onset time (about 50 s after flare onset) of the shock deposition at given depths of the interior. The shock parameters are confirmed by the radiative signatures in hard X-rays and white light emission observed from this flare. The shock propagation in the interior beneath the flare is found to generate acoustic waves elongated in the direction of shock propagation, that results in an anisotropic wavefront seen on the solar surface. Matching the detected seismic signatures on the solar surface with the acoustic wave front model derived for the simulated shock velocities, we infer that the shock has to be deposited under an angle of about 30° to the local solar vertical. Hence, the improved seismic detection technique combined with the double hydrodynamic model reported in this study opens new perspectives for observation and interpretation of seismic signatures in solar flares. Title: On a role of quadruple component of magnetic field in defining solar activity in grand cycles Authors: Popova, E.; Zharkova, V.; Shepherd, S.; Zharkov, S. Bibcode: 2018JASTP.176...61P Altcode: In this paper we revise our prediction of solar activity using a solar background magnetic field as a proxy by the inclusion of eigen vectors of solar magnetic waves produced by quadruple magnetic sources, in addition to the principal eigen modes generated by two-layer dipole sources (Zharkova et al., 2015). By considering the interference of two dipole and one quadruple waves we produce the revised summary curve for the last 400 years accounting for the additional minima of solar activity occurred at the beginning of 19th (Dalton minimum) and 20th centuries. Using the dynamo model with meridional circulation and selecting the directions of circulation for quadruple waves, we estimate the parameters of quadrupole waves best fitting the observations in the past grand cycle. The comparison shows that the quadruple wave has to be generated in the inner layer of the solar convective zone, in order to provide the additional minima observed in 19 and 20 centuries, thus, naturally accounting for Gleissberg centennial cycle. The summary dynamo wave simulated for the dipole and quadruple sources reveals much closer correspondence of the resulting summary curve derived from the principal components of magnetic field variations to the solar activity oscillations derived from the average sunspot numbers in the current grand cycle. Title: Reply to comment on the paper " on a role of quadruple component of magnetic field in defining solar activity in grand cycles" by Usoskin (2017) Authors: Zharkova, V.; Popova, E.; Shepherd, S.; Zharkov, S. Bibcode: 2018JASTP.176...72Z Altcode: In this communication we provide our answers to the comments by Usoskin (2017) on our recent paper (Popova et al, 2017a). We show that Principal Component Analysis (PCA) allows us to derive eigen vectors with eigen values assigned to variance of solar magnetic field waves from full disk solar magnetograms obtained in cycles 21-23 which came in pairs. The current paper (Popova et al, 2017a) adds the second pair of magnetic waves generated by quadruple magnetic sources. This allows us to recover a centennial cycle, in addition to the grand cycle, and to produce a closer fit to the solar and terrestrial activity features in the past millennium. Title: Comparing two acoustically active September 6 X-class Flares of Solar Cycle 24. Authors: Zharkov, Sergei; Matthews, Sarah A.; Zharkova, Valentina; Macrae, Connor Bibcode: 2018cosp...42E3856Z Altcode: Two of the larger X-class flares of the current cycle have taken place on September 6, one near the peak of the cycle in 2011 and the other one approaching the minimum in 2017. We show that both have been accompanied by two sun quakes exhibiting very different properties. We analyse both events and their photospheric impact using helioseismic techniques and SDO HMI data supplemented by atmospheric observations from GOES, AIA and Hinode, and consider energies and momenta to look at possible mechanisms of sun quake generation in each case. Title: Solar magnetic field oscillations and activity on a millennium timescale derived with Principal Component Analysis Authors: Zharkova, Valentina; Popova, Helen; Zharkov, Sergei; Shepherd, Simon Bibcode: 2018cosp...42E3860Z Altcode: Applying Principal Components Analysis (PCA) to the full-disk synoptic maps of solar magnetic field variations obtained by Wilcox Solar Observatory in solar cycles 21-24 we derive 4 pairs of eigen values and eigen vectors (Zharkova et al, 2015) and analytical expressions as the sums of periodic sin and cosine functions for the first pair of eigen vectors (principal components). The analytical expression for the summary curve of the pair is applied for prediction of solar magnetic field variations in the two layers of the solar interior in the past three millennia. Extrapolation of the summary curve of PCs in the past 3000 years confirms the eight grand cycles of 350-400-years superimposed on 22 year-cycles caused by beating effect of the two dynamo waves generated by dipole magnetic sources in the two (deep and shallow) layers of the solar interior. The grand cycles in different periods comprise a different number of individual 22-year cycles. Furthermore, the summary curve reproduces a remarkable resemblance to the sunspot and terrestrial activity reported in the past: known grand minima- Maunder Minimum, Wolf minimum, Homer minimum and many other grand minima occurring every 350-400 years, a medieval warmth period and Roman warmth Period. Temporal variations of the dynamo waves are modelled for dipole sources with the two-layer mean dynamo model with meridional circulation. The addition of quadruple magnetic waves in the inner layer allowed us to recover Dalton minimum and the other minima of Gleissberg's centennial cycle (Popova et al, 2017). The modelled dynamo waves reveal a remarkable resemblance of the temporal variations and butterfly diagrams to those derived with PCA and predict the upcoming modern grand minimum in 2020-2055 (Zharkova et al, 2017). We expand our summary curve back to 100000 years to discover further periods of activity of 11000 years confirmed by the terrestrial data. Title: Particle acceleration in a reconnecting current sheet: coalescent and squashing magnetic islands Authors: Zharkova, Valentina; Xia, Qian Bibcode: 2018cosp...42E3858Z Altcode: We investigate particle acceleration in 3D reconnecting current sheets (RCSs) containing multiple O- and X-nullpointsand different topologies: coalescent (moving towards each other) and squashed islands using a test particle and particle-in-cell (PIC) approach. The inclusion of multiple O-nullpoints, or magnetic islands, reveals that acceleration of protons and electrons in a current sheet with strong guiding field remains asymmetric towardsthe midplane, e.g. electrons and protons are ejected into the opposite directions from the midplane. Both types of particles (electrons and protons) mainly gain energy in a vicinity of X-nullpoints or inside O-nullpoints and, depending on their initial energy, these gains can reach relativistic energies in a single island. Accelerated particleswith critical energies can escape O-nullpoints, or magnetic islands, only through neighbouring X-nullpointsescape along the midplane. As result, there are electron clouds formed between the magnetic islands while electronsgain the critical energy to break from an RCS. The energy gains in coalescent islands are much smaller thanfrom the squashed ones. Electrons are shown to form clouds about X-nullpoints between the magnetic islandswhere they become ejected after gaining the critical energies required to break from the RCS magnetic topology. Particle accelerationin 3D RCSs with multiple X- and O-nullpoints is probed with some observational features in the solar corona andheliosphere. This research is funded by the US Airforce grant. Title: Particle Acceleration in Coalescent and Squashing Magnetic Islands: TP and PIC approach Authors: Zharkova, Valentina; Xia, Qian Bibcode: 2018cosp...42E3859Z Altcode: We investigate particle acceleration in 3D reconnecting current sheets (RCSs) containing multiple O- and X-nullpointsand different topologies: coalescent (moving towards each other) and squashed islands using a test particle and particle-in-cell (PIC) approach. The inclusion of multiple O-nullpoints, or magnetic islands, reveals that acceleration of protons and electrons in a current sheet with strong guiding field remains asymmetric towardsthe midplane, e.g. electrons and protons are ejected into the opposite directions from the midplane. Both types of particles (electrons and protons) mainly gain energy in a vicinity of X-nullpoints or inside O-nullpoints and, depending on their initial energy, these gains can reach relativistic energies in a single island. Accelerated particleswith critical energies can escape O-nullpoints, or magnetic islands, only through neighbouring X-nullpointsescape along the midplane. As result, there are electron clouds formed between the magnetic islands while electronsgain the critical energy to break from an RCS. The energy gains in coalescent islands are much smaller thanfrom the squashed ones. Electrons are shown to form clouds about X-nullpoints between the magnetic islandswhere they become ejected after gaining the critical energies required to break from the RCS magnetic topology. Particle accelerationin 3D RCSs with multiple X- and O-nullpoints is probed with some observational features in the heliosphere. This research is funded by the US Airforce grant. Title: Upcoming modern grand minimum and solar activity prediction backwards five millennia Authors: Zharkova, Valentina; Shepherd, Simon; Popova, Elena; Zharkov, Sergei; Xia, Qian Bibcode: 2018EGUGA..20.8066Z Altcode: In this study using a summary curve of two eigen vectors of solar magnetic field oscillations derived with Principal Components Analysis (PCA) from synoptic maps for solar cycles 21-24 we extrapolate solar activity backwards five millennia showing the occurrence grand cycles of 350-400 years. The summary curve shows a remarkable resemblance to the past sunspot and terrestrial activity: grand minima - Maunder Minimum (1645-1715AD), Wolf minimum (1280-1350 AD), Oort minimum (1010-1050 AD) and Homer minimum (800-900 BC) and grand maxima - modern warm period (1990-2015), medieval warm period (900-1200 AD), Roman warm period (400-10 BC) and others. We verify the extrapolated activity curve by pre-telescope observations of large sunspots, by maximum of the terrestrial temperature and extremely intense terrestrial auroras seen in 14-16 centuries and observed and simulated butterfly diagram for the Maunder Minimum (MM). We confirm the occurrence of upcoming Modern grand minimum in 2020-2055 and show it will have higher solar activity and shorter duration compared to MM. The results are probed with the terrestrial features and the two-layer solar dynamo model with different meridional circulation velocities. We argue that Sporer minimum (1450-1550) derived from the increased abundances of isotopes C14 and Be10 are likely produced by a strong increase of the terrestrial background radiation caused by galactic cosmic rays of powerful supernovae. Title: Particle acceleration in a reconnecting current sheet with multiple X- and O-nullpoints Authors: Xia, Qian; Zharkova, Valentina Bibcode: 2018EGUGA..20.8325X Altcode: We investigate particle acceleration in 3D reconnecting current sheets (RCSs) containing multiple O- and X-nullpoints. The inclusion of multiple O-nullpoints, or magnetic islands, combined with different dynamics (coalescent or squashed islands) reveals the following points: Acceleration of protons and electrons in the current sheet with multiple X-nullpoints, or magnetic islands associated with O-nullpoints with a strong guiding field remains asymmetric towards the midplane. Both types of particles mainly gain energy either in a vicinity of X-nullpoints or inside O-nullpoints, depending on the initial energy of particles. Strongly accelerated particles can escape O-nullpoints, or magnetic islands, only through the neighbouring X-nullpoints. As a result, electron clouds are formed about the X-nullpoints between the magnetic islands. The particles with sufficient energy to leave the RCS escape along the midplane and never across the midplane. The energy gains in coalescent islands are smaller than in the squashed islands when the two nearby O-nullpoints are moving towards each other. Under certain conditions, the particles are shown to gain sub-relativistic energies in a single O-nullpoint. Electrons are shown to form clouds about X-nullpoints between the magnetic islands where they become ejected. Particle acceleration in 3D RCSs with multiple X- and O-nullpoints is probed with some observational features in the solar corona and heliosphere. Title: On a role of quadruple component of magnetic field in defining solar activity in grand cycles Authors: Popova, E.; Zharkova, V.; Shepherd, S.; Zharkov, S. Bibcode: 2017simi.conf...34P Altcode: The aim of this work is revise our prediction of solar activity using a solar background magnetic field as a proxy by the inclusion of eigen vectors of solar magnetic waves produced by quadruple magnetic sources [Popova et al, 2017], in addition to the principal eigen modes generated by two-layer dipole sources [Zharkova et al., 2015]. By considering the interference of two dipole and one quadruple waves we produce the revised summary curve for the last 400 years accounting for the additional minima of solar activity occurred at the beginning of 19th (Dalton minimum) and 20th centuries. Using the dynamo model with meridional circulation and selecting the directions of circulation for quadruple waves, we estimate the parameters of quadruple waves best fitting the observations in the past grand cycle. The comparison shows that the quadruple wave has to be generated in the inner layer of the solar convective zone, in order to provide the additional minima observed in 19 and 20 centuries naturally accounting for Gleissberg centennial cycle. The summary dynamo waves simulated for the dipole and quadruple sources with longer periods of centennial cycle reveal closer correspondence to the solar activity oscillations derived from the average sunspot numbers in the current grand cycle. Title: Beam electrons as a source of Hα flare ribbons Authors: Druett, Malcolm; Scullion, Eamon; Zharkova, Valentina; Matthews, Sarah; Zharkov, Sergei; Rouppe van der Voort, Luc Bibcode: 2017NatCo...815905D Altcode: The observations of solar flare onsets show rapid increase of hard and soft X-rays, ultra-violet emission with large Doppler blue shifts associated with plasma upflows, and Hα hydrogen emission with red shifts up to 1-4 Å. Modern radiative hydrodynamic models account well for blue-shifted emission, but struggle to reproduce closely the red-shifted Hα lines. Here we present a joint hydrodynamic and radiative model showing that during the first seconds of beam injection the effects caused by beam electrons can reproduce Hα line profiles with large red-shifts closely matching those observed in a C1.5 flare by the Swedish Solar Telescope. The model also accounts closely for timing and magnitude of upward motion to the corona observed 29 s after the event onset in 171 Å by the Atmospheric Imaging Assembly/Solar Dynamics Observatory. Title: Two principal components of solar magnetic field variations and prediction of solar activity on multi-millennium timescale Authors: Zharkova, Valentina; Popova, Helen; Zharkov, Sergei; Shepherd, Simon Bibcode: 2016cosp...41E2176Z Altcode: We present principal components analysis (PCA) of temporal magnetic field variations over the solar cycles 21-24 and their classification with symbolic regression analysis using Hamiltonian method. PCA reveals 4 pairs of magnetic waves with a significant variance and the two principal components with the highest eigen values covering about 40% of this variance. The PC waves are found to have close frequencies while travelling from the opposite hemispheres with an increasing phase shift. Extrapolation of these PCs through their summary curve backward for 5000 years reveals a repeated number of ~350-400 year grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past including Maunder, Dalton and Wolf minima, as well as the modern, medieval and roman warmth periods. The summary curve calculated forward for the next millennium predicts further three grand cycles with the closest grand minimum (Maunder minimum) occurring in the forthcoming cycles 25-27 when the two magnetic field waves approach the phase shift of 11 years. We also note a super-grand cycle of about 2000 years which reveal the 5 repeated grand cycles of 350 years with the similar patterns. We discuss a role of other 3 pairs of magnetic waves in shaping the solar activity and compare our predicted curve with the previous predictions of the solar activity on a long timescale based on the terrestrial proxies. These grand cycle variations are probed by Parker's two layer dynamo model with meridional circulation revealing two dynamo waves generated with close frequencies. Their interaction leads to beating effects responsible for the grand cycles (300-350 years) and super-grand cycles of 2000 years superimposed on standard 22 year cycles. This approach opens a new era in investigation and prediction of solar activity on long-term timescales. Title: Energy Transport Effects in Flaring Atmospheres Heated by Mixed Particle Beams Authors: Zharkova, Valentina; Zharkov, Sergei; Macrae, Connor; Druett, Malcolm; Scullion, Eamon Bibcode: 2016cosp...41E2175Z Altcode: We investigate energy and particle transport in the whole flaring atmosphere from the corona to the photosphere and interior for the flaring events on the 1st July 2012, 6 and 7 September 2011 by using the RHESSI and SDO instruments as well as high-resolution observations from the Swedish 1-metre Solar Telescope (SST3) CRISP4 (CRisp Imaging Spectro-polarimeter). The observations include hard and soft X-ray emission, chromospheric emission in both H-alpha 656.3 nm core and continuum, as well as, in the near infra-red triplet Ca II 854.2 nm core and continuum channels and local helioseismic responses (sunquakes). The observations are compared with the simulations of hard X-ray emission and tested by hydrodynamic simulations of flaring atmospheres of the Sun heated by mixed particle beams. The temperature, density and macro-velocity variations of the ambient atmospheres are calculated for heating by mixed beams and the seismic response of the solar interior to generation of supersonic shocks moving into the solar interior. We investigate the termination depths of these shocks beneath the quiet photosphere levels and compare them with the parameters of seismic responses in the interior, or sunquakes (Zharkova and Zharkov, 2015). We also present an investigation of radiative conditions modelled in a full non-LTE approach for hydrogen during flare onsets with particular focus on Balmer and Paschen emission in the visible, near UV and near IR ranges and compare them with observations. The links between different observational features derived from HXR, optical and seismic emission are interpreted by different particle transport models that will allow independent evaluation of the particle transport scenarios. Title: On the Generation of Hydrodynamic Shocks by Mixed Beams and Occurrence of Sunquakes in Flares Authors: Zharkova, Valentina; Zharkov, Sergei Bibcode: 2015SoPh..290.3163Z Altcode: 2015SoPh..tmp..165Z Observations of solar flares with sunquakes by space- and ground-based instruments reveal essentially different dynamics of seismic events in different flares. Some sunquakes are found to be closely associated with the locations of hard X-ray (HXR) and white-light (WL) emission, while others are located outside either of them. In this article we investigate possible sources causing a seismic response in a form of hydrodynamic shocks produced by the injection of mixed (electron plus proton) beams, discuss the velocities of these shocks, and the depths where they deposit the bulk of their energy and momentum. The simulation of hydrodynamic shocks in flaring atmospheres induced by electron-rich and proton-rich beams reveals that the linear depth of the shock termination is shifted beneath the level of the quiet solar photosphere on a distance from 200 to 5000 km. The parameters of these atmospheric hydrodynamic shocks are used as initial condition for another hydrodynamic model developed for acoustic-wave propagation in the solar interior (Zharkov, Mon. Not. Roy. Astron. Soc.431, 3414, 2013). The model reveals that the depth of energy and momentum deposition by the atmospheric shocks strongly affects the propagation velocity of the acoustic-wave packet in the interior. The locations of the first bounces from the photosphere of acoustic waves generated in the vicinity of a flare are seen as ripples on the solar surface, or sunquakes. Mixed proton-dominated beams are found to produce a strong supersonic shock at depths 200 - 300 km under the level of the quiet-Sun photosphere and in this way produce well-observable acoustic waves, while electron-dominated beams create a slightly supersonic shock propagating down to 5000 km under the photosphere. This shock can only generate acoustic waves at the top layers beneath the photosphere since the shock velocity very quickly drops below the local sound speed. The distance Δ of the first bounce of the generated acoustic waves is discussed in relation to the minimal phase velocities of wave packets defined by the acoustic cutoff frequency and the parameters of atmospheric shock termination beneath the photosphere. Title: Sunquakes and their relationship with coronal magnetic topology Authors: Green, Lucie; Zharkov, Sergei; Matthews, Sarah; Zharkova, Valentina Bibcode: 2015IAUGA..2253942G Altcode: Sunquakes were first predicted in 1972 by Wolff and are seen in the Sun’s photosphere as a burst of outwardly emanating ripples, caused by sudden a release of energy below the surface that produces sound waves. Typically the formation of a sunquake is discussed in the context of a solar flare in which a propagation of energy and momentum downward from the corona occurs via accelerated particles, Lorentz force transients, MHD wave conversion or so-called back-warming from coronal and chromospheric radiation at the footpoints of the flare loops. But many sunquakes also occur in concert with a coronal mass ejection and therefore within a magnetic field that is evolving on an active region-wide scale. More specifically, the locations of some of these sunquakes have a magnetic connection to the erupting magnetic field rather than the flare loops themselves.So, how can the sunquake generation scenarios be informed/constrained by considering the overall magnetic field configuration in which they are formed? This talk will use data spanning the photosphere to corona to reveal the magnetic field configuration and its evolution, so that sunquake generation scenarios can be placed in the context of an erupting magnetic configuration with associated energy and momentum transport. Title: Probing observations of the heliospheric current sheet at various distances from the Sun with 3D PIC simulations Authors: Zharkova, Valentina; Khabarova, Olga; Kuznetsov, Vladimir Bibcode: 2014cosp...40E3825Z Altcode: Our previous investigation has shown that observed peculiarities of the solar wind plasma behaviour around sector boundaries at 1 AU are most possibly resulted from a quasi-permanent magnetic reconnection at the heliocentric current sheet (HCS) (Zharkova, Khabarova, ApJ, 2012). In the current research we explore the heliospheric current sheet variations through the space and time, and compare observed dynamics of electrons and ions in the HCS vicinity with 3D PIC calculations of particle motion through a current sheet. By using different spacecraft’s data over whole the space era we analyze the radial and longitudinal transformation of the HCS at different phases of the solar cycle. We carry out a comparison of the observed solar wind plasma parameters with the those derived from PIC modeling for particle and electro-magnetic fields dynamics and evaluate the level of turbulence inside the HCS occurring at different distances from the Sun. Title: Transport of particles in the low- and high-energy solar wind from the Sun to the Jupiter orbit Authors: Khabarova, Olga; Obridko, Vladimir; Zharkova, Valentina Bibcode: 2014cosp...40E1456K Altcode: In this report a comparison between the low- and high-energy solar wind as seen from the multi-satellite observations is presented combined with some effects of the large-scale structure interplanetary magnetic field (IMF) on particle transport in the inner heliosphere. We will present a comparison of the low-energy solar wind near the ecliptic plane with those at high latitudes, at least up, to the Jupiter’s orbit. The behaviour of solar wind particles in the low-energy range up to 10 keV is determined by the solar wind expansion from the Sun, and strongly depends on the quasi-stationary distribution of the interplanetary magnetic field (IMF). At the same time, the origin and dynamics of high-energy solar particles (with energies >10 keV) at heliocentric distances up to 1 AU are not significantly impacted by this quasi-stationary interplanetary magnetic field. We explore the contributions to the solar wind of impulsive SEP events from flares in comparison with gradual SEP events, which can fill a big part of the inner heliosphere. We will argue that transport of particles through the heliosphere in the gradual SEP events can be affected by the IMF variations caused by either small-scale processes like magnetic turbulence often present in the interplanetary space or by a deviation of the IMF from the classic model predictions. Observations show that a decrease of the IMF radial component with distance has a slope of -5/3 instead of -2 predicted by Parker’s model. We explore a few possible reasons for this deviations and their impact on the characteristics of the solar wind particles. Title: Principal Component Analysis of Solar Background and Sunspot Magnetic Field in cycles 21-24 and its implications for the solar activity prediction in cycles 25-27 Authors: Zharkova, Valentina; Popova, Helen; Zharkov, Sergei; Shepherd, Simon Bibcode: 2014cosp...40E3826Z Altcode: Principle component analysis (PCA) of the solar background magnetic field (SBMF) measured from Wilcox Solar Observatory (WSO) and sunspot magnetic field (SMF) measured by SOHO/MDI magnetograms reveals the two principal components (PCs) of waves travelling in time. In addition, the independent components analysis helps to uncover 8 pairs of SBMF waves in latitudes: two large symmetric magnetic waves , which are the same for all cycles 21-23, and three pairs of asymmetric magnetic waves, which are unique for each cycle. In each pair the waves travel slightly off phase with different phase shift for each cycle and have a different number of equator crossings (Zharkova et al, 2012). These SBMF variations are assumed to be those of poloidal magnetic field traveling slightly off-phase from pole to pole which are caused by a joint action of dipole and quadruple magnetic sources in the Sun. The simulations with the two layer Parker's dynamo model with meridional circulation revealed that the dominant pair of PCs can be produced by a magnetic dipole accounting for the two main dynamo waves operating between the two magnetic poles. The further three pairs of the waves are unique to each cycle and associated with the multiple magnetic sources in the solar interior: with a quadruple symmetry in both layers for cycle 21, with quadruple magnetic sources in the upper layer and dipole sources in the inner layer for cycle 22 and with the quadruple magnetic sources in the inner layer and the dipole sources in the upper layer for cycle 23 (Popova et al, 2013). The PCs derived for all three cycles from SMBF were used as a training set for the magnetic wave prediction for the cycles 24-27 by using Hamiltonian approach (Shepherd and Zharkova, 2014) and verifying by the SBMF observations in the current cycle 24. The prediction results indicate that the solar activity is defined mainly by the solar background magnetic fields while the sunspots and their magnetic fields seem to be derivatives of the SBMF variations. Title: Investigation of Zebra-structure in the flare of 4 April 2011 associated with electron beam precipitation from the corona Authors: Zharkova, Valentina; Meshalkina, Natalia; Altyntsev, Alexander; Dobranskis, Rytis; Zhdanov, Dmitrii Bibcode: 2014cosp...40E3827Z Altcode: We present the study of multi-wavelength observations of the flare of 4th April 2011 obtained by Siberian Solar Radio Telescope (SSRT) , Siberian Solar Broadband Spectropolarimeter 4-8 GHz (SSBS) and other instruments. We report a burst-like increase of radio emission and the occurrence of well defined zebra-structure firstly registered by the new instrument (SBRS). The findings are tested by the model of electron beam precipitation with return current while generating of Langmuir turbulence and causing a formation of negative charge condensations induced by anomalous doppler resonance of electrons on the generated Langmuir waves. Title: Flares, CMEs and sunquakes Authors: Zharkov, Sergei; Matthews, Sarah A.; Green, Lucie M.; Zharkova, Valentina Bibcode: 2014cosp...40E3823Z Altcode: Solar flares and coronal mass ejections (CMEs) are believed to be manifestations of a sudden and rapid release of the accumulated magnetic energy in the corona. Only recently, the photospheric changes due to the reconnection and coronal magnetic field reconfiguration have been seriously considered from the theoretical point of view. Analysis of seismic emission (sun-quakes) induced in the solar interior in the vicinity of flares offers us an opportunity to explore the physical processes of energy transport in flaring atmospheres. Only a limited number of M and X-class flares have been reported to show seismic signatures in the form or ripples or egression sources, revealing that some of the most powerful flares often do not produce any seismic signatures. In fact, the most powerful signatures were recorded from an M-class flare. This raises important questions about how the flare energy and momentum are transported to the solar surface and interior in order to produce sun-quakes. Using observations by Hinode, RHESSI and SDO we analyse and test the new theories, gaining insight into the flare physics using flare seismology. Title: Large-scale properties of the solar wind in the inner heliosphere Authors: Khabarova, Olga; Obridko, Vladimir; Zharkova, Valentina; Veselov, Mikhail Bibcode: 2014cosp...40E1457K Altcode: Since the solar wind phenomenon has been revealed and confirmed, one of the most intriguing problems was to understand processes in the solar atmosphere and their relation with the solar wind characteristics at different distances from the Sun. Analysis of multi-spacecraft measurements of plasma parameters and the interplanetary magnetic field provides us with knowledge about the heliosphere from global to small scales. Comparisons of observations with models, describing small-scale processes, usually give more positive results than in the case of models comparison with the solar wind properties at the scales larger than several proton gyroradii. For example, Parker-like models face with big problems in their attempts to predict the solar wind plasma and, especially, the behaviour of the interplanetary magnetic field. Observations show that the radial component of the interplanetary magnetic field depends on heliolatitude and radially decreases with a slope of -5/3 instead of the predicted slope of -2 (Khabarova, Obridko, ApJ, 2012; Khabarova, Astronomy Reports, 2013). This may be determined by small-scale processes occurring in some vicinity of the heliospheric current sheet and related to the magnetic reconnection (Zharkova, Khabarova, ApJ, 2012). In this report we present results of data analysis of eight spacecraft to study variations of plasma, the electric and magnetic field with distance and heliolatitude. begin{enumerate}

Zharkova V., Khabarova O., Particle Acceleration in the Reconnecting Heliospheric Current Sheet: Solar Wind Data Versus 3D PIC Simulations, Astrophysical Journal, 2012, V.752, 1, 35 doi:10.1088/0004-637X/752/1/35 begin{enumerate} Khabarova Olga, and Obridko Vladimir, Puzzles of the Interplanetary Magnetic Field in the Inner Heliosphere, 2012, Astrophysical Journal, 761, 2, 82, doi:10.1088/0004-637X/761/2/82 begin{enumerate} Khabarova Olga V., The interplanetary magnetic field: radial and latitudinal dependences. Astronomy Reports, 2013, Vol. 57, No. 11, pp. 844-859, DOI: 10.1134/S1063772913110024 Title: The Seismic Response of the 14 December 2006 Flare Authors: Matthews, S.; Zharkov, S.; Zharkova, V. Bibcode: 2012ASPC..454..277M Altcode: Observations of the lower atmosphere and below the surface of flares, including changes in the photospheric magnetic field and appearance of strong optical and seismic emission, are challenging tasks to explain in the context of existing flare models. Such observations indicate the poorly understood connections between the primary energy release occurring in the corona via dissipation of the magnetic field and its further transport to lower atmospheric levels. In the current paper, by using data from Hinode, TRACE, RHESSI and GONG, we study the changes in the photosphere, including those in the magnetic field, occurring during the X-class flare of 14 December 2006 and the associated dynamics of the overlying corona to gain an insight into these connections. In particular, we explore the origin of the seismic responses observed by GONG in the locations close to sunspots and hard X-ray emission. The observational results are probed by kinetic and hydrodynamic models applied to the simulations of white light flare and seismic emission. Title: Solar wind data versus 3D PIC simulations of particle acceleration in the reconnecting heliospheric current sheet Authors: Zharkova, Valentina; Khabarova, Olga Bibcode: 2012cosp...39.2271Z Altcode: 2012cosp.meet.2271Z We present particle trajectories, densities and energy distributions are investigated with full kinetic particle-in-cell (PIC) approach in the reconnecting heliospheric current sheet (HCS) for magnetic field configurations deduced from solar wind observations. This approach managed (1) to show that electrons and protons/ions, are separated at acceleration in the current sheet with respect to its midplane, thus, dividing their populations on 'transit' and 'bounced' particles depending on the side where particles entered the sheet and where they are to be ejected; (2) to reproduce the magnitudes of electron and proton velocities gained at acceleration in the HCS and (3) to explain asymmetric distributions of proton velocities measured across the sector boundary by their motion along the polarisation electric field induced by accelerated protons and electrons separated into the opposite semiplanes from the sector boundary; (4) to reproduce measured distributions of particle densities across the heliospheric current sheet defined by the distributions of 'transit' and bounced protons and (5) to explain often observed medalion-like pitch angle distributions of electrons with respect to the sector boundary. Possible triggers of a reconnection process in the HCS are discussed. Title: Diagnostics of electron beam precipitation with zebra pattern formation from HXR and MW emission Authors: Zharkova, Valentina; Meshalkina, Natalia; Siversky, Taras Bibcode: 2012cosp...39.2272Z Altcode: 2012cosp.meet.2272Z In this paper we investigate stability of an electron beam with power law energy distributions to generation of Langmuir waves during its precipitation into the solar atmosphere in a presence of collisional and Ohmic losses. We explore analytically and numerically electron beam instabilities and derive the conditions of the beam pinching with formation of periodic patterns with positive and negative charges in both space and energy domains. The effect of self-induced electric field on the pattern dynamics is also investigated. The outcome of theoretical estimations is used as a diagnostic tool for understanding the electron beam dynamics from short-periodic impulses and zebra pattern structure often observed in HXR and MW emission Title: Particle Dynamics In The Reconnecting Heliospheric Current Sheet: Solar Wind Data Versus 3d PIC Simulations Authors: Zharkova, Valentina; Khabarova, O. Bibcode: 2012AAS...22020112Z Altcode: In this paper trajectories, densities, velocity and pitch angle distributions of particles accelerated by a super-Dreicer electric field are investigated with 2.5D full kinetic particle-in-cell (PIC) approach in the heliospheric current sheet (HCS) assumed to undergo a slow magnetic reconnection process with magnetic field configurations deduced from the solar wind observations.This approach reveals that during motion in a current sheet both kinds of particles, electrons and protons, are to be separated, either fully or partially, with respect to its midplane that can lead to their ejection to the opposite semiplanes that was also observed during the HCS crossings. This separation is found to form Hall's currents and polarisation electric field across the current sheet, which distribution over the current sheets allows to reproduce the magnitudes and temporal profiles of proton and ion velocities measured across the sector boundary (current sheet midplane).This separation process, in turn, divides both kinds of particles on 'transit' and 'bounced' ones depending on a side of the current sheet where they enter it and where they are supposed to be ejected. The transit and bounced protons reproduce rather closely the measured distributions of proton/ion densities about the current sheet midplane with a larger maximum occurring at the heliospheric sector boundary to be formed by the bounced protons and the other two smaller maximums on both sides from the central one to be formed by 'transit' protons. The observed electron distributions of density and energy before and after SBCs are found to fit the simulated ones revealing a sharp increase of density from one side from the HCS boundary and a depression from the other side.The bounced electrons are shown responsible for the increased density of electrons detected at some distance from the HCS boundary (midplane) with the shoe-like or medallion-type distributions in pitch angles. Title: Principle Component Analysis of the Solar Background and Sunspot Excess Magnetic Fields in the Cycles 21-23 Authors: Zharkov, Sergei; Zharkova, V.; Shepherd, S. Bibcode: 2012AAS...22020213Z Altcode: In this study we carry out Principle Component Analysis (PCA) (a) the solar background magnetic field (SBMF) measured by the Wilcox Solar Observatory with low spatial resolution for solar cycles 21-23, and, (b) the sunspot excess magnetic field (SEMF) in cycle 23 obtained by SOHO/MDI. PCA analysis reveals two independent temporal SBMF components of opposed polarities originating in the opposite hemispheres and running noticeably off-phase (with about a two and half year delay), with their maxima overlapping in the most active hemisphere for a given cycle. Their maximum magnitudes are progressively reduced from cycle 21 to 23 while overlapping in the Northern hemisphere for cycles 21 and 22 and in the Southern one in cycle 22. The reduction of magnitudes and slopes of the maxima of the SBMF waves from cycle 21 towards cycle 23 leads us to expect lower magnitudes of the SBMF wave in cycle 24. These SBMF waves modulate the occurrence and magnitudes of sunspot excess magnetic field in time and latitude. Also PCA allowed us to detect 4 pairs of independent SBMF components in latitude. The latitudinal coupling of SBMF is comprised of eight independent principal components; the two main latitudinal components attributed to symmetric and another six assigned to asymmetric types of meridional flows.

Similar components were found in the SEMF temporal and latitudinal distributions for cycle 23 revealing the polarities opposite to the SBMF polarities with the double maxima corresponding to the maxima of the SBMF residuals. The results allow us to postulate the existence of dipole and quadruple magnetic structures in the SBMF, which varies from cycle to cycle and takes the form of two waves travelling off phase, with a shift of one quarter of the cycle's period. Title: Generation of Langmuir turbulence by an electron beam steadily-injected into flaring atmospheres with density gradients Authors: Zharkova, Valentina; Siversky, Taras Bibcode: 2010cosp...38.1818Z Altcode: 2010cosp.meet.1818Z In this paper we investigate timescales and atmospheric depths of Langmuir turbulence gen-eration during precipitation of beam electrons into flaring atmospheres with density and tem-perature gradients by finding the simultaneous solutions of Fokker-Planck and wave diffusion equations. Implications of these finding to the interpretation of HXR emission from solar flares are also discussed. Title: Diagnostics of the beam anisotropy from the HXR and MW emission data in the flare of 10 March 2001. Authors: Meshalkina, Natalia; Zharkova, Valentina; Kashapova, Larisa; Altyntsev, Alexander; Kuznetsov, Alexey Bibcode: 2010cosp...38.1963M Altcode: 2010cosp.meet.1963M Microwave and hard X-ray data are thought to be powerful mean for investigating the mech-anisms of particle acceleration and precipitation in solar flares. In this paper X-ray and mi-crowave emission is investigated for the flare of 10 March 2010 previously studied by Altyntsev et al. (2008), who concluded there was a beamlike anisotropy in the particle distribution in the event. The simulations of HXR and MW emissions produced by beam electrons with en-ergies from 12keV to 1.2 MeV are carried out by taking into account anisotropic scattering in converging magnetic field of beam electrons in Coloumb collisions and Ohmic losses by using time-dependent Fokker-Planck approach (Zharkova at al, AA, 2010; Kuznetsov and Zharkova, AA, 2010). The simulated HXR photons spectra, MW emission spectra (1-80 GHz) and polar-ization are compared with the observed ones using the magnetic field values updated with new calibrated MDI. Similar to the previous simulations (Altyntsev et al, 2008), we conclude the absence of a detectable magnetic field convergence in both HXR and MW emission. However, the simulated HXR photon spectra, MW emission and polarization reveal the best fit for the models including the effect of electric field induced by beam electrons show the both emission emitted from a slightly tilted loop in the flare location and not in the perpendicular direction deduced in earlier simulations. Title: The effect of self-induced electric field on Langmuir turbulence formed by a steadily injected electron beam Authors: Zharkova, Valentina; Siversky, Taras Bibcode: 2010cosp...38.3034Z Altcode: 2010cosp.meet.3034Z We investigated the stability of a steadily injected electron beam with lower energy knee and its interaction with the ambient plasma via a generation of Langmuir turbulence at various depths of flaring atmospheres. The solutions are sought of simultaneous Fokker-Planck and wave diffusion equations for the atmospheres being a result of hydrodynamic response to electron beam injection. We identify a few time and length scales of the increased Langmuir turbulence and the effect of self-induced electric field on the level of this turbulence at different atmospheric levels. Title: On a role of different agents in the dynamics and helioseismic activity of the flare 14 December 2006 Authors: Zharkova, Valentina; Matthews, Sarah A.; Zharkov, Serhij Bibcode: 2010cosp...38.2953Z Altcode: 2010cosp.meet.2953Z In this paper we discuss the theoretical implications for the interpretation of the recent observa-tions of fast changes in magnetic field and doppler velocities observed with Hinode and GONG leading to a sunquake associated with the flare 14 December 2006 (Matthews et al. 2010). For this purpose we consider a few models of flare heating by electrons, protons and their mixture, evaluate hydrodynamic responses produced by these agents and derive those which provide the best fit to the observations. Title: Automated techniques for the analysis of magnetic field inversion in filaments with the Solar Feature Catalogue Authors: Ipson, S.; Zharkova, V.; Zharkov, S.; Benkhalil, A.; Aboudarham, J.; Fuller, N. Bibcode: 2009AdSpR..43..282I Altcode: No abstract at ADS Title: Electric Field Induced by Particles Accelerated in a Reconnecting Current Sheet Authors: Siversky, T.; Zharkova, V. Bibcode: 2008ESPM...12.3.42S Altcode: Particle acceleration in a reconnecting current sheet is studied by using 2D-3V particle-in-cell (PIC) simulation code which takes into account the electric and magnetic field induced by particles. The simulations are performed for a reduced particles mass ratio that allows to simulate simultaneously the dynamics of both electrons and protons. The size of a simulation region is chosen to be large enough to include the whole particles trajectories during their acceleration, on the other hand this size is much smaller than the current sheet length. The background electromagnetic field configuration is adopted from an MHD model and involves all three components of magnetic field. Since the time of particle acceleration is much shorter than the typical time of magnetic field variation the background field is assumed to be stationary.

Acceleration rates of electrons and protons are essentially different, thus the electric field may arise due to separation of particles with opposite charges and their different giroradii. In this work we compare particle trajectories found earlier in test-particle simulation with those obtained in PIC simulation. We found that the polarisation electric field and the electric field associated with the Langmuir wave can essentially influence electron trajectories. The corrections of energy spectra of accelerated particles are investigated. Obtained results are applied for particle acceleration in solar flares and Earth's magnetotail. Title: Simultaneous microwave and X-ray emission from accelerated electrons in solar flares Authors: Kuznetsov, A.; Zharkova, V. Bibcode: 2008ESPM...12.3.50K Altcode: Accelerated particles play a key role in development of solar flares. Hard X-rays (produced due to thick-target bremsstrahlung) and microwave emission (produced due to incoherent gyrosynchrotron radiation) are the direct observable manifestations of non-thermal electrons. We analyze the microwave and X-ray emission produced by the same anisotropic population of accelerated electrons precipitating from a loop top into footpoints. The distribution function of precipitating electrons is obtained by solving Fokker-Planck equation with pitch-angle diffusion including energy losses in collisions, self-induced electric field and inhomogeneous magnetic field. The parameters of plasma are calculated by using hydrodynamic simulation of plasma heating by an electron beam. The emission and polarization in hard X-rays and microwaves produced by beam electrons with different parameters at different times are calculated. The anisotropy of energetic electrons and effective depths of formation are found to strongly affect the resulting photon spectra from a flaring atmosphere and the beam parameters deduced from microwave and X-ray observations. The simulation results are fit very well to the simultaneous observations by RHESSI payload and Nobeyama radioheliograph obtained for a few flares. Title: The Effect or Particle Anisotropy during Precipitation on Resulting Hard X-ray and MW Emission and Polarisation Authors: Zharkova, V.; Kuznetsov, A.; Siverskyi, Taras Bibcode: 2008ESPM...12.3.52Z Altcode: We explore two types of mechanisms during particle precipitation into flaring atmospheres which can cause particle anisotropy: self-induced electric field combined with collisions versus magnetic mirroring in strongly converging magnetic field by using time-dependent Fokker-Plank equation with pitch-angle diffusion. . The anisotropy of precipitating particles is shown to be the key factor in observation of hard X-ray and radio emission owing to the scattering directivity for emitted photons meaning that pure collisional models cannot reproduce the emission observed from the atmosphere top.The resulting hard X-ray and radio emission and directivity are calculated for each model distributions for different times and various depths and compared with those observed in a few solar flares located at different parts of the solar disk. We show that a combination of viewing angle and particle anisotropy strongly affects the observed emission. Title: Particle Acceleration in a 3D Reconnecting Current Sheet with the Polarization Electric Field Authors: Zharkova, V.; Siverskyj, T. Bibcode: 2008AGUSMSH51C..03Z Altcode: Particle acceleration is investigated in a 3D magnetic field topology with a guiding field corresponding to reconnecting current sheets with different compressibility. The solutions are compared from solving 3D motion equation in the test particle and particle-in-cell approaches. Three types of electric fields are considered: a drifted one brought by the VxB force, the polarization one caused by a difference in gyroradii of protons and electrons and the turbulent one appeared from waves induced by accelerated electron beams. The effect of magnetic and electric field magnitudes, the component ratios and a size of the reconnection region on particle energy distributions is investigated for protons and electrons. Title: The Observed Long- and Short-Term Phase Relation between the Toroidal and Poloidal Magnetic Fields in Cycle 23 Authors: Zharkov, S.; Gavryuseva, E.; Zharkova, V. Bibcode: 2008SoPh..248..339Z Altcode: 2008SoPh..tmp...16Z The observed phase relations between the weak background solar magnetic (poloidal) field and strong magnetic field associated with sunspots (toroidal field) measured at different latitudes are presented. For measurements of the solar magnetic field (SMF) the low-resolution images obtained from Wilcox Solar Observatory are used and the sunspot magnetic field was taken from the Solar Feature Catalogues utilizing the SOHO/MDI full-disk magnetograms. The quasi-3D latitudinal distributions of sunspot areas and magnetic fields obtained for 30 latitudinal bands (15 in the northern hemisphere and 15 in the southern hemisphere) within fixed longitudinal strips are correlated with those of the background SMF. The sunspot areas in all latitudinal zones (averaged with a sliding one-year filter) reveal a strong positive correlation with the absolute SMF in the same zone appearing first with a zero time lag and repeating with a two- to three-year lag through the whole period of observations. The residuals of the sunspot areas averaged over one year and those over four years are also shown to have a well defined periodic structure visible in every two - three years close to one-quarter cycle with the maxima occurring at − 40° and + 40° and drifts during this period either toward the equator or the poles depending on the latitude of sunspot occurrence. This phase relation between poloidal and toroidal field throughout the whole cycle is discussed in association with both the symmetric and asymmetric components of the background SMF and relevant predictions by the solar dynamo models. Title: Collective electric field effect on particle acceleration in a 3D reconnecting current sheet Authors: Zharkova, V.; Agapitov, A. Bibcode: 2007AGUSMSH23B..04Z Altcode: Dynamics of proton and electron energy spectra at acceleration in 3D reconnecting current sheet (RCS) is investigated simultaneously with the collective electric field effects. In addition to the drift electric field, a polarisation electric field caused by the electron and proton separation and small scale electric field caused by Buneman and low-hybrid plasma turbulences are considered. The polarisation electric field parameters and turbulence growth rate are linked to the parameters and locations of the particles drifted and accelerated in an RCS. The small-scale electric fields increase mostly electron energies up to tens MeV while the polarisation field accelerates mostly protons up to GeV energies. Particle distributions in an RCS and their energy spectra are presented for different magnetic field topologies and combination of electric fields. Title: The effects of a magnetic field topology on particle acceleration in a 3D reconnecting current sheet with the guiding field Authors: Agapitov, A.; Zharkova, V. Bibcode: 2007AGUSMSH22A..04A Altcode: We investigate particle trajectories and energy spectra at acceleration by a super-Dreiser electric field occurring in 3D reconnecting current sheets with different magnetic field topologies deduced from the MHD simulations. The transversal magnetic field is considered to vary exponentially as z± with the distance z from the X-null point and to be linked to a reconnection rate. The dependence on ± for different guiding field magnitudes of proton and electron trajectories and spectra is obtained. The distributions of the accelerated particles density in an RCS and energy spectra at ejection are evaluated for different magnetic field topologies [1] and reconnection rates [2] and compared with some observational signatures. The proposed method can be used for a diagnostics of magnetic reconnection dynamics from high energy particle spectra observed with a high temporal resolution. 1. Craig I.J.D. and McClymont A.N. Dynamic magnetic reconnection at an X-type neutral point, Astronomical Journal, 371, L41, 1991 2. Arber T.D. and Haynes M. A generalized Petchek magnetic reconnection rate, Physics of Plasmas, 13, 112105, 2006 Title: Statistical properties of H-alpha and HXR flares in the cycle 23 in relation to sunspots and active regions detected from the Solar Feature Catalogues Authors: Zharkova, V.; Zharkov, S. Bibcode: 2006AGUFMSH43A1507Z Altcode: The statistical properties of H-alpha and hard X-ray solar flares are investigated in relation to the cycle variations in 1996-2006 of sunspots and active regions (plages) obtained from the automated Soar Feature Catalogues (SFC, http://solar.inf.brad.ac.uk). Cross-correlation analysis is carried out between flare sizes, locations, significance and active region/sunspot parameters including magnetic field extracted in SFC. Sunspot and plage area distributions reveals a strong North-South asymmetry of about 0.2 and the period of about 7-8 years for sunspots and of 0.5 and period of 9 years for plages with both asymmetries decreasing towards the next cycle minimum. The temporal distribution of solar flare occurrences in Northern and Southern hemispheres, at different latitudes and longitudes are compared with those of plage and sunspot areas and LOS magnetic fields. The spectral indices of HXR and gamma-ray emission wer used to estimate magnetic field components and their variations with the cycle. The application of these results to the solar activity forecast is discussed. Title: Asymmetric Statistical Properties of the Solar Cycle 23 Deduced from Sunspots, Plages and Flare Occurrences Authors: Zharkova, Valentina; Zharkov, S. Bibcode: 2006SPD....37.0513Z Altcode: 2006BAAS...38..225Z The statistical properties of sunspot, active regions (plages) and filament distributions obtained from the automated Solar Feature Catalogues (SFC, http://solar.inf.brad.ac.uk) and their relation to flare distributions are presented for 1996-2005. We present distributions of sunspot numbers with given areas for different phases and the whole solar cycle 23. Statistical sunspot and plage area distributions revealed a strong North-South asymmetry of about 0.2-0.6 for sunspots, plages and flare occurrences with two basic periods of about 9 and 2.5 years. The distributions of sunspot and flare occurrences at different latitudes and longitudes in Northern and Southern hemispheres and their magnetic tilts are compared with their total and excess magnetic fields during the whole period of observations. The application of these results to the solar dynamo models is discussed. Title: Magnetic Field and Sunspot Group Tilts in the Cycle 23 With Solar Feature Catalogues Authors: Zharkova, V.; Zharkov, S. Bibcode: 2006AGUSMSH52A..07Z Altcode: We present sunspot group (GT) and magnetic field (MT) tilts extracted from the Solar Feature Catalogues for the period of 1997-1999 and 2004-2005. We detected 21104 sunspot groups from which tilts were extracted from 12823. The average tilts were found to increase towards the solar activity maxima for MT: from 4.56 (1997) to 6.54 (1999) decerasing to 5.48(2004) and for GT from 2.83 (1997) to 5.11 (1999) and 1.87 (2004). In general, both magnetic and group tilts increase with heliolatitude according to Joy's law with some deviations for the lower and higher latitudes revealing also some periodicity. The separation of the opposite polarities also varies with the latitude for all the groups and for those passing through central meridian. The latitude variations of the ratio of measured tilt- to-separation in the presented data were fit by a linear function and the coefficients are presented. Title: A New Way to look at Observations with EGSO Authors: Aboudarham, J.; Scholl, I.; Fuller, N.; Csillaghy, A.; Bentley, R. D.; Antonucci, E.; Ciminiera, L.; Finkelstein, A.; Ipson, S.; Messerotti, M.; Pike, D.; Vial, J. C.; Zharkova, V. Bibcode: 2006IAUS..233..229A Altcode: The European Grid of Solar Observations (EGSO) is a Solar virtual observatory (see Hill et al., 2002). It has been funded through the 5th Framework Program of the European Community. A dozen of laboratories, mixing Solar Physics and Information Technology, in Great Britain, France, Italy and Swiss have been involved in this project during 3 years. A grid accessing several dozens of databases and archives scattered all around the world has been developped as well as a Solar Event Catalogue and a Solar Feature Catalogue. The original aspect of this work consists in the possibility not only to search through the characteristics of observations, but also search for available data corresponding to specific kinds of events. So it is now very important to be able to follow the Sun 24 hours a day in order to enrich the events database for future queries. More informations on EGSO, catalogues and user interface can be accessd through the web site: http://www.egso.org/ Title: European Grid of Solar Observations (EGSO) Authors: Aboudarham, J.; Scholl, I.; Csillaghy, A.; Bentley, R. D.; Antonucci, E.; Ciminiera, L.; Finkelstein, A.; Ipson, S.; Messerotti, M.; Pike, D.; Vial, J. C.; Zharkova, V. Bibcode: 2006ihy..conf...18A Altcode: The EGSO project addresses the problem of combining heterogeneous data into a single "virtual" solar data resource. Wider access to other catalogues is enabled, including both pre-existing lists and new compilations generated using feature-recognition techniques on existing data. Scientists are also able to perform much richer data searches, based on solar events. Informations concerning EGSO can be found at http://www.egso.org/ Title: Spatial separation of the 3, 5 and 15 min oscillation sources above sunspots Authors: Sych, R.; Zharkova, V. Bibcode: 2006cosp...36.1177S Altcode: 2006cosp.meet.1177S We present a new method to obtain a spatial location of the oscillation sources in a narrow band frequency range of quasi-periodic radio emission above sunspots by using the continuous Wavelet transform From the high quality NoRH 17 GHz observations of sunspots with 10 sec cadence on the August 16 1992 July 22 1994 and June 30 1993 we detect well separated spatial shifts between the sources of 3 5 and 15 min oscillations The sources of 5 min oscillation also reveal a fine spatial structure appearing at the radio source boundaries as some patched details with its own dynamics The 3 min sources are associated with oscillations of the source as a whole with the period of modulation in the pulse group about 15 min The emission of 15 min oscillations comes from the central parts of spots and coincides with the maximum radio brightness and umbra location The size of this source is minimal that is likely to be associated with the footpoints of coronal loops where the 15 minute oscillations prevail These oscillations are interpreted to be caused by the shifts in locations of the third and or second harmonics of a gyro-frequency due to propagation of magneto-acoustic waves in magnetic tubes This research was supported by the grants of RFFI 04-02-39003 05-07-90147 Title: Correlation of the Global Photospheric Magnetic Field Structure with the Latitudinal Sunspot Distribution in the solar cycles 23 Authors: Gavryuseva, E.; Zharkov, S.; Zharkova, V. Bibcode: 2006cosp...36.1129G Altcode: 2006cosp.meet.1129G begin table htbp begin center begin tabular p 442pt hline begin itemize item We compare a basic topology of large scale solar magnetic field with newline the distribution of the sunspot activity in latitude and newline in time in the past 2 solar cycles newline The large scale magnetic fields were composed from the data of WSO observatory the sunspot characteristics we extracted for the cycle 23 from the Solar Feature Catalogues underline http solar inf brad ac uk newline newline The magnetic field variations reveal a 4-zonal structure with 22-year periodicity and running waves through the solar latitudes with the two years periods The results are compared with the sunspot latitudinal variations in time and cumulitative variations in the butterfly diagrams The comparison results are used to explain the double peaks and variable character of the solar activity that can be used for its modelling and prediction end itemize hline end tabular label tab6 end center end table Title: Active region AR484 tracking with Solar Feature Catalogue Authors: Zharkova, V.; Benkhalil, A.; Zharkov, S.; Ipson, S.; Bentley, R. D. Bibcode: 2006AdSpR..37.1152Z Altcode: This paper presents a morphological analysis of the active region NOAA AR 484 as well as its intensity and magnetic field variations associated with flare occurrences. The active region is tracked during a one solar rotation with the automated technique used in Solar Feature Catalogue (SFC). The location and intensity parameters of region AR484 were extracted from 1 minute cadence Hα solar images from the Big Bear observatory (BBSO), SOHO/EIT images in Fe XII, 195 Å and the SOHO/MDI magnetograms. During the whole period of tracking from October, 19 until November, 11, 2003 the AR484 produced many flares of different significance including a few X-class flares. We investigate the total AR intensity variations in each band leading to a flare production and compare these with the magnetic field changes before and during a flare for five flares of different significance. Based on this comparison the key parameters defining the region activity in a flare production are found that include the resulting, or excess, flux and the ratio between areas covered by negative and positive pixels. These parameters can be used for a preliminary pre-flare classification of active regions in addition to other classifiers associated with a magnetic field. Title: EGSO - A maturing VO for Solar Physics Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham, J.; Antonucci, E.; Gurman, J.; Hill, F.; Pike, D.; Vial, J.; Zharkova, V. Bibcode: 2005AGUSMSH43B..01B Altcode: The European Grid of Solar Observations, EGSO, is a Grid test-bed funded under the Information Societies Thematic Priority of the European Commission's Fifth Framework Programme (FP5). In the case of EGSO, the application chosen was the use of Grid technology to establish a virtual observatory for solar physics, and the project addresses the generic problem of how to provide access to a distributed, heterogeneous data set for a scattered user community. In order to identify observations that match a user's search criteria, EGSO has been building an environment that will support complex searches. Because of the absence of the metadata needed to tie the heterogeneous data together, EGSO has placed emphasis on the provision of databases that can be accessed from the Internet through special providers. The provision of appropriate metadata is of extreme importance in establishing a virtual observatory, and the approach used can be adapted to facilitate the inclusion of any data, including non-solar data. We report on the capabilities of EGSO and discuss experience gained in creating the facility. We also discuss how EGSO has been working with other virtual observatories that support the solar, heliospheric and space plasma communities in order to try to achieve interoperability between the numerous data sets. We highlight what we consider are the most profitable ways of doing this. Title: Energy spectra of fully or partially separated electron beam at ejection from an current sheet with the guiding magnetic field Authors: Zharkova, V.; Gordovskyy, M. Bibcode: 2005AGUSMSH51A..02Z Altcode: Electron and proton energy spectra gained at acceleration by a super-Dricer electric field are investigated in the non-neutral reconnecting current sheet (RCS) with a non-zero longitudinal component of magnetic field (a guiding field) directed along the electric field. The other transverse and tangential magnetic component are considered varying with the distances from the X null-point. The proton and electron energy spectra are calculated numerically from a motion equation using the particle-in-cell approach for the model RCSs with constant and variable densities. In the presence of a strong or moderate guiding field protons were found fully or partially separated from electrons at ejection from a RCS into the opposite semiplanes, 'electron' and 'proton' ones while for a weak guiding field they are ejected symmetrically as neutral beams. The particles ejected from a RCS with a very strong guiding field have the power-law energy spectra with spectral indices about 1.5 for protons and 2.0 for electrons. For a moderate guiding field the electron and proton spectra are a combination of power law and thermal-like ones. Title: Sunspot Statistical Properties in the Cycle 23 from the Solar Feature Catalogue Authors: Zharkov, S.; Zharkova, V. Bibcode: 2005AGUSMSP32A..05Z Altcode: The statistical analysis of sunspot area and magnetic field distributions in 1996-2004 are presented. The sunspot parameters are automatically extracted from the SOHO/NDI white light solar images (4 per day) and magnetograms (15 per day) and stored in the Solar Feature Catalogues (SFC). The number of sunspots is found to increase exponentially with the area decrease with a slightly increasing index from the solar minimum to its maximum. The N-S asymmetry in sunspot area distributions and its periodicity for different phases of the solar cycle and hemispheres is investigated with the period deduced. Longitudinal sunspot distributions also reveal a strong North-South asymmetry in the active longitude appearance and the relation to latitudinal distributions that depends on the phase of the solar cycle. The magnetic field distributions for the total and excess fluxes as a function of the sunspot heliospheric longitude and latitude are also presented for different phases of the solar cycle. These statistical properties of sunspots and their magnetic field are tested versus those predicted by the turbulent dynamo theory. Title: Search for solar quakes induced by the proton flares on 28 October 2004 and 20 January 2005 Authors: Zharkova, V.; Zharkov, S.; Gordovskyy, M.; Share, G.; Murphy, R. Bibcode: 2005AGUSMSH51A..01Z Altcode: We present the analysis of the SOHO/MDI 1 minute cadence dopplergrams obtained for the proton-rich flares on 28 October 2004 and 20 January 2005 and search for the helioseismic ripples induced by these flares. The obtained time-distance diagrams are used to deduce possible heliosesimic characteristics induced by these flares. These are compared with the theoretical models produced by electron or proton beam precipitation after their ejection from an RCS with the guiding magnetic field. We compare the responses to the momentums delivered by these particles with those deduced from the RHESSI observations. Title: Solving Science Use Cases that relate to the Sun and Heliosphere with EGSO Authors: Bentley, R. D.; Scholl, I.; Csillaghy, A.; Aboudarham, J.; Antonucci, E.; Gurman, J. B.; Hill, F.; Pike, D.; Vial, J.; Zharkova, V. Bibcode: 2004AGUFMSH21B0415B Altcode: The European Grid of Solar Observations (EGSO) is a grid testbed funded by the European Commission's Fifth Framework Programme under its Information Society Technologies (IST) thematic priority. The project started in 2002 and is designed to provide enhanced access to solar and related data around the world. The EGSO grid is composed of two main components, Roles to set up the grid and, catalogs and registries to allow roles to answer users queries. Catalogs are made of lists of observations, events and features (a new service provided by EGSO). Registries are built from these catalogs and organized in order to enhance search capabilities. EGSO is working closely with other virtual observatory (VO) projects in the solar physics and related domains. This includes the US Virtual Solar Observatory (VSO) and the Collaborative Sun-Earth Connector (CoSEC). More recently we have been working with the Virtual Space Plasma Observatory (VSPO) and have contact with the Virtual Heliospheric Observatory (VHO). Through discussions with future missions, and within the new IAU Working Group on ``International Data Access'' (Solar and Heliospheric), the VOs are studying ways of ensuring interoperability from the ``sun to dirt''. This type of integrated access will be particularly important to missions such as STEREO and Living Witha Star. In this paper we will report the current status of EGSO, demonstrate how the catalogs and registries model serves within the user interface, and show how the user can retrieve solar and heliospheric data to match a scientific query. EGSO Release 4 is now being Beta-tested by users and anyone interested should view the Web page detailing all the EGSO capabilities under http://www.egso.org/demo Title: Tracking of Solar Active Regions and Search for Classification parameters Authors: Benkhalil, A.; Zharkova, V.; Bentley, R.; Zharkov, S.; Ipson, S. Bibcode: 2004cosp...35.3115B Altcode: 2004cosp.meet.3115B This paper presents the application of Solar Feature Catalogue (SFC) created with an automated technique for active region detection from SOHO/MDI, SOHO/EIT and Hα images from Meudon. The two active regions (NOAA 484 and 486) producing many flares in October and November '03 were tracked during their lifetime on a solar disk in Hα and Fe XII, 195 Å wavelengths. These regions produced a large number of flares with different significance including a few X-class flares. We investigate their morphology and evaluation leading to a flare production and compare these with the magnetic field changes before and during a flare. In SFC each region is characterized by a number of physical and photometric properties, which are stored in the database. These include: the center of gravity in pixel and heliographic coordinates; minimum, maximum and mean intensity within the active region; area in square degrees and dimensions in pixels; contrast ratios; and a chain-code representation of the active region boundary. Based on a comparison of the active region parameters selected from the SFC with the magnetic field configuration and strength we try to select the key parameters defining a region activity in flare production that can be used for a preliminary active region classification. Title: Tracking of solar active regions and search for classification parameters Authors: Benkhalil, A.; Zharkova, V.; Bentley, R.; Zharkov, S.; Ipson, S. Bibcode: 2004cosp...35.3125B Altcode: 2004cosp.meet.3125B This paper presents the application of Solar Feature Catalogue (SFC) created with an automated technique for active region detection from SOHO/MDI, SOHO/EIT and Hα images from Meudon. The two active regions (NOAA 484 and 486) producing many flares in October and November '03 were tracked during their lifetime on a solar disk in Hα and Fe XII, 195 Å wavelengths. These regions produced a large number of flares with different significance including a few X-class flares. We investigate their morphology and evaluation leading to a flare production and compare these with the magnetic field changes before and during a flare. In SFC each region is characterized by a number of physical and photometric properties, which are stored in the database. These include: the center of gravity in pixel and heliographic coordinates; minimum, maximum and mean intensity within the active region; area in square degrees and dimensions in pixels; contrast ratios; and a chain-code representation of the active region boundary. Based on a comparison of the active region parameters selected from the SFC with the magnetic field configuration and strength we try to select the key parameters defining a region activity in flare production that can be used for a preliminary active region classification. Title: Energy Transport and Dynamics Authors: Schmieder, B.; Peres, G.; Enome, S.; Falciani, R.; Heinzel, P.; Hénoux, J. C.; Mariska, J.; Reale, F.; Rilee, M. L.; Rompolt, B.; Shibasaki, K.; Stepanov, A. V.; Wülser, J. P.; Zarro, D.; Zharkova, V. Bibcode: 1994SoPh..153...55S Altcode: We report findings concerning energy transport and dynamics in flares during the impulsive and gradual phases based on new ground-based and space observations (notably fromYohkoh). A preheating sometimes occurs during the impulsive phase. CaXIX line shifts are confirmed to be good tracers of bulk plasma motions, although strong blue shifts are not as frequent as previously claimed. They often appear correlated with hard X-rays but, forsome events, the concept that electron beams provide the whole energy input to the thermal component seems not to apply. Theory now yields: new diagnostics of low-energy proton and electron beams; accurate hydrodynamical modeling of pulse beam heating of the atmosphere; possible diagnostics of microflares (based on X-ray line ratio or on loop variability); and simulated images of chromospheric evaporation fronts. For the gradual phase, the continual reorganization of magnetic field lines over active regions determines where and when magnetic reconnection, the mechanism favoured for energy release, will occur. Spatial and temporal fragmentation of the energy release, observed at different wavelengths, is considered to be a factor as well in energy transport and plasma dynamics. Title: Scientific objectives of solar XUV radiation studies by the project CORONAS. Authors: Zhitnik, I.; Urnov, A.; Zharkova, V.; Ivanchuk, V. Bibcode: 1991BSolD..11..101Z Altcode: No abstract at ADS