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Author name code: zharkova
ADS astronomy entries on 2022-09-14
author:"Zharkova, Valentina A."
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Title: Kinetic turbulence generated in a 3D current sheet with two
magnetic islands
Authors: Zharkova, Valentina; Xia, Qian
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.
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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
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.
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Title: Comparison of solar activity proxies: eigen vectors versus
averaged sunspot numbers
Authors: Zharkova, V.; Vasilieva, I.; Shepherd, S. J.; Popova, E.
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.
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Title: Terrestrial volcanic eruptions and their association with
solar activity
Authors: Vasilieva, I.; Zharkova, V.
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.
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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
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.
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Title: Particle Pitch Angle Distributions after Passing Through 3d
Current Sheets in the Heliosphere
Authors: Zharkova, Valentina; Malandraki, Olga; Khabarova, Olga;
Xia, Qian
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.
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Title: Plasma turbulence generated in 3D current sheets with single
and multiple X-nullpoints
Authors: Zharkova, Valentina; Xia, Qian
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.
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Title: Pitch-angle distribution of accelerated electrons in 3D
current sheets with magnetic islands
Authors: Zharkova, V.; Xia, Q.
2021A&A...648A..51Z Altcode:
<BR /> 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. <BR /> 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. <BR /> 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°. <BR /> 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.
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Title: Particle acceleration in erupting 3D coronal mass ejections
in the breakout model
Authors: Xia, Qian; Zharkova, Valentina; Dahlin, Joel; Antiochos, Spiro
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.
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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
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.
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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
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
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.
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Title: Solar magnetic field and irradiance variations on millennial
timescale and their effects on the terrestrial temperature
Authors: Zharkova, Valentina; Popova, Helen
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.
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Title: Solar activity, solar irradiance and terrestrial temperature
Authors: Zharkova, Valentina
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.
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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
2020A&A...639A..78Z Altcode:
<BR /> 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). <BR
/> 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. <BR /> 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. <BR /> 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
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<SUP>-1</SUP> 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.
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Title: Millennial solar irradiance forcing (Hallstatt's cycle)
in the terrestrial temperature variations
Authors: Zharkova, Valentina; Shepherd, Simon; Popova, Elena
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.
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Title: Solar wind re-acceleration in local current sheets and their
diagnostics from observations
Authors: Xia, Qian; Zharkova, Valentina
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.
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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
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).
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Title: Effects of local particle acceleration in the solar wind
Authors: Khabarova, Olga; Zharkova, Valentina; Xia, Qian; Malandraki,
Olga
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.
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Title: Acceleration of particles in different parts of erupting
coronal mass ejections
Authors: Zharkova, Valentina; Xia, Qian; Dahlin, Joel; Antiochos, Spiro
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.
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Title: Particle Acceleration and Transport during 3D CME Eruptions
Authors: Xia, Qian; Dahlin, Joel T.; Zharkova, Valentina; Antiochos,
Spiro K.
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.
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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.
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.
2020A&A...635A.116X Altcode:
<BR /> 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. <BR
/> 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 10<SUP>8</SUP> -
10<SUP>12</SUP> m<SUP>-3</SUP>, proton-to-electron mass ratios, and
island aspect ratios. <BR /> 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. <BR /> 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.
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Title: Overview of appearance of energetic particles in the solar
corona and heliosphere
Authors: Zharkova, Valentina
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.
2018A&A...620A.121X Altcode:
<BR /> 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. <BR /> 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 10<SUP>6</SUP> thermal particles dragged
into the current sheets from different sides and distances. <BR />
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. <BR /> 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.
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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
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<SUP>-1</SUP>) 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.
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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.
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.
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.
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Title: Comparing two acoustically active September 6 X-class Flares
of Solar Cycle 24.
Authors: Zharkov, Sergei; Matthews, Sarah A.; Zharkova, Valentina;
Macrae, Connor
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.
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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
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.
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Title: Particle acceleration in a reconnecting current sheet:
coalescent and squashing magnetic islands
Authors: Zharkova, Valentina; Xia, Qian
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.
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Title: Particle Acceleration in Coalescent and Squashing Magnetic
Islands: TP and PIC approach
Authors: Zharkova, Valentina; Xia, Qian
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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} <P />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.
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
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
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.
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.
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. <P
/>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
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
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
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
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.
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.
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. <P />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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
1991BSolD..11..101Z Altcode:
No abstract at ADS
