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What can we learn from the Sun's interior useful for understanding Solar-Terrestrial links?

Rozelot J.P.

ABSTRACT

The baryonic Universe is mainly composed by plasma and so, magnetism plays a fundamental role. However, magnetism is still poorly known. Equations of magnetic field are not yet taken into account in all the equations describing our Universe, and in particular in stellar (and solar) equations. Nevertheless, it is known that the magnetism of the solar interior has a key role. Understanding this role will permit also to better understand our terrestrial climate, as all the interplanetary medium is bathing into this magnetic field. New results from various space and ground-based experiments monitoring the radiative and particle emissions of the Sun, together with their movement in space and their terrestrial impact, have opened a new era in both solar and atmospheric physics. These studies clearly show that the variable solar radiative and particle output affects the Earth's atmosphere and climate in many fundamental ways. The main goal of this paper is to emphasize the Sun as a unique object for which we may hope a quantitative approach before generalization to other more energetic objects. The slow and organized activity of the Sun is not a superficial phenomenon: it implies the core, where most of the mass is concentrated, and we are still far to control mechanisms (rotation, spin…). The surface manifestation of the irradiance might be not only a surface manifestation of the magnetic activity, and could take its origin in deeper layers. Some dedicated space joint missions, such as SDO, GOLF-NG or PICARD will help us to make significant progresses on this way.

GALACTIC COSMIC RAY PROCESSES AS KEY GOVERNING THE SOLAR INFLUENCE ON EARTH AND PLANETS

P. Velinov

ABSTRACT

not available

Solar Variability and Climate – UTLS amplification of Solar Signal

N. A. Kilifarska

ABSTRACT

The solar signal in atmospheric interannual variability is well tracked till the stratosphere. However, it is still not clear how this signal propagates into the troposphere and does it affect Earth’s climate. The mechanism suggesting downward propagation of solar effect from the stratopause levels could account for strato- tropospheric teleconnections at middle to high latitudes, but is not applicable for very low latitudes, where the atmospheric angular momentum is almost constant. Some model experiments concerning tropical upwelling, point out the limitations of the concept of extratropical pump and downward control and contribution of stratospheric - tropospheric heating to the net tropical upwelling [Plumb and Eluszkiewicz, 1999; Scott, 2002]. Meanwhile, different sources of measurements show that at high solar activity the Upper Troposphere and Lower Stratosphere (UTLS) are warmer than at low solar activity. Based on this result and taking into account above-mentioned modelling, we propose an additional amplifying mechanism of the solar influence on climate. In brief: 1) the warmer tropical UTLS at solar maximum affects vertical propagation of equatorial waves, altering the duration of westerly QBO phase; 2) the equatorial upwelling (enhanced in solar max), on its turn is modulated by QBO. This means that westerly phase of QBO will decrease the equatorial upwelling and respectively Brewer-Dobson circulation, but easterly phase of QBO will force additionally Brewer-Dobson cell.

Solar activity and global warming revisited

K.Georgieva, B.Kirov

ABSTRACT

While in general the changes in surface air temperature follow the changes in solar activity proving the solar influences on climate, in the last few decades solar activity has remained more or less constant while temperature has continued increasing which is a strong argument in favour of anthropogenic influences on climate. In the same period the correlation between solar and geomagnetic activity has decreased, both in the 11-year cycle and on secular time scale. The solar activity index commonly used for long-term studies is the sunspot number as it has the longest data record. But sunspots reflect only the solar activity originating from closed magnetic field regions. The regions of open magnetic field - coronal holes, sources of high speed solar wind and drivers of recurrent geomagnetic activity, are not accounted for in the sunspot index. It appears that in the last decades the impact of coronal holes has increased which can be explained by the increasing tilt of the heliospheric current sheet. This increased tilt means that the Earth encounters two high speed streams from coronal holes per solar rotation and higher geomagnetic activity. On the other hand, the tilt of the heliospheric current sheet is related to the galactic cosmic rays modulation, and galactic cosmic rays are considered a key agents mediating solar activity influences on terrestrial temperature. Therefore, using the sunspot number alone as a measure of solar activity leads to the underestimation of the role of solar activity for the global warming in the recent decades

Geo-Effective Helio-Physical Variations and Human Physiological State

S. Dimitrova

ABSTRACT

A group of 86 volunteers was examined on each working day in autumn 2001 and in spring 2002. These periods were chosen because of maximal expected geomagnetic activity. There were 26 persons in the group on a drug treatment, mainly because of hypertension. Systolic and diastolic blood pressure and heart rate were registered. Pulse pressure was calculated. Data about subjective psycho-physiological complaints of the persons examined were also gathered. Altogether 2799 recordings were obtained and analysed. MANOVA was employed to check the significance of the influence of three factors on the physiological parameters under consideration. The factors were as follows: 1) geomagnetic activity estimated by H-component of the local geomagnetic field and divided into five levels; 2) gender – males and females; 3) presence of medication. Post hoc analysis was performed to elicit the significance of differences in the factors’ levels. The average arterial blood pressure, pulse pressure and the percentage of the persons in the group with subjective psycho-physiological complaints were found to increase significantly with the increase of geomagnetic activity. The maximal increment of systolic and diastolic blood pressure was 10-11% and for pulse pressure 13.6%. Analyses revealed that females and persons on a medication were more sensitive to the increase of geomagnetic activity than respectively males and persons with no medication.

Field-aligned current response to ICME on 11 April 1997 as seen by INTERBALL-Au satellite at mid-altitude cusp magnetosphere

A.Z. Bochev, I.I.A.-Dimitrova, I.N.Boshnakov, K. Kudela

ABSTRACT

We present magnetograms suggestive for unusual field-aligned currents (FACs) appearance in mid-altitude cusp of the magnetosphere at height 20000 km during ejecta on 11 April 1997. In fact FACs are different as compared with Potemra model nevertheless that current direction may coincide with the classical system. We demonstrate: (1) an appearance of two or more current sheets with opposite polarities in the dusk flank of the cusp; (2) appearance of FAC system in a comparatively large magnetic field depletion or diamagnetic cavity. The examination of energetic particles gives evidence to suppose a simultaneous formation of cusp energetic particle (CEP) event in the region of field-aligned currents and diamagnetic cavity; (3) An unusually intense FAC system is documented in the cusp during low geomagnetic activity (Kp=2), when the magnetic field disturbance was in the order of 150 nT. This result together with POLAR study (G. Le et al., 2001) is a more confident conclusion that the driving process for this event including the reversed convection (sunward) through the polar cap was the reconnection between interplanetary field lines and the lobe field lines.

CORONAL MASS EJECTION OF 28 JUN 2000: Coupling of the CME Evolution and the Flare Energy Release

D.Maricic', D.Rosa, B. Vrsnak

ABSTRACT

We study the initiation and development of the limb coronal mass ejection (CME) of 28 Jun 2000, utilizing observations from Mauna Loa Solar Observatory (MLSO), the Solar and Heliospheric Observatory (SOHO), the Geostationary Operational Environmental Satellite (GOES) and Yohkoh. Also, we analyze the relation between dynamics of the CME and the energy release in the associated flare.

The basic structure of the CME (prominence imbedded in bright coronal arcade) is clearly recognizable already in the low corona during the pre-eruption phase of slow rise. This provided measurements of kinematics of various features from the very beginning of the eruption up to the post-acceleration phase which was followed up to 32 solar radii. Such events are observed only occasionally, and are of great importance for the comprehension of the nature of forces driving CMEs. The acceleration maximum was attained at the radial distance of 1.45 solar radii from the Sun's center and ceased beyond 4 solar radii. The acceleration phase was synchronized with the impulsive phase of the associated two-ribbon flare.

Observations provide clear evidence that the CME eruption caused a global restructuring of the magnetic field in the outer and inner corona.

The Solar Rotational Activity Variation during the 23^th Solar Cycle

R.Werner¹, A.Hempelmann², D.Valev¹, I. Kostadinov^1,3, At.Atanassov¹, G.Giovanelli³, A.Petritoli³, D.Bortoli³, F.Ravegnani³

ABSTRACT

The study of the solar activity variability has been of great interest since its discovery. On the one hand it is important for the understanding of the Sun as an active star and on the other hand – for the investigations of the solar-terrestrial connections. The solar magnetic field reverses approximately every 22 years, and manifests the 11-year solar cycle, in which the Sun changes its activity from its maximum value to the minimum one. The activity variations, developed by the sun surface rotation in connection with the nonsymmetrical distribution of active regions over the solar disc appear in a shorter time scale. As it is well known, these variations have periods of about 27 days. The solar surface rotates with different velocity, depending on the latitude. The differential solar rotation period, observed from the Earth, varies from 26.75 days at the solar equator up to approximately 29 days at higher latitudes. However the observed periodicity is generally in a wider range: from 20 up to 36 days. This wider spread is a result of the combination of both active-region evolution and solar rotation. A simple empirical solar activity model is proposed, which describes the obtained behaviour by harmonic oscillations with simultaneous amplitude and phase modulation. The solar rotational periodicity is analyzed using wavelet. It is demonstrated, that the model describes well the separate episodes of the active region evolution. Both kinds of modulations are the consequence of activity region growth or decay and hence, they are a result of a variable pattern of spots and active regions on the solar surface.

Photometric and Spectrometric Investigations of the Solar Corona and Atmospheric Effects during the March 29, 2006 Total Solar Eclipse

P.V. Stoeva, A.D. Stoev, I.N. Kostadinov

ABSTRACT

A great part of the information about large-scale structure of the solar corona comes from solar observations during total solar eclipses. Space coronagraphs overoccult the sun, omitting from view exactly the inner and coronal reasons well imaged at total solar eclipses. The total eclipse of the Sun on 2006 March 29, will be visible from within a narrow corridor, which transverse half the Earth. We foresee observations from the territory of Turkey. The aims of observations are:

1. Photometric investigation of the White corona structure and polarization;
2. Investigation of the structure of monochromatic emission corona in green (Fe XIV, λ=5303Å) and red (Fe X, λ=6374Å) line, Hα, and the thermal corona in the 2-5 µm region of the Infrared spectrum;
3. Tropospheric and stratospheric O₃ and NO₂ photochemistry study;
4. Determining of the dynamics of basic microclimatic parameters of the 10 m ground atmospheric layer.

The following methods will be used: Taking of photograph of the corona (telescope-refractor 100/1000mm, spectrozonal photoemulsions, polarization and infrared barrier filters), registration of the investigated emissions (telescope-refractor 150/1600mm, high sensitive photo-emulsions, narrow band filters), Differential Optical Absorption Spectroscopy method, measuring of the microclimatic parameters with automatic meteorological station; processing and analysis of the photographs and data, seeking for wave structures in the O₃ and NO₂ concentration, comparison with other measurements during an eclipse.

The results we expect are: Determining of the Solar corona characteristics, finding of regularities in the O3 and NO₂ behaviour in conditions of reduced solar radiation, and clarifying the dynamical and photochemical processes in the stratosphere and climate of the ground atmosphere.

Study of Atmospheric Trace Gas Amounts at the Stara Zagora Ground-Based Station

R.Werner, D.Valev, I. Kostadinov, At.Atanassov, G.Giovanelli, A.Petritoli, D.Bortoli, F.Ravegnani

ABSTRACT

Since the end of August 1999 twilight daily measurements of scattered zenith sky radiation have been carried out at Stara Zagora for determination of trace gas amounts, deploying GASCOD instrument. It was developed at the Institute of Atmospheric Science and Climate, Bologna. Reference spectra are obtained at midday. The instrument, appearing a UV-VIS spectrometer, registers the zenith sky spectra automatically and 410 nm to 460 nm spectral interval is used to retrieve NO₂ and O₃ slant column amounts (SCA) by application of the DOAS methodology. The spectral analysis uses minimum least squares fitting of the cross sections at the expected absorbers to a logarithm of the twilight spectrum and a reference spectrum.

The accumulated time series show the well-known typical seasonal variations, caused by the solar insulation. The residual time series of the removed semi-annual seasonal cycles from the measured original series show many different variations, with short periods up to inter-annual variations. Single spikes of SCA are detected and we consider them a result of overpassing weather fronts and/or lightning. Variations of SCA with time scale up to about 10 days are the consequence of weather cyclones. Some short-term variations of NO₂ and O₃ SCA are a result of intensive stratospheric-tropospheric exchange. Other residual time series periods are caused by Rossby waves, by overpassing of the polar vortex filaments. The inter-annual variations can be affected by QBO and NAO. Applying wavelet analysis of the obtained NO₂ slant column amount data series, and the total O₃ amount obtained by the GOME instrument, during the 23^-rd solar cycle maximum, time intervals are found with periods of 27 days on the time scale. The applied cross-correlation analysis demonstrates a phase lag of some days of the NO₂ and O₃ response to the 27-days solar cycle.

The calculated vertical column amounts of NO2 are used for validation of the satellite measurements, e.g. SCIAMACHY NO₂ data.

INVESTIGATION OF SOLAR DIFFERENTIAL ROTATION BY MEANS OF LONG-LIVED FEATURES OF SOLAR MAGNETIC FIELD

D. Japaridze, M. Gigolashvili, V. Kukhianidze

ABSTRACT

The differential rotation of the large-scale magnetic features by using Solar Synoptic Charts (1965-1976) is investigated. Variations of the rotation rate of the large-scale formations both in the northern and southern solar hemispheres for various latitudinal intervals are revealed. The large rotation rate of magnetic formations is obtained for patterns having the sign of the global magnetic field. The change of rotation rate of magnetic features studied in all latitudinal intervals coincides with the sign reversal of the global magnetic field.

Structure and Physical Parameters of the Corona Material during the August 11, 1999 Total Solar Eclipse

P.V. Stoeva, A.D. Stoev

ABSTRACT

Solar corona was observed during the total solar eclipse on August 11, 1999 from the village of Ravnets, General Toshevo municipality, Bulgaria. The white light solar corona images are obtained by a large-aperture camera (200/1000 mm) and telescope – refractor, using black and white professional photographic film. Intensities of the red and green coronal lines (forbidden line emissions of the multiply ionized iron atoms - Fe X and Fe XIV) are measured by specially constructed astrographs with 63 mm aperture of the objective and 840 mm focal length. Interference filters (λ_max = 6350 Å and λ_max = 5350 Å) were placed just before the main focal points. The basic details of the solar corona from the total solar eclipse on August 11, 1999 are “helmet” type streamers and system of polar streamers. The solar corona type has been determined as “pre-maximum” by the help of isophot maps (the solar corona flattening is ? = 0.19 and the solar cycle phase is ? = 0.66).

It has been found that the form of outer solar corona is different in red, green and white light up to two solar radii (R?). Distribution of the intensities of the red and green emission lines are different in the polar and equatorial region of the solar corona. Emisions are much stronger in the equatorial region. For comparison, the white light emission intensity of the solar corona is almost symmetrically distributed.

It has been also obtained that red corona is weaker than green corona, which is characteristic for epochs near the maximum solar activity. For our observations, the ion concentration ratio of the iron atoms FeXIV and FeX necessary for determining the temperature of the inner corona is about 1.8.

Derivation of Heliophysical Scientific Data from Amateur Observations of Solar Eclipses

A.D. Stoev, P.V. Stoeva

ABSTRACT

The basic scientific aims and observational experiments included in the complex observational programme “Total solar eclipse’99” are described in the work. Results from teaching and training students of total solar eclipse (TSE) observation in the Public Astronomical Observatory (PAO) in Stara Zagora and their selection for participation in different observational teams are also discussed. During the final stage, a special system of methods for investigation of the level of pretensions (the level of ambition as to what he/she feels capable of achieving in the context of problem solving/observation) of the students is applied. Results obtained from the observational experiments are interpreted mainly in the following themes: Investigation of the structure of the white-light solar corona and evolution of separate coronal elements during the total phase of the eclipse; Photometry of the white-light solar corona and specific emission lines; Meteorological, actinometrical and optical atmospheric investigations; Astrometry of the Moon during the phase evolution of the eclipse; Biological and behavioral reactions of highly organized colonies (ants and bats) during the eclipse. It is also shown that data processing, observational results and their interpretation, presentation and publishing in specialized and amateur editions is a peak in the independent creative activity of students and amateur astronomers. This enables students from the Astronomy schools at Public Astronomical Observatories and Planetaria (PAOP) to develop creative skills, emotional – volitional personal qualities, orientation towards scientific work, observations and experiments, and build an effective scientific style of thinking.

Cosmic Rays and 11-Year Solar Modulation

M. Buchvarova, P.I.Y. Velinov

ABSTRACT

The proposed model generalizes the differential D(E) and integral D(>E) spectra of galactic (GCR) and anomalous (ACR) cosmic ray protons and heavier elements during the 11-year solar cycle. The model takes into account the cosmic ray (CR) modulation by the solar wind in the heliosphere. The measurements with the CAPRICE94 and IMAX experiments are examined with numerical solutions of the model equations. We analyze variations of the parameters during the solar activity for outer and Earth planets. The radial gradient G0 of GCR is relatively small in the inner heliosphere. After a transition region between 10 and 20 AU, G0 increases to a much larger value that remains constant between ~25 and 80 AU. This shows that the contribution of GCRs and ACRs to the ionization of the atmospheres of outer planets Uranus, Neptune and Pluto will be increased drastically. We discuss here the errors in the predictions of the model and we compute the limits on estimated model parameters.

Main Features of Quasi-Electrostatic Fields in Atmospheric Regions due to Lightning Discharge

P. Tonev

ABSTRACT

The most important features of the strong quasi-electrostatic fields, generated in the region ionosphere-ground after a single lightning discharge, due to succeeding redistribution of capacitive spatial charges, are studied in this work. The investigation of these fields is of great importance, particularly since they are considered to be responsible for generation of red sprites in the mesosphere and lower ionosphere over thunderstorms. As experimental measurements show, these quasi-electrostatic fields can cause, more often than sprites, electron heating and conductivity modifications in the mesosphere and ionosphere as well. The temporal behavior and relaxation time of the quasi-electrostatic fields, as well as their spatial extent and orientation are studied. For this purpose an analytical model based on the Maxwell equations under conditions of curl-free electric field is proposed. Such conditions are fulfilled short (less than a millisecond) after beginning of a lightning discharge and last until another discharge. Isotropic conductivity in the region of interest is assumed. Computations are made for the time-course of the quasi-electrostatic fields up to the lower ionosphere. The dynamics of spatial charges in this region, responsible for the quasi-electrostatic fields, is analyzed also. The quasi-electrostatic fields at an altitude observed reach their maximum at a time close to the local relaxation time. Up to the ionosphere this maximum is of an order of V/m per 1 Coulomb of a charge transported by lightning. The field decreases immediately after reaching its maximum in the mesosphere; however, at stratospheric and tropospheric altitudes its maximum forms a plateau, which becomes wider at lower heights. The relaxation of the quasi-electrostatic field at altitudes above 40 km is essentially slower than the local relaxation time of an electrical charge.

O₂ Absorption Measurements and Modeling. Connection with the Troposphere Temperature

V.H. Guineva, R. Werner

ABSTRACT

Ground-based measurements of the A(0,0) and b(1,0) bands of the O2 atmospheric system are carried out using a spectrometric system designed for direct solar spectrum measurements in the region 3000 – 8000 A*, with a spectral resolution of about 0.3 A*.

Theoretical modeling of the O2 absorption is performed presuming plane-parallel atmosphere, divided into equal homogeneous parallel layers, and applying line-by-line calculations. The A and b bands intensities are computed at different altitudes and zenith angles. The comparison of the modeled spectra to the detailed measured ones shows that the absorption calculation method is reliable.

The ground-based spectrometric measurements afford opportunities to obtain information for the atmospheric parameters, including the temperature and its change with the height. Up to now methods for temperature profile retrieval using ground-based measurements have not been developed. The creation of such a method would be a contribution to the atmospheric studies because of the importance of the temperature as well as the cheaper implementation of the needed measurements. The temperature profile can be retrieved resolving the non-linear system equations for the equivalent widths of the rotational O2 lines. Such system equations for the equivalent widths are obtained in both cases - of weak and strong absorption, they are linearized and the systems are resolved towards the temperature in the separate layers, using an iteration method. The solution stability is studied with respect to the deviation of the input initial temperature values from the real ones, as well as with respect to the error in determining the equivalent widths. The system equations are found to be ill-conditioned, and the solution is highly sensitive to the input data. In order to provide the solution stability and a better convergence, a regularization algorithm should be applied. The application limits of the weak and strong absorption equations are studied.

Rocket Measurements of the Direct Solar Lyman-alpha Radiation Penetrating in the Atmosphere

V.H. Guineva, G. Witt, J. Gumbel, M. Khaplanov, V.L. Tashev

ABSTRACT

The resonance transition 2P-2S of the atomic hydrogen (Lyman-alpha emission) is the strongest and most conspicuous feature in the solar EUV spectrum. Due to the favorable circumstance that the Lyman-alpha wavelength (121.5 nm) coincides with a minimum of the O₂ absorption spectrum, the direct Lyman-alpha radiation penetrates well in the mesosphere. The interaction of the Lyman-alpha with the atmospheric constituents produces the NO molecules ionization, thus generating the ionospheric D-layer, and the water vapour photolysis, being one of the main H2O loss processes. The Lyman-alpha radiation transfer depends on the resonance scattering from the hydrogen atoms in the atmosphere and on the O₂ absorption. Since the Lyman-alpha extinction in the atmosphere is a measure for the column density of the oxygen molecules, the atmospheric temperature profile can be calculated thereof.

Rocket measurements of the direct Lyman-alpha radiation vertical profile in the summer mesosphere and thermosphere (up to 120 km), at high latitudes will be carried out in June 2006. The Lyman-alpha flux will be registered by a detector of solar Lyman-alpha radiation, manufactured in the Stara Zagora Department of the Solar-Terrestrial Influences Laboratory (STIL). Its basic part is an ionization camera, filled in with NO. The scientific data analysis will include raw data reduction, radiative transfer simulations, temperature retrieval as well as co-analysis with other parameters, measured near the polar summer mesopause.

Public Astronomical Observatories and Planetaria – Possibilities of Observations, Education and Public Outreach

Alexey Stoev

ABSTRACT

no abstract available

Solar Cycle 24 Forecasts

G. Maris, A. Oncica

ABSTRACT

The forecasts of the solar cycle 24 activities using the neural network method were made. For the sunspot relative number, June 2006 as the next minimum epoch with a value around 18 and, December 2009 as the next maximum epoch with a value of around 145 were obtained. For the 2800 MHz solar radio flux, the next minimum epochs with an approximate value of 75, on May 2006, and the next maximum epoch with a value of about 195, on December 2009, were forecasted. The time phase of both minima and maxima agrees nicely which gives us hope in a good behaviour of our approach. The forecasts of the geomagnetic aa, Dst, Ap and Kp indices were also done with the same pre-processing (gaussian monthly smoothed mean) and the same neural net for the same forecast horizon.

Space Weather Influence on Technological, Biological and Ecological Systems: Some Major Results of Complex Investigations Conducted in Azerbaijan

Elchin S. Babayev

ABSTRACT

Some major results of studies carried out in Azerbaijan on the possible influence of space weather, namely, periodical changes of solar and geomagnetic activities as well as non-periodic large solar energetic events on certain technological, ecological and biological systems are described in this review paper. Special attention is paid to the results of investigations on influence of violent solar events and severe geomagnetic storms on the above-mentioned systems.