Radio emission from the quiet sun and local sources at wavelengths 5, 10.7, 12, and 95 cm from observations of the January 4, 2011 eclipse in Crimea

The radio radii of the Sun at wavelengths of 5, 10.7, 12, and 95 cm have been determined from eclipse observations as R₅ ?? (1.0 ± 0.015)R _??, R _10,12 = (1.05 ± 0.003)R _??, and R ₉₅ = (1.2 ± 0.02)R _??. The bright-ness temperatures of quiet solar disk areas at these wavelengths have turned out to be Td ₅ = (22 ± 2) × 10³, Td ₁₀ = (44 ± 3) × 10³, Td ₁₂ = (47 ± 3) × 10³, and Td ₉₅ = (1000 ± 30) × 10³ K. There were local sources of radio emission with angular sizes from 1.9 to 2.4 arcmin and brightness temperatures from 80 × 10³ to 1.75 × 10⁶ K above sunspot groups at short wavelengths of 5, 10.7, and 12 cm. The radio flux from the local sources at 95 cm turned out to be below the detection threshold of 1.0 × 10^?22 W m^?2 Hz^?1. Comparison of the values obtained with the results of observations of another eclipse on August 1, 2008, occurred at the epoch of minimum of the 11-year solar cycle has shown that the radio radius of the Sun at 10.7 and 12 cm increased from 1.016 R _?? to 1.05 ± 0.003R _??, the height of the emitting layer at these wavelengths moved from 11 × 10³ km to (30 ± 7) × 10³ K, and the brightness temperature of the quiet Sun rose from (35.8 ± 0.4) × 10³ K to (44 ± 3) × 10³ K at 10.7 cm and from (37.3 ± 0.4) × 10³ K to (47 ± 3) × 10³ K at 12 cm. Consequently, the parameters of the solar atmosphere changed noticeably in 2 years in connection with the beginning of the new solar cycle 24. The almost complete absence of local sources at the longest wavelength of 95 cm suggests that the magnetic fields of the sunspot groups on January 4, 2011, were weak and did not penetrate to the height from where their emission could originate. If this property is inherent in most sunspot groups of cycle 24, then it can be responsible for its low flare activity.     

Large-Scale Variation of Solar Wind Electron Properties from Quasi-Thermal Noise Spectroscopy: Ulysses Measurements

The transport of energy in space plasmas, especially in the solar wind, is far from being understood. Measuring the temperature of the electrons and their non-thermal properties is essential to understand the transport properties in collisionless plasmas. Quasi-thermal noise spectroscopy is a reliable tool for measuring the electron temperature accurately since it is less sensitive to the spacecraft perturbations than particle detectors. We apply this method to Ulysses radio data obtained during the first pole-to-pole fast latitude scan in the high-speed solar wind, using a kappa function to describe the electron velocity distribution. We deduce the variations with heliocentric distance between 1.5 and 2.3 AU in the fast solar wind at high latitude in terms of three fitting parameters: the electron density varies as n _e??R ^?1.96±0.08, the electron temperature as T _e??R ^?0.53±0.15, and the kappa index of the distribution remains constant at ??=2.0±0.2. These observations agree with the predictions of the exospheric theory.     

Kinematic Properties of Slow ICMEs and an Interpretation of a Modified Drag Equation for Fast and Moderate ICMEs

We report kinematic properties of slow interplanetary coronal mass ejections (ICMEs) identified by SOHO/LASCO, interplanetary scintillation, and in situ observations and propose a modified equation for the ICME motion. We identified seven ICMEs between 2010 and 2011 and compared them with 39 events reported in our previous work. We examined 15 fast (V _SOHO?V _bg>500 km?s^?1), 25 moderate (0 km?s^?1≤V _SOHO?V _bg≤500 km?s^?1), and 6 slow (V _SOHO?V _bg<0 km?s^?1) ICMEs, where V _SOHO and V _bg are the initial speed of ICMEs and the speed of the background solar wind. For slow ICMEs, we found the following results: i) They accelerate toward the speed of the background solar wind during their propagation and reach their final speed by 0.34±0.03 AU. ii) The acceleration ends when they reach 479±126 km?s^?1; this is close to the typical speed of the solar wind during the period of this study. iii) When γ ₁ and γ ₂ are assumed to be constants, a quadratic equation for the acceleration a=?γ ₂(V?V _bg)|V?V _bg| is more appropriate than a linear one a=?γ ₁(V?V _bg), where V is the propagation speed of ICMEs, while the latter gives a smaller χ ² value than the former. For the motion of the fast and moderate ICMEs, we found a modified drag equation a=?2.07×10^?12(V?V _bg)|V?V _bg|?4.84×10^?6(V?V _bg). From the viewpoint of fluid dynamics, we interpret this equation as indicating that ICMEs with 0 km?s^?1≤V?V _bg≤2300 km?s^?1 are controlled mainly by the hydrodynamic Stokes drag force, while the aerodynamic drag force is a predominant factor for the propagation of ICME with V?V _bg>2300 km?s^?1.     

Multi-band Solar Full-disk Extreme Ultraviolet Imager

Solar Extreme Ultraviolet (EUV) imaging observation is an important measure for the researches of solar activities and coronal plasma physics. But the traditional EUV imager and spectrograph can hardly achieve simultaneously the high spectral resolution and wide field-of-view of solar imaging. This paper has designed a new type of solar EUV multi-band imager, by adopting a kind of slitless grating and grazing incidence structure, it can realize the solar full-disk imaging of high spectral and spatial resolution. The field-of-view of the imager can be as broad as 47′. The spectral resolution is 2×10^?3nm per pixel, and the spatial resolution is 1.4′ per pixel. The temporal resolution of the solar full-disk is better than 60 s. The analysis of the solar full-disk spectral image and system response shows that the imager can observe the morphological evolutions of various solar activities, and can provide more comprehensive data for the researches of solar physics and space weather forecast.     

Radial Speed Evolution of Interplanetary Coronal Mass Ejections During Solar Cycle 23

We report radial-speed evolution of interplanetary coronal mass ejections (ICMEs) detected by the Large Angle and Spectrometric Coronagraph onboard the Solar and Heliospheric Observatory (SOHO/LASCO), interplanetary scintillation (IPS) at 327 MHz, and in-situ observations. We analyze solar-wind disturbance factor (g-value) data derived from IPS observations during 1997?–?2009 covering nearly the whole period of Solar Cycle 23. By comparing observations from SOHO/LASCO, IPS, and in situ, we identify 39 ICMEs that could be analyzed carefully. Here, we define two speeds [V _SOHO and V _bg], which are the initial speed of the ICME and the speed of the background solar wind, respectively. Examinations of these speeds yield the following results: i) Fast ICMEs (with V _SOHO?V _bg>500 km?s^?1) rapidly decelerate, moderate ICMEs (with 0 km?s^?1≤V _SOHO?V _bg≤500 km?s^?1) show either gradually decelerating or uniform motion, and slow ICMEs (with V _SOHO?V _bg<0 km?s^?1) accelerate. The radial speeds converge on the speed of the background solar wind during their outward propagation. We subsequently find; ii) both the acceleration and the deceleration are nearly complete by 0.79±0.04 AU, and those are ended when the ICMEs reach a 480±21 km?s^?1. iii) For ICMEs with (V _SOHO?V _bg)≥0 km?s^?1, i.e. fast and moderate ICMEs, a linear equation a=?γ ₁(V?V _bg) with γ ₁=6.58±0.23×10^?6 s^?1 is more appropriate than a quadratic equation a=?γ ₂(V?V _bg)|V?V _bg| to describe their kinematics, where γ ₁ and γ ₂ are coefficients, and a and V are the acceleration and speed of ICMEs, respectively, because the χ ² for the linear equation satisfies the statistical significance level of 0.05, while the quadratic one does not. These results support the assumption that the radial motion of ICMEs is governed by a drag force due to interaction with the background solar wind. These findings also suggest that ICMEs propagating faster than the background solar wind are controlled mainly by the hydrodynamic Stokes drag.     

Electron density diagnostics for various plasma structures of the solar corona based on Fe XI-FeXIII lines in the range 176–207 Å measured in the SPIRIT/CORONAS-F experiment

The relative intensities of FeXI-Fe XIII lines in the range 176–207 Å have been measured for various plasma structures of the solar corona using data from the XUV spectroheliograph of the SPIRIT instrumentation onboard the CORONAS-F satellite with an improved spectral sensitivity calibration. Electron density diagnostics of a plasma with temperatures 0.8–2.5 MK has been carried out in active regions, quiet-Sun and off-limb areas, and, for the first time, in extremely intense solar flares. The density range is (1.6–8) × 10⁹ cm^?3 for flares, (0.6–1.6) × 10⁹ cm^?3 for active regions, and ～5 × 10⁸ cm^?3 for quiet-Sun areas. The calibration accuracy of the spectral sensitivity for the spectroheliograph has been analyzed based on spectral lines with density-independent intensity ratios.     

For infrared spectrophotometry of Jupiter and Saturn

Infrared spectral observations of Mars, Jupiter, and Saturn were made from 100 to 470 cm^?1 using NASA's G. P. Kuiper Airborne Observatory. Taking Mars as a calibration source, we determined brightness temperatures of Jupiter and Saturn with approximately 5 cm^?1 resolution. The data are used to determine the internal luminosities of the giant planets, for which more than 75% of the thermally emitted power is estimated to be in the measured bandpass: for Jupiter L_J = (8.0 ± 2.0) × 10^?10L_⊙ and for Saturn L_S = (3.6 ± 0.9) × 10^?10. The ratio R of thermally emitted power to solar power absorbed was estimated to be R_J = 1.6 ± 0.2, and R_S = 2.7 ± 0.8 from the observations when both planets were near perihelion. The Jupiter spectrum clearly shows the presence of the rotational ammonia transitions which strongly influence the opacity at frequencies ?250 cm^?1. Comparison of the data with spectra predicted from current models of Jupiter and Saturn permits inferences regarding the structure of the planetary atmospheres below the temperature inversion. In particular, an opacity source in addition to gaseous hydrogen and ammonia, such as ammonia ice crystals as suggested by Orton, may be necessary to explain the observed Jupiter spectrum in the vicinity of 250 cm^?1.     

High resolution scans of Comet Kohoutek in the vicinity of 5015, 5890, and 6563 Å

High resolution scans were made of Comet Kohoutek (1973f) using the McMath solar telescope at Kitt Peak National Observatory. The data were taken on January 1 and 4, 1974 UT, just after the comet perihelion. Hα emission (～4.1 × 10²⁷ photon sec^?1) was observed from the head of the Comet. An upper limit on the He I(5015) radiation was determined to be less than 2% of the observed Hα emission. The Na D1/D2 line intensities on both nights were approximately 0.5, indicating an optically thin emission region.     

Altitude profile of H in the atmosphere of Venus from Lyman α observations of Venera 11 and Venera 12 and origin of the hot exospheric component

Two extreme ultraviolet (EUV) spectrophotometers flown in December 1978 on Venera 11 and Venera 12 measured the hydrogen Lyman α emission resonantly scattered in the atmosphere of Venus. Measurements were obtained across the dayside of the disk, and in the exosphere up to 50,000 km. They were analyzed with spherically symmetric models for which the radiative transfer equation was solved. The H content of the Venus atmosphere varies from optically thin to moderately thick regions. A shape fit at the bright limb allows one to determine the exospheric temperature T_c and the number density n_c independently of the calibration of the instrument or the exact value of the solar flux. The dayside exospheric temperature was measured for the first time in the polar regions, with T_c = 300 ± 25°K for Venera 11 (79°S) and T_c = 275 ± 25°K (59°S) for Venera 12. At the same place, the density is n_c = 4_?2⁺³ × 10⁴ atom.cm^?3, and the integrated number density N_t from 250 to 110 km (the level of CO₂ absorption) is 2.1 × 10¹² atom.cm^?2, a factor of 3 to 6 lower than that predicted in aeronomical models. This probably indicates that the models should be revised in the content of H-bearing molecules and should include the effect of dynamics. Across the disk the value of N_t decreases smoothly with a total variation of two from the morning side to the afternoon side. Alternately it could be a latitude effect, with less hydrogen in the polar regions. The nonthermal component if clearly seen up to 40,000 km of altitude. It is twice as abundant as at the time of Mariner 10 (solar minimum). Its radial distribution above 4000 km can be simulated by an exospheric distribution with T = 10³⁰K and n = 10³ atom.cm^?3 at the exobase level. However, there are less hot atoms between 2000 and 4000 km than predicted by an ionospheric source. A by-product of the analysis is a determination of a very high solar Lyman α flux of 7.6 × 10¹¹ photons (cm² sec Å)^?1 at line center (1 AU) in December 1978.     

Redetermination of galactic spiral density wave parameters based on spectral analysis of masers radial velocities

To redetermine the Galactic spiral density wave parameters, we have performed a spectral (Fourier) analysis of the radial velocities for 44 masers with known trigonometric parallaxes, proper motions, and line-of-sight velocities. The masers are distributed in awide range of Galactocentric distances (3.5 kpc < R < 13.2 kpc) and are characterized by a wide scatter of position angles ?? in the Galactic XY plane. This has required an accurate allowance for the dependence of the perturbation phase both on the logarithm of the Galactocentric distances and on the position angles of the objects. To increase the significance of the extraction of periodicities from data series with large gaps, we have proposed and implemented a spectrum reconstruction method based on a generalized maximum entropy method. As a result, we have extracted a periodicity describing a spiral density wave with the following parameters from the maser radial velocities: the perturbation amplitude f _R = 7.7 _?1.5 ^+1.7 km s^?1, the perturbation wavelength ?? = 2.2 _?0.1 ^+0.4 kpc, the pitch angle of the spiral density wave i = ?5 _?0.9° ^+0.2° , and the phase of the Sun in the spiral density wave ?? _?? = ?147 _?17° ^+3° .     

The Imaging Magnetograph eXperiment (IMaX) for?the?Sunrise Balloon-Borne Solar Observatory

The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by four institutions in Spain that flew on board the Sunrise balloon-borne solar observatory in June 2009 for almost six days over the Arctic Circle. As a polarimeter, IMaX uses fast polarization modulation (based on the use of two liquid crystal retarders), real-time image accumulation, and dual-beam polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the instrument uses a LiNbO₃ etalon in double pass and a narrow band pre-filter to achieve a spectral resolution of 85 mÅ. IMaX uses the high-Zeeman-sensitive line of Fe i at 5250.2 Å and observes all four Stokes parameters at various points inside the spectral line. This allows vector magnetograms, Dopplergrams, and intensity frames to be produced that, after reconstruction, reach spatial resolutions in the 0.15??C?0.18 arcsec range over a 50×50 arcsec field of view. Time cadences vary between 10 and 33 s, although the shortest one only includes longitudinal polarimetry. The spectral line is sampled in various ways depending on the applied observing mode, from just two points inside the line to 11 of them. All observing modes include one extra wavelength point in the nearby continuum. Gauss equivalent sensitivities are 4 G for longitudinal fields and 80 G for transverse fields per wavelength sample. The line-of-sight velocities are estimated with statistical errors of the order of 5??C?40 m?s^?1. The design, calibration, and integration phases of the instrument, together with the implemented data reduction scheme, are described in some detail.     

Using a New Sky Brightness Monitor to Observe the Annular Solar Eclipse on 15 January 2010

For the future development of Chinese Giant Solar Telescope (CGST) in Western China, a new sky brightness monitor (SBM) has been produced for the site survey for CGST. To critically examine the performance and sensitivity of SBM, we used it in the observation of the annular solar eclipse in Dali City, Yunnan, on 15 January 2010. The observation met good weather conditions with an almost clear sky during the eclipse. The SBM measurement translates into the solar illuminance changes at a level of 2.4×10^?4 I?s^?1 during the eclipse. The time of the minimal sky brightness in the field of view (FOV) is found consistent with the time of maximum eclipse. Two local sky regions in the FOV are chosen to make a time series of the calibrated skylight profiles. The evolution of the sky brightness thus calibrated also shows good consistency with the eclipse, particularly between the second and the third contacts. The minimal sky brightness in each local sky region took place within half a minute from the corresponding predicted contact time. Such small time delays were mainly caused by occasional cirri. The minimal sky brightness measured during the eclipse is a few millionths of I _?? with standard deviation of 0.11 millionths of I _??. The observation supports that the single-scattering process (optically thin conditions) is the main contributor to the atmospheric scattering. We have demonstrated that many important aerosol optical parameters can be deduced from our data. We conclude that the new SBM is a sensitive sky photometer that can be used for our CGST and coronagraph site surveys.     

Multi-Wavelength Eclipse Observations of a Quiescent Prominence

We construct the maps of temperatures, geometrical thicknesses, electron densities and gas pressures in a quiescent prominence. For this we use the RGB signal of the prominence visible-light emission detected during the total solar eclipse of 1 August 2008 in Mongolia and quasi-simultaneous Hα spectra taken at Ond?ejov Observatory. The method of disentangling the electron density and geometrical (effective) thickness was described by Jej?i? and Heinzel (Solar Phys. 254, 89?–?100, 2009) and is used here for the first time to analyse the spatial variations of prominence parameters. For the studied prominence we obtained the following range of parameters: temperature 6000?–?15?000 K, effective thickness 200?–?15000 km, electron density 5×10⁹?–?10¹¹ cm^?3 and gas pressure 0.02?–?0.2 dyn?cm^?2 (assuming a fixed ionisation degree n _p/n _H=0.5). The electron density increases towards the bottom of the prominence, which we explain by an enhanced photoionisation due to the incident solar radiation. To confirm this, we construct a two-dimensional radiative-transfer model with realistic prominence illumination.     

A search for H2O and Ch4 in Comet Kohoutek

A spectroscopic search for H₂O and CH₄ in Comet Kohoutek (1973f) was made using a Pepsios interferometer. No evidence was found for either molecule, allowing us to set an upper limit on their production rates (on about 21 January 1974) of Q(H₂O) < 6.2 × 10²⁸ sec^?1 and Q(CH₄) < 2.0 × 10³⁰ sec^?1. If the cometary surface is water-ice, this production rate leads to a product (1 ? A)·(πR₀²) < 2.2 km², where A is the Bond albedo, R₀ is the nuclear radius, and we assume that all the absorbed solar energy is used to evaporate H₂O.     

The State of Self-organized Criticality of the Sun During the Last Three Solar Cycles. I. Observations

We analyze the occurrence-frequency distributions of peak fluxes [P], total fluxes [E], and durations [T] of solar flares over the last three solar cycles (during 1980??C?2010) from SMM/HXRBS, CGRO/BATSE, and RHESSI hard X-ray data. From the synthesized data we find powerlaw slopes with mean values of ?? _P =1.73±0.07 for the peak flux, ?? _E =1.62±0.12 for the total flux, and ?? _T =1.99±0.35 for flare durations. We find a tendency of an anti-correlation of the powerlaw slope of peak fluxes with the flare rate or sunspot number as a function of the solar cycle. The occurrence powerlaw slope is always steeper by ??????0.1 during a solar-cycle minimum compared with the previous solar-cycle maximum, but the relative amplitude varies for each cycle or instrument. Since each solar cycle has been observed with a different instrument, part of the variation could be attributed to instrumental characteristics and different event selection criteria used in generating the event catalogs. The relatively flatter powerlaw slopes during solar maxima could indicate more energetic flares with harder electron-energy spectra, probably due to a higher magnetic complexity of the solar corona. This would imply a non-stationarity (or solar-cycle dependence) of the coronal state of self-organized criticality.     

Replenishment of electrons lost in the south atlantic anomaly by gyroresonant pitch-angle diffusion

Experimental data describing the effect of the South Atlantic anomaly on E? 280 keV electron flux at L = 2 and high B values, are compared to the numerical solution of a pitch-angle diffusion equation with a varying loss cone. The diffusion coefficient needed to explain replenishment of the electrons lost over the anomaly is found to be 3.2 × 10^?2 sec^?1 Calculation of the diffusion coefficient due to cyclotron resonant interaction with VLF electro-magnetic waves leads to the conclusion that the observed wave spectral density can yield the needed diffusion coefficient.     

Spectral atlases of the Sun from 3980 to 7100 Å at the center and at the limb

In this work, we present digital and graphical atlases of spectra of both the solar disk-center and of the limb near the Solar poles using data taken at the UTS-IAP & RIAAM (the University of Tabriz Siderostat, telescope and spectrograph jointly developed with the Institut d’Astrophysique de Paris and Research Institute for Astronomy and Astrophysics of Maragha). High resolution and high signal-to-noise ratio (SNR) CCD-slit spectra of the sun for 2 different parts of the disk, namely for μ=1.0 (solar center) & for μ=0.3 (solar limb) are provided and discussed. While there are several spectral atlases of the solar disk-center, this is the first spectral atlas ever produced for the solar limb at this spectral range. The resolution of the spectra is about R～70?000 (Δλ～0.09 Å) with the signal-to-noise ratio (SNR) of 400–600. The full atlas covers the 3980 to 7100 Å spectral regions and contains 44 pages with three partial spectra of the solar spectrum put on each page to make it compact. The difference spectrum of the normalized solar disk-center and the solar limb is also included in the graphic presentation of the atlas to show the difference of line profiles, including far wings. The identification of the most significant solar lines is included in the graphic presentation of the atlas. Telluric lines are producing a definite signature on the difference spectra which is easy to notice. At the end of this paper we present only two sample pages of the whole atlas while the graphic presentation of the whole atlas along with its ASCII file can be accessed via the ftp server of the CDS in Strasbourg via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via this link: http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/other/ApSS.     

The GREGOR Fabry‐Pérot Interferometer

The GREGOR Fabry‐Pérot Interferometer (GFPI) is one of three first‐light instruments of the German 1.5‐meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated mounting. Thanks to its large‐format, high‐cadence CCD detectors with sophisticated computer hard‐ and software it is capable of scanning spectral lines with a cadence that is sufficient to capture the dynamic evolution of the solar atmosphere. The field‐of‐view (FOV) of 50″×38″is well suited for quiet Sun and sunspot observations. However, in the vector spectropolarimetric mode the FOV reduces to 25″×38″. The spectral coverage in the spectroscopic mode extends from 530–860 nm with a theoretical spectral resolution of R ≈250 000, whereas in the vector spectropolarimetric mode the wavelength range is at present limited to 580–660 nm. The combination of fast narrow‐band imaging and post‐factum image restoration has the potential for discovery science concerning the dynamic Sun and its magnetic field at spatial scales down to ∼50 km on the solar surface (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of Differences Between Sunspot and White Light Facular Area Data Determined from SDO/HMI and SOHO/MDI Observations

Sunspot and white light facular areas are important data for solar activity and are used, for example, in the study of the evolution of sunspots and their effect on solar irradiance. Solar Dynamic Observatory??s Helioseismic and Magnetic Imager (SDO/HMI) solar images have much higher resolution (??0.5????pixel^?1) than Solar and Heliospheric Observatory??s Michelson Doppler Imager (SOHO/MDI) solar images (??2????pixel^?1). This difference in image resolution has a significant impact on the sunspot and white light facular areas measured in the two datasets. We compare the area of sunspots and white light faculae derived from SDO/HMI and SOHO/MDI observations. This comparison helps the calibration of the SOHO sunspot and facular area to those in SDO observations. We also find a 0.22 degree difference between the North direction in SDO/HMI and SOHO/MDI images.