Solar Origin of the Radio Attributes of a Complex Type III Burst Observed on 11 April 2001

We report here on the solar origin of distinctive radiation characteristics observed for a decametric type III solar radio burst that was associated with a major solar flare and CME on 11 April 2001. The associated decimeter (Ond?ejov) and meter (Potsdam) wavelength emissions, as well as the GOES soft X-ray lightcurve, suggest that there were two successive events of energy release and electron acceleration associated with this solar eruption. The Nançay radioheliograph images and additional evidence of plasmoid propagation suggest that the second event of electron acceleration resulted from coronal reconfigurations, likely caused by the erupting CME. These observational analyses provide new insights into the physical origin of the distinguishing characteristics of complex type III-like radio emissions that are typically observed at decameter wavelengths during major solar eruptive events.     

Hard Burst Emission from the Soft Gamma Repeater SGR 1900+14

We present evidence for burst emission from SGR 1900+14 with a power-law high-energy spectrum extending beyond 500 keV. Unlike previous detections of high-energy photons during bursts from soft gamma repeaters (SGRs), these emissions are not associated with extraordinarily bright flares. Not only is the emission hard, but the spectra are better fitted by D. Band's gamma-ray burst (GRB) function rather than by the traditional optically thin thermal bremsstrahlung model. We find that the spectral evolution within these hard events obeys a hardness/intensity anticorrelation. Temporally, these events are distinct from typical SGR burst emissions in that they are longer ( approximately 1 s) and have relatively smooth profiles. Despite a difference in peak luminosity of greater, similar1011 between these bursts from SGR 1900+14 and cosmological GRBs, there are striking temporal and spectral similarities between the two kinds of bursts, aside from spectral evolution. We outline an interpretation of these events in the context of the magnetar model.     

Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe‐Mg‐Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg‐ and Fe‐rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion.     

Changes in the Martian atmosphere induced by auroral electron precipitation

Typical auroral events in the Martian atmosphere, such as discrete and diffuse auroral emissions detected by UV spectrometers onboard ESA Mars Express and NASA MAVEN, are investigated. Auroral electron kinetic energy distribution functions and energy spectra of the upward and downward electron fluxes are obtained by electron transport calculations using the kinetic Monte Carlo model. These characteristics of auroral electron fluxes make it possible to calculate both the precipitation-induced changes in the atmosphere and the observed manifestations of auroral events on Mars. In particular, intensities of discrete and diffuse auroral emissions in the UV and visible wavelength ranges (Soret et al., 2016; Bisikalo et al., 2017; Gérard et al., 2017). For these conditions of auroral events, the analysis is carried out, and the contribution of the fluxes of precipitating electrons to the heating and ionization of the Martian atmosphere is estimated. Numerical calculations show that in the case of discrete auroral events the effect of the residual crustal magnetic field leads to a significant increase in the upward fluxes of electrons, which causes a decrease in the rates of heating and ionization of the atmospheric gas in comparison with the calculations without taking into account the residual magnetic field. It is shown that all the above-mentioned impact factors of auroral electron precipitation processes should be taken into account both in the photochemical models of the Martian atmosphere and in the interpretation of observations of the chemical composition and its variations using the ACS instrument onboard ExoMars.     

Wave-particle interactions in the ulf range: GEOS-1 and -2 results

Electromagnetic waves in the frequency range 0.2–11 Hz have been detected onboard the GEOS-1 and -2 satellites. The purpose of this paper is to report on these observations. The three orthogonal magnetic sensors allow us to determine the polarization of the waves. Two kinds of waves are commonly observed, which can easily be distinguished by their polarization.

(1) Waves with a magnetic field aligned with the DC magnetic field. These events often present a typical harmonic structure. The fundamental—which is not always observed—is often in the neighbourhood of the proton gyrofrequency F_H+. These waves are generally observed above F_H+. We will show that these emissions can be interpreted as magnetosonic waves destabilized by energetic protons (E 15 keV) with a ringlike distribution function.

(2) Waves with a magnetic field in a plane perpendicular to the DC magnetic field. These emissions are identified as Ion Cyclotron Waves (ICW's). These waves can, under certain conditions, propagate along the line of force of the magnetic field and reach the ground. They can be identified with the well-known Pcl oscillations, which generally have a clear periodic structure. In contrast these periodic structures are seldom observed onboard the satellites. At the geostationary orbit, these emissions exist in limited frequency domains, which are well organized by the helium gyrofrequency F_He+.     

On the S- and B-components of solar radio and X-emission and their relationships to energetic solar events

The slowly varying solar radio and X-ray emissions are considered theoretically and statistically concerning their significance as potential indicators of energy storage processes in active regions leading to large flare-burst events. A correlation analysis has been carried out in order to test different global emission parameters accessable by daily routine measurements regarding their connection with type IV bursts and proton flares. From all investigated quantities systematically best (though not very high) correlations have been verified for both the 3 cm radio and 0–8 Å X-ray fluxes. Increasing correlation coefficients resulted for running averages indicating possible storage processes over several days.There is some evidence favouring the assumption of a small contribution of nonthermal processes to the spectrum of the S-component at burst-active periods which possibly lead to the development of flare-burst instabilities.     

The characteristics of impulsive solar EUV bursts

We examine a number of high time resolution intensity-time profiles of EUV impulsive bursts as observed by the Harvard College Observatory EUV Spectroheliometer carried aboard the Skylab Apollo Telescope Mount. These bursts are found to be synchronous (to within the instrumental time resolution of 5.5 s) in all wavelengths observed, corresponding to emissions from temperatures ranging from upper chromospheric to coronal. The distribution with temperature of a suitably defined emission measure parameter is also examined as a function of time throughout the bursts and a marked similarity in the shape of this distribution, both between different events and throughout the time history of any particular event, is noted. The significance of these observations for physical processes associated with EUV bursts is briefly discussed.On leave from Dept. of Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.     

The impact of Eurasian dust storms and anthropogenic emissions on atmospheric nutrient deposition rates in forested Japanese catchments and adjacent regional seas

Bulk precipitation and stream water chemistry data from 1993 to 2005 are used to analyze the relationship between Eurasian dust storms and nutrient deposition rates in the Kutsuki experimental forest (near Lake Biwa). From 2000 to 2005, atmospheric deposition, total nitrogen (TN), total phosphorus (TP) and dissolved silica (DSi) deposition rates increased by 26%, 132%, and 38%, respectively in the Kutsuki experimental forest. These TN and TP increases are associated with three seasonal factors: the increasing frequency and intensity of Eurasian spring dust events (March/April); the annual typhoon period (late August/September); and autumn/early winter (October to December) monsoons. The annual typhoon and monsoon winter periods are drivers for atmospheric TP and DSi deposition due to the correlation between the deposition and precipitation. In addition, increased spring dust deposition is a primarily driver for TN deposition changes. Increased emissions from urbanized areas in China (and likely Korea) affect the chemical properties of aerosols reaching downwind Japanese regions. Aerosol processes are responsible for increasing TN in aerosols, which are affected primarily by anthropogenic emissions. From 2000 to 2005, coal burning emissions from East Asia have contributed to an increase in TP (and possibly DSi) deposition rates. The observed increase in nutrient deposition did not noticeably impact short-term (5 year) stream water fluxes in the Kutsuki experimental forest. Due to plant uptake, the forest ecosystem retained atmospherically deposited N and P. Finally, the observed increases in nutrient deposition rates over the East China Sea and the Sea of Japan may significantly influence intra-annual net primary production. It is recommended that earth system modelling incorporate changes in atmospheric nutrient deposition rates and their impacts on the regional carbon cycle as well as aquatic and terrestrial ecosystems.     

Non-thermal continuum emissions associated with electron injections: Remote plasmapause sounding

Energetic electron injection events result in the arrival of loss-cone distributions of electrons at energies of a few keV close to the plasmapause at local midnight. These distributions favour the growth of strong electrostatic waves with some conversion to electromagnetic nonthermal continuum emissions near to the geomagnetic equator.GEOS2 located at the geostationary orbit (L = 6.6, 3.3° South) has observed these continuum emissions for a number of electron injection events. Their unique frequency structure provides a measurement of the geomagnetic field strength at the source and hence its radial position, while direction finding measurements at GEOS2 complete the source location determination.Measurements of source locations as a function of time after the start of an electron injection event, yield typical inwards motions of 1R_Eh^?1. In this way the emissions provide a remote sensing of the plasmapause location from the geostationary orbit.     

Analyses Of Jovian Decametric Radiation -Bursts Interacting With N-Bursts

Dynamic spectra of S-bursts of Jovian decametric radiations are obtained by using a high time resolution radio spectrograph which has a time resolutionof 2 msec and the bandwidth of 2 MHz.Within occurrence of 65 S-burst events observed in the period from 1983 to 1999, 26 events have been identified as the S-N burst events, which are characterized by the interaction between the S-burst emissions and the Narrow band emissions. In the dynamic spectra of the S-N burst, the trend of emissions with negative and slower frequency drift named as “Trailing Edge Emission” are often observed shortly after the appearance of the S-burst.Detailed analyses of these phenomena revealed that the Trailing Edge Emission is not a manifestation of S-burst with slower drift rate but a variation ofN-burst. The results suggested that S-burst and the associated Trailing Edge Emission are formed simultaneously started from a common region with different drift rates. It has been further suggested that the appearance of the S-burstsis not controlled by the geometrical effect between the source region and theobserver, but directly reflects the generation of the source region widelydistributed in an altitude range from a few thousands km to 30,000 km, alongthe Io flux tube. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solar radio continuum storms

Radio noise continuum emissions observed in metric and deca-metric wave frequencies are, in general, associated with actively varying sunspot groups accompanied by the S-component of microwave radio emissions. It is known that these continuum emission sources, often called type I storm sources, are often associated with type III burst storm activity from metric to hectometric wave frequencies. This storm activity is, therefore, closely connected with the development of these continuum emission sources.It is shown that the S-component emission in microwave frequencies generally precedes by several days the emission of these noise continuum storms of lower frequencies. In order for these storms to develop, the growth of sunspot groups into complex types is very important with the increase of the average magnetic field intensity and area of these groups. In particular, the types of these groups such as and are very important on the generation of noise continuum storm sources and sharp increase of the flux of these continuum emissions. This fact suggests that sunspot magnetic configuration and its variation, both space and time, are very effective on the growth of the sources for these noise continuum emissions.Although we have not known yet the true mechanism of these emissions, it is very likely that energetic electrons, 10 to 100 keV, accelerated in association with the variation of sunspot magnetic fields, are responsible as the sources of those radio emissions. Furthermore it seems that these electrons are contributing to the emission of type III burst storms, which are associated with the noise continuum storm sources. In explaining the origin of these storms, some plasma processes must be taken into consideration. Furthermore, it should be remarked that the storage mechanism of the electrons mentioned above plays an important role in generating both the noise continuum emissions and type III burst storms, because on-fringe type III bursts are all generated above these noise continuum storms sources. After reviewing the theories of these noise continuum storm emissions, a model is briefly considered to explain the relation between these continuums and type III bursts, and a discussion is given on the role of energetic electrons on these two emissions. It is pointed out that instabilities associated with these electrons and their relation to their own stabilizing effects are important in interpreting both of these storm emissions.Astrophysics and Space Science Review Paper.     

Optical and infrared observations of SN 2002dj: some possible common properties of fast-expanding Type Ia supernovae

As part of the European Supernova Collaboration, we obtained extensive photometry and spectroscopy of the Type Ia supernova (SN Ia) SN 2002dj covering epochs from 11 d before to nearly two years after maximum. Detailed optical and near-infrared observations show that this object belongs to the class of the high-velocity gradient events as indicated by Si, S and Ca lines. The light curve shape and velocity evolution of SN 2002dj appear to be nearly identical to SN 2002bo. The only significant difference is observed in the optical to near-infrared colours and a reduced spectral emission beyond 6500 Å. For high-velocity gradient SNe Ia, we tentatively identify a faster rise to maximum, a more pronounced inflection in the V and R light curves after maximum and a brighter, slower declining late-time B light curve as common photometric properties of this class of objects. They also seem to be characterized by a different colour and colour evolution with respect to 'normal' SNe Ia. The usual light curve shape parameters do not distinguish these events. Stronger, more blueshifted absorption features of intermediate-mass elements and lower temperatures are the most prominent spectroscopic features of SNe Ia displaying high-velocity gradients. It appears that these events burn more intermediate-mass elements in the outer layers. Possible connections to the metallicity of the progenitor star are explored.     

Venera 11 and Venera 12 observations of e.u.v. emissions from the upper atmosphere of Venus

The results obtained by two extreme ultra violet (e.u.v.) spectrophotometers flown near Venus on VENERA 11 and VENERA 12 in December 1978 are presented. Detectors were placed at discrete wavelength positions to measure e.u.v. emissions from the upper atmosphere of Venus while the spacecraft were drifting on their fly-by orbits. The emissions of HI 121.6 nm (Ly-α), HeI 58.4 nm, and OI 130.4 nm were measured with unprecedented sensitivity and spatial resolution. An OI signal of 500 Rayleigh (R) measured outside the disc suggested the existence of a large bulge of oxygen atoms. The e.u.v. emissions of two ionic species. OII 83.4 nm and HeII 30.4 nm, were measured for the first time in the atmosphere of Venus. The zero order detector of VENERA 12 indicated the presence of a very intense e.u.v. emission (28 kR) lying between the monitored wavelengths. This emission, which was only 3 kR for VENERA 11, is likely to be associated with the solar wind-ionosphere interaction.An attempt to measure ArI and NeI resonance emissions failed.The Lyman alpha (Ly-α) interplanetary background was 4 to 5 times larger than expected, suggestive of a very intense solar flux or an increase of the interplanetary density. The distribution of hydrogen indicates two populations with temperatures of 400 and 700 K.     

Transient emissions on the wavelength of helium I, 5876 Å recorded during auroral break-up

During the break-up phase of two strong auroral events, emissions of short duration on the wavelength of He I, 5876 Å have been observed. These records are accurate within 0.5 Å and intensities of up to 120 R have been measured. This high value is not consistent with the theoretical limit suggested by other authors. Simultaneous observations of H, 6563 Å show that the He I and H emissions are not closely related to each other with time, which may be one reason for explaining the discrepancy with the predicted intensity derived from observed ratios of He⁺⁺/H⁺ in the solar wind. The emission on 5876 Å has only been detected at the lowest border of very intense ray bundles towards north but not yet in auroral arcs and diffuse glow. It is suggested that two principally different helium events in aurora may be observable, one resulting in a low level He emission lasting for longer time and another in a stronger He emission of short duration. The observational difficulties caused by the presence of OH bands are discussed.     

A systematic description of shocks in gamma-ray bursts – II. Simulation

In Paper I, we presented a detailed formulation of the relativistic shocks and synchrotron emission in the context of gamma-ray burst (GRB) physics. To see how well this model reproduces the observed characteristics of the GRBs and their afterglows, here we present the results of some simulations based on this model. They are meant to reproduce the prompt and afterglow emissions in some intervals of time during a burst. We show that this goal is achieved for both short and long GRBs and their afterglows, at least for part of the parameter space. Moreover, these results are evidence of the physical relevance of the two phenomenological models we have suggested in Paper I for the evolution of the active region – synchrotron emitting region in a shock. The dynamical active region model seems to reproduce the observed characteristics of prompt emissions and late afterglow better than the quasi-steady model which is more suitable for the onset of afterglows. Therefore, these simulations confirm the arguments presented in Paper I about the behaviour of these models based on their physical properties.     

Coronal Shocks Associated with Impulsive and Decaying Phases of Solar Flares

We have analyzed a set of 147 metric Type II radio bursts observed by Culgoora radio spectrograph from November 1997 to December 2006. These events were divided into two sets: The first subset contains Type II events that started during the impulsive phase of the associated solar flares and the second subset contains those starting during the decaying phase of flares. Our main aim is to differentiate the metric Type IIs, flares and coronal mass ejections (CMEs) of these two subsets. It is found that while Type II burst characteristics of both subsets are very similar, there are significant differences between flare and CME properties for these two subsets. Considering all analyzed relationships between the characteristics of Type IIs, flares and CMEs in these two Type II subsets, we conclude that most of the coronal shocks causing metric Type II bursts are driven by CMEs, but that a fraction of events are probably ignited by solar flares.     

Multispectral observations complementary to the study of high-energy solar phenomena

Non-thermal phenomena on the Sun are characterized by the transient acceleration of electrons and ions to energies ranging from several keV to tens of GeV, and the impulsive heating of plasma to temperatures exceeding 5 × 10⁷ K. These energetic processes result in the emission of a broad spectrum of electromagnetic radiation and of high-energy neutrons, as well as the escape of high energy electrons and ions from the acceleration region. The determination of the energy spectrum, polarization, and spatial distribution of these emissions, which contain detailed information on the acceleration and heating process, and the conditions at the sites at which this energy is generated and dissipated, is the principal objective of high-energy solar studies.The study of the evolution of magnetic structures in the solar convection zone and atmosphere which underlie the metastable conditions which precede these energetic processes, of the conditions that trigger the release of energy, and of the impact of the energy released on the solar atmosphere, is most effectively carried out by observations of thermal and quasi-thermal phenomena which precede, coincide with, and follow the impulsive acceleration and heating event itself. Multispectral observations of the phenomena associated with non-thermal events on the Sun are reviewed, and the requirements for visible, ultraviolet, extreme ultraviolet, and soft X-ray observations which are necessary for future advances are briefly described.     

Modeling mineral dust emissions from Chinese and Mongolian deserts

The present study investigates the frequency and intensity of mineral dust emissions over the deserts of eastern Asia from 1996 to 2001. Mineral dust emissions are simulated using a physical dust emission scheme over a region extending from 35.5°N to 47°N and from 73°E to 125°E. The input parameters required by the dust emission model are (1) surface features data including aerodynamic roughness length, soil dry size distribution and texture; and (2) meteorological surface data, mainly wind speed, soil moisture and snow cover. The way by which these surface features and meteorological data can be assessed is described and discussed. The influence of soil moisture and snow cover is taken into account and their effects on simulated dust emission are quantified.The simulations reproduce on a daily basis the location and intensity of the severe events of April 1998 and spring 2001 as recorded by the meteorological stations and/or described in various studies. Based on 6 yr of simulations, the main dust source regions are identified and their relative contributions to the total dust emissions are quantified.The seasonal cycle of the dust storms frequency is well reproduced with a maximum in spring. The simulations suggest that it is mainly controlled by the emissions occurring in the Taklimakan desert in latter spring and in summer, and by those occurring in the northern deserts of China in winter. The Taklimakan desert appears to be the most frequent and steady source of dust emissions during the studied period. On the other hand, in the Gobi desert, only a few dust emission events are simulated, but the dust amount emitted during each event is generally very large. In the northern deserts of China, dust emissions are frequent and their intensity is variable.These results show an important annual and inter-annual variability of the emitted dust (between 100 Mt yr^− 1 and 460 Mt yr^− 1), mainly controlled by the occurrence of severe events in the Gobi desert and in the northern deserts of China.     

Cassini UVIS observations of Jupiter's auroral variability

The Cassini spacecraft Ultraviolet Imaging Spectrograph (UVIS) obtained observations of Jupiter's auroral emissions in H₂ band systems and H Lyman-α from day 275 of 2000 (October 1), to day 81 of 2001 (March 22). Much of the globally integrated auroral variability measured with UVIS can be explained simply in terms of the rotation of Jupiter's main auroral arcs with the planet. These arcs were also imaged by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope (HST). However, several brightening events were seen by UVIS in which the global auroral output increased by a factor of 2-4. These events persisted over a number of hours and in one case can clearly be tied to a large solar coronal mass ejection event. The auroral UV emissions from these bursts also correspond to hectometric radio emission (0.5-16 MHz) increases reported by the Galileo Plasma Wave Spectrometer (PWS) and Cassini Radio and Plasma Wave Spectrometer (RPWS) experiments. In general, the hectometric radio data vary differently with longitude than the UV data because of radio wave beaming effects. The 2 largest events in the UVIS data were on 2000 day 280 (October 6) and on 2000 days 325-326 (November 20-21). The global brightening events on November 20-21 are compared with corresponding data on the interplanetary magnetic field, solar wind conditions, and energetic particle environment. ACE (Advanced Composition Explorer) solar wind data was numerically propagated from the Earth to Jupiter with an MHD code and compared to the observed event. A second class of brief auroral brightening events seen in HST (and probably UVIS) data that last for ∼2 min is associated with auroral flares inside the main auroral ovals. On January 8, 2001, from 18:45-19:35 UT UVIS H₂ band emissions from the north polar region varied quasiperiodically. The varying emissions, probably due to auroral flares inside the main auroral oval, are correlated with low-frequency quasiperiodic radio bursts in the 0.6-5 kHz Galileo PWS data.     

Properties of storm-time magnetospheric VLF emissions as deduced from the Ariel 3 satellite and ground-based observations

The characteristics of VLF emissions during the two magnetic storms on 5–7 June and 19–21 September, 1967 are investigated based on the Ariel 3 satellite data and ground observation at a low-latitude station in Japan. During the study of the June event, the satellite lay in the dawn-dusk plane. Soon after the onset of the main phase there appeared VLF emissions on the morning side of the magnetosphere on the ground as well as on the satellite, but the emissions were at very low level in the evening. It was not until the recovery phase that we could recognize the stationary occurrence of intense emissions in the evening. Furthermore, it is found that the chorus-type morning emissions are observed outside the plasmapause, while the narrow-banded hiss-type evening emissions lay within the plasmapause. It is shown that the cyclotron instability of ring current electrons can, on the whole, account for the many properties of the storm-like emissions. Similarly, we discuss the characteristics of the September event.