Flaring loop parameters estimated from solar decimeter type U-like and type J-like fine structures

This work presents the analysis of five fine structures in the solar radio emission, observed between June 2000 and October 2001 by the Brazilian Solar Spectroscope (BSS), in the decimeter frequency band of 950–2500 MHz. Based on their morphological characteristics identified in the dynamic spectra, the fine structures had been classified as type U-like or type J-like bursts. Such emissions are variants of the type III bursts. They support the hypothesis of generation by plasma emission mechanism, from interaction of electron beams accelerated during solar flares, propagating along closed magnetic structures, within the trapped plasma of the solar corona. The spectral and temporal characteristics of the five fine structures had been obtained from the dynamic spectra and the parameters of the agent and the emitting source have been determined, assuming both fundamental and harmonic emissions. The analysis revealed the flux density of the structures is less than 20–80 s.f.u. For assumption of harmonic emission, the interval of values for the source parameters estimated are: the loop size is (0.3–5.1) × 10¹⁰ cm; the electron beam velocity is in the range of 0.16–0.53 c; the temperature of coronal loop top is of the order of (0.25–1.55) × 10⁷ K; and the low limit for the magnetic field is of 7–26 G. These results are in agreement with previous determinations reported in the literature.     

VHF radio response of the near Earth space during solar activity growth in October, 2003

The analysis of observations of very high frequency radio noise intensity at the middle latitude on a frequency f = 500 MHz from 14th till 26th of October, 2003 is presented. These data are compared with the solar radio bursts in the range of frequencies 1–14 MHz registered by RAD2 receiver of the WAVES device installed on board the WIND spacecraft.     

Magnetospheric application of high-altitude long-duration balloon technology: Daylight auroral observations

Daylight auroral imaging is a proposed application of the NASA high-altitude long-duration balloon technology. This paper discusses the theoretical background of this application and test observations, for proof of the feasibility. It is demonstrated that nitrogen auroral emissions in the near-infrared band are detectable at altitudes of 35–40 km and above using a near-infrared InGaAs camera. The purpose of such observations is to identify auroral small-scale structures that are manifestations of auroral particle accelerations and the solar wind – magnetosphere – ionosphere interaction. Use of this new approach will enable studies of the dayside aurora, low-latitude aurora, and storm-time and substorm-time auroral conjugacy.     

High energy charged particle experiment – A payload proposal to KuaFu-B mission

High Energy Charged Particle Experiment (HECPE) is to measure the fluxes of MeV electrons and tens of MeV protons. The two satellites of KuaFu-B are in the same polar orbit with apogee 7.0R_E, perigee 1.8R_E. They can sweep large L values and pass through the inner and outer radiation belts. The high energy electrons and protons in the radiation belts are principal sources for failures of satellites and spacecrafts in the Earth orbits. The enhancements of the high energy electrons and protons, so-called energetic particle events, are important phenomena of the Space Weather. The energy ranges monitored by HECPE are 0.3–0.5 MeV, 0.5–1.0 MeV, 1.0–2.0 MeV, and E > 2.0 MeV for electrons, 5–10 MeV, 10–20 MeV, 20–40 MeV, and 40–80 MeV for protons.     

Photoelectron flux variations observed from the FAST satellite

This paper examines high resolution (ΔE/E = 0.15) photoelectron energy spectra from 10 eV to 1 keV, created by solar irradiances between 1.2 and 120 nm. The observations were made from the FAST satellite at ∼3000 km, equatorward of the auroral oval for the July–August, 2002 solar rotation. These data are compared with the solar irradiance observed by the Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite and fluxes calculated using the Field Line Interhemispheric Plasma (FLIP) code. The 41 eV photoelectron flux, which corresponds to solar EUV fluxes near 20 nm, shows a clear solar rotation variation in very good agreement with the EUV flux measurements. This offers the possibility that the 41 eV photoelectron flux could be used as a check on measured solar EUV fluxes near 20 nm. Because of unexpected noise, the solar rotation signal is not evident in the integral photoelectron flux between 156 and 1000 eV corresponding to EUV wavelengths between 0.1 and 7 nm measured by the SEE instrument. Examination of daily averaged photoelectron fluxes at energies between 25 and 500 eV show significant changes in the photoelectron spectra in response X and M class flares. The intensity of photoelectrons produced in this energy region is primarily due to two very narrow EUV wavelength regions at 2.3 and 3 nm driving Auger photoionization in O at 500 eV and N₂ at ∼360 eV. Comparison of calculated and daily averaged electron fluxes shows that the HEUVAC model solar spectrum used in the FLIP code does not reproduce the observed variations in photoelectron intensity. In principle, the 21 discrete photoelectron energy channels could be used to improve the reliability of the solar EUV fluxes at 2.3 and 3 nm inferred from broad band observations. In practice, orbital biases in the way the data were accumulated and/or noise signals arising from natural and anthropogenic longitudinally restricted sources of ionization complicate the application of this technique.     

Laser measurements to space debris from Graz SLR station

In order to test laser ranging possibilities to space debris objects, the Satellite Laser Ranging (SLR) Station Graz installed a frequency doubled Nd:YAG pulse laser with a 1 kHz repetition rate, a pulse width of 10 ns, and a pulse energy of 25 mJ at 532 nm (on loan from German Aerospace Center Stuttgart – DLR). We developed and built low-noise single-photon detection units to enable laser ranging to targets with inaccurate orbit predictions, and adapted our standard SLR software to include a few hundred space debris targets. With this configuration, we successfully tracked – within 13 early-evening sessions of each about 1.5 h – 85 passes of 43 different space debris targets, in distances between 600 km and up to more than 2500 km, with radar cross sections from >15 m² down to <0.3 m², and measured their distances with an average precision of about 0.7 m RMS.     

Simultaneous observations of Pc 1 micropulsation activity and stratospheric electrodynamic perturbations on 27 January 2003

The 2nd Polar Patrol Balloon campaign (2nd-PPB) was carried out at Syowa Station in Antarctica during 2002–2003. Identical stratospheric balloon payloads were launched as close together in time as allowed by weather conditions to constitute a cluster of balloons during their flights. A very pronounced negative ion conductivity enhancement was observed at 32 km in the stratosphere below the auroral zone on 27 January 2003 from 1500 to 2200 UT. During this event, the conductivity doubled for an interval of about 7 h. This perturbation was associated with an extensive Pc 1 or Pi 1 wave event that was observed by several Antarctic ground stations, balloon PPB 10, and the Polar spacecraft. No appreciable X-ray precipitation was observed in association with this event, which would point to >60 Mev proton precipitation as a possible magnetosphere–stratosphere coupling mechanism responsible for the conductivity enhancement. Such precipitation is consistent with the wave data. During the latter half of the event, E_z was briefly positive. There was a tropospheric Southern Ocean storm system underneath the balloon during this interval. If the event was associated with this storm system and not energetic proton precipitation, the observations imply an electrified Southern Ocean storm and major perturbations in stratospheric conductivity driven by a tropospheric disturbance. This event represents a poorly understood source for global circuit current. Precipitating energetic proton data from Akebono and NOAA POES spacecraft show significant >16 MeV precipitation was occurring at the location of PPB 8 but not PPB 10, suggesting that proton precipitation was, in fact, the responsible coupling mechanism.     

Numerical simulation of equatorial plasma bubbles over Cachimbo: COPEX campaign

The problem of day-to-day variability in onset of equatorial spread F (ESF) is addressed using data from the 2002 COPEX observational campaign in Brazil and numerical modeling. The observational results show that for values of virtual height of the F layer base less than 355 km at around 18:35 LT, and for the prereversal peak enhancement of the vertical plasma drift (Vp) less than 30 m/s, the spread-F (ESF) was absent on four nights over Cachimbo (9.5°S, 54.8°W, dip latitude = −2.1°). In this work we analyze the geophysical conditions for the generation of the irregularities by comparing the nights with and without the ESF. In the comparison a numerical code is used to simulate plasma irregularity development in an extended altitude range from the bottom of the equatorial F   layer. The code uses the flux corrected transport method with Boris–Book’s flux limiter for the spatial integration and a predictor–corrector method for the direct time integration of the continuity equation for O⁺${\mathrm{O}}^{+}$ and the SOR (Successive-Over-Relaxation) method for electric potential equation. The code is tested with different evening eastward electric fields (or vertical drifts Vp < 30 m/s and Vp > 30 m/s) in order to study the influence of the prereversal enhancement in the zonal electric field on plasma bubble formation and development. The code also takes into account the zonal wind, the vertical electric field and the collision frequency of ions with neutrals and the amplitude of initial perturbation. The simulation shows a good agreement with the observational results of the ESF. The results of the code suggest that the instability can grow at the F layer bottomside by the Rayleigh–Taylor mechanism only when the Vp > 30 m/s. In the analyzed cases we have considered the competition of other geophysical parameters in the generation of plasma structures.     

Status of the GAMMA-400 project

The preliminary design of the new space gamma-ray telescope GAMMA-400 for the energy range 100 MeV–3 TeV is presented. The angular resolution of the instrument, 1–2° at E_γ ∼ 100 MeV and ∼0.01° at E_γ > 100 GeV, its energy resolution ∼1% at E_γ > 100 GeV, and the proton rejection factor ∼10⁶ are optimized to address a broad range of science topics, such as search for signatures of dark matter, studies of Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, as well as high-precision measurements of spectra of cosmic-ray electrons, positrons, and nuclei.     

Cosmic ray detection on the Foton-M2 satellite by a track etch detector stack

In the frame of the European Space Agency (ESA) project called “Biology and Physics in Space”, the returning satellite, Foton-M2, carried an open-to-space exposure platform outside of the satellite body, called as BIOPAN-5, loaded with exo-biological experiments and facilities for radiation dosimetry (RADO). One of the RADO experiments was dedicated to the detection of the primary galactic cosmic rays (GCR) and secondary neutrons by a track etch detector stack. The daily absorbed dose (D) and dose equivalent (H) were calculated from the experimental LET spectra (LET > 10 keV/μm). Under a shielding of ∼2.8 g/cm² the averaged H was found to be 658 ± 8 μSv/d, with a quality factor (Q) of 6.2 ± 1.2. The LET spectra showed a local peak at ∼105 keV/μm suggesting that the majority of tracks were created by trapped protons as it has been predicted by calculations. The low LET dose of the cosmic radiation was determined by 4 TLD stacks, and the total dose was found to be 795 ± 14 μSv/d.     

Polarization pattern of low and mid-frequency magnetic pulsations in the polar cap: A comprehensive analysis at Terra Nova Bay (Antarctica)

The polarization pattern of ULF pulsations (f ≈ 1–100 mHz) at Terra Nova Bay (Antarctica, CGM λ ∼ 80°) has been determined for the entire 2003, soon after the solar maximum. A comparison with the results of previous investigations, conducted at the same station close to the solar minimum (1994–96), allows to focus common elements and major differences among different frequency bands which persist through the entire solar cycle. Basically, between f ∼ 1.5 and 5 mHz, the day can be divided into four sectors with alternate polarizations. The local time and latitudinal dependence of the observed pattern can be tentatively interpreted in terms of a latitude of resonant field lines reaching λ ∼ 80° in the noon sector; on the other hand, resonance effects of lower latitude field lines can be clearly identified also far from the noon meridian when the station moves into the deep polar cap. Moreover, in the morning sector the resonance region would extend to lower latitudes than in the evening sector. The proposed profile of the resonant region can interpret also the results obtained at other cusp/auroral stations and appears consistent with that one inferred in the northern hemisphere at smaller latitudes. The resonance region progressively shifts toward lower latitude with increasing frequency; correspondingly, the four-sector pattern progressively disappears at TNB. Above f ∼ 20 mHz, the experimental observations might suggest an additional contribution from Sunward propagating waves, possibly via the magnetotail lobes.     

Standing Alfvén waves with m ≫ 1 in a dipole magnetosphere with moving plasma and aurorae

The structure of standing Alfvén waves with large azimuthal wave numbers (m ? 1) is studied in a dipole model of the magnetosphere with rotating plasma. In the direction across magnetic shells the structure of such waves is determined by their dispersion associated with curvature of geomagnetic field lines and corresponds to the travelling wave localized between toroidal and poloidal resonant surfaces. In projection into the ionosphere (along geomagnetic field lines) this structure is similar to the structure of a discrete auroral arc. The azimuthal structure of an auroral arc is similar to azimuthal structure of Alfvén waves with m ∼ 100. Possible interaction mechanisms between the Alfvén waves and energetic electron fluxes forming auroral arcs are discussed.     

Acceleration of charged particles by fluctuating and steady electric fields in a X-type magnetic field

Release of stored magnetic energy via particle acceleration is a characteristic feature of astrophysical plasmas. Magnetic reconnection is one of the mechanisms for releasing energy from magnetized plasmas. Collisionless magnetic reconnection could provide both the energy release mechanism and the particle accelerator in space plasmas. Here we studied particle acceleration when fluctuating (in-time) electric fields are superposed on an static X-type magnetic field in collisionless hot solar plasma. This system is chosen to mimic the reconnective dissipation of a linear MHD disturbance. Our results are compared to particle acceleration from constant electric field superposed on an X-type magnetic field. The constant electric field configuration represents the effects of steady state magnetic reconnection. Time evolution of ion and electron distributions are obtained by numerically integrating particle trajectories. The frequencies of the electric field represent a turbulent range of waves. Depending on the frequency and amplitude of the electric field, electrons and ions are accelerated to different degrees and have energy distributions of bimodal form consisting of a lower energy part and a high energy tail. For frequencies (ω in dimensioless units) in the range 0.5 ? ω ? 1.0 a substantial fraction (20%–30%) of the proton distribution is accelerated to gamma-ray producing energies. For frequencies in the range 1 ? ω ? 100.0 the bulk of the electron distribution is accelerated to hard X-ray producing energies. The acceleration mechanism is important for solar flares and solar noise storms but it could be applicable to all collisionless astrophysical plasmas.     

Differential emission measure distributions in X-ray solar flares

X-ray spectrometer RESIK has observed spectra in the four wavelength bands from 3.3 Å to 6.1 Å. This spectral range contains many emission lines of H- and He-like ions for Si, S, Ar and K. These lines are formed in plasma of coronal temperatures (T > 3 MK). Analysis of their intensities allows studying differential emission measure distributions (DEM) in temperature range roughly between 3 MK and 30 MK. The aim of present study was to check whether any relationship exists between the character of DEM distribution, the event phase and the X-ray flare class. To do this we have calculated and analyzed the DEM distributions for a set of flares belonging to different GOES classes from the range B5.6–X1. The DEM distributions have been calculated using “Withbroe–Sylwester” multiplicative, maximum likelihood iterative algorithm. As the input data we have used absolute fluxes observed by RESIK in several spectral bands (lines + continuum). Respective emission functions have been calculated using the CHIANTI v. 5.2 atomic data package.     

Theoretical properties of offset bipolar electric field solitary structures in space plasmas

The bipolar electric field solitary (EFS) structures have been frequently observed in the near Earth plasma regions, such as auroral zone, magnetopause, cusp regions, and magneto-tail. Sometimes these structures are observed as offset bipolar structures. In this paper, the properties of the offset bipolar EFS structures parallel to the magnetic field are studied with an ion fluid model in a cylindrical symmetry by considering electrostatic condition. The model results show that the offset bipolar EFS structures can develop from both ion-acoustic waves and ion cyclotron waves, and propagate along the magnetic field line in the space plasmas if plasma satisfies some conditions. The offset bipolar EFS structures can have both polarities. It will be first negative pulse and then positive pulse if the initial electric field E₀ < 0 or reverse in order if E₀ > 0. The amplitude of the offset bipolar EFS structures first decreases and then increases with the wave propagation velocity. Some results from our model are consistent with the observations.     

The hydroxyl radical as an indicator of SEP fluxes in the high-latitude terrestrial atmosphere

The low background values at nighttime of the mesospheric hydroxyl (OH) radical make it easier to single out the atmospheric response to the external solar forcing in Polar Regions. Because of the short lifetime of HO_x, it is possible to follow the trails of Solar Energetic Particle (SEP) events in the terrestrial atmosphere, as shown by Storini and Damiani (2008). The sensitivity of this indicator makes discernible not only extreme particle events with a flux peak of several thousand pfu [1 pfu = 1 particle/(cm² s sr)] at energies >10 MeV, but also those with lower flux up to about 300 pfu. Using data from the Microwave Limb Sounder (MLS) on board the EOS AURA satellite, we examined the correlation of OH abundance vs. solar proton flux for almost all the identified SEP events spanning from November 2004 to December 2006 (later on no more SEP events occurred during Solar Cycle no. 23). The channels at energies greater than 5 MeV and 10 MeV showed the best correlation values (r ∼ 0.90–0.95) at altitudes around 65–75 km whereas, as expected, the most energetic channels were most highly correlated at lower altitudes. Therefore, it is reasonably possible to estimate the solar proton flux from values of mesospheric OH (and viceversa) and it could be useful in studying periods with gaps in the records of solar particles.     

Forward and reverse CIR shocks at 4–5 AU: Ulysses

In this article, we study fast shocks at CIR boundaries during an extended interval of 15 consecutive major high speed solar wind streams in 1992–1993. Ulysses was 4–5 AU from the sun. The Abraham-Schrauner shock normal method and the Rankine-Hugoniot relations were used to determine fast shock directions and speeds. Out of 33 potential CIR shocks, 14 were determined to be fast forward shocks (FSs) and 14 were fast reverse shocks (RSs). Of the remaining 5 events, 2 were forward waves and 3 were reverse waves. CIR edges at latitudes below ∼30^o were, for the most part, bounded by fast magnetosonic shocks. The forward shocks were generally quasi-perpendicular (average θ_nBo = 67^o). The reverse shocks were more oblique (average θ_nBo = 52^o), but they extended to all angles. Both FSs and RSs had magnetosonic Mach numbers ranging from 1 to 5 or 6. The average Mach numbers were 2.4 and 2.6 for FSs and RSs, respectively. The shock Mach numbers were noted to generally decrease with increasing latitude. The non-shock events or waves were noted to occur preferentially at high (∼−30° to −35°) heliolatitudes where stream-stream interactions were presumably weaker. These results are consistent with expectations, indicating the general accuracy of the Abraham-Schrauner technique.     

Simultaneous observations of some unusual whistlers and VLF hiss emission at a low L-value (L = 1.17)

The purpose of this paper is to describe some unusual whistlers (doublets and triplets) and VLF hiss emission recorded simultaneously on February 18, 1998 during nighttime at a low latitude Indian ground station Jammu (geomag. lat., 22° 26′ N; L = 1.17), and to make some discussions about their origin. The detailed structures of the observed VLF hiss emission clearly show that these emissions confined to a narrow continuous frequency band. Some times the frequency of hiss band oscillates and subsequently touches the upper edge of the first whistler component of the doublet. Detailed structures of the dynamic spectra of whistler and VLF hiss emission are briefly presented. From the dispersion analysis of the whistler doublets and triplets, it is found that the individual whistlers of the doublets and triplets simultaneously observed on the same day are one-hop whistlers having propagation path along higher and closely spaced L-values. Our result also shows that VLF hiss has been generated in the equatorial region of higher L-values. Generation and propagation mechanisms are briefly discussed.     

Jovian periodicities (∼10 h, ∼40 min) on Ulysses’ Distant Jupiter Encounter observations around the Halloween CIR events

We analyzed data from four different instruments (HI-SCALE, URAP, SWOOPS, VHM/FGM) onboard Ulysses spacecraft (s/c) and we searched for possible evidence of Jovian emissions when the s/c approached Jupiter during the times of Halloween events (closest time approach/position to Jupiter: February 5, 2004/R = 1683 R_J,θ = ∼49°). In particular, we analyzed extensively the low energy ion measurements obtained by the HI-SCALE experiment in order to examine whether low energy ion/electron emissions show a symmetry, and whether they are observed at north high latitudes upstream from the jovian bow shock, as is known to occur in the region upstream from the south bow shock as well ( Marhavilas et al., 2001). We studied the period from October 2003 to March 2004, as Ulysses moved at distances 0.8–1.2 AU from the planet at north Jovicentric latitudes <75°, and we present here an example of characteristic Jovian periodicities in the measurements around a CIR observed by Ulysses on days ∼348–349/2003 (R = 1894 R_J,θ = 72°). We show that Ulysses observed low energy ion (∼0.055–4.7 MeV) and electron (>∼40 keV) flux and/or spectral modulation with the Jupiter rotation period (∼10 h) as well as variations with the same period in solar wind parameters, radio and magnetic field directional data. In addition, characteristic strong ∼40 min periodic variations were found superimposed on the ∼10 h ion spectral modulation. Both the ∼10 h and ∼40 min ion periodicities in HI-SCALE measurements were present in several cases during the whole period examined (October 2003 to March 2004) and were found to be more evident during some special conditions, for instance during enhanced fluxes around the start (forward shock) and the end (reverse shock) of CIRs. We infer that the Jovian magnetosphere was triggered by the impact of the CIRs, after the Halloween events, and it was (a) a principal source of forward and reverse shock-associated ion flux structures and (b) the cause of generation of ∼10 h quasi-periodic magnetic field and plasma modulation observed by Ulysses at those times.     

Correlation between the cosmic noise absorption calculated from the SARINET data and the energetic particles measured by MEPED: Simultaneous observations over SAMA region

The cosmic noise absorption is presented in terms of two-dimensional images obtained from the imaging riometers operated at the Southern Space Observatory (geographic coordinate: 29.4° S, 53.1° W), in São Martinho da Serra, Brazil, Concepcion (geographic coordinate: 36.5° S, 73.0° W) and Punta Arenas (geographic coordinate: 53.0° S, 70.5° W) in Chile, which belong to the South American Riometer Network and are located at the central and periphery regions of the South American Magnetic Anomaly. Correlations are performed between the maximum cosmic noise absorption observed at these stations and the energetic electron flux in two energy channels (>30 and >300 keV) and the proton flux in three energy channels (80–240, 800–2500 and >6900 keV) as measured by the Medium Energy Proton and Electron Detector, during a moderate geomagnetic storm that occurred on September 3, 2008. The results show high correlations between the cosmic noise absorption detected at São Martinho da Serra and the flux of protons with energy between 80 and 240 keV, and the flux of electrons with energies higher than 300 keV, while an additional ionization at Concepcion was correlated with electrons of energies higher than 30 keV. The cosmic noise absorption detected at Punta Arenas was probably caused by the increase of the protons flux with energy between 80 and 240 keV.