E. Correia

Combined effect of two different polymorphic sequences within the β globin gene cluster on the level of HbF

β thalassemia and Hb Lepore heterozygotes included in this study exhibit fetal hemoglobin levels varying from trace quantities to 14% (1.74 g/dl) of total hemoglobin in the adult. In this work, we have examined the correlation of DNA sequence polymorphisms with the observed HbF level. The analysis of polymorphic markers within the β globin cluster in 39 individuals heterozygous for β thalassemia or Hb Lepore confirms the previous findings for homozygous β thalassemia: the presence of both an (AT)9 T5 sequence configuration at position −540 of the β globin gene and a (C → T) variation at −158 of the Gγ globin gene is associated with elevated expression of HbF. However, at least one defective β globin gene is required to reveal this association. The best evidence is from the study of individuals heterozygous for Hb Lepore with various levels of HbF. In these individuals it was possible to explore the effect of a single (AT)x Ty motif (the other being absent from the rearranged Lepore chromosome) on HbF expression. The presence of the (AT)9 T5 configuration increases HbF level from a median of 0.515 g/dl observed in (AT)7 T7 subjects, to 1.39 g/dl.

A multibeam antenna for solar MM-wave burst observations with high spatial and temporal resolution

In this paper a new method for the determination of the position of microwave burst sources on the Sun, its implementation and first observational results, are presented. The 13.7 m antenna at Itapetinga with a five-channel receiver operating at 48 GHz and with a time resolution of 1 ms is used. Five horn antennas clustered around the focus of the Cassegrain reflector provide 5 beams diverging by about 2′. This configuration allows the observation of different parts of an active region and the determination of the center of the burst position with an accuracy of 5″ to 20″ depending on the angular distance relative to the antenna axis. The field of view is ≈ 2′ by ≈ 4′. The time resolution of 1 ms is suitable to search for fast structures at 48 GHz. A total bandwidth of 400 MHz is used in order to achieve a sensitivity of 0.04 s.f.u. sufficient for the detection of weak bursts. First observational results of the flare on May 11, 1991 show a well-located source position during all stages.

Spatial positions of fast-time structures of a solar burst observed at 48 GHz

The impulsive solar burst of October 28, 1992 showed temporal and spatial fine structures that were observed at 48 GHz with the multi-beam antenna of the Itapetinga Radio Observatory. The relative positions of burst centroids were determined with a spatial accuracy of 2″, with a temporal resolution of 1 millisecond. The burst intensity time profile shows fast pulses of about one second duration, superimposed by subsecond time structures. The spatial analysis of the fast pulses suggests that the emission originated from distinct locations, separated by about 5″. Our results favour the idea that impulsive solar bursts are a superposition of small elementary events spread both in time and space, probably resulting from discontinuous energy release processes.

On removal of the gradual component in analyses of solar impulsive bursts

Three methods are considered for the removal of the gradual component in solar flare time profiles. It is emphasized that a time-dependent gradual component can introduce apparent delays between impulsive extrema which may be misinterpreted in terms of physical processes. Running mean subtraction always produces negligible delays in comparison with the period of the fast component; thus, it has major advantages compared with second derivatives and Fourier filtering for recovering the impulsive component. 9 refs.

SOLAR-T : Terahertz Photometers to Observe Solar Flare Emission on Stratospheric Balloon Flights

A new solar flare spectral component has been found with intensities increasing for larger sub-THz frequencies, spectrally separated from the well known microwaves component, bringing challenging constraints for interpretation. Higher THz frequencies observations are needed to understand the nature of the mechanisms occurring in flares. A twofrequency THz photometer system was developed to observe outside the terrestrial atmosphere on stratospheric balloons or satellites, or at exceptionally transparent ground stations. 76 mm diameter telescopes were designed to observe the whole solar disk detecting small relative changes in input temperature caused by flares at localized positions at 3 and 7 THz. Golay cell detectors are preceded by low-pass filters to suppress visible and near IR radiation, band-pass filters, and choppers. It can detect temperature variations smaller than 1 K with time resolution of a fraction of a second, corresponding to small burst intensities. The telescopes are being assembled in a thermal controlled box to which a data conditioning and acquisition unit is coupled. While all observations are stored on board, a telemetry system will forward solar activity compact data to the ground station. The experiment is planned to fly on board of long-duration stratospheric balloon flights some time in 2013-2015. One will be coupled to the GRIPS gamma-ray experiment in cooperation with University of California, Berkeley, USA. One engineering flight will be flown in the USA, and a 2 weeks flight is planned over Antarctica in southern hemisphere summer. Another long duration stratospheric balloon flight over Russia (one week) is planned in cooperation with the Lebedev Physics Institute, Moscow, in northern hemisphere summer.

Solar Flare Observations at Submm-waves

First 405 GHz and 212 GHz solar flare observations were obtained during short campaigns while the new solar submillimeter-wave telescope (SST) was still undergoing adjustments at the CASLEO EI Leoncito observatory in the Argentina Andes. We show here preliminary results for a large X1.1 class X-ray event occurred on 2000 March 22, which exhibited a small submm-w continuum response to the slow (minutes) bulk flare emission, and numerous subsecond spikes (100-300 ms), the brightest spikes reaching about 180 and 50 s.f.u. at 405 and 212 GHz, respectively. Solar flare observations are nearly unknown in the submm-IR range of wavelengths. Few results limited to time resolution of about one minute have suggested brightness variations of 10-100 K in active regions without clear flare associations (Clark & Park 1970; Hudson 1975). The six SST beams (Kaufmann et al. 1994) are superimposed on a Kitt Peak solar magnetogram (NOAA 2000) shown in Figure 1 (left) at about the time of the event on 2000 March 22. The flare emission light-curves in compressed time scales are shown in Figure 1 (right) for different frequencies. The H-a telescope is described elsewhere (Bagala et al. 1999). The bottom plot of Figure 1 (right) shows the rate of submm-w brightest (~ 20 K) spikes incidence with time. An example of such a bright spike (labeled A in Figure 1 (right)) is shown in Figure 2 (A) in a five seconds time interval, compared to data obtained tracking a quiet solar region, near its center, in Figure 2 (B), labeled B in Figure 1 (right). The spiky incidence increases drastically after about 1730 UT approximately together with the soft X-ray level. There is a pronounced concentration of brightenings in correspondence to the bulk emissions at X-rays and H-a. Clusters of spikes seem to be added at about 1745 UT and 1820 UT coincident to flares occurring in AR

Multiwavelength observations of the impulsive flare of November 19, 1990

We present the observation and interpretation of a solar radio burst whose evolution of the source position at 48 GHz has been correlated with microwave spectral observations from 3.1 to 19.6 GHz and Hα imaging spectrograms. The event of November 19, 1990 showed 4 impulsive peaks in microwaves and 2 Hα kernels. There exists strong evidence that the impulsive emission has originated from nonthermal electrons including an electron beam during the rising phase of the third microwave peak. The complex evolution of the source position at 48 GHz is attributed to two inhomogeneous and spatially separated sources with changing relative brightness.

The Relationship between Synchrotron and Bremsstrahlung Emission of Nonthermal Electrons during a Solar Flare. A detailed study during the August 30, 2002 X1.5 event

Synchrotron emission from nonthermal electrons has a strong dependence on the magnetic field of the medium. On the contrary, Bremsstrahlung emission does not depend on the magnetic field. The simultaneous observations of both forms of radiation may give us clues about local magnetic field configuration. In this report we use the optically thin part of the radio spectrum during the microwave maximum of the flare occurred on August 30, 2002, at 1328 UT to determine different mean magnetic field intensities and nonthermal electron density distributions compatible with the observed data. Assuming that the same electrons emit by coulomb interactions, the obtained distributions are used to compute the photon spectrum of the X‐Ray emission by Bremsstrahlung and the spectra are compared with observations obtained by instruments on board the RHESSI satellite. We discuss the effects of the trapping on the Bremsstrahlung emitted radiation, giving constraints on both magnetic field intensity and trapping time.

New technique for dynamic burst position determination with high spatial definition/time resolution at a mm‐wavelength

The position of solar burst maximum emission can be monitored with spatial resolution of few arcseconds, and and millisecond time resolution, simultaneously using a multifeed/multiradiometer front‐end system placed at the focus of the 13.7‐m Itapetinga radio‐telescope. This new concept was developed in a cooperative program between the Institute of Applied Physics of the University of Bern, and the Center of Radio Astronomy and Space Applications, Sao Paulo. The five independent radiometer front‐end operates at 48 GHz and produces five beams in space, partially overlapping to each other. Dynamic position images of the centroid of burst emission can be derived. Various events have been investigated, and the first results suggest that the fast time structures superimposed to the bursts’ time profiles, may originate from distinct spatial positions in certain events, or close to a main generating stable source for other events. The dynamic images suggest apparent burst source displacements, or distinct and in...

Mid- and low-latitude response of the ionosphere to solar proton events on January 2012

We present and discuss the ionosphere behavior under the impact of two X-ray solar flares (M8.7 and X1.7) that occurred on January 23 and 27, respectively, and were accompanied by Solar Proton Events (SPEs). The ionosphere response to these solar phenomena was detected using riometers (30 and 38.2 MHz), ionosonde and VLF systems operating at the Comandante Ferraz Brazilian Station in Antarctica and at the Itapetinga Radio Observatory in Sao Paulo (SP)/Brazil. The results suggest the ionosphere was affected by both SPEs, as evidenced by absorption detected in the cosmic noise, F2 layer critical frequency and VLF amplitude measurements. These absorptions started before the beginning of the main X-ray flare events and > 100 MeV proton events detected by GOES, suggesting the ionosphere was impacted by protons with energies above 2 GeV in Antarctica and above 10-12 GeV in SP as estimated from the particle geomagnetic rigidity (Rc) at each place. The results also suggest a long-lasting presence (hours) of high energy protons.