ترغب بنشر مسار تعليمي؟ اضغط هنا

Goldstone Apple Valley Radio Telescope Observations of 2012 Solar Eclipse: A Multi-wavelength study of cm-wavelength Gyroresonance Emission from Active Regions

76   0   0.0 ( 0 )
 نشر من قبل Thangasamy Velusamy
 تاريخ النشر 2020
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

Goldstone Apple Valley Radio Telescope (GAVRT) is a science education partnership among NASA, the Jet Propulsion Laboratory (JPL), and the Lewis Center for Educational Research (LCER), offering unique opportunities for K -12 students and their teachers. The GAVRT program operates a 34-m radio telescope with a wide-band, low noise receiver, which is tunable in four independent dual-polarization bands from 3 to 14 GHz. The annular eclipse of the Sun on 2012 May 20 was observed by GAVRT as part of education outreach. In this paper we present the results of this eclipse data and discuss the multi-wavelength strip scan brightness distribution across three active regions. We derive the source brightness temperatures and angular sizes as a function of frequency and interpret the results in terms of the gyroresonance mechanism. We show examples of the increasing brightness and widening of source size (isogauss surface) with wavelength as evidence for gyroresonance emission layers of broader (diverging ) isogauss surfaces of the magnetic field geometry in the corona above solar surface. We present an example how the derived frequency - brightness temperature relationship is translated to a magnetic field - brightness temperature relationship under the frame-work of gyroresonance emission. Our results demonstrate the usefulness of GAVRT bands as excellent probes to study the layers of the corona above the active regions (sun spots), in particular the prevalence of the gyroresonance mechanism. Our results provide a frame-work for multiwavelength cm-wavelength eclipse observations and illustrate how the GAVRT program and K- 12 student/teacher participation can produce science data useful to the scientific community and science missions.



قيم البحث

اقرأ أيضاً

Goldstone Apple Valley Radio Telescope (GAVRT) is a science education partnership among NASA, the Jet Propulsion Laboratory (JPL), and the Lewis Center for Educational Research (LCER), offering unique opportunities for K -12 students and their teache rs. As part of a long-term Jupiter synchrotron radiation (JSR) flux density monitoring program, LCER has been carrying out Jupiter observations with some student participation. In this paper we present the results of processed data sets observed between March 6, 2015 and April 6 2018. The data are divided into 5 epochs, grouped by time. We derive JSR beaming curves at different epochs and Earth declinations. We present a comparison of the observed beaming curves with those derived from most recent models for the radiation belts. Our results show an increasing trend of the JSR flux density which seem consistent with the models for the magnetospheric solar wind interactions.
311 - A. Archer , W. Benbow , R. Bird 2020
The radio source 3C 264, hosted by the giant elliptical galaxy NGC 3862, was observed with VERITAS between February 2017 and May 2019. These deep observations resulted in the discovery of very-high-energy (VHE; E $>100$ GeV) $gamma$-ray emission from this active galaxy. An analysis of $sim$57 hours of quality-selected live time yields a detection at the position of the source, corresponding to a statistical significance of 7.8 standard deviations above background. The observed VHE flux is variable on monthly time scales, with an elevated flux seen in 2018 observations. The VHE emission during this elevated state is well-characterized by a power-law spectrum with a photon index $Gamma = 2.20 pm 0.27$ and flux F($>315$ GeV) = ($7.6pm 1.2_{mathrm stat} pm 2.3_{mathrm syst})times 10^{-13}$ cm$^{-2}$ s$^{-1}$, or approximately 0.7% of the Crab Nebula flux above the same threshold. 3C 264 ($z = 0.0217$) is the most distant radio galaxy detected at VHE, and the elevated state is thought to be similar to that of the famously outbursting jet in M 87. Consequently, extensive contemporaneous multi-wavelength data were acquired in 2018 at the time of the VHE high state. An analysis of these data, including VLBA, VLA, HST, Chandra and Swift observations in addition to the VERITAS data, is presented, along with a discussion of the resulting spectral energy distribution.
The large crescents imaged by ALMA in transition disks suggest that azimuthal dust trapping concentrates the larger grains, but centimetre-wavelengths continuum observations are required to map the distribution of the largest observable grains. A pre vious detection at ~1cm of an unresolved clump along the outer ring of MWC758 (Clump1), and buried inside more extended sub-mm continuum, motivates followup VLA observations. Deep multiconfiguration integrations reveal the morphology of Clump 1 and additional cm-wave components which we characterize via comparison with a deconvolution of recent 342GHz data (~1mm). Clump1, which concentrates ~1/3 of the whole disk flux density at ~1cm, is resolved as a narrow arc with a deprojected aspect ratio Chi>5.6, and with half the azimuthal width than at 342 GHz. The spectral trends in the morphology of Clump1 are quantitatively consistent with the Lyra-Lin prescriptions for dust trapping in an anticyclonic vortex, provided with porous grains (f~0.2+-0.2) in a very elongated (Chi~14+-3) and cold (T~23+-2K) vortex. The same prescriptions constrain the turbulence parameter alpha and the gas surface density Sigma_g through log10( alpha x Sigma_g /g/cm2)~-2.3+-0.4, thus requiring values for Sigma_g larger than a factor of a few compared to that reported in the literature from the CO isotopologues, if alpha <~ 1E-3. Such physical conditions imply an appreciably optically thick continuum even at cm-wavelengths (tau(33GHz)~0.2). A secondary and shallower peak at 342GHz is about twice fainter relative to Clump1 at 33GHz. Clump2 appears to be less efficient at trapping large grains.
We present measurements of the linear diameter of the emission region of the Vela pulsar at observing wavelength lambda=18 cm. We infer the diameter as a function of pulse phase from the distribution of visibility on the Mopra-Tidbinbilla baseline. A s we demonstrate, in the presence of strong scintillation, finite size of the emission region produces a characteristic W-shaped signature in the projection of the visibility distribution onto the real axis. This modification involves heightened probability density near the mean amplitude, decreased probability to either side, and a return to the zero-size distribution beyond. We observe this signature with high statistical significance, as compared with the best-fitting zero-size model, in many regions of pulse phase. We find that the equivalent full width at half maximum of the pulsars emission region decreases from more than 400 km early in the pulse to near zero at the peak of the pulse, and then increases again to approximately 800 km near the trailing edge. We discuss possible systematic effects, and compare our work with previous results.
There are a number of very high energy sources in the Galaxy that remain unidentified. Multi-wavelength and variability studies, and catalogue searches, are powerful tools to identify the physical counterpart, given the uncertainty in the source loca tion and extension. This work carries out a thorough multi-wavelength study of the unidentified, very high energy source HESS J1858+020 and its environs. Giant Metrewave Radio Telescope observations at 610 MHz and 1.4 GHz have been done to obtain a deep, low-frequency radio image of the region surrounding HESS J1858+020. Archival radio, infrared, and X-ray data have been analysed as well. This observational information, combined with molecular data, catalogue sources, and a nearby Fermi gamma-ray detection of unidentified origin, are combined to explore possible counterparts to the very high energy source. We provide with a deep radio image of a supernova remnant that might be related to the GeV and TeV emission in the region. We confirm the presence of an H II region next to the supernova remnant and coincident with molecular emission. A potential region of star formation is also identified. We identify several radio and X-ray sources in the surroundings. Some of these sources are known planetary nebulae, whereas others may be non-thermal extended emitters and embedded young stellar objects. Three old, background Galactic pulsars also neighbour HESS J1858+020 along the line of sight. The region surrounding HESS J1858+020 is rich in molecular structures and non-thermal objects that may potentially be linked to this unidentified very high energy source. In particular, a supernova remnant interacting with nearby molecular clouds may be a good candidate, but a star forming region, or a non-thermal radio source of yet unclear nature, may also be behind the gamma-ray source. Further observational studies are needed.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا