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Register a new userGoldstone Apple Valley Radio Telescope Monitoring Flux Density of Jupiters Synchrotron Radiation during the Juno Mission
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Thangasamy Velusamy
Publication date
2020
fields
Physics
and research's language is
English
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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. 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.
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In 2016, the NASA Juno spacecraft will initiate its one-year mission around Jupiter and become the first probe to explore the polar regions of Jupiter. The HST UV instruments (STIS and ACS) can greatly contribute to the success of the Juno mission by providing key complementary views of Jupiters UV aurora from Earth orbit. Juno carries an ultraviolet Spectrograph (UVS) and an infrared spectral mapper (JIRAM) that will obtain high-resolution spectral images providing the auroral counterpart to Junos in situ particles and fields measurements with the plasma JADE and JEDI particle detectors. The Juno mission will be the first opportunity to measure simultaneously the energetic particles at high latitude and the auroral emissions they produce. Following programmatic and technical limitations, the amount of UVS data transmitted to Earth will be severely restricted. Therefore, it is of extreme importance that HST captures as much additional information as possible on Jupiters UV aurora during the one-year life of the Juno mission. This white paper is a plea for a Juno initiative that will ensure that a sufficient number of orbits is allocated to this unique solar system mission.
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.
The UVS instrument on the Juno mission recorded transient bright emission from a point source in Jupiters atmosphere. The spectrum shows that the emission is consistent with a 9600-K blackbody located 225 km above the 1-bar level and the duration of the emission was between 17 ms and 150 s. These characteristics are consistent with a bolide in Jupiters atmosphere. Based on the energy emitted, we estimate that the impactor had a mass of 250-5000 kg, which corresponds to a diameter of 1-4 m. By considering all observations made with Juno UVS over the first 27 perijoves of the mission, we estimate an impact flux rate of 24,000 per year for impactors with masses greater than 250-5000 kg.
The Parkes telescope has been monitoring 286 radio pulsars approximately monthly since 2007 at an observing frequency of 1.4 GHz. The wide dispersion measure (DM) range of the pulsar sample and the uniformity of the observing procedure make the data-set extremely valuable for studies of flux density variability and the interstellar medium. Here, we present flux density measurements and modulation indices of these pulsars over this period. We derive the structure function from the light curves and discuss the contributions to it from measurement noise, intrinsic variability and interstellar scintillation. Despite a large scatter, we show that the modulation index is inversely correlated with DM, and can be generally described by a power-law with an index of $sim-0.7$ covering DMs from $sim10$ to 1000 cm$^{-3}$ pc. We present refractive timescales and/or lower limits for a group of 42 pulsars. These often have values significantly different from theoretical expectations, indicating the complex nature of the interstellar medium along individual lines of sight. In particular, local structures and non-Kolmogorov density fluctuations are likely playing important roles in the observed flux density variation of many of these pulsars.
We report the discovery of two hot Jupiters using photometry from Campaigns 4 and 5 of the two-wheeled Kepler (K2) mission. K2-30b has a mass of $ 0.65 pm 0.14 M_J$, a radius of $1.070 pm 0.018 R_J$ and transits its G dwarf ($T_{eff} = 5675 pm 50$ K), slightly metal rich ([Fe/H]$=+0.06pm0.04$ dex) host star in a 4.1 days circular orbit. K2-34b has a mass of $ 1.63 pm 0.12 M_J$, a radius of $1.38 pm 0.014 R_J$ and has an orbital period of 3.0 days in which it orbits a late F dwarf ($T_{eff} = 6149 pm 55$ K) solar metallicity star. Both planets were validated probabilistically and confirmed via precision radial velocity (RV) measurements. They have physical and orbital properties similar to the ones of the already uncovered population of hot Jupiters and are well-suited candidates for further orbital and atmospheric characterization via detailed follow-up observations. Given that the discovery of both systems was recently reported by other groups we take the opportunity of refining the planetary parameters by including the RVs obtained by these independent studies in our global analysis.
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