Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session X08: Solar and Exoplanets |
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Sponsoring Units: DAP Chair: Judy Rascusin, NASA GSFC Room: Sheraton Governor's Square 10 |
Tuesday, April 16, 2019 10:45AM - 10:57AM |
X08.00001: Modeling the 2017 September 10 Long Duration Gamma Ray Flare James M Ryan, Georgia A de Nolfo, Dale Gary The large flares of 2017 September 4 to 10 were significant microwave events with revealing multi-wavelength images of the flare environment. The event on September 10 was a large long-duration, gamma-ray flare (LDGRF). The event also produced a Ground Level Enhancement (GLE). Using the microwave imaging data from the Expanded Owens Valley Solar Array (EVOSA) we interpret and model the behavior of the energetic-flare protons of September 10 as measured with the Large Area Telescope (LAT) on the Fermi mission. We do this in the context of stochastic acceleration in a large coronal bipolar structure to produce the high-energy long-duration gamma-ray emission. Our preliminary analysis suggests that the acceleration of the GeV protons takes place in a large structure about 1.4 solar radii in length. The requirements for the magnetic field and turbulence in this structure will be presented. |
Tuesday, April 16, 2019 10:57AM - 11:09AM |
X08.00002: Using the Miniature X-ray Solar Spectrometer (MinXSS) CubeSats to Probe HOT Plasma in the Atmosphere of a COOL Star Christopher S Moore, Thomas N Woods, Amir Caspi, Phillip Clyde Chamberlin, Andrew Jones, James Paul Mason The Sun is the closest star to Earth and hence provides a unique opportunity to study numerous stellar phenomena in detail unprecedented to other stars. One such phenomena, which is a longstanding mystery, is coronal heating of low mass stars. The solar corona contains plasma in excess of 1 MK at all times, strong concentrations of magnetic field called active regions contain plasma at least up to 3 MK, and large flares heat plasma above 10 MK. Detection of soft X-rays (sxr) from the Sun provide direct information on coronal plasma of temperatures in excess of ~1 MK. CubeSats are a low-cost alternative to rapidly fill astrophysical observation gaps, that large missions are currently missing. The twin Miniature X-ray Solar Spectrometer (MinXSS) CubeSats are the first solar science oriented CubeSat missions flown for the NASA Science Mission Directorate. The twin MinXSS have provided measurements from 0.8 -12 keV, with resolving power ~40 at 5.9 keV, at a nominal ~10 second time cadence and have proven to be consistent with numerous solar observations, proving the scientific capability of CubeSats. |
Tuesday, April 16, 2019 11:09AM - 11:21AM |
X08.00003: Ring Currents Induce the Solar Magnetism and Cause the Oscillations in Brightness Maria Kuman Recent observations with the NASA’a Solar Dynamic Observatory (SDO) revealed that magnetic fields rule the solar dynamic. These magnetic fields result from ring currents induced by the different angular velocity of different layers of the spinning sun. The article is about these ring currents, which can give us information about the structure of the sun and its layers in depth. We offer in this article a better model of the ring currents, which better reflects the solar dynamic, than Dr. Zhao’s model. We also offer explanation of the observed oscillations in the brightness of the sun and we don’t think it is a systematic error in measurements, as Dr. Zhao thinks. We consider the oscillations in brightness result from Doppler Shifts (of the spectral lines) in opposite direction for clockwise and counterclockwise ring currents. |
Tuesday, April 16, 2019 11:21AM - 11:33AM |
X08.00004: Monte Carlo Simulations of a Near-Solar Orbit Neutrino Detector Caleb J Gimar, Nickolas Solomey, Lynn Buchele, Mark Christl, Robert J McTaggart, Holger Meyer, Austin Nelsen A solar neutrino detection experiment in a solar orbit of 7 to 3 solar-radii perihelion could revolutionize solar interior studies. At such proximity, the neutrino flux increases by several orders of magnitude allowing for a much smaller detector design than Earth-based devices. An off-ecliptic orbital location also allows for fusion core geometry studies. To pursue these improvements, a scintillation detector using gallium-doped liquid scintillator and veto array methods has been devised. Neutrino-gallium interactions can result in a sequentially released electron and gamma-ray/X-ray, giving distinct double-pulse signals in the detector. A veto array would filter external-source charged particles. This presentation focuses on Monte Carlo simulations of particle events visible to the detector. The Monte Carlo code incorporates background event rates obtained from Geant4 simulations of the detector assembly, and neutrino interaction rates based on scaling of similar, Earth-based experiments’ performance to the detector’s parameters. The code output is examined to find the number of true double-pulse signals versus those of false signals. Establishing experiment parameters necessary for a false event detection rate less than 20 percent is a primary goal. |
Tuesday, April 16, 2019 11:33AM - 11:45AM |
X08.00005: A Partially Eclipsing Triple in the Kepler Field Exhibiting Doppler Beaming Ben H Placek, Kevin H Knuth, Daniel Angerhausen To date, the Kepler Space Telescope has discovered 3872 exoplanets with an additional 2454 Kepler objects of Interest (KOIs). Using publicly available HiRes spectra along with Kepler photometry we present a detailed analysis of a peculiar KOI. Through a simultaneous spectroscopic and photometric analysis this system has been determined to most likely consist of a central K-dwarf along with two ultra-short period M-dwarfs that collectively orbit the central host star in a highly inclined s-type orbit. The small M-dwarfs eclipse each other, but not the central host star indicating a significant non-coplanarity of the orbits. Finally, the reflex motion of the host star leads to relativistic Doppler beaming appearing in the photometric time series, which allows for the estimation of the mass of the companions. |
Tuesday, April 16, 2019 11:45AM - 11:57AM |
X08.00006: A 30 GHz laser frequency comb for high-precision radial velocity calibration and exoplanet searches Connor D Fredrick, Andrew Metcalf, Ryan Terrien, Jeff Jennings, Wesley Brand, David Carlson, Daniel Hickstein, Joe Ninan, Gudmundur Stefansson, Sam Halverson, Arpita Roy, Kyle Kaplan, Chad Bender, Suvrath Mahadevan, Scott Papp, Scott Diddams Radial velocity precision at and below the 1 m/s level is necessary for the detection of earth-mass exoplanets within the habitable zones of M-dwarfs. Laser frequency combs provide a dense and absolute array of frequencies ideal for the in-situ calibration of high-resolution astronomical spectrographs. However, the challenges of generating large mode spacings, wide optical bandwidth, and the operational robustness suitable for remote facilities have prevented their widespread use. Overcoming these obstacles, we built a 30 GHz frequency comb spanning 800 nm to 1300 nm and achieved long term, on-sky, 1.5 m/s rms radial velocity precision with the near-infrared Habitable-Zone Planet Finder spectrograph at the 10 m Hobby-Eberly Telescope in Texas. Our frequency comb is generated through robust, fiber integrated electro-optic modulation of a single frequency laser and subsequent supercontinuum generation in a highly nonlinear fiber and a nano-photonic device. All frequencies are traceable to a GPS disciplined atomic clock. The frequency comb has been running continuously since May 2018. We detail the architecture, performance, and long-term operation of the comb. |
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