Gabrielle Beach, Peter Cheimets, Edward Hertz
The COronal Spectrographic Imager in the Extreme ultraviolet (EUV) instrument is a proposed mission of opportunity that,if selected, will launch in July 2023 and will be mounted on the International Space Station. It is designed to observe the full sun out to 3.3 solar radii atwavelengths of18.6 to 20.5 nm with 500x more sensitivity than the EUV imager on the AtmosphericImaging Assembly (AIA). COSIE’s observations will be used to better understand the coronal magnetic structure, the evolution of coronal mass ejections (CMEs), and the origin of the solar wind. The instrument is composed of COSIE-C, a wide-field EUV coronagraph, and COSIE-S, a no-slit EUV spectrograph.
The alignment of optical elements directly affects an instrument’s performance. Since an EUV laser is remarkably expensive, COSIE-S will be aligned with a different wavelength of light (632.8 nm) and a different grating groovedensity than what will be used in operation (18.6 -20.5 nm, 5000 l/mm). This restriction complicates the alignment process because the angle of diffraction is a function of wavelength, groovespacing, order of diffraction, and incident angle. For the optical components to be aligned correctly with the 632.8 nm HeNe laser, the groovedensity and incident angle were calculatedtoproduce the same diffraction angle with the alignment laser as the EUV light would produce with the 5000 l/mm flight grating. Since the precision required on the incident angle was unknown, an error budget was established to determinewhich optical element misalignments would cause the most detrimental effects to the image and their allowable error values. It was found that translating the focus mirror or detector along the optical axis would have the largesteffect on the image. Acomputer model of the COSIE optical design was created to compare to the error budget results.
Keywords: Solar telescopes, Ultraviolet telescopes, Spectroscopy
This work supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313.
Bore (Annie) Gao
Supervisor: Qizhou Zhang, Andrew Burkhardt
Protostellar outflows are crucial for the formation of protostarsby shedding excess angular momentum in the infalling gas to allow accretion to continue onto the central star. Outflowing gas travelling at supersonic speeds creates shocks and alters the chemical composition in the ambient medium. However, the chemistry in these outflows is not well constrained. Here, we utilized archival Submillimeter Array (SMA) observations of the young, high mass protostar IRAS 20126+4104 in order to study the chemical diversity of both the disk and the outflow. We found that there are complex chemistry in both disk and outflow regions, and we assessed column densities for different molecules.
Keywords: Astrochemistry, Interferometry, Stellar jets
Carson Goettlicher (1) (2), Christopher S. Moore (2), and Steven Saar (2)
(1) Towson University, (2) Harvard-Smithsonian Center for Astrophysics
Solar flares are magnetic reconnection events resulting in sudden bursts of electromagneticenergy, particle acceleration, and hot plasma heated to over 10 MK. Hot solar flare plasma gener-ates copious soft X-rays. Hence, spectral soft X-ray measurements provide great constraints onflare plasma temperature and dynamics. Flare observations from Low-Earth orbiting satelliteslike the first Miniature X-ray Solar Spectrometer (MinXSS-1) CubeSat can be occulted for 30minutes of the 90 minute orbit, missing vital portions of the temporal evolution of the spectrumand plasma. In this project, the eclipsed MinXSS-1 spatially integrated spectra from 0.8 - 15keV is reconstructed using non-oculted data by fitting an empirical piecewise temporal-spectralfunction consisting of Gaussian, Lorentian, and polynomial components. This automated pro-cedure fits the original data and adds synthetic data points to the eclipse period in the temporalprofile, which can be used to reconstruct the spectral profile for energy range specified in thetime series. At both points of egress and ingress there are larger decreases in the low energy(<3 keV) soft X-ray flux due to absorption by nitrogen and oxygen in Earth’s atmosphere.Results from this project could be used in future projects focusing on exoplanet atmospheresand models of flare plasma evolution.
Keywords: Sun, X-Ray, Flares, Earth Atmosphere, Exoplanet, Atmosphere, Corona
This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313
Anthony J. Iampietro, Steven H. Saar, Raphaëlle D. Haywood, Timothy W. Milbourne
Analysing the periodic radial-velocity variations of a star caused by an orbiting planet is a highly successful way of inferring the masses of exoplanets around bright, nearby stars. A major limitation to this method comes from rotationally modulated stellar activity signals that hide orbits of small exoplanets by creating variations in radial-velocity measurements. We look to the Sun as a test of concept to understand the effects of solar and stellar activity on radial-velocity variations. We construct a physicallygrounded model for the suppression of convective blueshift and rotation of active regions across the solar/stellar disk. Additionally and for the first time, we model horizontal velocity flows in and around active regions (Evershed and moat flows directedradially outward from sun/starspots, inflows around plage regions). We use SORCE photometry and HARPS-N Ca II H&K line emission as proxies for these physical effects, and fit to measured radial-velocity variations of the Sun seen as a star from the HARPS-N spectrograph. We also model radial-velocity measurements of the rocky-planet host star CoRoT-7, using CoRoT photometry and HARPS Ca II H&K emission observations. We apply our model for stellar activity and compare to previous models that did not account for horizontal velocity flows. This work is an essential step towards modelling the physical effects of stellar activity on radial-velocity variations, which is crucial to uncovering Earth-like exoplanets orbiting Sun-like stars.
Keywords: solar active regions, sunspots, sunspot flows, starspots, exoplanets, radial velocity
This work is supported under the NSF-REU solar physics program at SAO, grant number AGS-1560313, performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute (R.D.H.), and supported in part by NASA award number NNX16AD42G, the Smithsonian Institution, NASA Heliophysics LWS grant NNX16AB79G (S.H.S.) and the HARPS-N project.
DeOndre Kittrell (1), Zhuofei Li (2), Katharine Reeves (3), and Mark Weber (3),
(1) Morgan State University, Physics, Baltimore, MD, United States, (2) Nanjing University, Nanjing, China, (3) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States
We examine the thermal state of plasma associated with a solar flare that occurred July 7,2012. In the plasma sheet located within the region above the flare, supra-arcade downflows (SADs) are observed using the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. The sunward traveling downflows give insight on the local heating mechanics of coronal plasma during the post-eruption period of the flare. We perform calculations of the differential emission measure (DEM) from the AIA data in order to determine the total emission measure and the average weighted temperature. Emission within the SADs are relatively low,and the temperature is much cooler compared to the surrounding plasma. Coupling the DEMs with the velocities within the plasma sheet, we can analyze potential heating terms that model dominant thermal processes in the supra-arcade region.
This work supported by the NSF-REU solar physics program at SAO, grant numberAGS-1560313, the NSF SHINE program, grant #AGS-1723425, and NASA grant#80NSSC18K0732.
Supra-arcade downflows (SADs) have been observed above flare loops during the decay phase of flare. They appear as tadpole-like dark plasma voids traveling towards the Sun. In areas surrounding where they appear, temperatures are often high. We aim to investigate temperature and heating mechanism of SADs. We apply our analysis to the M1.7 flare that occurred on 2012 July 12 and was observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. There are many obvious SADs above the arcade during this event in the AIA 131 Å channel. We calculate velocities of SADs using the Fourier Local Correlation Tracking (FLCT, Fisher & Welsch, 2008) method to derive velocities in the supra-arcade region. Using corks to track the calculated velocities, we find our velocity results are consistent with the SAD motions in the AIA 131 Å intensity movie. We use the velocities to derive the adiabatic heating caused by the compression of plasma. Preliminary results indicate that there is adiabatic heating in front of the SADs.
Keywords: Solar activity, Solar flares
This work supported by the NSF-REU solar physics program at SAO, grant number AGS- 1560313, the NSF SHINE program AGS-1723425, and NASA grant number 80NSSC18K0732.
Naylynn Tañón Reyes, Ed DeLuca, Jenna Samra, and Chad Madsen
The Sun's dynamic outermost atmospheric layer, the corona, routinely has extremely high temperatures and violent eruptions. This means the corona is in a state of hydrostatic and thermodynamic disequilibrium which leads to extreme coronal heating and solar activity, such as flares and coronal mass ejections. This activity can dramatically affect humanity's infrastructure and technology in space and on Earth. Understanding the coronal magnetic field would allow for predictions of these violent events caused by magnetic reconnection. Measuring the magnetic field is possible through the study of the magnetically sensitive emission lines in the infrared (IR) with the Zeeman effect. The corona emits some IR emission lines, however, the solar surface’s intensity overwhelms the corona's. To study these coronal lines, we can use the moon during a total solar eclipse to block out the surface's continuous emission spectrum.
The Airborne Infrared Spectrometer (AIR-Spec) is a pathfinder for future infrared spectrometers and spectro-polarimeters that will measure the coronal magnetic field. On July 2nd, 2019 AIR-Spec observed the total solar eclipse over the South Pacific from onboard an aircraft. The NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) flew at 13km to avoid low altitude water vapor, the primary absorber of infrared radiation on Earth. We present the first look at the results so far. AIR-Spec characterized four emission lines to determine which would work best for future instruments to measure the coronal magnetic field. Comparing the intensity gradients for the observed IR lines with EUV lines from the EUV Imaging Spectrometer (EIS) gives us information regarding the excitation processes in the corona, providing improvements to the atomic models of the associated ions. The radiatively excited IR lines will allow us to measure the magnetic field further out from the solar limb than non-radiatively excited IR lines.We also determine the value of the IR lines as plasma temperature and density diagnostics, using EIS data to supplement our analysis. The analysis of the temperature and density will help explain the behavior of the plasma, which will allow the mapping of the coronal magnetic field. Lastly, we discuss how AIR-Spec will continue its mission during both the 2020 and 2024 total solar eclipses as well as influence a proposed balloon-based coronagraph for coronal magnetic field measurements.
Keywords:Solar eclipses, Solar instruments, Solar electromagnetic emission, Solar corona, Solar atmosphere, Spectral line identification, Spectroscopy, Infrared telescope
Broader Keywords:Solar atmosphere, Solar physics
This work is supported by the NSF-REU solar physics program at SAO [grant number AGS-1560313] and the NSF Airborne InfraRed Spectrograph (AIR-Spec) 2019 Eclipse Flight [award number 1822314].
Exoplanet research has become a major focus due to advancements like the transit method, which allows us to observe the features of exoplanet atmospheres. Shared features between exoplanetary atmospheres and their host stars limits confidence on any atmospheric interpretation. Our ability to characterize the variability of these shared stellar features is critical in accurately characterizing planetary atmospheres. The Helium I 1083 nm line is one such shared feature and is an ideal absorption line to study when probing the upper atmosphere of certain exoplanets for atmospheric escape. By investigating the variability of the He I 1083nm absorption line in the Sun we can begin to understand how the feature behaves in other sunlike stars. I analyzed publicly available SOLIS/ISS spectra of the Sun as a star to document how the He I 1083nm line strength changed as a function of time. Using the Sherpa model-fitting python package, I was able to calculate the equivalent widths for nearly 3,000 observations between 2007 and 2017. Tracking these fluctuations through both low and high stellar activity, which can be approximated by the S-index, can reveal more precise constraints on how we expect the line to vary during specific points in a star’s cycle. This analysis will allow us to better disentangle the stellar component of the He I 1083nm signal from exoplanetary atmospheres.
Keywords: Sun: atmosphere, line: profiles, planets and satellites: atmospheres, planets and atmospheres: gaseous planets
This work was supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313
William J. Wainwright, Antonia Savcheva, Samaiyah Farid
Throughout the eleven year cycle of the sun, solar eruptions are constantly taking place. Thought to be caused by reconnection of magnetic field lines, coronal jets are one of several types of such eruptions. Jet formation and eruption is not well understood. In some cases, jets occur when small filaments of chromospheric material are lofted into the corona. The filaments have strong magnetic flux, and are often the site of magnetic reconnection and subsequent eruption. In order to better understand the constraints on these coronal jets, we have modeled the conditions required for stable filaments and eruptions using nonlinear force-free (NLFF) field modeling. NLFF models are 3-D topological models that are used to show the morphological evolution of magnetic fields. Using the CMS2 modeling suite, we modeled two regions with jet eruptions: a coronal jet near a larger filament, and a coronal jet near an AR sigmoid. In both cases, Solar Dynamics Observatory’s HMI magnetograms and observations from AIA images are used to constrain the input parameters of the model. In this presentation, we will present our model results and discuss how they help understand solar coronal jet eruptions.
This work is supported by NSF-REU solar physics program at SAO, grant number AGS-1560313, and NASA grant number NNX15AF43G.