Solar Soft X-ray Irradiance with Hinode/XRT, and
Solar Spectral Study with SOHO/SUMER.

Project descriptions

• Project "X" : "Solar Soft X-ray Irradiance with Hinode/XRT"
  • maily by Stefanie and Aki
  • Montana State University (MSU) is home of Hinode/XRT Synoptic Composite Image Archive ( SCIA ), which is the archive of soft X-ray full-Sun images obtained with the X-Ray Telescope aboard the Hinode satellite. Our images are posted daily to the SolarMonitor , a popular site for solar researchers to check the current solar condition.

    With this archive, we can study solar activities in terms of the Sun's radiation in soft X-ray wavelengths. In this project, we will process the XRT/SCIA images taken from 2006 to date to derive the solar soft X-ray irradiance during this period. The student will learn how to process Hinode/XRT FITS data for quantitative analysis: selection of data files and area of interest, derivation of temperature and emission measure, calculation of the XRT irradiance in the physical unit comparable with other instruments. The student will also learn about data calibration applied to the original data to be used for analysis. Just like us, XRT instruments are aging during more than 12 years of operation in space. We should carefully separate the variation of the solar signals from that caused by the characteristic change of the instrument.

    As a bonus, the student will have a few opportunities to watch and learn how an international satellite project like Hinode is operated. As one of US institutes participating the Hinode satellite operation, we have a duty week in July, in which we take control of the XRT observation.

• Project "S" : "Solar Spectral Study with SOHO/SUMER"
  • maily by Alyssa and Suman
  • For this project the student will get a chance to work with SOHO/SUMER and UARS/SOLSTICE data. SUMER(Solar Ultraviolet Measurements of Emitted Radiation) is a UV telescope and spectrometer onboard the ESA/NASA spacecraft SOHO(SOlar Heliospheric Observatory). During its period of operation 1996-2014, SUMER took a few full disk solar spectra in different wavelength bands. The student will learn to look at SUMER spectral data including C IV and Ne VIII lines and synthesize a full disk image/datacube out of spectral data of a slit scanning across the solar disk. We will produce a disk averaged spectra and use the data from UARS/SOLSTICE (Upper Atmosphere Research Satellite/Solar Stellar Irradiance Comparison Experiment) to cross-calibrate SUMER data.

    Our team at MSU is currently developing a sounding rocket spectrometer called Full-sun Ultraviolet Rocket SpecTrometer(FURST). The student will also have an opportunity to interact with our research group at MSU and learn about their work.

Weekly goals

• Week 1 (6/1 -- 6/4) : common to Project "X" and "S".
  Get familiar with IDL and Read "Encyclopedia of the Sun". sections 8.4, 8.5.
  solar spectrum. solar spectrum.
  On Friday, we had a special guest: Prof. Charles Kankelborg, who gave a talk about the FURST project and showed us his Lab.

• Week 2 (6/7 -- 6/11) : learn about Hinode/XRT instruents. read XRT SCIA files with IDL.
• Week 3 (6/14 -- 6/18) : finish thin_Be & Al_mesh pair selection, collect signals within 1.1Rs.
  devide the process into steps:
  • step 1: data selection (find usable image pairs of thin_Be and Al_mesh)
  • step 2: collect total intensity within 1.1 Rs.
  • step 3: derive averaged temperature(Te) and Emisison Measure(EM) for each pair.
  • step 4: convert Te and EM to solar irradiance in the unit of W/m^2.
  to finish step 2 is the goal of this week.
• Week 4 (6/21 -- 6/25) : understand the Filter Ratio Method, apply a sample code to the step 2 data.
• Week 5 (6/28 -- 7/1) : understand Chianti atomic database. Derive Te and EM for all the pairs (perform step 3).
• Week 6 (7/6 -- 7/9) : prepare for the mid-term presentaion.
• Week 7 (7/12 -- 7/16) : start to calculate solar spectrum and get irradiance in the unit of W/m^2. analyze additional data (2021 Jan -- June) for the step 1-4.
• Week 8 (7/19 -- 7/23) : compare our Te and EM with the previous study done with other filter pairs. Prepare a presentation file for a Friday group meeting.
• Week 9 (7/26 -- 7/30) : add comparison of irradiance. start to look at the SunSpotNumber data at the SILSO site for comparison.
• Week 10 (8/2 -- 8/6) : prepare for the final presentation (8/4) and wrap up.

• Week 2 (6/7 -- 6/11) : learn about SOHO/SUMER instruments. download data from the data site. read with IDL.
• Week 3 (6/14 -- 6/18) : make 3D data cubes of full disk images of the Sun from slit scan data of SUMER.
• Week 4 (6/21 -- 6/25) : continue to make 3D data cube.
• Week 5 (6/28 -- 7/1) : start to look at the UARS/SOLSTICE data.
• Week 6 (7/6 -- 7/9) : prepare for the mid-term presentaion.
• Week 7 (7/12 -- 7/16) : download some SOLSTICE data and take a look.
• Week 8 (7/19 -- 7/23) : interporlate SOLSTICE spectrum for the time of SUMER observation, extract the line contribution from the SOLSTICE spectrum.
• Week 9 (7/26 -- 7/30) : interpretation of the results: explain large difference in data magnitude.
• Week 10 (8/2 -- 8/6) : prepare for the final presentation (8/4) and wrap up.

Resources

• Section 8.4 and 8.5 of "Encyclopedia of the Sun" by Kenneth R. Lang (2001) Cambridge University Press
• about XRT Synoptic Composite Images
• about solar irradiance study with SUMER
• Other References
• IDL sample programs

just a memo for the 6/16 meeting

• free-free emission
• free-bound emission
• bound-bound emission

a memo for the 6/21 meeting

• The Filter Ratio Method
• XRT's effective area functions and spectral response functions
• XRT's CCD camera gain constant is 57 electrons/DN

a memo for the 6/28 meeting

• an up-to-date atomic database and associated codes (IDL, Python),
• for the analysis of optically-thin line and continuum plasma emission (like solar corona).
• developed by a group of scientist from US(NRL) UK(Cambridge) and Italy(Arceri Astrophysical Obs.
• version 1 released in 1997.

• H-alpha line
• emitted by Hydrogen atom at 656.3nm.
• transition of an electron from principal quantum number 3 to 2.
• emitted from the Sun's atmospheric layer at roughly 10000K.

a memo for the 7/6 meeting

• X1.5 flare on 7/3
• Hinode operations , daily event page
• Suman presented examples of SUMER spectra of explosive events.

a memo for the 7/12 meeting

• review of solar magnetic activity cycle.
  Sunspont Index and Long-term Solar Observation page ,
  Solar Cycle Science page by David Hathaway at Stanford Univ.
• Calibration of XRT data (Quick Look v.s. Level_0)
  • contamination accumulation on CCD and filters.
  • stray light (visible light contamination)
  • satellite pointing correction.
• XRT daily operation meeting sneak peak on 7/12 at 19:30.

a memo for the 7/19 meeting

• NOAA AR numbering started on 5-Jan-1972, according to NASA Q&A page
• irradiance vs radiance
  • Energy: E (J)
  • Energy flux : F (J/s = W)
  • Irradiance : I (W/m²) img1

    Irradiance at SOHO  : Is (at the L1 point : let R1 the distance from the Sun)
    Irradiance at Earth : Ie (at 1 AU, let R2 the distance from the Sun)
    When Is is measured, total Energy flux from the Sun: F_total = Is * 4*π*R12
    Earth will receive this flux as Ie = F_total / 4*π*R22
    This gives Ie = Is * R12 / R22
    From R1 = 0.99 AU, R2=1 AU. We get Ie = 0.98 Is
    

  • Radiance : L (W/m²/str) steradian(youtube), steradian(wiki) , img2 , img3
    

     dω1=Ar/r2
     dω2=As/r2
     Fs = Ls * As * dω1  = Ls * As * Ar / r2 
     Fr = Lr * Ar * dω2  = Lr * Ar * As / r2
     if Fs = Fr then Ls = Lr : Radiance is invariant along the conserved flux.
    

a memo for the 7/29 meeting

a memo for the 8/2 meeting

Examples of Abstract

• Takeda et al at Hinode 12th Science meeting 2018 Sept in Spain
• Takeda at AGU meeting 2020 Dec. (virtual)

Aki Takeda (Research Scientist, Dept. of Physics at MSU)