SPECTRAL ANALYSIS AND MODELING OF THE FLARING LOWER SOLAR ATMOSPHERE IN MULTI-WAVELENGTHS

Project: Research project

Project Details

Description

FLARES ARE ONE OF THE MOST PROMINENT PHENOMENA ON THE SOLAR DISK AND HAVE BEEN OBSERVED AND STUDIED EXTENSIVELY SINCE THE FIRST REPORT IN 1859. IT IS WIDELY ACCEPTED THAT DURING FLARES ELECTRONS ARE ACCELERATED TO HIGH ENERGIES. AS THESE ELECTRONS PROPAGATE THEY HEAT THE SOLAR ATMOSPHERE THEREBY PRODUCING DRAMATIC INCREASES IN EMISSION THROUGHOUT THE ELECTROMAGNETIC SPECTRUM. HOWEVER THE ORIGINS OF FLARE EMISSIONS IN PARTICULAR IN UV VISIBLE AND NEAR INFRARED REMAIN PUZZLING. BY TAKING ADVANTAGE OF HIGH-RESOLUTION OBSERVATIONS OBTAINED BY THE INTERFACE REGION IMAGING SPECTROGRAPH (IRIS) AND THE GOODE SOLAR TELESCOPE (GST) AT BIG BEAR SOLAR OBSERVATORY (BBSO) THIS PROPOSAL PLANS TO STUDY THE RESPONSE OF THE LOWER SOLAR ATMOSPHERE TO THE ENERGETIC ELECTRONS AT THE INITIAL PRECIPITATING SITE BY MEANS OF HIGH-RESOLUTION OBSERVATIONS AND MODELING. RECENT JOINT IRIS-GST OBSERVATIONS DISCOVERED SPECIAL PROPERTIES ON NARROW FRONTS (100 150 KM) OF PROPAGATING FLARE RIBBONS. FOR INSTANCE ENHANCED ABSORPTION IN HE I 10830 AND HIGHLY BROADENED MG II LINES WERE FOUND IN AN M1.5 FLARE (XU ET AL. APJ 2016) AND A STRONG DOPPLER SIGNAL WAS IDENTIFIED IN AN M6.6 FLARE (JING ET AL. NATURE SCIENTIFIC REPORT 2017). THESE OBSERVATIONS SUGGEST THAT INTENSE PRECIPITATIONS OF ELECTRONS CONCENTRATE ON THE VERY NARROW (LESS THAN 1 ARCSEC) LEADING EDGE OF THE FLARE RIBBON CORRESPONDING TO THE NEWLY RECONNECTED MAGNETIC LOOPS. MOTIVATED BY THESE PRELIMINARY RESULTS WE PLAN TO FURTHER INVESTIGATE THE SPECTRAL/SPATIAL DISTRIBUTION OF FLARE EMISSION IN MORE DETAIL AND PERFORM MODELING USING THE RADYN (FOR H-ALPHA AND HELIUM LINES) AND RH (FOR MG II LINES) PACKAGES. THE RADYN MODEL SOLVES THE EQUATIONS OF RADIATION HYDRODYNAMICS WITH FLARE HEATING INPUT FROM NON-THERMAL ELECTRON DISTRIBUTIONS DERIVED FROM THE REUVEN RAMATY HIGH ENERGY SOLAR SPECTROSCOPIC IMAGER (RHESSI) HXR SPECTRA. THE RH CODE SOLVES A STATIC RADIATIVE TRANSFER EQUATION INCLUDING PARTIAL REDISTRIBUTION WHICH IS NEEDED TO MOST ACCURATELY MODEL THE MG II LINE. BOTH OF THESE CODES ARE WELL TESTED AND HAVE PROVEN TO BE ROBUST AND RELIABLE BASED ON MANY PREVIOUS STUDIES. WE WILL ANALYZE DATA OBTAINED BY NASA S RHESSI AND IRIS MISSIONS AND FROM BBSO/GST THAT CURRENTLY PROVIDES THE HIGHEST SPATIAL RESOLUTION (0.034 AND 0.085 ARCSECOND/PIXEL AT H-ALPHA AND HE I 10830 RESPECTIVELY). IN THIS PROPOSAL WE PLAN TO STUDY THE RESPONSES IN LOWER SOLAR ATMOSPHERE TO THE ENERGETIC ELECTRONS AROUND THE INITIAL PRECIPITATING SITE BY ANALYZING OBSERVATIONS AND CARRYING OUT NUMERICAL SIMULATIONS. SPECIFICALLY THE FOLLOWING SCIENTIFIC ISSUES ARE BEING ADDRESSED: 1. WHAT ARE THE UNIQUE SPECTRAL PROPERTIES THAT DISTINGUISH THE RIBBON FRONT AND THE TRAILING PARTS IN MG II H-ALPHA AND HE I 10830? 2. USING NEW CONSTRAINTS FROM HIGH RESOLUTION OBSERVATIONS CAN WE DETERMINE THE PHYSICAL CONDITIONS THAT DOMINATE THE SPECTRAL CHARACTERISTICS ON THE ELECTRON PRECIPITATION SITE SUCH AS DOPPLER SHIFTS IN UV AND H-ALPHA AND ENHANCED ABSORPTION IN 10830 BLUEWING FROM NUMERICAL MODELING? FLARES ARE IDEAL LABORATORIES FOR STUDYING THE FUNDAMENTAL PROCESSES OF ENERGY TRANSFER IN ASTROPHYSICAL PLASMAS. THIS RESEARCH PROPOSAL IS HIGHLY RELEVANT TO THE HIGH-LEVEL HELIOPHYSICS DECADAL SURVEY THAT IS TO DETERMINE THE ORIGINS OF THE SUN'S ACTIVITY AND PREDICT THE VARIATIONS IN THE SPACE ENVIRONMENT; AND DISCOVER AND CHARACTERIZE FUNDAMENTAL PROCESSES THAT OCCUR BOTH WITHIN THE HELIOSPHERE AND THROUGHOUT THE UNIVERSE.
StatusFinished
Effective start/end date4/16/194/15/22

Funding

  • NASA Headquarters

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