Arun Kumar Awasthi (IAUWR)

Transcription

1 Multi-thermal Diagnostics of emission measure for a B8.3 flare of July 04, 2009 Arun Kumar Awasthi 1 1. Ins'tute of Astronomy University of Wroclaw, Poland awasthi@astro.uni.wroc.pl, arun.awasthi.87@gmail.com Collaborators: Barbara Sylwester 2, Janusz Sylwester 2 and Rajmal Jain 3 2. Solar Physics Division, Space Research Centre, Polish Academy of Sciences, Wroclaw, Poland 3. Kadi Sarva Vishwavidyalaya, Gandhinagar, Gujarat, India Arun Kumar Awasthi (IAUWR) November 17, 2015 Acknowledgement: The research leading to these results has received funding from the European Community s Seventh Framework Programme (FP7/ ) under grant agreement no (F- CHROMA). Also, this has the support of the Polish NCN grant 2011/01/B/ST9/05861 and from the European Commissions Seventh Framework Programme under the grant agreement No (eheroes project). SOL T04:37

2 OUTLINE v IntroducWon Ø Underlying energy release processes during a flares Ø X-ray emission during solar flares Ø DifferenWal Emission Measure: Inversion problem v SOL T04:37 Ø ObservaWons Ø Thermal CharacterisWcs of the flare plasma o Single Gaussian DEM[T] o Power-law DEM[T] o Withbroe-Sylwester Inversion Ø Thermal EnergeWcs Ø Summary Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015

3 IntroducWon Solar Flares Energy Release processes during a flare o Solar flare is one of the most impulsive phenomena occurring in the atmosphere of our Sun, releasing typically ergs of energy in 10 3 s. Underlying physical processes: A Glance o Powered by magnewc reconnecwon o Electrons are accelerated to high speed, generawng a burst of radio energy as well as impulsive loop-top hard x-ray emission. o Non-thermal electrons are channelled down to strike the chromosphere emifng hard x-rays. o Beams of accelerated protons cause nuclear reacwons that result in gamma-ray spectral lines and energewc neutrons. o Chromospheric evaporawon, accompanied by a slow, gradual increase in sog x-ray radiawon. Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (1/14)

4 X-ray and Gamma-ray spectrum IntroducWon Solar Flares ü A typical M-class solar flare can be observed across almost enwre electromagnewc spectrum. ü X-ray emission during solar flares mainly originates from corona and upper chromosphere. ü X-ray spectrum observed during a flare can serves as the best probe of studying various plasma processes of thermal and nonthermal origin. ü Thermal emission Ø Isothermal Ø MulW-thermal ü Non-thermal emission Ø Energies much larger than mean thermal energy of the background plasma Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (2/14)

5 DifferenWal Emission measure IntroducWon Inversion Problems in Flares o Various energy release processes occurring in the different layers of solar atmosphere can be probed by the inversion of the observed mulw-wavelength flare emission. o The study of thermal characteriswcs of the flare plasma by the inversion of observed X-ray spectrum is made by forward-fifng model photon flux generated by: 1. Isothermal Emission Measure 2. MulW-thermal plasma through assuming a funcwonal form of DEM[T]. Craig & Brown, A&A (1976) o DEM[T] is known with large uncertainwes owing to inversion problem. o Several funcwonal forms are available to forward-fit the observed spectra. Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (3/14)

6 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (4/14) SOL T04:37 Observa_ons Solar Photometer in X-rays (SphinX) SOL T04:37, is the only event common between Solar X-ray Spectrometer (SOXS, Indian) and SphinX (Polish) instruments. SOL T04:37 X-Ray light-curve of AR as seen by SphinX SphinX -> kev - Temporal and spectral cadence -> 6μs and 0.4 kev. SOXS -> 4-25 kev - Temporal and spectral resoluwon -> 3s and 0.7 kev.

7 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (5/14) SphinX & SOXS SOL T04:37 Observa_ons

8 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (5/14) SphinX & SOXS Spectrum SOL T04:37 Observa_ons ü Empirical normalizawon factor of 2.5 is employed in count rate observawons obtained from SOXS in order to accommodate a systemawc difference of sensiwviwes between the SphinX and SOXS instruments. ü The normalizawon factor, although empirically obtained, however, eswmated considering the fact that the flux recorded by SphinX is the accurate.

9 SOL T04:37 Observa_ons EUV emission: STEREO A & B; EIT/SOHO STEREO-A Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (6/14)

10 SOL T04:37 Observa_ons EUV emission: STEREO A & B; EIT/SOHO STEREO-B Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (6/14)

11 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (7/14) ü We derive the best-fit DEM[T] for input X-ray spectrum in three energy bands: kev (Low energy part of SXR) kev (High energy part of SXR) 3. Combined ( kev) SXR spectrum. SOL T04:37 Best-fit DEM[T] Single Gaussian funcwonal form of DEM[T] ü FuncWonal form of DEM[T] is assumed to be single Gaussian ü Firstly, we find the best-fit on synthesized mulw-thermal theorewcal photon flux

12 SOL T04:37 Best-fit DEM[T]: Synthesized Spectra Single Gaussian funcwonal form of DEM[T] Energy DEM p (10 49 ) T p EM (10 49 ) Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (8/14)

13 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (9/14) SOL T04:37 Best-fit DEM[T]: Observa_ons Single Gaussian funcwonal form of DEM[T]

14 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (10/14) SOL T04:37 Best-fit DEM[T] Power-law funcwonal form of DEM[T] T min =0.5 kev (fixed)

15 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (11/14) SOL T04:37 Best-fit DEM[T] Withbroe-Sylwester DEM inversion ü The WS algorithm is a numerical technique which employs maximum likelihood approach in which the DEM distribuwon in one step of iterawon [j] (DEM j (T )) is eswmated from that derived in the preceding iterawon (DEM j 1 (T )), and by employing a correcwon factor (c i ) as well as weight factor (w i ) as:

16 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (12/14) SOL T04:37 Best-fit DEM[T] Withbroe-Sylwester DEM inversion

17 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (13/14) SOL T04:37 Best-fit DEM[T]

18 Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 (14/14) Thermal EnergeWcs SOL T04:37 Thermal Energe_cs

19 Summary Arun Kumar Awasthi (IAUWR) SOL T04:37 17/11/2015 ü We inveswgate the thermal characteriswcs of the flare plasma by analysing X-ray emission in the energy band kev observed during SOL T04:37. ü We find large values of DEMp, however at low Tp for the lower band in comparison to the relawvely lower values of DEMp at higher Tp derived for the best- fit of high energy band part of the spectrum. ü Energy eswmated from parameters derived only from spectral inversion of the low-energy part ( kev) of sog X-ray spectrum results in high thermal energy content than that obtained from combined spectral analysis. ü Same eswmated with from only higher energy part of SXR spectra leads to low thermal energy eswmates in comparison to that calculated from combined energy band analysis. ü Pre-assumed funcwonal form of DEM[T] results in higher thermal energy content in general.

20 The research leading to these results has received funding from the European Community s Seventh Framework Programme (FP7/ ) under grant agreement no (F-CHROMA) This work was supported by the grant of Polish Ministry of Science and Higher Education No. 3243/7.PR/14/2015/2 ( )