See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/319522921 X-Ray Spectrometers On-Board Aditya-L1 for Solar Flare Studies Article in Current science · August 2017 DOI: 10.18520/cs/v113/i04/625-627 CITATIONS 2 READS 108 27 authors, including: Some of the authors of this publication are also working on these related projects: X-ray Binaries View project Scanning Sky Monitor onboard AstroSat View project Manju Sudhakar Indian Space Research Organization 10 PUBLICATIONS 23 CITATIONS SEE PROFILE Ramadevi m c Indian Space Research Organization 25 PUBLICATIONS 155 CITATIONS SEE PROFILE Ankur Kushwaha Indian Space Research Organization 3 PUBLICATIONS 15 CITATIONS SEE PROFILE Arjun Dey Government of India 208 PUBLICATIONS 1,273 CITATIONS SEE PROFILE All content following this page was uploaded by Bhuwan Joshi on 28 October 2017. The user has requested enhancement of the downloaded file. ASTRONOMY: ADITYA MISSION X-ray spectrometers on-board Aditya-L1 forsolar flare studies K. Sankarasubramanian1,2,3,*, Manju Sudhakar1, Anuj Nandi1, M. C. Ramadevi1, Abhijit Avinash Adoni1, Ankur Kushwaha1, Anil Agarwal1, Arjun Dey1, Bhuwan Joshi4, Brajpal Singh1, V. Girish1, Ishan Tomar1, Kamal Kumar Majhi1, Kumar1, Manjunath Olekar1, Monoj Bug1, Manohar Pala1, Mukund Kumar Thakur1, Rajeev R. Badagandi1, B. T. Ravishankar1, Sarthak Garg1, N. Sitaramamurthy1, N. Sridhara1, C. N. Umapathy1, Vinod Kumar Gupta1, Vivek Kumar Agrawal1 and B. Yougandar1 1ISITE Campus, ISRO Satellite Centre, Outer Ring Road, Marathahalli, Bengaluru 560 037, India 2Indian Institute of Astrophysics, 2nd Block, Koramangala, Bengaluru 560 034, India 3CESSI, Indian Institute of Science Education and Research, Kolkata 741 246, India 4Udaipur Solar Observatory, Physical Research Laboratory, Udaipur 313 004, India of the solar atmosphere (corona, chromosphere and Aditya-L1 mission will carry two high-spectral resolu photosphere). tion X-ray spectrometers to study solar flares. The Though solar flares are observed in all energy bands, soft X-ray spectrometer will cover the energy range from 1 to 30 keV, while the hard X-ray spectrometer X-ray energies provide the best observations due to high will cover from 10 to 150 keV. These two instruments temperatures generated during the flares. Solar flares are together will provide opportunities to study the plasma parameters during solar flares as well as acceleration mechanisms of energetic particles during the flaring time. Keywords: Coronal heating, solar flares, X-ray spectrometers. Introduction SOLAR flares were first observed by Carrington and Hodgson in 1859 as a sudden increase of brightness for a few minutes on the solar atmosphere. Flares have then been observed regularly in the hydrogen alpha line originating in the chromosphere. The complex nature of structures like different source sizes, associated plasma ejections and Morton waves have been reported. Radio observations during the flaring time indicated that the flares not only heat up the plasma, but also accelerate electrons which produce these radio emissions. In late 1950s when space observations were feasible, flares were well observed in X-ray energies. It has been realized from these observations that a sizeable portion of the flare energy is emitted in hard X-rays. Gamma-ray emissions are also seen during solar flares, making it a phenomenon observed in all wavebands (Figure 1)1. It is now understood that although the flaring phenomenon is initiated in the corona, energy is deposited by the flare in all layers *For correspondence. (e-mail: sankark@isac.gov.in) CURRENT SCIENCE, VOL. 113, NO. 4, 25 AUGUST 2017 Figure 1. Typical flare brightening at different wavelengths1. ASTRONOMY: ADITYA MISSION classified as A, B, C, M and X by their brightening in the soft X-ray band, with the X-class flare having an energy range 10–4 Wm–2 (X1) to 10–3 Wm–2 (X10) with M1 flux smaller by an order to X1 flux, and so on. Two solar spectrometers covering soft (1 to 30 keV) and hard (10 to 150 keV) X-ray bands will be flown on Aditya-L1 mission to study solar flares and their dynamics. Overall science objectives The two X-ray spectrometers covering the energy band from 1 to 150 keV will allow us to carry out the following science objectives: (i) Study of heating mechanisms during the flare2. (ii) Quantitative measure of flare energies by measuring the temperature of the plasma (thermal energy) and also studying the acceleration of particles (non-thermal energy)2. (iii) Coronal abundance during flare evolution3. (iv) Precursor phase activities possibly related to reconnection mechanisms4. (v) Time variation of spectral parameters as well as quasi-periodic oscillations, especially seen in hard X-ray energy5. (vi) Association of flare and Coronal Mass Ejections (CMEs)6. (vii) Prominence eruption and flare trigger7. Figure 2. (Top) Light curve of X1 class flare of 19 January 2005 showing pulsations during the impulsive phase. (Bottom) Temporal variation of low-energy cut-off of the hard X-ray emitting electron distribution and its spectral index. A typical X1 class flare and the spectral parameters of the hard X-ray (HXR) emitting electrons8 have been studied and plotted in Figure 2 as the flare evolves over time. Solar Low Energy X-ray Spectrometer Solar Low Energy X-ray Spectrometer (SoLEXS) will cover the energy band from 1 to 30 keV with a spectral resolution of <4% (i.e. <250 eV at 6 keV). This energy band will help in obtaining the thermal energy of the flares. To cover the large class of flares, from A-to X-class, SoLEXS will carry two identical detectors with different apertures. The large area aperture will cater to small flares (A-to C-class), while the small aperture will observe intense flares (other classes). SoLEXS is configured as two packages, viz. detector package and electronics package (Figure 3). The detector package carries the two detectors and the associated high voltage power supply along with charge sensitive preamplifiers. The electronics package carries the required processing and power electronics to cater to the instrument. SoLEXS will also carry an on-board calibration source for the gain calibration over time to obtain high spectral quality for its data. With its on-board processing, SoLEXS will provide spectra with 1 s cadence during a flare. A flare trigger using the count rate threshold is implemented to operate this instrument in quiet as well as flare mode. This flare trigger is also provided as a hardware line to the SUIT instrument on-board Aditya-L1. Currently, the engineering model of SoLEXS (both the packages) is being integrated to test for its performance9. High Energy L1 Orbiting X-ray Spectrometer High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) is a high-energy X-ray spectrometer (10 to 150 keV) for studying the impulsive phase of solar flares. HEL1OS aims to take advantage of the location of the spacecraft at Sun–Earth L1 in order to obtain uninterrupted observations Figure 3. Solar low energy X-ray spectrometer engineering model. CURRENT SCIENCE, VOL. 113, NO. 4, 25 AUGUST 2017 ASTRONOMY: ADITYA MISSION CURRENT SCIENCE, VOL. 113, NO. 4, 25 AUGUST 2017 627 Figure 4. Engineering model of the HEL1OS payload. of the short-lived impulsive phase of solar flares. This energy band helps identify the non-thermal energy release during the flares. HEL1OS is being developed with two different types of detectors10: CZT and CdTe. The CZT detector is a state-of-the-art, near-room-temperature device. In order to achieve a total geometric area of 32 sq. cm, two such detectors (16 sq. cm per detector) are used to cover the energy range 20 to 150 keV and operate in the temperature range 5.C to 20.C. The individual detectors are pixelated with 256 pixels, with pixel dimension 2.46 mm . 2.46 mm. The CdTe detector, which has better resolution at lower energies, is used for detailed spectroscopic studies from 10 to 40 keV, and operates in the temperature range –35.C to –25.C. The overall geometric area of 0.5 sq. cm will be achieved using two CdTe detectors, each with an area of 0.25 sq. cm. The field-of-view of the instrument has been constrained to 6. . 6. using a stainless steel mesh-type collimator. At present, the engineering model of HEL1OS is under development (Figure 4). All electronics cards (front-end electronics with detectors mounted, processing electronics and power conditioning electronics) are fabricated and populated; electrical testing and performance verification with detectors is underway. Summary Solar flares in X-rays have been studied in detail using the RHESSI mission for the last several years, albeit with low spectral resolution. The X-ray instruments on-board Aditya-L1 will provide a large energy coverage (1 to 150 keV) with a spectral resolution better than of RHESSI providing opportunities to study coronal abundances, break energy shift for different classes of flares, separation of thermal and non-thermal energies, etc. These two instruments will also carry out flare–CME studies in combination with coronagraph and also prominence– flare–CME relations with SUIT and coronagraph. Aditya-L1 being at Sun–Earth L1 point provides us with a unique opportunity to study the flare phenomenon continuously in X-rays without any data gap, like in previous missions. 1. Benz, A. O., Flare observations. Living Rev. Sol. Phys., 2017, 14(2), 1–59. 2. Hannah, I. G. et al., Microflares and the statistics of X-ray flares. Space Sci. Rev., 2011, 159, 263–300. 3. Narendranath, S. et al., Elemental abundances in the solar corona as measured by the X-ray solar monitor onboard Chandrayaan-1. Sol. Phys., 2014, 289, 1585–1595. 4. Joshi, B. et al., Pre-flare activity and magnetic reconnection during the evolutionary stages of energy release in a solar eruptive flare. ApJ, 2011, 743, 195–208. 5. Rao, A. R. et al., RT-2 detection of quasi-periodic pulsations in the 2009 July 5 solar hard X-ray flare. ApJ, 2010, 714, 1142– 1148. 6. Yashiro, S. et al., Spatial relationship between solar flares and coronal mass ejections. ApJ, 2008, 673, 1174–1180. 7. Chifor, C. et al., The early phases of a solar prominence eruption and associated flare: a multi-wavelength analysis. A&A, 2006, 458, 965–973. 8. Warmuth, A. et al., Rapid changes of electron acceleration characteristics at the end of the impulsive phase of an X-class solar flare. ApJ, 2009, 699, 917. 9. SoLEXS Team, SoLEXS PDR document, ISRO-ISACADITYAL1- RR-1343, 2016. 10. HEL1OS Team, HEL1OS PDR document, ISRO-ISAC-ADITYAL1- RR-1342, 2016. doi: 10.18520/cs/v113/i04/625-627 View publication stats