Aditya-L1 and further Indian missions to the Sun

[Indx TechStyle]

Dedicating the thread India's upcoming probes for studying the Sun, here, we do start with Aditya L-1.

 

[Indx TechStyle]

From ISRO:
Aditya - L1 First Indian mission to study the Sun

The Aditya-1 mission was conceived as a 400kg class satellite carrying one payload, the Visible Emission Line Coronagraph (VELC) and was planned to launch in a 800 km low earth orbit. A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/ eclipses. Therefore, the Aditya-1 mission has now been revised to “Aditya-L1 mission” and will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth. The satellite carries additional six payloads with enhanced science scope and objectives.

Image credit: Udaipur Solar Observatory – PRL (Ground-based)

The project is approved and the satellite will be launched during 2019 – 2020 timeframe by PSLV-XL from Sriharikota.

Aditya-1 was meant to observe only the solar corona. The outer layers of the Sun, extending to thousands of km above the disc (photosphere) is termed as the corona. It has a temperature of more than a million degree Kelvin which is much higher than the solar disc temperature of around 6000K. How the corona gets heated to such high temperatures is still an unanswered question in solar physics.

Aditya-L1 with additional experiments can now provide observations of Sun's Photosphere (soft and hard X-ray), Chromosphere (UV) and corona (Visible and NIR). In addition, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit, and the magnetometer payload will measure the variation in magnetic field strength at the halo orbit around L1. These payloads have to be placed outside the interference from the Earth’s magnetic field and could not have been useful in the low earth orbit.

The main payload continues to be the coronagraph with improved capabilities. The main optics for this experiment remains the same. The complete list of payloads, their science objective and lead institute for developing the payload is provided below:

• Visible Emission Line Coronagraph (VELC): To study the diagnostic parameters of solar corona and dynamics and origin of Coronal Mass Ejections (3 visible and 1 Infra-Red channels); magnetic field measurement of solar corona down to tens of Gauss – Indian Institute of Astrophysics (IIA)

• Solar Ultraviolet Imaging Telescope (SUIT): To image the spatially resolved Solar Photosphere and Chromosphere in near Ultraviolet (200-400 nm) and measure solar irradiance variations - Inter-University Centre for Astronomy & Astrophysics (IUCAA)

• Aditya Solar wind Particle Experiment (ASPEX) : To study the variation of solar wind properties as well as its distribution and spectral characteristics – Physical Research Laboratory (PRL)

• Plasma Analyser Package for Aditya (PAPA) : To understand the composition of solar wind and its energy distribution –Space Physics Laboratory (SPL),VSSC

• Solar Low Energy X-ray Spectrometer (SoLEXS) : To monitor the X-ray flares for studying the heating mechanism of the solar corona – ISRO Satellite Centre (ISAC)

• High Energy L1 Orbiting X-ray Spectrometer (HEL1OS): To observe the dynamic events in the solar corona and provide an estimate of the energy used to accelerate the particles during the eruptive events - ISRO Satellite Centre (ISAC)and Udaipur Solar Observatory (USO), PRL

• Magnetometer: To measure the magnitude and nature of the Interplanetary Magnetic Field –Laboratory for Electro-optic Systems (LEOS) and ISAC.

With the inclusion of multiple payloads, this project also provides an opportunity to solar scientists from multiple institutions within the country to participate in space based instrumentation and observations. Thus the enhanced Aditya-L1 project will enable a comprehensive understanding of the dynamical processes of the sun and address some of the outstanding problems in solar physics.

 

[Indx TechStyle]

Experimental Budget for FY-2016-17 was Rs. 3 crores.
http://defenceforumindia.com/forum/threads/isro-news-and-updates.33401/page-97#post-1202662
ISRO will be third space agency after NASA and ESA to place any probe at Lagrangian Point-1 if succeeds.

 

[Indx TechStyle]

From Wikipedia:

Aditya (Sanskrit: आदित्य, lit: Sun,[3] pronunciation ) or Aditya-L1 is aspacecraft whose mission is to study the Sun. It was conceptualised by theAdvisory Committee for Space Researchin January 2008.[2] It has been designed[4] and will be built in collaboration between Indian Space Research Organisation (ISRO)[2] and various Indian research organizations and will be launched by ISRO around 2019-2020.[5] This will be the first Indian space mission to study the Sun, and also the first Indian mission to be placed at Lagrangian point L1[6] -- far away from the Earth from where continuous solar observations are possible. Only NASA and ESA have successfully placed satellites at the L1 point as of date. An experimental budget of 3 Crore INR has been allocated it for the financial year 2016-17.[7]

Overview:

Aditya-1 is a solar mission. It was initially envisaged as a small, Low-Earth Orbiting Satellite with a coronagraph to study the million-degree solar outer atmosphere known as the solar corona. Subsequently, the scope of the mission has been enhanced and it is now planned to be a comprehensive solar and space environment observatory to be placed at the Lagrangian point L1. This enhanced mission named Aditya-L1 has recently been approved by the Government of India.

A Satellite placed in the halo orbit around the Lagrangian point L1 of the Sun-Earth system has the major advantage of continuously viewing the Sun without any occultation/ eclipses. The Aditya-L1 mission will be inserted in a halo orbit around the L1, which is 1.5 million km from the Earth. The satellite carries a total of seven payloads with diverse objectives, including but not limited to, the coronal heating problem, solar wind acceleration, coronal magnetometry, origin and monitoring of near-UV solar radiation (which drives Earth's upper atmospheric dynamics and global climate), coupling of the solar photosphere to chromosphere and corona, in-situ characterizations of the space environment around Earth by measuring energetic particle fluxes and magnetic fields of the solar wind and solar magnetic storms that have adverse effects on space and ground-based technologies.

The outer layers of the Sun, extending to thousands of km above the disc (photosphere) is termed as the corona. It has a temperature of more than a million degree Kelvin which is much higher than the solar disc temperature of around 6000K. How the corona gets heated to such high temperatures is still an unanswered question in solar physics with far reaching implications for the heating of stellar atmospheres and magnetic reconnection or wave induced plasma phenomena across the Universe. Aditya-L1 with additional experiments can now provide observations of Sun's Photosphere, Chromosphere and corona. In addition, particle payloads will study the particle flux emanating from the Sun and reaching the L1 orbit, and the magnetometer payload will measure the variation in magnetic field strength at the halo orbit around L1. These payloads have to be placed at a location with minimal influence from the Earth’s magnetic field which could not have been achieved at the low earth orbit.

30 characters rule.

 

[Indx TechStyle]

http://defenceforumindia.com/forum/threads/isro-news-and-updates.33401/page-116#post-1233223

Kumar added that ISRO would soon launch Aditya-L1, a scientific mission for solar studies. "The major objective is to study solar corona and achieve fundamental understanding of physical processes that heat the corona, accelerate solar wind and produce coronal mass ejection (CMEs)."

Aditya-L1 would be put into halo orbit which is 1.5 million km from the Earth. It would carry additional six payloads with enhanced science scope and objectives. Scheduled to be launched in 2019-20 from the Satish Dhawan Space Centre in Sriharikota, the spacecraft "aims to answer fundamental questions in solar physics by studying dynamic processes on the Sun".

• Aditya-L1 to be launched for solar studies
• To study solar corona and understand processes that heat the corona, accelerate solar wind and produce coronal mass ejection
• To be put into halo orbit, is 1.5 million km from the Earth
• To carry additional 6 payloads with enhanced science scope and objectives
• Scheduled to be launched in 2019-20

 

[Indx TechStyle]

Aditya-L1 Mission
Plasma Analyser Package for Aditya (PAPA)

Plasma Analyser Package for Aditya (PAPA) payload for the Aditya-L1 mission aims at studying the composition of solar wind and its energy distribution continuously throughout the mission’s life time. PAPA contains two sensors: Solar Wind Electron Energy Probe (SWEEP) to measure the solar wind electron flux and Solar Wind Ion Composition AnalyseR (SWICAR) to measure the ion flux and composition as a function of direction and energy. Data from PAPA would provide detailed knowledge of the solar wind condition with high time resolution.

Name of the payload is PAPA! LOL :biggrin2:
Hoping that it's proved to be "Papa" of capabilities of many space agencies as well.

 

[Chinmoy]

Aditya-L1 Mission
Plasma Analyser Package for Aditya (PAPA)

Name of the payload is PAPA! LOL :biggrin2:
Hoping that it's proved to be "Papa" of capabilities of many space agencies as well.

I told you earlier. Atleast change your name to "TO BE PAPA" now...............

 

[Indx TechStyle]

Aditya - L1 Mission

The original Aditya - L1 mission was conceived as a small satellite in a ~800km orbit carrying one payload to study solar corona. The mission has been enhanced and termed as Aditya-L1 mission carrying seven payloads, which was approved in 2015. It is scheduled for launch during 2020 timeframe by PSLV-XL.

Aditya-L1 can provide observations on the corona and in addition can provide observations on the solar chromosphere using an UV payload and on the photosphere and flares using X-ray payloads. These payloads taken together are expected to provide a comprehensive understanding of how solar flares originate and propagate. In addition, the charged particle detectors and the magnetometer payloads can provide information on charged particles and the magnetic field which emanate from the eruptive events. To enable this, the Aditya L1 spacecraft is to be placed in a halo orbit around the Sun-Earth Lagrangian point 1 (L1) which is about 1.5 million km from the Earth.

Baseline Design Review (BDR) for all the mechanisms is completed. MoUs were signed with IIA and IUCAA for the development of Visible Emission Line Coronagraph (VELC) and Solar Ultraviolet Imaging Telescope (SUIT) payloads. Design and development of all the payloads are in progress. The Preliminary Design Review (PDR) is expected to be completed by December 2016.

Source: ISRO's Annual Report 2016-17

 

[Indx TechStyle]

https://www.devdiscourse.com/Articl...econd-lunar-exploration-mission-chandrayaan-2

PRL is also developing instruments for 'Aditya-L1 mission', which is aimed at studying the Sun through a satellite placed in the halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system, said Bharadwaj. An instrument for the measurement of charged particles has also been developed, he said.

"With this instrument, we will be able to study solar winds, charged particles and its energy range," said Bhardwaj. As per ISRO (Indian Space Research Organisation) the website, the satellite will be inserted in a halo orbit around the L1, which is 1.5 million kms from the earth.

The project is approved and the satellite will be launched during 2019 2020 time frame by PSLV-XL from Sriharikota.

Aditya L1, L3 & L5.
3 probes for 3 langrangian points.

 

[Indx TechStyle]

India's first solar mission in 2020: ISRO chairman

Kanyakumari: India’s first mission to study the sun, Aditya-L1, will be launched in the first half of next year, chairman of Indian Space Research Organisation (Isro) K Sivan told reporters at Sarakkalvilai in Kanyakumari district on Friday.

“There are still a lot of things that are to be learnt about the sun,” Sivan said. According to Isro, Aditya-L1 mission is expected to be inserted in a halo orbit around the Lagrangian point 1 (L1) – which is 1.5 million km from the earth – so that there is a major advantage of continuously viewing the sun without any occultation/ eclipses. Aditya-L1 was meant to observe only the solar corona.

When asked about Isro’s contribution at the time of Fani, Sivan said that satellite images helped in the accurate prediction of the cyclone. “It helped in more efficient evacuation and potentially reduce the loss of life as much as possible,” he added.

The Isro chairman also stated that the whole world was eagerly waiting to see Chandrayaan 2 land at the predetermined site close to the south pole, which had not been explored by anyone before. He added that so far only Rovers used to land in the equator region. Chandrayaan 2 is set to be launched between July 9 and 16 and the expected moon landing is on September 6. Sivan added that the design phase for India's human spaceflight mission, Gaganyaan has been completed and is set to be launched before 2022.

Sivan also spoke about Isro’s programme Yuvika 2019 through which school students would be taken to Isro for a two-week stint and how it will benefit them. “We’re planning to conduct it every year,” he said.

Sivan said that Isro has also so far given Tamil Nadu a total of 250 NavIC devices that provides information about weather and real-time updates for fishermen.

 

[Indx TechStyle]

The next two deep space missions immediately after the lunar probe would be Aditya-L1 for studying the Sun and Xposat (X-ray Polarisation Satellite) that would seek to throw new light on mysterious celestial bodies like Black Hole and Neutron Stars.

Aditya-L1 too would be a path-breaking mission in which a 400 kg class satellite carrying the payload will be placed in an orbit around the Sun in such a way so that it can continuously view the star without any occultation or eclipses during which the Sun is hidden by other planetary bodies. The orbit would be located 1.5 million km away from the Earth.

The solar mission will seek to enhance the current understanding of the Solar Corona besides provide vital data for space weather studies.

https://www.deccanherald.com/amp/na...to-study-solar-system-black-holes-748212.html

 

[Indx TechStyle]

Mission postponed to late 2020 or early 2021.
https://www.deccanherald.com/opinio...-astro-is-investing-in-technology-794295.html

Regards

 

[sorcerer]

Isro to attempt solar mission by end of 2021

Isro to attempt solar mission by end of 2021

The scientific mission will see the satellite travel 1.5 million kilometres from the Earth to study the Sun’s atmosphere.

www.hindustantimes.com

 

[sorcerer]

Novel technique for tracking solar eruptions that disrupt space weather to be used in India’s first solar mission


Scientists have developed a new technique to track the huge bubbles of gas threaded with magnetic field lines that are ejected from the Sun, disrupting space weather and causing geomagnetic storms, satellite failures, and power outages.


As the ejections from the Sun, technically called Coronal Mass Ejections (CMEs), cause various disturbances of the space environment, forecasting their arrival time is very important. However, forecasting accuracy is hindered by limited CME observations in interplanetary space.


Software named Computer Aided CME Tracking Software (CACTus) based on a computer vision algorithm was so far used to detect and characterise such eruptions automatically in the outer corona where these eruptions cease to show accelerations and propagate with a nearly constant speed.


However, this algorithm could not be applied to the inner corona observations due to the vast acceleration experienced by these eruptions. This severely limited the capability to track the eruptions as CMEs accelerate in the lower corona. Moreover, with the advancement in space technology, there has been a tremendous increase in the amount of data obtained from spacecraft. To identify and track the solar eruptions in huge number of images can become tedious if done manually.


Research led by Mr. Ritesh Patel, Dr. Vaibhav Pant, and Prof. Dipankar Banerjee from Aryabhatta Research Institute of observational sciences (ARIES), Nainital, an autonomous institute under DST, Government of India, along with their collaborators from Royal Observatory of Belgium, have led to the development of an algorithm, CMEs Identification in Inner Solar Corona (CIISCO) to detect and track the accelerating solar eruption in the lower corona. CIISCO has been successfully tested on several eruptions observed by space observatories, including Solar Dynamics Observatory and Solar-Terrestrial Relations Observatory, PROBA2/SWAP launched by NASA and ESA, respectively. The research was published in the Solar Physics journal.

(a) (b) (c)





Figure 1: (a) Solar corona observed in EUV image of SWAP instrument. An erupting structure at the west limb is pointed at by the red arrow, (b) height-time plot corresponding to the eruption. A parabolic profile could be observed, (c) Identified parabolic profile by CIISCO overplotted on (b) by dashed line.





The parameters determined by CIISCO are useful to characterise these eruption in the lower corona, a region where the properties of such eruptions are less known. An implementation of CIISCO on the large volume of data available from space observatories mentioned above will be helpful to improve our understanding of eruptions in the inner corona. As India’s first solar mission, Aditya-L1, will be observing this region of the solar corona, implementation of CIISCO on the Aditya-L1 data will provide new insight into the CME properties in this less explored region.





Link to Publication:

Automated Detection of Accelerating Solar Eruptions Using Parabolic Hough Transform - Solar Physics

Solar eruptions such as coronal mass ejections (CMEs) observed in the inner solar corona (up to 4 R⊙) show acceleration profiles that appear as parabolic ridges in height–time plots. Inspired by the white-light automated detection algorithms Computer Aided CME Tracking System (CACTus) and Solar...

link.springer.com

https://arxiv.org/abs/2010.14786

 

[Indx TechStyle]

The Isro chief also told TOI that launches of Chandrayaan-3 and Aditya L1 solar missions will happen in the first half of next year as these "missions have a limited and specific launch window within which we have to launch them".

Launch of India's new-age earth imaging satellite by May 15: K Sivan | India News - Times of India

India News: NEW DELHI: The launch of the country’s most advanced earth observation satellite Gisat-1, which will allow India to better monitor the subcontinent, i.

m.timesofindia.com

 

[Indx TechStyle]

Jun 22, 2021
Unraveling the mysteries of the Solar Corona: New results from Chandrayaan-2 Solar X-ray Monitor

Our Sun, being the primary source of energy for our solar system has a significant influence on our lives, and has always instilled a curiosity in humankind.. Though we have a fairly good understanding of the origin of energy and other various aspects of the Sun, several potentially life-changing phenomena still remain a mystery. Being the nearest star, understanding the Sun also allows us to learn about other distant stars better.

Some of these mysteries are related to the hot outer atmosphere of the Sun, known as ‘corona’, which emits profusely in ultra-violet and X-ray wavelengths of the electromagnetic spectrum. We know that the corona consists of ionized gas at temperatures exceeding one million Kelvin, which is much higher than photospheric temperature of 6000 K, the visible surface temperature of the Sun. However, this observation is against the natural expectation that the temperatures should reduce as we go away from the source of energy, and this is known as the ‘coronal heating problem’. From observations, such as the presence of even hotter corona, called active regions above the Sunspots (dark patches seen in visible images of the Sun) where the magnetic fields are known to be stronger, it is suggested that the magnetic fields have an important role in the coronal heating. While there are different theories regarding the actual mechanism, one of these relies on the occurrence of a large number of small solar flares called ‘nanoflares’. Another puzzling observation about the corona is that certain elements are found to have abundances three to four times higher in active regions than in the photosphere. This happens for elements which are easier to ionize, or require lesser energy to ionize. In more technical terms, these elements have their First Ionization Potential (FIP) lower than 10 eV, and hence this phenomenon is generally termed as ‘FIP bias’. The exact reason behind the FIP bias and its origin remains an open question.

A team of scientists from the Physical Research Laboratory (PRL), Ahmedabad, used observations of the Sun in soft X-rays with Solar X-ray Monitor (XSM) onboard ISRO's Chandrayaan-2 mission during the deepest solar minimum of the past hundred years to learn exciting details about the solar corona. For the first time, absolute abundances of elemental Mg, Al, Si in the quiet solar corona are derived. The team discovered and characterized around 100 “sub-A class” microflares in the quiet corona providing new insight into coronal heating puzzle.

The XSM, designed and developed by PRL with support from various ISRO centres, provides measurement of soft X-ray (1-15 keV) spectrum of the Sun. The XSM also supports the quantitative measurements of elemental abundances of the lunar surface using the companion payload CLASS (Chandrayaan-2 Large Area Soft X-ray Spectrometer) developed by URSC, Bangalore, which measures the X-ray fluorescence spectrum from the lunar surface. At present, XSM is the only instrument that provides soft X-ray spectral measurements of the Sun, i.e., measures the intensity of X-ray in different energies over the 1 to 15 keV. More importantly, XSM provides such measurements with very good energy resolution at every second, the highest cadence for any instrument so far.

XSM started observations of the Sun in September 2019, during the period of solar minimum when typically there were very few Sunspots and active regions on the Sun. The solar minimum of 2019-2020 was even more peculiar as the Sun was extremely quiet, and its activity was at the lowest level over the past century. This provided a unique opportunity for XSM to observe the quiet corona without active regions for long periods. The solar X-ray flux as observed by the XSM during this period is shown in the figure. Intervals highlighted with blue color correspond to a period of 76 days when no active regions were present on the solar disk, and XSM was observing the quiet corona.

A remarkable and surprising observation is the detection of a large number (98) of extremely small flares in the quiet corona (see Figure below). These flares are so small that their intensity is well below the standard scale to classify solar flares (i.e. A, B, C, M, and X class flares, where each class is 10 times more intense than previous), and hence these are termed as “sub-A class microflares”. Using the X-ray spectra of these microflares obtained with the XSM and contemporary images in Extreme Ultra-violet obtained with the Atmospheric Imaging Assembly (AIA) of NASA's Solar Dynamics Observatory (SDO), the energy content of these flares could be estimated. This was the first observation and statistical study of such a large sample of microflares in the quiet Sun, supporting the hypothesis of the presence of even smaller scale flares everywhere on the solar corona that could be responsible for the coronal heating.
The X-ray emission over these 76 days, excluding the durations of the microflares, is unusually constant. This is the lowest intensity of X-ray emission observed from the Sun since space-borne observations began. Analysis of the XSM spectra of the quiet Sun, excluding the microflares, provided the measurement of abundances of various elements. The abundances of the low FIP elements Mg, Al, and Si were estimated and found to be lower than the abundances seen in active region corona but higher than that in the photosphere. This is the first report of measurement of abundances as well as reduced FIP bias in the quiet Sun. Our observations of FIP bias in the quiet Sun provides significant inputs towards understanding the FIP bias and suggests that it arises due to the presence of Alfvén waves in the closed magnetic loops.
These outstanding science results on the solar corona and heliophysics obtained during a unique solar extremely quiet period using a sensitive instrument XSM aboard Chandryayaan-2 observations are published in two companion papers in the May issue of the Astrophysical Journal Letters.

Both the Chandrayaan-2 orbiter and the XSM instrument are performing extremely well, and expected to provide many more exciting and new results.

Figure : Panels (a) and (b) show the X-ray flux in the 1–15 keV energy range with a time cadence of 120 seconds, as measured by the XSM during two observing seasons. Different background shades represent activity levels on the Sun, with orange representing periods when active regions are present; pink representing periods of enhanced activity visible in both the XSM light curve as well as EUV/X-ray images but not classified as Active Regions; and blue representing periods selected for the present study when no major activity was observed on the Sun. The micro flares detected during the quiet periods are marked with red points, representing their peaks; and red vertical bars, representing their time.
Publications:

1. "Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Elemental Abundances in the Quiescent Corona”

Vadawale, Santosh V.; Mondal, Biswajit; Mithun, N. P. S.; Sarkar, Aveek; Janardhan, P.; Joshi, Bhuwan; Bhardwaj, Anil; Shanmugam, M.; Patel, Arpit R.; Adalja, Hitesh Kumar L.; Goyal, Shiv Kumar; Ladiya, Tinkal; Tiwari, Neeraj Kumar; Singh, Nishant; Kumar, Sushil,
Astrophysical Journal Letters, Vol. 912, Id. L12 (7pp), 2021, https://doi.org/10.3847/2041-8213/abf35d

1. "Observations of the Quiet Sun During the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Sub-A Class Microflares Outside Active Regions”

Vadawale, Santosh V.; Mithun, N. P. S.; Mondal, Biswajit; Sarkar, Aveek; Janardhan, P.; Joshi, Bhuwan; Bhardwaj, Anil; Shanmugam, M.; Patel, Arpit R.; Adalja, Hitesh Kumar L.; Goyal, Shiv Kumar; Ladiya, Tinkal; Tiwari, Neeraj Kumar; Singh, Nishant; Kumar, Sushil, Astrophysical Journal Letters, Vol. 912, Id. L13(11pp), 2021, https://doi.org/10.3847/2041-8213/abf0b0

 

[sorcerer]

‘India’s first solar mission likely to launch next year’: ISRO


3-4 minutes


India’s first solar mission, which was pushed from early 2020 due to the Covid-19 pandemic, is likely to be launched in the third quarter of 2022, when the country’s second space observatory Xposat, aimed at helping astronomers study cosmic sources such as pulsars and supernova, will also be launched, senior officials from the Indian Space Research Organisation (ISRO) said.

‘India’s first solar mission likely to launch next year’: ISRO

The solar mission, Aditya L1, will provide more insights into the origin of the universe and many other unknowns.

www.hindustantimes.com

 

[Indx TechStyle]

Spoiler

 

[Varoon2]

A discovery revealed from Mangalyaan , which is still going strong 7 years and 5 months after launch

Indian Mars Orbiter Mission (MOM) used for Investigating the Solar Corona by ISRO Scientists - ISRO

Utilizing the solar conjunction event, when the Earth and Mars are on the opposite sides of the Sun, a team of scientists from Space Physics Laboratory of Vikram Sarabhai Space Centre, Trivandrum; Physical Research Laboratory, Ahmedabad; and ISRO Telemetry Tracking and Command Network (ISTRAC)...

www.isro.gov.in

 

[Indx TechStyle]

Copied content from above link in case link expires.
Feb 28, 2022
Indian Mars Orbiter Mission (MOM) used for Investigating the Solar Corona by ISRO Scientists
Utilizing the solar conjunction event, when the Earth and Mars are on the opposite sides of the Sun, a team of scientists from Space Physics Laboratory of Vikram Sarabhai Space Centre, Trivandrum; Physical Research Laboratory, Ahmedabad; and ISRO Telemetry Tracking and Command Network (ISTRAC), Bangalore; used S-band radio signals coming from the Indian Mars Orbiter Mission (MOM) to study the Solar Corona. During conjunction events, which usually happens once in approximately two years for Mars, the radio signals from MOM passes through the solar corona, as close as 10 solar radii (1 solar radii (Rʘ) = 696,340 km = about 100 Earth radii), from the center of the Sun, thus providing a unique opportunity to study solar dynamics. ISRO scientists used the conjunction event of May-June 2015 – a time when the Sun's activity was quite low, to study the turbulence in the solar corona and found that transition of solar wind from sub-alfvenic to super-alfvenic flow occurs around 10–15 Rʘ during low solar activity period.
The outer atmosphere of the Sun, called the solar corona, is the region where the temperature is several million degrees Kelvin, rendering it quite inaccessible for in-situ measurements thereby challenging the experimenters. The reason for such a high temperature of the corona is still an enigma. The solar wind, which originates in the corona and accelerates in this region, passes through the interplanetary spaces, shapes the magnetosphere of planets, as well as affects the near-Earth space environment through a phenomenon known as "Space Weather".
Since the solar corona is an ionized medium (plasma) and has its intrinsic turbulence, it is a dispersive medium for an electromagnetic radio wave passing through it. The radio signals from MOM spacecraft crossing through the solar corona during the conjunction event (cf. Figure 1) consequently experience dispersive effects. The turbulence in the corona produces fluctuations in plasma density which get registered as fluctuations in the phase of radio waves passing through it. Thus, the radio signals received at the ground station (Indian Deep Space Network, ISTRAC for MOM) contain the signature of propagating medium (solar corona) and can be spectrally analyzed to derive the turbulence spectrum of the medium. This forms the basis of the coronal radio-sounding technique which has been used by spacecraft to study coronal regions spanning maximum and minimum phases of different solar cycles.

ISRO scientists obtained coronal turbulence spectrum at heliocentric distances between 4 and 20 Rʘ by spectrally analyzing the Doppler frequency residuals from radio signals received from MOM spacecraft. This is the region where the solar wind primarily gets accelerated to velocities of a few hundreds of kilometers per second. The changes in turbulence regime are well reflected in spectral index values of the temporal frequency fluctuation spectrum. The scientists found that the turbulence power spectrum at a lower heliocentric distance (<10 Rʘ) has flattened at shorter frequencies with a smaller spectral index, which corresponds to the solar wind acceleration region. Smaller spectral index values closer to the Sun’s surface signify the energy input regime where turbulence is still underdeveloped. For larger heliocentric distances (> 10 Rʘ), the curve steepens with a spectral index close to 2/3, which is indicative of the inertial regime of a developed Kolmogorov-type turbulence, where energy is transported through cascading. This finding is consistent with those of theoretical models of solar wind turbulence and substantiates the process of turbulence energy transport and dissipation of magnetohydrodynamic waves, leading to coronal heating and solar wind acceleration in the near-Sun region.

Incidentally, this finding of ISRO scientists is also supported by the first direct observation of solar corona by Parker Probe, published very recently in an independent study.

Another intriguing observation is when the results of studies by MOM are compared with similar experiments conducted by the earlier missions which spanned past solar cycles. The work based on MOM data reports an insight into the feeble maxima of solar cycle 24, which is recorded as a peculiar solar cycle in terms of overall lower activity than any other previous solar cycle.

These outstanding science results on the solar coronal dynamics using MOM in an innovative way is published in the refereed journal Monthly Notices of the Royal Astronomical Society, titled "A study on the solar coronal dynamics during the post-maxima phase of the solar cycle 24 using S-band radio signals from the Indian Mars Orbiter Mission", authored by Richa N. Jain,R. K. Choudhary, Anil Bhardwaj, Umang Parikh, Bijoy K. Dai, and Roopa M. V.

Monthly Notices of the Royal Astronomical Society, DOI: 10.1093/mnras/stac056

https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/stac056/6506470

PS: - India’s first mission to Mars, the MOM, was launched on 5 November 2013, and arrived at Mars on 24 September 2014. The MOM was planned for a mission lifetime of 6 months, but has successfully surpassed it by a factor of 10 – now in Martian orbit for more than 7 years, and is doing well in the extended mission phase. The MOM has provided the first measurements of the evening time exosphere of Mars (1) and has discovered hot Argon in its upper atmosphere-exosphere by the MENCA experiment onboard MOM (2).

(1) MENCA observed the evening exosphere of Mars

(2) Observation of Suprathermal Argon in Mars Exosphere



Figure 1. Schematic of positions of Earth and MOM spacecraft relative to the Ecliptic plane of Sun (XY plane) as seen from Earth. Radio signals sent by spacecraft (dashed line) pass closer to the solar coronal region during this period.