Atul Mohan

• Mohan, Atul; Wedemeyer, Sven; Hauschildt, Peter, H.; Pandit, Sneha & Saberi, Maryam (2022). EMISSA (Exploring Millimeter Indicators of Solar-Stellar Activity) II. Towards a robust indicator of stellar activity. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 664. doi: 10.1051/0004-6361/202244385. Fulltekst i vitenarkiv Vis sammendrag

  Context: An activity indicator, which can provide a robust quantitative mapping between the stellar activity and the physical properties of its atmosphere, is important in exploring the evolution of the observed active phenomena across main-sequence stars of different spectral types. Common activity indicators do provide qualitative correlations with physical properties such as Teff and the rotation period, among others. However, due to the large variability in their values, even for a single star, defining robust quantitative mappings between activity and physical properties is difficult. Millimetre (mm) wavelengths probe the different atmospheric layers within the stellar chromosphere, providing a tomographic view of the atmospheric dynamics. Aims: The project aims to define a robust activity indicator by characterising mm brightness temperature spectra (TB(ν)) of the cool main-sequence stars (Teff ∼ 5000 – 7000 K) compiled by paper I in this series. The sample contains 13 stars, including the Sun. Methods: We derived the mm TB(ν) spectral indices (αmm) for cool stars, including the Sun, based on observations in the 30 – 1000 GHz range. The derived values for αmm are explored as a function of various physical parameters and empirical power-law functions were derived. We also compared αmm estimates with other activity indicators. Results: Despite the estimation errors, αmm values could distinguish the cool stars well, unlike common activity indicators. The low estimation errors on the derived trends of αmm versus physical parameters suggest that αmm could be a robust activity indicator. Conclusions: We note that αmm, which is linked to chromospheric thermal stratification and activity in cool stars, can well distinguish and physically characterise the stars more robustly than common activity indicators. We emphasise the need for multi-frequency data across the mm band for stars, with a range of physical parameters and gathered at multiple epochs during their activity cycles. This will help to explore αmm in a statistically robust manner and to study the emergence of chromospheric heating on the main sequence

• de Jorge Henriques, Vasco Manuel; Jafarzadeh, Shahin; Guevara Gomez, Juan Camilo; Eklund, Henrik; Wedemeyer, Sven & Szydlarski, Mikolaj [Vis alle 8 forfattere av denne artikkelen] (2022). The Solar ALMA Science Archive (SALSA): First release, SALAT, and FITS header standard. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 659. doi: 10.1051/0004-6361/202142291. Fulltekst i vitenarkiv
• Mohan, Atul (2021). Discovery of Correlated Evolution in Solar Noise Storm Source Parameters: Insights on Magnetic Field Dynamics during a Microflare. Astrophysical Journal Letters. ISSN 2041-8205. 909(1). doi: 10.3847/2041-8213/abe70a.
• Mohan, Atul; Wedemeyer, Sven; Pandit, Sneha; Saberi, Maryam & Hauschildt, Peter H. (2021). EMISSA (Exploring Millimeter Indicators of Solar-Stellar Activity): I. The initial millimeter–centimeter main-sequence star sample. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 655. doi: 10.1051/0004-6361/202142095. Fulltekst i vitenarkiv
• Mohan, Atul (2021). Characterising coronal turbulence using snapshot imaging of radio bursts in 80–200 MHz. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 655. doi: 10.1051/0004-6361/202142029. Fulltekst i vitenarkiv
• Mondal, Surajit; Oberoi, Divya & Mohan, Atul (2020). First Radio Evidence for Impulsive Heating Contribution to the Quiet Solar Corona. Astrophysical Journal Letters. ISSN 2041-8205. 895(2). doi: 10.3847/2041-8213/ab8817.

Se alle arbeider i Cristin

• Mohan, Atul (2022). Stellar atmospheric tomography with mm - cm spectroscopic imaging.
• Mohan, Atul; Wedemeyer, Sven; Pandit, Sneha; Saberi, Maryam & Hauschildt, Peter, H. (2022). A potential robust millimeter activity index & its links to atmospheric structure and physical parameters.
• Mohan, Atul (2022). Tomographic exploration of solar/stellar activity with modern radio & mm arrays.
• Pandit, Sneha; Wedemeyer, Sven & Mohan, Atul (2022). The Formation of Activity Indicators in 3D Model Atmosphere.
• Pandit, Sneha; Wedemeyer, Sven & Mohan, Atul (2022). Formation of Activity Indicators in a 3D model Atmosphere.
• Mohan, Atul (2022). Characterising coronal turbulence using snapshot imaging of radio bursts in 80 - 200 MHz.
• Mohan, Atul; Wedemeyer, Sven; Pandit, Sneha; Saberi, Maryam & Hauschildt, Peter, H. (2021). New insights on solar/stellar activity using the tomographic potential of mm & radio spectroscopic imaging.
• Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Henriques, Vasco; Guevara Gomez, Juan Camilo & Eklund, Henrik [Vis alle 10 forfattere av denne artikkelen] (2021). Lessons learned from 5 years of solar observing with ALMA.
• Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Henriques, Vasco; Eklund, Henrik & Guevara Gomez, Juan Camilo [Vis alle 11 forfattere av denne artikkelen] (2021). A brief introduction to solar observing with ALMA .
• Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Henriques, Vasco; Eklund, Henrik & Guevara Gomez, Juan Camilo [Vis alle 10 forfattere av denne artikkelen] (2021). Five years observing the solar chromosphere with ALMA - First results and future opportunities.
• Mohan, Atul (2021). Discovery of correlated evolution in radio burst source paramters: Properties and links to local magnetic field evolution during a microflare.
• Mohan, Atul (2021). Discovery of correlated evolution in noise storm source parameters: Insights on magnetic field dynamics during a microflare .
• Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; de Jorge Henriques, Vasco Manuel; Eklund, Henrik & Guevara Gomez, Juan Camilo [Vis alle 10 forfattere av denne artikkelen] (2021). Observing the Sun with ALMA - First results and future opportunities.
• Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; de Jorge Henriques, Vasco Manuel; Eklund, Henrik & Guevara Gomez, Juan Camilo [Vis alle 10 forfattere av denne artikkelen] (2021). Five years observing the solar chromosphere with ALMA - First results and future opportunities.
• Mohan, Atul; McCauley, Patrick; Oberoi, Divya & Mastrano, Alpha (2021). Quasi-periodic particle acceleration episodes during a microflare.
• Mohan, Atul; McCauley, Patrick; Oberoi, Divya; Mondal, Surajit & Mastrano, Alpha (2020). New insights on weak coronal events from HDR snapshot spectroscopic imaging at meter-wavebands.

Se alle arbeider i Cristin