• G. Yellaiah

      Articles written in Journal of Astrophysics and Astronomy

    • Lowering of Asymmetry

      K. K. Pandey K. M. Hiremath G. Yellaiah

      More Details Abstract Fulltext PDF

      Asymmetry, a well established fact, can be extracted from various solar atmospheric activity indices. Although asymmetry is being localized within short time scale, it also persists at different time scales. In the present study we examine the character and nature of asymmetry at various time scales by optimizing the data set, in units of Carrington Rotations (CRs), for Sunspot Area (SA) and soft X-ray flare index (FISXR). We find from three solar cycles (21-23) that at a small time scale (viz., daily, CRs and monthly) activity appears to be asymmetric with less significance. At larger time scales (≥01 CRs) strength of asymmetry enhances. Number of significant asymmetry points probably depends upon the solar heights. For different combination of data, asymmetry strength appears to be lowered at certain periods ∼06, ∼12, ∼18 CRs (164, 327 and 492 days i.e., harmonics of ∼1.3 years. Owing to similar behavior of emergence of magnetic flux, it is conjectured that emergence of flux on the surface probably contributes to the asymmetry of the solar activity.

    • Prediction of meteoroid stream structure based on meteoroid fragmentation


      More Details Abstract Fulltext PDF

      Every day, large number of meteoroids enter the Earth’s atmosphere and deposit their mass either in atomic form or in ionic form depending on whether it has undergone ablation or fragmentation. The heavier meteoroids undergo fragmentation while the lighter ones are more prone to ablate. In this paper, wewould like to speculate meteoroid stream structure of Leonid meteor shower based on fragmenting meteoroids. A 23 revolutions old meteoroid trail left behind by the comet 55P/Tempel-Tuttle in the year 1213 AD, which instigated Leonid meteor shower in the year 2010 is considered for our study. We have calculatedmass of the meteoroids, echo durations and percentage of fragmentation. From the observed echo durations of meteoroids, estimated masses and from the percentage of fragmentation, we visualize the stream structure to be like the lighter particles wrapping up the heavier ones. The results we draw from these three different studies are matching with each other. To our knowledge, we are the first to speculate on the meteor stream structure based on fragmentation and making it a new tool in meteor stream evolution. Based on echo durations, it has been observed that 72% of the activity during the shower is contributed by lighter particles of the stream. It is found that about 20% of the meteoroids have undergone fragmentation indicating the minimal role of heavier particles (>10$^{-6}$ g) during Leonid Meteor Shower (LMS). The masses of the meteors are estimated to be in the range of 10$^{-10}$–10$^{-5}$ g.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2022-2023 Indian Academy of Sciences, Bengaluru.