Possibility of continuous monitoring of celestial X-ray sources through their ionization effects in the nocturnal D-region ionosphere

Sharma, Devendra; Jain, Abhay; Chakravarty, S. C.; Kasturirangan, K.; Ramanathan, K. R.; Rao, U. R.

doi:10.1007/bf00642911

Cited by 11 publications

(3 citation statements)

References 39 publications

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“…The ionosphere of the earth is a gigantic detector and it characteristically responds to the ionizing agents of terrestrial and extra-terrestrial origin. In particular, it is long known that the hard and soft X-rays originating from solar flares (Mitra 1974;Pant 1993) and strong compact celestial sources like X-ray novae, galactic centre do perturb the lower ionospheric D-region (Sharma et al 1972;Kasturirangan et al 1976). The excess EUV and X-ray radiations produced during the solar flares cause excess ionization (Basak et al 2010;Garcia-Rigo et al 2007;.…”

Section: Introductionmentioning

confidence: 99%

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

Basak

Chakrabarti

2013

Astrophys Space Sci

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delay is anti-correlated with the flare peak energy flux φ max independent of these time slots, the goodness of fit, as measured by reduced-χ 2 , actually worsens as the day progresses. The variation of the Z dependence of reduced-χ 2 seems to follow the variation of standard deviation of Z along the T x -R x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between △t and φ max was observed.

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Section: Introductionmentioning

confidence: 99%

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

Basak

Chakrabarti

2013

Astrophys Space Sci

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“…One is the effect of interstellar ionization by Sco X-1 (Silk etal., 1972;Johnson, 1976 and his references) and another is the effect on upper atmosphere or lower ionosphere by X-rays from Sco X-1 (Ananthakrishnan and Ramanathan, 1969;Sharma et al, 1972). It is interesting to investigate these problems to understand the effect by strong X-rays and to apply the knowledge of X-rays of Sco X-1 to other fields.…”

Section: Resultsmentioning

confidence: 96%

Sco X-1

Miyamoto

Matsuoka

1977

Space Sci Rev

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Abstract. The physical properties of X-ray, optical and radio emissions from Sco X-1 are reviewed. Sco X-I is a typical X-ray source which has an optically thick hot plasma. The observational spectra of X-ray and optical emissions are consistent with theoretical ones from the hot plasma, but the radio emission shows a non-thermal feature. The restrictive conditions for the model of Sco X-1 are discussed from the observational facts. In spite ot numerous observational facts on Sco X-1 further detailed and elaborate studies are necessary to understand this object and general compact X-ray sources comprehensively.Contents:

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“…Astronomical ionizing radiation (X-rays and g-rays), for example from solar flares, has been thought to be important only insofar as it affects phenomena associated with the ionosphere. Previous models and observations for estimating the ionization profiles (Sharma et al 1972, Brown 1973, Kasturirangan et al 1976, O'Mongain and Baird 1976, Fishman and Inan 1988, Inan et al 1999 or ozone chemistry (Gehrels et al 2003) in the Earth's atmosphere due to X-ray and g-ray events have not been concerned with the possibility of direct biological effects at planetary surfaces. Other planets and satellites in the solar system and exoplanetary systems with thin or no atmospheres that directly transmit substantial fractions of incident ionizing radiation are only marginally relevant for the question of extraterrestrial life, and discussions of biological effects have been restricted to bodies like present-day Mars and Europa, or the space environment (e.g., Baumstark-Khan and Facius 2000).…”

Section: Introductionmentioning

confidence: 99%

Importance of Biologically Active Aurora-like Ultraviolet Emission: Stochastic Irradiation of Earth and Mars by Flares and Explosions

Smith

Scalo

Wheeler

2004

Orig Life Evol Biosph

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Habitable planets will be subject to intense sources of ionizing radiation and fast particles from a variety of sources-from the host star to distant explosions-on a variety of timescales. Monte Carlo calculations of high-energy irradiation suggest that the surfaces of terrestrial-like planets with thick atmospheres (column densities greater than about 100 g cm -2 ) are well protected from directly incident X-rays and g-rays, but we find that sizeable fractions of incident ionizing radiation from astrophysical sources can be redistributed to biologically and chemically important ultraviolet wavelengths, a significant fraction of which can reach the surface. This redistribution is mediated by secondary electrons, resulting from Compton scattering and X-ray photoabsorption, the energies of which are low enough to excite and ionize atmospheric molecules and atoms, resulting in a rich aurora-like spectrum. We calculate the fraction of energy redistributed into biologically and chemically important wavelength regions for spectra characteristic of stellar flares and supernovae using a Monte-Carlo transport code and then estimate the fraction of this energy that is transmitted from the atmospheric altitudes of redistribution to the surface for a few illustrative cases. For atmospheric models corresponding to the Archean Earth, we assume no significant ultraviolet absorbers, only Rayleigh scattering, and find that the fraction of incident ionizing radiation that is received at the surface in the form of redistributed ultraviolet in the biologically relevant 200-320 nm region (UV-C and UV-B bands) can be up to 4%. On the present-day Earth with its ultraviolet ozone shield, this fraction is found to be 0.2%. Both values are many orders of magnitude higher than the fraction of direct ionizing radiation reaching the surface. This result implies that planetary organisms will be subject to mutationally significant, if intermittent, fluences of UV-B and harder radiation even in the presence of a narrowband ultraviolet shield like ozone. We also calculate the surficial transmitted fraction of ionizing radiation and redistributed ultraviolet radiation for two illustrative evolving Mars atmospheres whose initial surface pressures were 1 bar. We discuss the frequency with which redistributed ultraviolet flux from parent star flares exceeds the parent star ultraviolet flux at the planetary surface. We find that the redistributed ultraviolet from parent star flares is probably a fairly rare intermittent event for habitable zone planets orbiting solar-type stars except when they are young, but should completely dominate the 2 direct steady ultraviolet radiation from the parent star for planets orbiting all stars less massive than about 0.5 solar masses. Our results suggest that coding organisms on such planets (and on the early Earth) may evolve very differently than on contemporary Earth, with diversity and evolutionary rate controlled by a stochastically varying mutation rate and frequent hypermutation episodes.

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Possibility of continuous monitoring of celestial X-ray sources through their ionization effects in the nocturnal D-region ionosphere

Cited by 11 publications

References 39 publications

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares

Sco X-1

Importance of Biologically Active Aurora-like Ultraviolet Emission: Stochastic Irradiation of Earth and Mars by Flares and Explosions

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