The impacts of solar wind on the Martian upper atmosphere

Since the first in-situ measurements of the altitude profile of upper atmospheric density and composition were carried out by the Viking lander missions in 1976, similar data are continuously gathered by MAVEN and MOM spacecraft orbiting Mars since their launch in September 2014 with mass spectrometers and other related payloads. Using near-simultaneous observations by the two orbiters, it is seen that both data sets indicate significant day-to-day variations of Argon density profiles in the thermosphere-exosphere, 150-300 km region, during the period 1-15, June 2018, when the solar EUV radiation did not show any appreciable change but the solar wind energetic particle fluxes did so. Extending this study to include the other parent atmospheric constituents carbon dioxide, helium, nitrogen and their photochemical products atomic oxygen, and carbon monoxide during the same period it is found that the density profiles of carbon dioxide and atomic oxygen also show similar variations with carbon dioxide densities showing an increasing trend similar to Argon, but a reversal of this trend for atomic oxygen densities. Using insitu and near simultaneous measurements of solar EUV fluxes and the solar wind plasma velocities and densities near MAVEN periapsis it is noted that, unlike the solar EUV radiation, solar wind parameters showed a decrease by a factor of 2-3. Hence, it is inferred that the energetic and penetrating solar wind charged particle impact-driven dissociation, ionisation and ion-chemical processes could decrease the carbon dioxide densities leading to an increase in atomic oxygen densities. This result is also discussed from the considerations of the proton gyro radius effect, pickup ions, sputtering, energetic neutral atoms driven ionisation and ion losses. Further data and modelling efforts would be necessary to confirm this finding.Comment: 20 pages, 10 figure

Climate Change Analysis using Satellite Data

Recent times have witnessed increasing impact of industrialization and urban growth on environment. In addition, the potential climate changes and possible adverse impacts on the economy and society at large are causing concern. In India, one of the major concerns is the variability of monsoon rainfall and effects on agriculture and water management. The various parameters associated with environment and climate change need to be monitored and analyzed. The effects of global warming on the Indian subcontinent vary from the submergence of low-lying islands, frequent flooding, coastal degradation and melting of glaciers in the Indian Himalayas. Indian satellites INSAT and IRS launched in early 1980s heralded the era of Space observations. The IRS satellites are providing observations of parameters such as land use/cover, forest, water bodies, crops etc. while INSAT provides quantitative products such as Cloud Motion Vectors (CMVs), Quantitative Precipitation Estimates (QPEs), Outgoing Long-wave Radiation (OLR), Vertical Temperature Profiles (VTPRs), Sea Surface Temperature. The satellite data is operationally used for generating long term database on vegetation, soil condition, rainfall, groundwater etc.. Some of the unique studies are Biosphere Reserve Monitoring, Mapping o

Improved Technique for Retrieval of Temperature and Humidity from Neutral Atmospheric Refractivity Profiles

This paper discusses some improvements to a technique for retrieving temperature and humidity from neutral atmospheric refractivities. A technique previously developed used auxiliary information in the form of surface temperature and pressure along with neutral atmospheric refractivity profiles in the troposphere to retrieve temperature and humidity profiles. The height at which water vapor is presumed to be negligible was based on criteria that most of the times it was around ~ 10 km altitude. A new set of criteria are developed wherein it is shown that it is possible to bring this height further down whenever troposphere is dry at altitudes below&nbsp

Electrical Conductivity of the Atmosphere over an Urban Location

The simultaneous measurements of atmospheric electrical conductivity and meteorological parameters during 2015 over an urban location were carried out, and their variations are presented. During fair weather days, the variations in air conductivity show a pronounced diurnal trend with early morning hour maxima and afternoon minima. A significant Pearson’s correlation coefficient was found between measured atmospheric electrical conductivity and most meteorological parameters; among them, the highest positive correlation of 0.79 was observed for relative humidity, and a negative correlation of 0.81, with wind speed. The trend in the variation of conductivity followed the activity of Radon over a day. The diurnally averaged monthly variations clearly show higher air conductivity values during winter months, and lowest, in monsoon months. A well-defined seasonal variation was observed, with the highest in winter and the lowest during the monsoon season. The results show that the correlation of air conductivity with meteorological parameters is strong and valid only when the atmosphere is stable, i.e., during the winter season. For 2015, the mean positive conductivity was 1.23 × 10−14 Ω−1 m−1, while the mean negative conductivity was 2.13 × 10−14 Ω−1 m−1, with a mean conductivity of 3.35 × 10−14 Ω−1 m−1 over Bengaluru. The measured air conductivity values are identical to those found in other similar conditions

A review on natural gamma radiation dose levels and its health effects

Exposure to the natural background gamma radiations in both indoor and outdoor environments is inevitable. The long-term exposure to such radiations could result in lung cancer (sometimes leukaemia, CNS tumours); and hence it must be constantly monitored. In this paper, an attempt is made to review the background natural gamma radiation doses reported at various locations for the south Indian environment and it was found that the gamma levels in coastal regions were relatively higher than those in sub continental locations but in most of the locations the annual effective dose rate was within the permissible limits as per UNSCEA