Longitudinal distribution of thermospheric densities and ionization rates in the upper atmosphere of Mars at mid-latitude using MGS ACC data

Seth, S. P.; Jayanthi, U. B.

doi:10.1016/j.asr.2007.05.056

Cited by 2 publications

(5 citation statements)

References 32 publications

(36 reference statements)

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“…The wave‐3 (semidiurnal wave frequency) oscillations of z m as a function of longitude, reported by Bougher et al . [] and Seth and Jayanthi [], are not detected in the present study. What is detected in Figure seems to be a wave‐2 (diurnal wave frequency) oscillation.…”

Section: Local Solar Time Variation Of Ionospheric Heightsmentioning

confidence: 99%

“…During the spring, the lower atmosphere is expanded because of enhanced solar heating helped by higher dust contents, and the expansion may elevate the ionospheric density peak by about 10 km [ Zhang et al ., ; Bougher et al ., ; Zou et al ., ; Gurnett et al ., ; Morgan et al ., ; Zhang et al ., ]. The peak height is also found to be linked to Martian longitude, which is attributed to the action of the nonmigrating global thermospheric tides [ Bougher et al ., ; Seth and Jayanthi , ]. The crustal magnetic anomalies, distributed mainly in the southern hemisphere and low‐latitude regions of the northern hemisphere [ Acuña et al ., ; Lillis et al ., ], are found to complicate the local morphology of the ionosphere.…”

Section: Introductionmentioning

confidence: 98%

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Relationship of dayside main layer ionosphere height to local solar time on Mars and implications for solar wind interaction influence

et al. 2015

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To understand the influence of solar wind on the daytime main layer ionosphere of Mars, we investigated the local solar time (LST) variations of three characteristic heights of the ionosphere, namely, the heights of the 1 MHz and 1.5 MHz reflection points (i.e., 1.24 × 10 10 m À3 and 2.79 × 10 10 m À3 isodensity contours, respectively) and the density peak. We used a total of 19,996 Mars Advanced Radar for Subsurface and Ionosphere Sounding observations distributed on the northern hemisphere, with solar zenith angle ≤80°, acquired from June 2005 to October 2013. We exploited the kernel partial least squares regression method to extract the nonlinear relationships of the heights to LST and a few other variables. The average height of the 1 MHz reflection point decreased from~218 km at 10:00 A.M. to~206 km at 16:00 P.M. local time; the height of the 1.5 MHz reflection point decreased simultaneously from~190 km to~181 km. These decreasing trends are in contrast to the LST variation of the density peak height, which increased from 128 km to~137 km over the same LST interval. Based on these findings and previous results, we suggest that the solar wind may penetrate the Martian ionosphere down to altitudes of about 50 km above the main density peak and may, in conjunction with the asymmetric draping of the interplanetary magnetic field, compress the upper part of the main ionosphere layer on the P.M. side~10 km more than on the A.M. side.

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Section: Local Solar Time Variation Of Ionospheric Heightsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Relationship of dayside main layer ionosphere height to local solar time on Mars and implications for solar wind interaction influence

et al. 2015

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“…The function was fitted analytically later. In the present paper, two dimensional AYS approach [ Seth , 2003; Seth and Jayanthi , 2008] is used to calculate the photoelectron impact ionization rates at solar zenith angle 78° between northern midlatitude (17–42°N) and high latitude (50–70°N) range for spring equinox and medium solar activity condition, appropriate for those season and location where accelerometer observations were carried out at Mars during phase 2 aerobraking period. This approach is used in the lower thermosphere (≤200 km) where the magnetic field is horizontal in direction such as observed by MGS in the dayside ionosphere of Mars.…”

Section: Calculation and Input Parametersmentioning

confidence: 99%

“…The branching ratios, photoabsorption and photoionization cross sections are taken from other references [cf., Seth and Jayanthi , 2008]. The solar flux is taken from SOLAR 2000 model [ Tobiska et al , 2000], which is an empirical model of the full solar spectrum drawing ground‐based and satellite measurements available for each day.…”

Section: Calculation and Input Parametersmentioning

confidence: 99%

“…These calculations are carried out at different altitudes and longitudes starting from 115 km to 220 km and from 0 to 360°E at the intervals of 0.1 km and 5°, respectively, for solar zenith angle 78° using Analytical Yield Spectrum (AYS) Approach [ Seth , 2003]. These orbits related to Phase 2 were chosen for this particular study because during this time period dust storm activity was minimum [ Seth et al , 2006a, 2006b; Seth and Jayanthi , 2008; Haider et al , 2006].…”

Section: Introductionmentioning

confidence: 99%

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Evidence of baroclinic waves in the upper atmosphere of Mars using the Mars Global Surveyor accelerometer data

Seth

Rao

2008

J. Geophys. Res.

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between latitude ranges (50-70°N), both under spring equinox and medium solar activity conditions. The neutral densities of different gases are derived from their mixing ratio. From these neutral densities, the longitudinal distribution of total peak ionization rates of CO 2 + , N 2 + , O 2 + , O + , and CO + are obtained for solar zenith angle 78°because of solar EUV and soft X-ray (1-102.57 nm) radiation using Analytical Yield Spectrum approach. These calculations are made at different altitudes and longitudes starting from 115 to 220 km and from 0 to 360°E using intervals of 0.1 km and 5°, respectively. These conditions are appropriate for Mars Global Surveyor Phase 2 aerobraking period from which the accelerometer data is used. The Fourier analysis is carried out on the calculated total peak ionization rates for different gases both at midlatitude (17-42°N) and high-latitude (50-70°N) range in the upper atmosphere of Mars. This analysis at high latitude indicates the presence of two dominant harmonic regions, in which the first is a class of long planetary-scale waves, associated with the fixed topography of Martian surface, while the second is a class of rapidly moving transient disturbances associated with baroclinic instability processes. The similar analysis carried out at midlatitude (17-42°N) region indicates the absence of second peak at higher wave number, confirming that the baroclinic instability is almost absent at this latitude region.

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Longitudinal distribution of thermospheric densities and ionization rates in the upper atmosphere of Mars at mid-latitude using MGS ACC data

Cited by 2 publications

References 32 publications

Relationship of dayside main layer ionosphere height to local solar time on Mars and implications for solar wind interaction influence

Relationship of dayside main layer ionosphere height to local solar time on Mars and implications for solar wind interaction influence

Evidence of baroclinic waves in the upper atmosphere of Mars using the Mars Global Surveyor accelerometer data

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