Enhancement in electron and ion temperatures due to solar flares as measured by SROSS-C2 satellite

Sharma, Dinesh K.; Rai, Jagdish; Israil, M.; Subrahmanyam, P.; Chopra, P.; Garg, S. C.

doi:10.5194/angeo-22-2047-2004

Cited by 14 publications

(10 citation statements)

References 21 publications

(21 reference statements)

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“…The model has assumed constant electron temperatures during the flare, whereas basic physical principles predict an increase in electron temperature during a flare. Observations of the terrestrial ionosphere have shown that during a solar flare, electron temperatures at 425–625 km can increase by 1.3–1.9 times [ Sharma et al , 2004]. Neglecting to include an increase in electron temperature would mean that the inferred W‐value is too small.…”

Section: Discussionmentioning

confidence: 99%

Numerical simulations of the ionosphere of Mars during a solar flare

et al. 2012

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[1] Electron densities in planetary ionospheres increase substantially during solar flares in response to the increased solar irradiance at soft X-ray and extreme ultraviolet wavelengths. Here we modify an existing model of the ionosphere of Mars to incorporate time-dependent solar irradiances and use it to simulate ionospheric conditions during the X14.4 and M7.8 solar flares of 15 and 26 April 2001, respectively. Simulations were validated by comparison to Mars Global Surveyor radio occultation measurements of vertical profiles of ionospheric electron density. Adjustments to the model's representation of the neutral atmosphere were required to adequately reproduce the observations before and during these solar flares. An accurate representation of electron-impact ionization, an important process in the lower ionosphere of Mars, is required in order to adequately simulate the doubling of electron densities that can occur in the lower ionosphere of Mars during a solar flare. We used the W-value representation of electron-impact ionization, in which the number of ion-electron pairs created per photon absorbed equals the ratio of the difference between photon energy and the ionization potential of carbon dioxide to the W-value. A range of possible W-values for Mars have been suggested in the literature, and a value of 28 eV led to the best reproduction of flare-affected observations. Simulated enhancements in the electron density are largest and persist the longest in the M1 region. We predict that the peak electron density in the M1 region can exceed that of the M2 region for short periods during intense solar flares.

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Section: Discussionmentioning

confidence: 99%

Numerical simulations of the ionosphere of Mars during a solar flare

et al. 2012

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“…(10), m avg = 4.8 × 10 −26 kg (Mitra 1992) and ρ = 34 eV (Whitten et al 1965). Using SROSS-C2 satellite data, Sharma et al (2004) measured electron and ion temperature changes of ionosphere and they showed that electron temperature (T e ) changes from 1.3 to 1.9 times and ion temperature (T i ) changes from 1.2 to 1.4 times respectively during flares in comparison with normal days. Thus the change of α ef f due to these T e , T i changes is less enough compared to other ion-chemical effect induced changes.…”

Section: Theoretical Understandingmentioning

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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“…In addition to these general responses to the change of solar activity in the 11 year cycle, the responses in a shorter timescale have also been studied. For example, solar flares were seen to affect total electron content, as well as electron and ion temperatures for the dayside, while the nightside ionosphere was not disturbed much [ Afraimovich et al , 2001; Sharma et al , 2004]. Measurements from the Dynamics Explorer‐2 and Atmosphere Explorer‐C satellites at altitudes of 300 to 400 km indicated that the daytime T e at low latitudes exhibited 27‐day variations [ Brace et al , 1987].…”

Section: Introductionmentioning

confidence: 99%

The 27‐day modulation of the low‐latitude ionosphere during a solar maximum

et al. 2009

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[1] The 27-day solar modulation of the low-latitude ionosphere is investigated for the solar maximum period using in situ satellite measurement data and the total electron contents (TEC) estimated from the satellite signals of the global positioning system (GPS). Whereas the density and temperature of the topside ionosphere observed at an altitude of 685 km manifest delayed responses to the 27-day variations in the daily F10.7 values, similar to those previously reported for an altitude of 840 km, the nighttime-scale height, obtained by comparing the densities observed at altitudes of 685 and 840 km at similar local times, was shown to vary in accordance with the changes in F10.7 with the same time delay. The oxygen ion fraction measured at an altitude of 840 km shows a similar response regardless of the local time. Moreover, the GPS TEC values, most of which come from the F peak region, also exhibit similar delayed modulations in accordance with solar rotation. The TEC value correlates well with the thermospheric neutral density, and both are observed to be modulated with the solar rotation with time delay, especially when a long-term variation is filtered out. The present result confirms that the whole thermospheric and ionospheric system is modulated with solar rotation.

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Enhancement in electron and ion temperatures due to solar flares as measured by SROSS-C2 satellite

Cited by 14 publications

References 21 publications

Numerical simulations of the ionosphere of Mars during a solar flare

Numerical simulations of the ionosphere of Mars during a solar flare

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

The 27‐day modulation of the low‐latitude ionosphere during a solar maximum

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