HIRISE: a ground-based high-resolution imaging spectrograph using echelle grating for measuring daytime airglow/auroral emissions

Magnetic storm-induced enhancement in neutral composition at low latitudes as inferred by O(<sup>1</sup>D) dayglow measurements from Chile

“…In this study, we report on the daytime OI 630.0 nm red line airglow emission enhancements generated by the geomagnetic-storm-induced changes in composition over low latitudes. The daytime measurements were carried out with the High-Resolution Imaging Spectrograph, using an Echelle grating (HIRISE) instrument (Pallamraju et al, 2002) from Carmen Alto in Chile. Unusual emission enhancements were obtained in the morning hours when the equatorial electrodynamics is not expected to show appreciable variations.…”

Electrodynamic influence on the diurnal behaviour of neutral daytime airglow emissions

“…However, it has been shown in earlier works (Raghavarao et al, 1978) that the integrated EEJ strength until noontime has a direct one-to-one correlation with the strength of the EIA. Although ionization is not measured through optical measurements, it has been shown by earlier studies that the ionization brought in from equatorial latitudes contributes to the OI 630.0 nm dayglow emissions through a dissociative recombination mechanism (Srid- haran et al, 1992;Pallam Raju et al, 1996;Pallamraju et al, 2002). Thus, the asymmetricity in time observed in optical measurements at all the emission wavelengths is compared with the values of the EEJ strengths (A EEJ ) integrated over 07:00-12:00 LT. On these days with symmetric and asymmetric diurnal patterns in dayglow emission intensities, the values of A EEJ were 147 and 214 nT h. As discussed above in this section, the larger value of A EEJ on the day with asymmetric diurnal behaviour enhances the strength of the EIA and results in higher values of AT.…”

“…A few methods have been put forth in the past (e.g. Narayanan et al, 1989;Sridharan et al, 1993bSridharan et al, , 1998Chakrabarti et al, 2001;Pallamraju et al, 2002Pallamraju et al, , 2013Gerard and Meriwether, 2011) to measure these emission intensities, which used low-and high-resolution Fabry-Pérot etalons, echelle and normal gratings, with varying fields of view.…”

“…The dayglow emission intensities are obtained by removing the scattering contribution with a data cadence of 5 min. This method of retrieval of dayglow is well-established and is described in detail in the literature (Pallamraju et al, 2002. The technical details of MISE have been described by Pallamraju et al (2013).…”

Initial daytime and nighttime SOFDI observations of thermospheric winds from Fabry-Perot Doppler shift measurements of the 630-nm OI line-shape profile

“…This ratio removes the solar continuum and leaves only atmospheric emission structure; namely the OI emission and contributions due to the Ring Effect (i.e., the filling of Fraunhoffer valleys due to atmospheric scattering (Barmore, 1975;Pallamraju et al, 2002)). The dayglow OI fringe is located very close to where one of the nighttime fringes would be located and is fit with a Voigt profile, while the Ring continuum is simultaneously fit with a broader Gaussian-shape and its contribution is removed from the Voigt fit as seen in Fig.…”